+++ /dev/null
-\input texinfo @c -*-texinfo-*-
-@c %**start of header
-
-@c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
-@c o
-@c GNAT DOCUMENTATION o
-@c o
-@c G N A T _ U G o
-@c o
-@c $Revision: 1.1.2.2 $
-@c o
-@c Copyright (C) 1992-2002 Ada Core Technologies, Inc. o
-@c o
-@c GNAT is free software; you can redistribute it and/or modify it under o
-@c terms of the GNU General Public License as published by the Free Soft- o
-@c ware Foundation; either version 2, or (at your option) any later ver- o
-@c sion. GNAT is distributed in the hope that it will be useful, but WITH- o
-@c OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY o
-@c or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License o
-@c for more details. You should have received a copy of the GNU General o
-@c Public License distributed with GNAT; see file COPYING. If not, write o
-@c to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, o
-@c MA 02111-1307, USA. o
-@c o
-@c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
-
-@c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
-@c
-@c GNAT_UG Style Guide
-@c
-@c 1. Always put a @noindent on the line before the first paragraph
-@c after any of these commands:
-@c
-@c @chapter
-@c @section
-@c @subsection
-@c @subsubsection
-@c @subsubsubsection
-@c
-@c @end smallexample
-@c @end itemize
-@c @end enumerate
-@c
-@c 2. DO NOT use @example. Use @smallexample instead.
-@c
-@c 3. Each @chapter, @section, @subsection, @subsubsection, etc.
-@c command must be preceded by two empty lines
-@c
-@c 4. The @item command must be on a line of its own if it is in an
-@c @itemize or @enumerate command.
-@c
-@c 5. When talking about ALI files use "ALI" (all uppercase), not "Ali"
-@c or "ali".
-@c
-@c oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
-
-@setfilename gnat_ug.info
-@ifset vms
-@settitle GNAT User's Guide for OpenVMS Alpha
-@end ifset
-
-@ifset wnt
-@settitle GNAT User's Guide for Windows NT
-@end ifset
-
-@ifset unx
-@settitle GNAT User's Guide for Unix Platforms
-@end ifset
-
-@ifset vxworks
-@settitle GNAT User's Guide for Cross Platforms
-@end ifset
-
-@setchapternewpage odd
-@syncodeindex fn cp
-@c %**end of header
-
-@titlepage
-
-@ifset vms
-@title GNAT User's Guide
-@center @titlefont{for OpenVMS Alpha}
-@end ifset
-
-@ifset wnt
-@title GNAT User's Guide
-@center @titlefont{for Windows NT}
-@end ifset
-
-@ifset unx
-@title GNAT User's Guide
-@center @titlefont{for Unix Platforms}
-@end ifset
-
-@ifset vxworks
-@title GNAT User's Guide
-@center @titlefont{for Cross Platforms}
-@end ifset
-
-@subtitle GNAT, The GNU Ada 95 Compiler
-@subtitle Document revision level $Revision: 1.1.2.2 $
-@subtitle GNAT Version 3.16w
-@subtitle Date: $Date: 2002/05/04 03:28:06 $
-
-@author Ada Core Technologies, Inc.
-
-@page
-@vskip 0pt plus 1filll
-
-Copyright @copyright{} 1995-2002, Free Software Foundation
-
-Permission is granted to copy, distribute and/or modify this document
-under the terms of the GNU Free Documentation License, Version 1.1
-or any later version published by the Free Software Foundation;
-with the Invariant Sections being ``GNU Free Documentation License'', with the
-Front-Cover Texts being
-@ifset vms
-``GNAT User's Guide for OpenVMS Alpha'',
-@end ifset
-@ifset wnt
-``GNAT User's Guide for Windows NT'',
-@end ifset
-@ifset unx
-``GNAT User's Guide for Unix Platforms'',
-@end ifset
-@ifset vxworks
-``GNAT User's Guide for Cross Platforms'',
-@end ifset
-and with no Back-Cover Texts.
-A copy of the license is included in the section entitled ``GNU
-Free Documentation License''.
-
-@end titlepage
-
-@ifinfo
-@node Top, About This Guide, (dir), (dir)
-@top GNAT User's Guide
-
-@ifset vms
-GNAT User's Guide for OpenVMS Alpha
-@end ifset
-
-@ifset wnt
-GNAT User's Guide for Windows NT
-@end ifset
-
-@ifset unx
-GNAT User's Guide for Unix Platforms
-@end ifset
-
-@ifset vxworks
-GNAT User's Guide for Cross Platforms
-@end ifset
-
-GNAT, The GNU Ada 95 Compiler
-
-GNAT Version 3.16w
-
-Date: $Date: 2002/05/04 03:28:06 $
-
-Ada Core Technologies, Inc.
-
-Copyright @copyright{} 1995-2002, Free Software Foundation
-
-Permission is granted to copy, distribute and/or modify this document
-under the terms of the GNU Free Documentation License, Version 1.1
-or any later version published by the Free Software Foundation;
-with the Invariant Sections being ``GNU Free Documentation License'', with the
-Front-Cover Texts being
-@ifset vms
-``GNAT User's Guide for OpenVMS Alpha'',
-@end ifset
-@ifset wnt
-``GNAT User's Guide for Windows NT'',
-@end ifset
-@ifset unx
-``GNAT User's Guide for Unix Platforms'',
-@end ifset
-@ifset vxworks
-``GNAT User's Guide for Cross Platforms'',
-@end ifset
-and with no Back-Cover Texts.
-A copy of the license is included in the section entitled ``GNU
-Free Documentation License''.
-
-@menu
-* About This Guide::
-@ifset vxworks
-* Preliminary Note for Cross Platform Users::
-@end ifset
-* Getting Started with GNAT::
-* The GNAT Compilation Model::
-* Compiling Using gcc::
-* Binding Using gnatbind::
-* Linking Using gnatlink::
-* The GNAT Make Program gnatmake::
-* Renaming Files Using gnatchop::
-* Configuration Pragmas::
-* Handling Arbitrary File Naming Conventions Using gnatname::
-* GNAT Project Manager::
-* Elaboration Order Handling in GNAT::
-* The Cross-Referencing Tools gnatxref and gnatfind::
-* File Name Krunching Using gnatkr::
-* Preprocessing Using gnatprep::
-@ifset vms
-* The GNAT Run-Time Library Builder gnatlbr::
-@end ifset
-* The GNAT Library Browser gnatls::
-@ifclear vms
-* GNAT and Libraries::
-* Using the GNU make Utility::
-@ifclear vxworks
-* Finding Memory Problems with gnatmem::
-@end ifclear
-@end ifclear
-* Finding Memory Problems with GNAT Debug Pool::
-* Creating Sample Bodies Using gnatstub::
-* Reducing the Size of Ada Executables with gnatelim::
-* Other Utility Programs::
-@ifset vms
-* Compatibility with DEC Ada::
-@end ifset
-* Running and Debugging Ada Programs::
-* Inline Assembler::
-@ifset wnt
-* Microsoft Windows Topics::
-@end ifset
-@ifset vxworks
-* VxWorks Topics::
-* LynxOS Topics::
-@end ifset
-* Performance Considerations::
-* GNU Free Documentation License::
-* Index::
-
- --- The Detailed Node Listing ---
-
-About This Guide
-
-* What This Guide Contains::
-* What You Should Know before Reading This Guide::
-* Related Information::
-* Conventions::
-
-@ifset vxworks
-Preliminary Note for Cross Platform Users::
-@end ifset
-
-Getting Started with GNAT
-
-* Running GNAT::
-@ifclear vxworks
-* Running a Simple Ada Program::
-@end ifclear
-@ifset vxworks
-* Building a Simple Ada Program::
-* Executing a Program on VxWorks::
-@end ifset
-* Running a Program with Multiple Units::
-* Using the gnatmake Utility::
-@ifset vms
-* Editing with Emacs::
-@end ifset
-
-The GNAT Compilation Model
-
-* Source Representation::
-* Foreign Language Representation::
-* File Naming Rules::
-* Using Other File Names::
-* Alternative File Naming Schemes::
-* Generating Object Files::
-* Source Dependencies::
-* The Ada Library Information Files::
-* Binding an Ada Program::
-* Mixed Language Programming::
-* Building Mixed Ada & C++ Programs::
-* Comparison between GNAT and C/C++ Compilation Models::
-* Comparison between GNAT and Conventional Ada Library Models::
-
-Foreign Language Representation
-
-* Latin-1::
-* Other 8-Bit Codes::
-* Wide Character Encodings::
-
-Compiling Ada Programs With gcc
-
-* Compiling Programs::
-* Switches for gcc::
-* Search Paths and the Run-Time Library (RTL)::
-* Order of Compilation Issues::
-* Examples::
-
-Switches for gcc
-
-* Output and Error Message Control::
-* Debugging and Assertion Control::
-* Run-Time Checks::
-* Stack Overflow Checking::
-* Run-Time Control::
-* Validity Checking::
-* Style Checking::
-* Using gcc for Syntax Checking::
-* Using gcc for Semantic Checking::
-* Compiling Ada 83 Programs::
-* Character Set Control::
-* File Naming Control::
-* Subprogram Inlining Control::
-* Auxiliary Output Control::
-* Debugging Control::
-* Units to Sources Mapping Files::
-
-Binding Ada Programs With gnatbind
-
-* Running gnatbind::
-* Generating the Binder Program in C::
-* Consistency-Checking Modes::
-* Binder Error Message Control::
-* Elaboration Control::
-* Output Control::
-* Binding with Non-Ada Main Programs::
-* Binding Programs with No Main Subprogram::
-* Summary of Binder Switches::
-* Command-Line Access::
-* Search Paths for gnatbind::
-* Examples of gnatbind Usage::
-
-Linking Using gnatlink
-
-* Running gnatlink::
-* Switches for gnatlink::
-* Setting Stack Size from gnatlink::
-* Setting Heap Size from gnatlink::
-
-The GNAT Make Program gnatmake
-
-* Running gnatmake::
-* Switches for gnatmake::
-* Mode Switches for gnatmake::
-* Notes on the Command Line::
-* How gnatmake Works::
-* Examples of gnatmake Usage::
-
-Renaming Files Using gnatchop
-
-* Handling Files with Multiple Units::
-* Operating gnatchop in Compilation Mode::
-* Command Line for gnatchop::
-* Switches for gnatchop::
-* Examples of gnatchop Usage::
-
-Configuration Pragmas
-
-* Handling of Configuration Pragmas::
-* The Configuration Pragmas Files::
-
-Handling Arbitrary File Naming Conventions Using gnatname
-
-* Arbitrary File Naming Conventions::
-* Running gnatname::
-* Switches for gnatname::
-* Examples of gnatname Usage::
-
-GNAT Project Manager
-
-* Introduction::
-* Examples of Project Files::
-* Project File Syntax::
-* Objects and Sources in Project Files::
-* Importing Projects::
-* Project Extension::
-* External References in Project Files::
-* Packages in Project Files::
-* Variables from Imported Projects::
-* Naming Schemes::
-* Library Projects::
-* Switches Related to Project Files::
-* Tools Supporting Project Files::
-* An Extended Example::
-* Project File Complete Syntax::
-
-Elaboration Order Handling in GNAT
-
-* Elaboration Code in Ada 95::
-* Checking the Elaboration Order in Ada 95::
-* Controlling the Elaboration Order in Ada 95::
-* Controlling Elaboration in GNAT - Internal Calls::
-* Controlling Elaboration in GNAT - External Calls::
-* Default Behavior in GNAT - Ensuring Safety::
-* Elaboration Issues for Library Tasks::
-* Mixing Elaboration Models::
-* What to Do If the Default Elaboration Behavior Fails::
-* Elaboration for Access-to-Subprogram Values::
-* Summary of Procedures for Elaboration Control::
-* Other Elaboration Order Considerations::
-
-The Cross-Referencing Tools gnatxref and gnatfind
-
-* gnatxref Switches::
-* gnatfind Switches::
-* Project Files for gnatxref and gnatfind::
-* Regular Expressions in gnatfind and gnatxref::
-* Examples of gnatxref Usage::
-* Examples of gnatfind Usage::
-
-File Name Krunching Using gnatkr
-
-* About gnatkr::
-* Using gnatkr::
-* Krunching Method::
-* Examples of gnatkr Usage::
-
-Preprocessing Using gnatprep
-
-* Using gnatprep::
-* Switches for gnatprep::
-* Form of Definitions File::
-* Form of Input Text for gnatprep::
-
-@ifset vms
-The GNAT Run-Time Library Builder gnatlbr
-
-* Running gnatlbr::
-* Switches for gnatlbr::
-* Examples of gnatlbr Usage::
-@end ifset
-
-The GNAT Library Browser gnatls
-
-* Running gnatls::
-* Switches for gnatls::
-* Examples of gnatls Usage::
-
-@ifclear vms
-
-GNAT and Libraries
-
-* Creating an Ada Library::
-* Installing an Ada Library::
-* Using an Ada Library::
-* Creating an Ada Library to be Used in a Non-Ada Context::
-* Rebuilding the GNAT Run-Time Library::
-
-Using the GNU make Utility
-
-* Using gnatmake in a Makefile::
-* Automatically Creating a List of Directories::
-* Generating the Command Line Switches::
-* Overcoming Command Line Length Limits::
-
-@ifclear vxworks
-Finding Memory Problems with gnatmem
-
-* Running gnatmem (GDB Mode)::
-* Running gnatmem (GMEM Mode)::
-* Switches for gnatmem::
-* Examples of gnatmem Usage::
-* GDB and GMEM Modes::
-* Implementation Note::
-
-@end ifclear
-@end ifclear
-
-Finding Memory Problems with GNAT Debug Pool
-
-Creating Sample Bodies Using gnatstub
-
-* Running gnatstub::
-* Switches for gnatstub::
-
-Reducing the Size of Ada Executables with gnatelim
-
-* About gnatelim::
-* Eliminate Pragma::
-* Tree Files::
-* Preparing Tree and Bind Files for gnatelim::
-* Running gnatelim::
-* Correcting the List of Eliminate Pragmas::
-* Making Your Executables Smaller::
-* Summary of the gnatelim Usage Cycle::
-
-Other Utility Programs
-
-* Using Other Utility Programs with GNAT::
-* The gnatpsta Utility Program::
-* The External Symbol Naming Scheme of GNAT::
-* Ada Mode for Glide::
-* Converting Ada Files to html with gnathtml::
-@ifset vms
-* LSE::
-@end ifset
-
-@ifset vms
-Compatibility with DEC Ada
-
-* Ada 95 Compatibility::
-* Differences in the Definition of Package System::
-* Language-Related Features::
-* The Package STANDARD::
-* The Package SYSTEM::
-* Tasking and Task-Related Features::
-* Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems::
-* Pragmas and Pragma-Related Features::
-* Library of Predefined Units::
-* Bindings::
-* Main Program Definition::
-* Implementation-Defined Attributes::
-* Compiler and Run-Time Interfacing::
-* Program Compilation and Library Management::
-* Input-Output::
-* Implementation Limits::
-* Tools::
-
-Language-Related Features
-
-* Integer Types and Representations::
-* Floating-Point Types and Representations::
-* Pragmas Float_Representation and Long_Float::
-* Fixed-Point Types and Representations::
-* Record and Array Component Alignment::
-* Address Clauses::
-* Other Representation Clauses::
-
-Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems
-
-* Assigning Task IDs::
-* Task IDs and Delays::
-* Task-Related Pragmas::
-* Scheduling and Task Priority::
-* The Task Stack::
-* External Interrupts::
-
-Pragmas and Pragma-Related Features
-
-* Restrictions on the Pragma INLINE::
-* Restrictions on the Pragma INTERFACE::
-* Restrictions on the Pragma SYSTEM_NAME::
-
-Library of Predefined Units
-
-* Changes to DECLIB::
-
-Bindings
-
-* Shared Libraries and Options Files::
-* Interfaces to C::
-@end ifset
-
-Running and Debugging Ada Programs
-
-* The GNAT Debugger GDB::
-* Running GDB::
-* Introduction to GDB Commands::
-* Using Ada Expressions::
-* Calling User-Defined Subprograms::
-* Using the Next Command in a Function::
-* Ada Exceptions::
-* Ada Tasks::
-* Debugging Generic Units::
-* GNAT Abnormal Termination or Failure to Terminate::
-* Naming Conventions for GNAT Source Files::
-* Getting Internal Debugging Information::
-* Stack Traceback::
-
-Inline Assembler
-
-* Basic Assembler Syntax::
-* A Simple Example of Inline Assembler::
-* Output Variables in Inline Assembler::
-* Input Variables in Inline Assembler::
-* Inlining Inline Assembler Code::
-* Other Asm Functionality::
-* A Complete Example::
-
-@ifset wnt
-Microsoft Windows Topics
-
-* Using GNAT on Windows::
-* GNAT Setup Tool::
-* CONSOLE and WINDOWS subsystems::
-* Temporary Files::
-* Mixed-Language Programming on Windows::
-* Windows Calling Conventions::
-* Introduction to Dynamic Link Libraries (DLLs)::
-* Using DLLs with GNAT::
-* Building DLLs with GNAT::
-* GNAT and Windows Resources::
-* GNAT and COM/DCOM Objects::
-@end ifset
-
-@ifset vxworks
-VxWorks Topics
-
-* Kernel Configuration for VxWorks::
-* Kernel Compilation Issues for VxWorks::
-* Handling Relocation Issues for PowerPc Targets::
-* Support for Software Floating Point on PowerPC Processors::
-* Interrupt Handling for VxWorks::
-* Simulating Command Line Arguments for VxWorks::
-* Debugging Issues for VxWorks::
-* Using GNAT from the Tornado 2 Project Facility::
-* Frequently Asked Questions for VxWorks::
-
-LynxOS Topics
-
-* Getting Started with GNAT on LynxOS::
-* Kernel Configuration for LynxOS::
-* Patch Level Issues for LynxOS::
-* Debugging Issues for LynxOS::
-* An Example Debugging Session for LynxOS::
-@end ifset
-
-Performance Considerations
-
-* Controlling Run-Time Checks::
-* Optimization Levels::
-* Debugging Optimized Code::
-* Inlining of Subprograms::
-@ifset vms
-* Coverage Analysis::
-@end ifset
-
-* Index::
-@end menu
-@end ifinfo
-
-@node About This Guide
-@unnumbered About This Guide
-
-@noindent
-@ifset vms
-This guide describes the use of of GNAT, a full language compiler for the Ada
-95 programming language, implemented on DIGITAL OpenVMS Alpha Systems.
-@end ifset
-@ifclear vms
-This guide describes the use of GNAT, a compiler and software development
-toolset for the full Ada 95 programming language.
-@end ifclear
-It describes the features of the compiler and tools, and details
-how to use them to build Ada 95 applications.
-
-@menu
-* What This Guide Contains::
-* What You Should Know before Reading This Guide::
-* Related Information::
-* Conventions::
-@end menu
-
-@node What This Guide Contains
-@unnumberedsec What This Guide Contains
-
-@noindent
-This guide contains the following chapters:
-@itemize @bullet
-@ifset vxworks
-@item
-@ref{Preliminary Note for Cross Platform Users}, describes the basic
-differences between the cross and native versions of GNAT.
-@end ifset
-@item
-@ref{Getting Started with GNAT}, describes how to get started compiling
-and running Ada programs with the GNAT Ada programming environment.
-@item
-@ref{The GNAT Compilation Model}, describes the compilation model used
-by GNAT.
-@item
-@ref{Compiling Using gcc}, describes how to compile
-Ada programs with @code{gcc}, the Ada compiler.
-@item
-@ref{Binding Using gnatbind}, describes how to
-perform binding of Ada programs with @code{gnatbind}, the GNAT binding
-utility.
-@item
-@ref{Linking Using gnatlink},
-describes @code{gnatlink}, a
-program that provides for linking using the GNAT run-time library to
-construct a program. @code{gnatlink} can also incorporate foreign language
-object units into the executable.
-@item
-@ref{The GNAT Make Program gnatmake}, describes @code{gnatmake}, a
-utility that automatically determines the set of sources
-needed by an Ada compilation unit, and executes the necessary compilations
-binding and link.
-@item
-@ref{Renaming Files Using gnatchop}, describes
-@code{gnatchop}, a utility that allows you to preprocess a file that
-contains Ada source code, and split it into one or more new files, one
-for each compilation unit.
-@item
-@ref{Configuration Pragmas}, describes the configuration pragmas handled by GNAT.
-@item
-@ref{Handling Arbitrary File Naming Conventions Using gnatname}, shows how to override
-the default GNAT file naming conventions, either for an individual unit or globally.
-@item
-@ref{GNAT Project Manager}, describes how to use project files to organize large projects.
-@item
-@ref{Elaboration Order Handling in GNAT}, describes how GNAT helps you deal with
-elaboration order issues.
-@item
-@ref{The Cross-Referencing Tools gnatxref and gnatfind}, discusses
-@code{gnatxref} and @code{gnatfind}, two tools that provide an easy
-way to navigate through sources.
-@item
-@ref{File Name Krunching Using gnatkr}, describes the @code{gnatkr}
-file name krunching utility, used to handle shortened
-file names on operating systems with a limit on the length of names.
-@item
-@ref{Preprocessing Using gnatprep}, describes @code{gnatprep}, a
-preprocessor utility that allows a single source file to be used to
-generate multiple or parameterized source files, by means of macro
-substitution.
-@item
-@ref{The GNAT Library Browser gnatls}, describes @code{gnatls}, a
-utility that displays information about compiled units, including dependences
-on the corresponding sources files, and consistency of compilations.
-@ifclear vms
-@item
-@ref{GNAT and Libraries}, describes the process of creating and using
-Libraries with GNAT. It also describes how to recompile the GNAT run-time
-library.
-
-@item
-@ref{Using the GNU make Utility}, describes some techniques for using
-the GNAT toolset in Makefiles.
-
-@ifclear vxworks
-@item
-@ref{Finding Memory Problems with gnatmem}, describes @code{gnatmem}, a
-utility that monitors dynamic allocation and deallocation activity in a
-program, and displays information about incorrect deallocations and sources
-of possible memory leaks.
-@end ifclear
-@end ifclear
-@item
-@ref{Finding Memory Problems with GNAT Debug Pool}, describes how to
-use the GNAT-specific Debug Pool in order to detect as early as possible
-the use of incorrect memory references.
-
-@item
-@ref{Creating Sample Bodies Using gnatstub}, discusses @code{gnatstub},
-a utility that generates empty but compilable bodies for library units.
-
-@item
-@ref{Reducing the Size of Ada Executables with gnatelim}, describes
-@code{gnatelim}, a tool which detects unused subprograms and helps
-the compiler to create a smaller executable for the program.
-
-@item
-@ref{Other Utility Programs}, discusses several other GNAT utilities,
-including @code{gnatpsta}.
-
-@item
-@ref{Running and Debugging Ada Programs}, describes how to run and debug
-Ada programs.
-
-@item
-@ref{Inline Assembler}, shows how to use the inline assembly facility in an Ada program.
-
-@ifset vxworks
-@item
-@ref{VxWorks Topics}, presents information relevant to the VxWorks target for cross-compilation
-configurations.
-
-@item
-@ref{LynxOS Topics}, presents information relevant to the LynxOS target for cross-compilation
-configurations.
-@end ifset
-
-@item
-@ref{Performance Considerations}, reviews the trade offs between using
-defaults or options in program development.
-@ifset vms
-@item
-@ref{Compatibility with DEC Ada}, details the compatibility of GNAT with
-DEC Ada 83 for OpenVMS Alpha.
-@end ifset
-@end itemize
-
-@node What You Should Know before Reading This Guide
-@unnumberedsec What You Should Know before Reading This Guide
-
-@cindex Ada 95 Language Reference Manual
-@noindent
-This user's guide assumes that you are familiar with Ada 95 language, as
-described in the International Standard ANSI/ISO/IEC-8652:1995, Jan
-1995.
-
-@node Related Information
-@unnumberedsec Related Information
-
-@noindent
-For further information about related tools, refer to the following
-documents:
-
-@itemize @bullet
-@item
-@cite{GNAT Reference Manual}, which contains all reference
-material for the GNAT implementation of Ada 95.
-
-@item
-@cite{Ada 95 Language Reference Manual}, which contains all reference
-material for the Ada 95 programming language.
-
-@item
-@cite{Debugging with GDB}
-@ifset vms
-, located in the GNU:[DOCS] directory,
-@end ifset
-contains all details on the use of the GNU source-level debugger.
-
-@item
-@cite{GNU Emacs Manual}
-@ifset vms
-, located in the GNU:[DOCS] directory if the EMACS kit is installed,
-@end ifset
-contains full information on the extensible editor and programming
-environment Emacs.
-
-@end itemize
-
-@node Conventions
-@unnumberedsec Conventions
-@cindex Conventions
-@cindex Typographical conventions
-
-@noindent
-Following are examples of the typographical and graphic conventions used
-in this guide:
-
-@itemize @bullet
-@item
-@code{Functions}, @code{utility program names}, @code{standard names},
-and @code{classes}.
-
-@item
-@samp{Option flags}
-
-@item
-@file{File Names}, @file{button names}, and @file{field names}.
-
-@item
-@var{Variables}.
-
-@item
-@emph{Emphasis}.
-
-@item
-[optional information or parameters]
-
-@item
-Examples are described by text
-@smallexample
-and then shown this way.
-@end smallexample
-@end itemize
-
-@noindent
-Commands that are entered by the user are preceded in this manual by the
-characters @w{"@code{$ }"} (dollar sign followed by space). If your system
-uses this sequence as a prompt, then the commands will appear exactly as
-you see them in the manual. If your system uses some other prompt, then
-the command will appear with the @code{$} replaced by whatever prompt
-character you are using.
-
-@ifset vxworks
-@node Preliminary Note for Cross Platform Users
-@chapter Preliminary Note for Cross Platform Users
-
-@noindent
-The use of GNAT in a cross environment is very similar to its use in a
-native environment. Most of the tools described in this manual have
-similar functions and options in both modes. The major
-difference is that the name of the cross tools includes the target for
-which the cross compiler is configured. For instance, the cross @command{gnatmake}
-tool is called @command{@i{target}-gnatmake} where @code{@i{target}} stands for the name of
-the cross target. Thus, in an environment configured for the
-target @code{powerpc-wrs-vxworks}, the @command{gnatmake} command is
-@code{powerpc-wrs-vxworks-gnatmake}. This convention allows the
-installation of a native and one or several cross development
-environments at the same location.
-
-The tools that are most relevant in a cross environment are:
-@code{@i{target}-gcc}, @code{@i{target}-gnatmake},
-@code{@i{target}-gnatbind}, @code{@i{target}-gnatlink} to build cross
-applications and @code{@i{target}-gnatls} for cross library
-browsing. @code{@i{target}-gdb} is also usually available for cross
-debugging in text mode. The graphical debugger interface
-@code{gvd} is always a native tool but it can be configured to drive
-the above mentioned cross debugger, thus allowing graphical cross debugging
-sessions. Some other tools such as @code{@i{target}-gnatchop},
-@code{@i{target}-gnatkr}, @code{@i{target}-gnatprep},
-@code{@i{target}-gnatpsta}, @code{@i{target}-gnatxref}, @code{@i{target}-gnatfind}
-and @code{@i{target}-gnatname} are also provided for completeness
-even though they do not differ greatly from their native counterpart.
-
-In the rest of this manual, the tools are sometimes designated with
-their full cross name, and sometimes with their simplified native
-name.
-
-@end ifset
-
-@node Getting Started with GNAT
-@chapter Getting Started with GNAT
-
-@ifclear vxworks
-@noindent
-This chapter describes some simple ways of using GNAT to build
-executable Ada programs.
-@end ifclear
-@ifset vxworks
-@noindent
-This introduction is a starting point for using GNAT to develop
-and execute Ada 95 programs in a cross environment.
-It provides some specifics
-about the GNAT toolchain targeted to the Wind River Sytems' VxWorks/Tornado platform;
-for other targets please refer to the corresponding chapter later in this manual.
-
-Basic familiarity with use of GNAT in a native environment is
-presumed. For the VxWorks specific part, a knowledge of how to start
-Tornado's @code{windsh} tool is also presumed.
-@end ifset
-
-@menu
-* Running GNAT::
-@ifclear vxworks
-* Running a Simple Ada Program::
-@end ifclear
-@ifset vxworks
-* Building a Simple Ada Program::
-* Executing a Program on VxWorks::
-@end ifset
-
-* Running a Program with Multiple Units::
-
-* Using the gnatmake Utility::
-@ifset vms
-* Editing with Emacs::
-@end ifset
-@ifclear vms
-* Introduction to Glide and GVD::
-@end ifclear
-@end menu
-
-@node Running GNAT
-@section Running GNAT
-
-@noindent
-Three steps are needed to create an executable file from an Ada source
-file:
-
-@enumerate
-@item
-The source file(s) must be compiled.
-@item
-The file(s) must be bound using the GNAT binder.
-@item
-@ifclear vxworks
-All appropriate object files must be linked to produce an executable.
-@end ifclear
-@ifset vxworks
-All appropriate object files must be linked to produce a loadable module.
-@end ifset
-@end enumerate
-
-@noindent
-All three steps are most commonly handled by using the @code{gnatmake}
-utility program that, given the name of the main program, automatically
-performs the necessary compilation, binding and linking steps.
-
-@ifclear vxworks
-@node Running a Simple Ada Program
-@section Running a Simple Ada Program
-@end ifclear
-@ifset vxworks
-@node Building a Simple Ada Program
-@section Building a Simple Ada Program
-@end ifset
-
-@noindent
-Any text editor may be used to prepare an Ada program. If @code{Glide} is
-used, the optional Ada mode may be helpful in laying out the program. The
-program text is a normal text file. We will suppose in our initial
-example that you have used your editor to prepare the following
-standard format text file:
-
-@smallexample
-@group
-@cartouche
-@b{with} Ada.Text_IO; @b{use} Ada.Text_IO;
-@b{procedure} Hello @b{is}
-@b{begin}
- Put_Line ("Hello WORLD!");
-@b{end} Hello;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-This file should be named @file{hello.adb}.
-With the normal default file naming conventions, GNAT requires
-that each file
-contain a single compilation unit whose file name is the
-unit name,
-with periods replaced by hyphens; the
-extension is @file{ads} for a
-spec and @file{adb} for a body.
-You can override this default file naming convention by use of the
-special pragma @code{Source_File_Name} (@pxref{Using Other File Names}).
-Alternatively, if you want to rename your files according to this default
-convention, which is probably more convenient if you will be using GNAT
-for all your compilations, then the @code{gnatchop} utility
-can be used to generate correctly-named source files
-(@pxref{Renaming Files Using gnatchop}).
-
-You can compile the program using the following command (@code{$} is used
-as the command prompt in the examples in this document):
-
-@ifclear vxworks
-@smallexample
-$ gcc -c hello.adb
-@end smallexample
-@end ifclear
-
-@ifset vxworks
-@smallexample
-$ @i{target}-gcc -c hello.adb
-@end smallexample
-@end ifset
-
-@noindent
-@code{gcc} is the command used to run the compiler. This compiler is
-capable of compiling programs in several languages, including Ada 95 and
-C. It assumes that you have given it an Ada program if the file extension is
-either @file{.ads} or @file{.adb}, and it will then call the GNAT compiler to compile
-the specified file.
-
-@ifclear vms
-The @option{-c} switch is required. It tells @command{gcc} to only do a
-compilation. (For C programs, @command{gcc} can also do linking, but this
-capability is not used directly for Ada programs, so the @option{-c}
-switch must always be present.)
-@end ifclear
-
-This compile command generates a file
-@file{hello.o}, which is the object
-file corresponding to your Ada program. It also generates an "Ada Library Information" file
-@file{hello.ali},
-which contains additional information used to check
-that an Ada program is consistent.
-@ifclear vxworks
-To build an executable file,
-@end ifclear
-@ifset vxworks
-To build a downloadable module,
-@end ifset
-use @code{gnatbind} to bind the program
-and @code{gnatlink} to link it. The
-argument to both @code{gnatbind} and @code{gnatlink} is the name of the
-@file{ali} file, but the default extension of @file{.ali} can
-be omitted. This means that in the most common case, the argument
-is simply the name of the main program:
-
-@ifclear vxworks
-@smallexample
-$ gnatbind hello
-$ gnatlink hello
-@end smallexample
-@end ifclear
-
-@ifset vxworks
-@smallexample
-$ @i{target}-gnatbind hello
-$ @i{target}-gnatlink hello
-@end smallexample
-@end ifset
-
-@noindent
-A simpler method of carrying out these steps is to use
-@command{gnatmake},
-a master program that invokes all the required
-compilation, binding and linking tools in the correct order. In particular,
-@command{gnatmake} automatically recompiles any sources that have been modified
-since they were last compiled, or sources that depend
-on such modified sources, so that "version skew" is avoided.
-@cindex Version skew (avoided by @command{gnatmake})
-
-@ifclear vxworks
-@smallexample
-$ gnatmake hello.adb
-@end smallexample
-@end ifclear
-
-@ifset vxworks
-@smallexample
-$ @i{target}-gnatmake hello.adb
-@end smallexample
-@end ifset
-
-@ifclear vxworks
-@noindent
-The result is an executable program called @file{hello}, which can be
-run by entering:
-
-@c The following should be removed (BMB 2001-01-23)
-@c @smallexample
-@c $ ^./hello^$ RUN HELLO^
-@c @end smallexample
-
-@smallexample
-$ hello
-@end smallexample
-
-@noindent
-assuming that the current directory is on the search path for executable programs.
-
-@noindent
-and, if all has gone well, you will see
-
-@smallexample
-Hello WORLD!
-@end smallexample
-
-@noindent
-appear in response to this command.
-
-@end ifclear
-
-@ifset vxworks
-@noindent
-The result is a relocatable object called @file{hello}.
-
-@emph{Technical note:} the result of the linking stage is a
-relocatable partially-linked object containing all the relevant GNAT
-run-time units, in contrast with the executable-format object file found in
-native environments.
-
-
-@node Executing a Program on VxWorks
-@section Executing a Program on VxWorks
-
-@noindent
-Getting a program to execute involves loading it onto the target, running it, and then (if re-execution is needed) unloading it.
-
-@menu
-* Loading and Running the Program::
-* Unloading the Program::
-@end menu
-
-@node Loading and Running the Program
-@subsection Loading and Running the Program
-
-@noindent
-An Ada program is loaded and run in the same way as a C program.
-Details may be found in the @cite{Tornado User's Guide}.
-
-In order to load and run our simple "Hello World" example, we assume that
-the target has access to the disk of the host containing this object and
-that its working directory has been set to the directory containing this
-object. The commands are typed in Tornado's Windshell. The @code{windsh} prompt
-is the @code{->} sequence.
-
-@smallexample
--> vf0=open("/vio/0",2,0)
-new symbol "vf0" added to symbol table.
-vf0 = 0x2cab48: value = 12 = 0xc
--> ioGlobalStdSet(1,vf0)
-value = 1 = 0x1
--> ld < hello
-value = 665408 = 0xa2740
--> hello
-Hello World
-value = 0 = 0x0
-->
-@end smallexample
-
-@noindent
-The first two commands redirect output to the shell window.
-They are only needed if the target server was started without the
-@code{-C} option. The third command loads the module, which is the file
-@file{hello} created previously by the @code{@i{target}-gnatmake} command.
-Note that for Tornado AE, the @command{ml} command replaces @command{ld}."
-
-The "Hello World" program comprises a procedure named @code{hello}, and this
-is the name entered for the procedure in the target server's symbol table
-when the module is loaded. To execute the procedure, type the symbol name @code{hello}
-into @code{windsh} as shown in the last command above.
-
-Note that by default the entry point of an Ada program is the name of the main
-Ada subprogram in a VxWorks environment. It is possible to use an alternative
-name; see the description of @code{gnatbind} options for details.
-
-@node Unloading the Program
-@subsection Unloading the Program
-
-@noindent
-It is important to remember that
-you must unload a program once you have run it. You
-cannot load it once and run it several times. If you don't follow
-this rule, your program's behavior can be unpredictable, and will most
-probably crash.
-
-This effect is due to the implementation of Ada 95's @emph{elaboration} semantics.
-The unit elaboration phase comprises a @emph{static} elaboration and a
-@emph{dynamic} elaboration. On a native platform they both take place
-when the program is run. Thus rerunning the program will repeat the complete
-elaboration phase, and the program will run correctly.
-
-On VxWorks, the process is a bit different.
-The static elaboration phase is handled by
-the loader (typically when you type @code{ld < program_name} in
-@code{windsh}). The dynamic phase takes place when the program is run. If the
-program is run twice and has not been unloaded and then reloaded, the
-second time it is run, the static elaboration phase is skipped.
-Variables initialized during the static elaboration phase
-may have been modified during the first execution of the program. Thus the
-second execution isn't performed on a completely initialized environment.
-
-Note that in C programs, elaboration isn't systematic. Multiple runs without reload
-might work, but, even with C programs, if there is an elaboration
-phase, you will have to unload your program before re-running it.
-@end ifset
-
-
-@node Running a Program with Multiple Units
-@section Running a Program with Multiple Units
-
-@noindent
-Consider a slightly more complicated example that has three files: a
-main program, and the spec and body of a package:
-
-@smallexample
-@cartouche
-@group
-@b{package} Greetings @b{is}
- @b{procedure} Hello;
- @b{procedure} Goodbye;
-@b{end} Greetings;
-
-@b{with} Ada.Text_IO; @b{use} Ada.Text_IO;
-@b{package} @b{body} Greetings @b{is}
- @b{procedure} Hello @b{is}
- @b{begin}
- Put_Line ("Hello WORLD!");
- @b{end} Hello;
-
- @b{procedure} Goodbye @b{is}
- @b{begin}
- Put_Line ("Goodbye WORLD!");
- @b{end} Goodbye;
-@b{end} Greetings;
-@end group
-
-@group
-@b{with} Greetings;
-@b{procedure} Gmain @b{is}
-@b{begin}
- Greetings.Hello;
- Greetings.Goodbye;
-@b{end} Gmain;
-@end group
-@end cartouche
-@end smallexample
-
-@noindent
-Following the one-unit-per-file rule, place this program in the
-following three separate files:
-
-@table @file
-@item greetings.ads
-spec of package @code{Greetings}
-
-@item greetings.adb
-body of package @code{Greetings}
-
-@item gmain.adb
-body of main program
-@end table
-
-@noindent
-To build an executable version of
-this program, we could use four separate steps to compile, bind, and link
-the program, as follows:
-
-@ifclear vxworks
-@smallexample
-$ gcc -c gmain.adb
-$ gcc -c greetings.adb
-$ gnatbind gmain
-$ gnatlink gmain
-@end smallexample
-@end ifclear
-
-@ifset vxworks
-@smallexample
-$ @i{target}-gcc -c gmain.adb
-$ @i{target}-gcc -c greetings.adb
-$ @i{target}-gnatbind gmain
-$ @i{target}-gnatlink gmain
-@end smallexample
-@end ifset
-
-@noindent
-Note that there is no required order of compilation when using GNAT.
-In particular it is perfectly fine to compile the main program first.
-Also, it is not necessary to compile package specs in the case where
-there is an accompanying body; you only need to compile the body. If you want
-to submit these files to the compiler for semantic checking and not code generation,
-then use the
-@option{-gnatc} switch:
-
-@ifclear vxworks
-@smallexample
- $ gcc -c greetings.ads -gnatc
-@end smallexample
-@end ifclear
-
-@ifset vxworks
-@smallexample
-$ @i{target}-gcc -c greetings.ads -gnatc
-@end smallexample
-@end ifset
-
-@noindent
-Although the compilation can be done in separate steps as in the
-above example, in practice it is almost always more convenient
-to use the @code{gnatmake} tool. All you need to know in this case
-is the name of the main program's source file. The effect of the above four
-commands can be achieved with a single one:
-
-@ifclear vxworks
-@smallexample
-$ gnatmake gmain.adb
-@end smallexample
-@end ifclear
-
-@ifset vxworks
-@smallexample
-$ @i{target}-gnatmake gmain.adb
-@end smallexample
-@end ifset
-
-@noindent
-In the next section we discuss the advantages of using @code{gnatmake} in
-more detail.
-
-@node Using the gnatmake Utility
-@section Using the @command{gnatmake} Utility
-
-@noindent
-If you work on a program by compiling single components at a time using
-@code{gcc}, you typically keep track of the units you modify. In order to
-build a consistent system, you compile not only these units, but also any
-units that depend on the units you have modified.
-For example, in the preceding case,
-if you edit @file{gmain.adb}, you only need to recompile that file. But if
-you edit @file{greetings.ads}, you must recompile both
-@file{greetings.adb} and @file{gmain.adb}, because both files contain
-units that depend on @file{greetings.ads}.
-
-@code{gnatbind} will warn you if you forget one of these compilation
-steps, so that it is impossible to generate an inconsistent program as a
-result of forgetting to do a compilation. Nevertheless it is tedious and
-error-prone to keep track of dependencies among units.
-One approach to handle the dependency-bookkeeping is to use a
-makefile. However, makefiles present maintenance problems of their own:
-if the dependencies change as you change the program, you must make
-sure that the makefile is kept up-to-date manually, which is also an
-error-prone process.
-
-The @code{gnatmake} utility takes care of these details automatically.
-Invoke it using either one of the following forms:
-
-@ifclear vxworks
-@smallexample
-$ gnatmake gmain.adb
-$ gnatmake ^gmain^GMAIN^
-@end smallexample
-@end ifclear
-
-@ifset vxworks
-@smallexample
-$ @i{target}-gnatmake gmain.adb
-$ @i{target}-gnatmake gmain
-@end smallexample
-@end ifset
-
-@noindent
-The argument is the name of the file containing the main program;
-you may omit the extension. @code{gnatmake}
-examines the environment, automatically recompiles any files that need
-recompiling, and binds and links the resulting set of object files,
-generating the executable file, @file{^gmain^GMAIN.EXE^}.
-In a large program, it
-can be extremely helpful to use @code{gnatmake}, because working out by hand
-what needs to be recompiled can be difficult.
-
-Note that @code{gnatmake}
-takes into account all the Ada 95 rules that
-establish dependencies among units. These include dependencies that result
-from inlining subprogram bodies, and from
-generic instantiation. Unlike some other
-Ada make tools, @code{gnatmake} does not rely on the dependencies that were
-found by the compiler on a previous compilation, which may possibly
-be wrong when sources change. @code{gnatmake} determines the exact set of
-dependencies from scratch each time it is run.
-
-@ifset vms
-@node Editing with Emacs
-@section Editing with Emacs
-@cindex Emacs
-
-@noindent
-Emacs is an extensible self-documenting text editor that is available in a
-separate VMSINSTAL kit.
-
-Invoke Emacs by typing "Emacs" at the command prompt. To get started,
-click on the Emacs Help menu and run the Emacs Tutorial.
-In a character cell terminal, Emacs help is invoked with "Ctrl-h" (also written
-as "C-h"), and the tutorial by "C-h t".
-
-Documentation on Emacs and other tools is available in Emacs under the
-pull-down menu button: Help - Info. After selecting Info, use the middle
-mouse button to select a topic (e.g. Emacs).
-
-In a character cell terminal, do "C-h i" to invoke info, and then "m"
-(stands for menu) followed by the menu item desired, as in "m Emacs", to get
-to the Emacs manual.
-Help on Emacs is also available by typing "HELP EMACS" at the DCL command
-prompt.
-
-The tutorial is highly recommended in order to learn the intricacies of Emacs,
-which is sufficiently extensible to provide for a complete programming
-environment and shell for the sophisticated user.
-@end ifset
-
-@ifclear vms
-@node Introduction to Glide and GVD
-@section Introduction to Glide and GVD
-@cindex Glide
-@cindex GVD
-@noindent
-Although it is possible to develop programs using only the command line interface (@command{gnatmake}, etc.) a graphical Interactive Development Environment can make it easier for you to compose, navigate, and debug programs. This section describes the main features of Glide, the GNAT graphical IDE, and also shows how to use the basic commands in GVD, the GNU Visual Debugger. Additional information may be found in the on-line help for these tools.
-
-@menu
-* Building a New Program with Glide::
-* Simple Debugging with GVD::
-* Other Glide Features::
-@end menu
-
-@node Building a New Program with Glide
-@subsection Building a New Program with Glide
-@noindent
-The simplest way to invoke Glide is to enter @command{glide} at the command prompt. It will generally be useful to issue this as a background command, thus allowing you to continue using your command window for other purposes while Glide is running:
-
-@smallexample
-$ glide&
-@end smallexample
-
-@noindent
-Glide will start up with an initial screen displaying the top-level menu items as well as some other information. The menu selections are as follows
-@itemize @bullet
-@item @code{Buffers}
-@item @code{Files}
-@item @code{Tools}
-@item @code{Edit}
-@item @code{Search}
-@item @code{Mule}
-@item @code{Glide}
-@item @code{Help}
-@end itemize
-
-@noindent
-For this introductory example, you will need to create a new Ada source file. First, select the @code{Files} menu. This will pop open a menu with around a dozen or so items. To create a file, select the @code{Open file...} choice. Depending on the platform, you may see a pop-up window where you can browse to an appropriate directory and then enter the file name, or else simply see a line at the bottom of the Glide window where you can likewise enter the file name. Note that in Glide, when you attempt to open a non-existent file, the effect is to create a file with that name. For this example enter @file{hello.adb} as the name of the file.
-
-A new buffer will now appear, occupying the entire Glide window, with the file name at the top. The menu selections are slightly different from the ones you saw on the opening screen; there is an @code{Entities} item, and in place of @code{Glide} there is now an @code{Ada} item. Glide uses the file extension to identify the source language, so @file{adb} indicates an Ada source file.
-
-You will enter some of the source program lines explicitly, and use the syntax-oriented template mechanism to enter other lines. First, type the following text:
-@smallexample
-with Ada.Text_IO; use Ada.Text_IO;
-procedure Hello is
-begin
-@end smallexample
-
-@noindent
-Observe that Glide uses different colors to distinguish reserved words from identifiers. Also, after the @code{procedure Hello is} line, the cursor is automatically indented in anticipation of declarations. When you enter @code{begin}, Glide recognizes that there are no declarations and thus places @code{begin} flush left. But after the @code{begin} line the cursor is again indented, where the statement(s) will be placed.
-
-The main part of the program will be a @code{for} loop. Instead of entering the text explicitly, however, use a statement template. Select the @code{Ada} item on the top menu bar, move the mouse to the @code{Statements} item, and you will see a large selection of alternatives. Choose @code{for loop}. You will be prompted (at the bottom of the buffer) for a loop name; simply press the @key{Enter} key since a loop name is not needed. You should see the beginning of a @code{for} loop appear in the source program window. You will now be prompted for the name of the loop variable; enter a line with the identifier @code{ind} (lower case). Note that, by default, Glide capitalizes the name (you can override such behavior if you wish, although this is outside the scope of this introduction). Next, Glide prompts you for the loop range; enter a line containing @code{1..5} and you will see this also appear in the source program, together with the remaining elements of the @code{for} loop syntax.
-
-Next enter the statement (with an intentional error, a missing semicolon) that will form the body of the loop:
-@smallexample
-Put_Line("Hello, World" & Integer'Image(I))
-@end smallexample
-
-@noindent
-Finally, type @code{end Hello;} as the last line in the program. Now save the file: choose the @code{File} menu item, and then the @code{Save buffer} selection. You will see a message at the bottom of the buffer confirming that the file has been saved.
-
-You are now ready to attempt to build the program. Select the @code{Ada} item from the top menu bar. Although we could choose simply to compile the file, we will instead attempt to do a build (which invokes @command{gnatmake}) since, if the compile is successful, we want to build an executable. Thus select @code{Ada build}. This will fail because of the compilation error, and you will notice that the Glide window has been split: the top window contains the source file, and the bottom window contains the output from the GNAT tools. Glide allows you to navigate from a compilation error to the source file position corresponding to the error: click the middle mouse button (or simultaneously press the left and right buttons, on a two-button mouse) on the diagnostic line in the tool window. The focus will shift to the source window, and the cursor will be positioned on the character at which the error was detected.
-
-Correct the error: type in a semicolon to terminate the statement. Although you can again save the file explicitly, you can also simply invoke @code{Ada} @result{} @code{Build} and you will be prompted to save the file. This time the build will succeed; the tool output window shows you the options that are supplied by default. The GNAT tools' output (e.g., object and ALI files, executable) will go in the directory from which Glide was launched.
-
-To execute the program, choose @code{Ada} and then @code{Run}. You should see the program's output displayed in the bottom window:
-
-@smallexample
-Hello, world 1
-Hello, world 2
-Hello, world 3
-Hello, world 4
-Hello, world 5
-@end smallexample
-
-@node Simple Debugging with GVD
-@subsection Simple Debugging with GVD
-
-@noindent
-This section describes how to set breakpoints, examine/modify variables, and step through execution.
-
-In order to enable debugging, you need to pass the @option{-g} switch to both the compiler and to @command{gnatlink}. If you are using the command line, passing @option{-g} to @command{gnatmake} will have this effect. You can then launch GVD, e.g. on the @code{hello} program, by issuing the command:
-
-@smallexample
-$ gvd hello
-@end smallexample
-
-@noindent
-If you are using Glide, then @option{-g} is passed to the relevant tools by default when you do a build. Start the debugger by selecting the @code{Ada} menu item, and then @code{Debug}.
-
-GVD comes up in a multi-part window. One pane shows the names of files comprising your executable; another pane shows the source code of the current unit (initially your main subprogram), another pane shows the debugger output and user interactions, and the fourth pane (the data canvas at the top of the window) displays data objects that you have selected.
-
-To the left of the source file pane, you will notice green dots adjacent to some lines. These are lines for which object code exists and where breakpoints can thus be set. You set/reset a breakpoint by clicking the green dot. When a breakpoint is set, the dot is replaced by an @code{X} in a red circle. Clicking the circle toggles the breakpoint off, and the red circle is replaced by the green dot.
-
-For this example, set a breakpoint at the statement where @code{Put_Line} is invoked.
-
-Start program execution by selecting the @code{Run} button on the top menu bar. (The @code{Start} button will also start your program, but it will cause program execution to break at the entry to your main subprogram.) Evidence of reaching the breakpoint will appear: the source file line will be highlighted, and the debugger interactions pane will display a relevant message.
-
-You can examine the values of variables in several ways. Move the mouse over an occurrence of @code{Ind} in the @code{for} loop, and you will see the value (now @code{1}) displayed. Alternatively, right-click on @code{Ind} and select @code{Display Ind}; a box showing the variable's name and value will appear in the data canvas.
-
-Although a loop index is a constant with respect to Ada semantics, you can change its value in the debugger. Right-click in the box for @code{Ind}, and select the @code{Set Value of Ind} item. Enter @code{2} as the new value, and press @command{OK}. The box for @code{Ind} shows the update.
-
-Press the @code{Step} button on the top menu bar; this will step through one line of program text (the invocation of @code{Put_Line}), and you can observe the effect of having modified @code{Ind} since the value displayed is @code{2}.
-
-Remove the breakpoint, and resume execution by selecting the @code{Cont} button. You will see the remaining output lines displayed in the debugger interaction window, along with a message confirming normal program termination.
-
-
-@node Other Glide Features
-@subsection Other Glide Features
-
-@noindent
-You may have observed that some of the menu selections contain abbreviations; e.g., @code{(C-x C-f)} for @code{Open file...} in the @code{Files} menu. These are @emph{shortcut keys} that you can use instead of selecting menu items. The @key{C} stands for @key{Ctrl}; thus @code{(C-x C-f)} means @key{Ctrl-x} followed by @key{Ctrl-f}, and this sequence can be used instead of selecting @code{Files} and then @code{Open file...}.
-
-To abort a Glide command, type @key{Ctrl-g}.
-
-If you want Glide to start with an existing source file, you can either launch Glide as above and then open the file via @code{Files} @result{} @code{Open file...}, or else simply pass the name of the source file on the command line:
-
-@smallexample
-$ glide hello.adb&
-@end smallexample
-
-@noindent
-While you are using Glide, a number of @emph{buffers} exist. You create some explicitly; e.g., when you open/create a file. Others arise as an effect of the commands that you issue; e.g., the buffer containing the output of the tools invoked during a build. If a buffer is hidden, you can bring it into a visible window by first opening the @code{Buffers} menu and then selecting the desired entry.
-
-If a buffer occupies only part of the Glide screen and you want to expand it to fill the entire screen, then click in the buffer and then select @code{Files} @result{} @code{One Window}.
-
-If a window is occupied by one buffer and you want to split the window to bring up a second buffer, perform the following steps:
-@itemize @bullet
-@item Select @code{Files} @result{} @code{Split Window}; this will produce two windows each of which holds the original buffer (these are not copies, but rather different views of the same buffer contents)
-@item With the focus in one of the windows, select the desired buffer from the @code{Buffers} menu
-@end itemize
-
-@noindent
-To exit from Glide, choose @code{Files} @result{} @code{Exit}.
-@end ifclear
-
-@node The GNAT Compilation Model
-@chapter The GNAT Compilation Model
-@cindex GNAT compilation model
-@cindex Compilation model
-
-@menu
-* Source Representation::
-* Foreign Language Representation::
-* File Naming Rules::
-* Using Other File Names::
-* Alternative File Naming Schemes::
-* Generating Object Files::
-* Source Dependencies::
-* The Ada Library Information Files::
-* Binding an Ada Program::
-* Mixed Language Programming::
-* Building Mixed Ada & C++ Programs::
-* Comparison between GNAT and C/C++ Compilation Models::
-* Comparison between GNAT and Conventional Ada Library Models::
-@end menu
-
-@noindent
-This chapter describes the compilation model used by GNAT. Although
-similar to that used by other languages, such as C and C++, this model
-is substantially different from the traditional Ada compilation models,
-which are based on a library. The model is initially described without
-reference to the library-based model. If you have not previously used an
-Ada compiler, you need only read the first part of this chapter. The
-last section describes and discusses the differences between the GNAT
-model and the traditional Ada compiler models. If you have used other
-Ada compilers, this section will help you to understand those
-differences, and the advantages of the GNAT model.
-
-@node Source Representation
-@section Source Representation
-@cindex Latin-1
-
-@noindent
-Ada source programs are represented in standard text files, using
-Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar
-7-bit ASCII set, plus additional characters used for
-representing foreign languages (@pxref{Foreign Language Representation}
-for support of non-USA character sets). The format effector characters
-are represented using their standard ASCII encodings, as follows:
-
-@table @code
-@item VT
-@findex VT
-Vertical tab, @code{16#0B#}
-
-@item HT
-@findex HT
-Horizontal tab, @code{16#09#}
-
-@item CR
-@findex CR
-Carriage return, @code{16#0D#}
-
-@item LF
-@findex LF
-Line feed, @code{16#0A#}
-
-@item FF
-@findex FF
-Form feed, @code{16#0C#}
-@end table
-
-@noindent
-Source files are in standard text file format. In addition, GNAT will
-recognize a wide variety of stream formats, in which the end of physical
-physical lines is marked by any of the following sequences:
-@code{LF}, @code{CR}, @code{CR-LF}, or @code{LF-CR}. This is useful
-in accommodating files that are imported from other operating systems.
-
-@cindex End of source file
-@cindex Source file, end
-@findex SUB
-The end of a source file is normally represented by the physical end of
-file. However, the control character @code{16#1A#} (@code{SUB}) is also
-recognized as signalling the end of the source file. Again, this is
-provided for compatibility with other operating systems where this
-code is used to represent the end of file.
-
-Each file contains a single Ada compilation unit, including any pragmas
-associated with the unit. For example, this means you must place a
-package declaration (a package @dfn{spec}) and the corresponding body in
-separate files. An Ada @dfn{compilation} (which is a sequence of
-compilation units) is represented using a sequence of files. Similarly,
-you will place each subunit or child unit in a separate file.
-
-@node Foreign Language Representation
-@section Foreign Language Representation
-
-@noindent
-GNAT supports the standard character sets defined in Ada 95 as well as
-several other non-standard character sets for use in localized versions
-of the compiler (@pxref{Character Set Control}).
-@menu
-* Latin-1::
-* Other 8-Bit Codes::
-* Wide Character Encodings::
-@end menu
-
-@node Latin-1
-@subsection Latin-1
-@cindex Latin-1
-
-@noindent
-The basic character set is Latin-1. This character set is defined by ISO
-standard 8859, part 1. The lower half (character codes @code{16#00#}
-... @code{16#7F#)} is identical to standard ASCII coding, but the upper half is
-used to represent additional characters. These include extended letters
-used by European languages, such as French accents, the vowels with umlauts
-used in German, and the extra letter A-ring used in Swedish.
-
-@findex Ada.Characters.Latin_1
-For a complete list of Latin-1 codes and their encodings, see the source
-file of library unit @code{Ada.Characters.Latin_1} in file
-@file{a-chlat1.ads}.
-You may use any of these extended characters freely in character or
-string literals. In addition, the extended characters that represent
-letters can be used in identifiers.
-
-@node Other 8-Bit Codes
-@subsection Other 8-Bit Codes
-
-@noindent
-GNAT also supports several other 8-bit coding schemes:
-
-@table @asis
-@cindex Latin-2
-@item Latin-2
-Latin-2 letters allowed in identifiers, with uppercase and lowercase
-equivalence.
-
-@item Latin-3
-@cindex Latin-3
-Latin-3 letters allowed in identifiers, with uppercase and lowercase
-equivalence.
-
-@item Latin-4
-@cindex Latin-4
-Latin-4 letters allowed in identifiers, with uppercase and lowercase
-equivalence.
-
-@item Latin-5
-@cindex Latin-5
-@cindex Cyrillic
-Latin-4 letters (Cyrillic) allowed in identifiers, with uppercase and lowercase
-equivalence.
-
-@item IBM PC (code page 437)
-@cindex code page 437
-This code page is the normal default for PCs in the U.S. It corresponds
-to the original IBM PC character set. This set has some, but not all, of
-the extended Latin-1 letters, but these letters do not have the same
-encoding as Latin-1. In this mode, these letters are allowed in
-identifiers with uppercase and lowercase equivalence.
-
-@item IBM PC (code page 850)
-@cindex code page 850
-This code page is a modification of 437 extended to include all the
-Latin-1 letters, but still not with the usual Latin-1 encoding. In this
-mode, all these letters are allowed in identifiers with uppercase and
-lowercase equivalence.
-
-@item Full Upper 8-bit
-Any character in the range 80-FF allowed in identifiers, and all are
-considered distinct. In other words, there are no uppercase and lowercase
-equivalences in this range. This is useful in conjunction with
-certain encoding schemes used for some foreign character sets (e.g.
-the typical method of representing Chinese characters on the PC).
-
-@item No Upper-Half
-No upper-half characters in the range 80-FF are allowed in identifiers.
-This gives Ada 83 compatibility for identifier names.
-@end table
-
-@noindent
-For precise data on the encodings permitted, and the uppercase and lowercase
-equivalences that are recognized, see the file @file{csets.adb} in
-the GNAT compiler sources. You will need to obtain a full source release
-of GNAT to obtain this file.
-
-@node Wide Character Encodings
-@subsection Wide Character Encodings
-
-@noindent
-GNAT allows wide character codes to appear in character and string
-literals, and also optionally in identifiers, by means of the following
-possible encoding schemes:
-
-@table @asis
-
-@item Hex Coding
-In this encoding, a wide character is represented by the following five
-character sequence:
-
-@smallexample
-ESC a b c d
-@end smallexample
-
-@noindent
-Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
-characters (using uppercase letters) of the wide character code. For
-example, ESC A345 is used to represent the wide character with code
-@code{16#A345#}.
-This scheme is compatible with use of the full Wide_Character set.
-
-@item Upper-Half Coding
-@cindex Upper-Half Coding
-The wide character with encoding @code{16#abcd#} where the upper bit is on (in
-other words, "a" is in the range 8-F) is represented as two bytes,
-@code{16#ab#} and @code{16#cd#}. The second byte cannot be a format control
-character, but is not required to be in the upper half. This method can
-be also used for shift-JIS or EUC, where the internal coding matches the
-external coding.
-
-@item Shift JIS Coding
-@cindex Shift JIS Coding
-A wide character is represented by a two-character sequence,
-@code{16#ab#} and
-@code{16#cd#}, with the restrictions described for upper-half encoding as
-described above. The internal character code is the corresponding JIS
-character according to the standard algorithm for Shift-JIS
-conversion. Only characters defined in the JIS code set table can be
-used with this encoding method.
-
-@item EUC Coding
-@cindex EUC Coding
-A wide character is represented by a two-character sequence
-@code{16#ab#} and
-@code{16#cd#}, with both characters being in the upper half. The internal
-character code is the corresponding JIS character according to the EUC
-encoding algorithm. Only characters defined in the JIS code set table
-can be used with this encoding method.
-
-@item UTF-8 Coding
-A wide character is represented using
-UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
-10646-1/Am.2. Depending on the character value, the representation
-is a one, two, or three byte sequence:
-@smallexample
-@iftex
-@leftskip=.7cm
-@end iftex
-16#0000#-16#007f#: 2#0xxxxxxx#
-16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx#
-16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
-
-@end smallexample
-
-@noindent
-where the xxx bits correspond to the left-padded bits of the
-16-bit character value. Note that all lower half ASCII characters
-are represented as ASCII bytes and all upper half characters and
-other wide characters are represented as sequences of upper-half
-(The full UTF-8 scheme allows for encoding 31-bit characters as
-6-byte sequences, but in this implementation, all UTF-8 sequences
-of four or more bytes length will be treated as illegal).
-@item Brackets Coding
-In this encoding, a wide character is represented by the following eight
-character sequence:
-
-@smallexample
-[ " a b c d " ]
-@end smallexample
-
-@noindent
-Where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
-characters (using uppercase letters) of the wide character code. For
-example, ["A345"] is used to represent the wide character with code
-@code{16#A345#}. It is also possible (though not required) to use the
-Brackets coding for upper half characters. For example, the code
-@code{16#A3#} can be represented as @code{["A3"]}.
-
-This scheme is compatible with use of the full Wide_Character set,
-and is also the method used for wide character encoding in the standard
-ACVC (Ada Compiler Validation Capability) test suite distributions.
-
-@end table
-
-@noindent
-Note: Some of these coding schemes do not permit the full use of the
-Ada 95 character set. For example, neither Shift JIS, nor EUC allow the
-use of the upper half of the Latin-1 set.
-
-@node File Naming Rules
-@section File Naming Rules
-
-@noindent
-The default file name is determined by the name of the unit that the
-file contains. The name is formed by taking the full expanded name of
-the unit and replacing the separating dots with hyphens and using
-^lowercase^uppercase^ for all letters.
-
-An exception arises if the file name generated by the above rules starts
-with one of the characters
-@ifset vms
-A,G,I, or S,
-@end ifset
-@ifclear vms
-a,g,i, or s,
-@end ifclear
-and the second character is a
-minus. In this case, the character ^tilde^dollar sign^ is used in place
-of the minus. The reason for this special rule is to avoid clashes with
-the standard names for child units of the packages System, Ada,
-Interfaces, and GNAT, which use the prefixes
-@ifset vms
-S- A- I- and G-
-@end ifset
-@ifclear vms
-s- a- i- and g-
-@end ifclear
-respectively.
-
-The file extension is @file{.ads} for a spec and
-@file{.adb} for a body. The following list shows some
-examples of these rules.
-
-@table @file
-@item main.ads
-Main (spec)
-@item main.adb
-Main (body)
-@item arith_functions.ads
-Arith_Functions (package spec)
-@item arith_functions.adb
-Arith_Functions (package body)
-@item func-spec.ads
-Func.Spec (child package spec)
-@item func-spec.adb
-Func.Spec (child package body)
-@item main-sub.adb
-Sub (subunit of Main)
-@item ^a~bad.adb^A$BAD.ADB^
-A.Bad (child package body)
-@end table
-
-@noindent
-Following these rules can result in excessively long
-file names if corresponding
-unit names are long (for example, if child units or subunits are
-heavily nested). An option is available to shorten such long file names
-(called file name "krunching"). This may be particularly useful when
-programs being developed with GNAT are to be used on operating systems
-with limited file name lengths. @xref{Using gnatkr}.
-
-Of course, no file shortening algorithm can guarantee uniqueness over
-all possible unit names; if file name krunching is used, it is your
-responsibility to ensure no name clashes occur. Alternatively you
-can specify the exact file names that you want used, as described
-in the next section. Finally, if your Ada programs are migrating from a
-compiler with a different naming convention, you can use the gnatchop
-utility to produce source files that follow the GNAT naming conventions.
-(For details @pxref{Renaming Files Using gnatchop}.)
-
-@node Using Other File Names
-@section Using Other File Names
-@cindex File names
-
-@noindent
-In the previous section, we have described the default rules used by
-GNAT to determine the file name in which a given unit resides. It is
-often convenient to follow these default rules, and if you follow them,
-the compiler knows without being explicitly told where to find all
-the files it needs.
-
-However, in some cases, particularly when a program is imported from
-another Ada compiler environment, it may be more convenient for the
-programmer to specify which file names contain which units. GNAT allows
-arbitrary file names to be used by means of the Source_File_Name pragma.
-The form of this pragma is as shown in the following examples:
-@cindex Source_File_Name pragma
-
-@smallexample
-@group
-@cartouche
-@b{pragma} Source_File_Name (My_Utilities.Stacks,
- Spec_File_Name => "myutilst_a.ada");
-@b{pragma} Source_File_name (My_Utilities.Stacks,
- Body_File_Name => "myutilst.ada");
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-As shown in this example, the first argument for the pragma is the unit
-name (in this example a child unit). The second argument has the form
-of a named association. The identifier
-indicates whether the file name is for a spec or a body;
-the file name itself is given by a string literal.
-
-The source file name pragma is a configuration pragma, which means that
-normally it will be placed in the @file{gnat.adc}
-file used to hold configuration
-pragmas that apply to a complete compilation environment.
-For more details on how the @file{gnat.adc} file is created and used
-@pxref{Handling of Configuration Pragmas}
-@cindex @file{gnat.adc}
-
-@ifclear vms
-GNAT allows completely arbitrary file names to be specified using the
-source file name pragma. However, if the file name specified has an
-extension other than @file{.ads} or @file{.adb} it is necessary to use a special
-syntax when compiling the file. The name in this case must be preceded
-by the special sequence @code{-x} followed by a space and the name of the
-language, here @code{ada}, as in:
-
-@smallexample
-$ gcc -c -x ada peculiar_file_name.sim
-@end smallexample
-@end ifclear
-
-@noindent
-@code{gnatmake} handles non-standard file names in the usual manner (the
-non-standard file name for the main program is simply used as the
-argument to gnatmake). Note that if the extension is also non-standard,
-then it must be included in the gnatmake command, it may not be omitted.
-
-@node Alternative File Naming Schemes
-@section Alternative File Naming Schemes
-@cindex File naming schemes, alternative
-@cindex File names
-
-In the previous section, we described the use of the @code{Source_File_Name}
-pragma to allow arbitrary names to be assigned to individual source files.
-However, this approach requires one pragma for each file, and especially in
-large systems can result in very long @file{gnat.adc} files, and also create
-a maintenance problem.
-
-GNAT also provides a facility for specifying systematic file naming schemes
-other than the standard default naming scheme previously described. An
-alternative scheme for naming is specified by the use of
-@code{Source_File_Name} pragmas having the following format:
-@cindex Source_File_Name pragma
-
-@smallexample
-pragma Source_File_Name (
- Spec_File_Name => FILE_NAME_PATTERN
- [,Casing => CASING_SPEC]
- [,Dot_Replacement => STRING_LITERAL]);
-
-pragma Source_File_Name (
- Body_File_Name => FILE_NAME_PATTERN
- [,Casing => CASING_SPEC]
- [,Dot_Replacement => STRING_LITERAL]);
-
-pragma Source_File_Name (
- Subunit_File_Name => FILE_NAME_PATTERN
- [,Casing => CASING_SPEC]
- [,Dot_Replacement => STRING_LITERAL]);
-
-FILE_NAME_PATTERN ::= STRING_LITERAL
-CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
-
-@end smallexample
-
-@noindent
-The @code{FILE_NAME_PATTERN} string shows how the file name is constructed.
-It contains a single asterisk character, and the unit name is substituted
-systematically for this asterisk. The optional parameter
-@code{Casing} indicates
-whether the unit name is to be all upper-case letters, all lower-case letters,
-or mixed-case. If no
-@code{Casing} parameter is used, then the default is all
-^lower-case^upper-case^.
-
-The optional @code{Dot_Replacement} string is used to replace any periods
-that occur in subunit or child unit names. If no @code{Dot_Replacement}
-argument is used then separating dots appear unchanged in the resulting
-file name.
-Although the above syntax indicates that the
-@code{Casing} argument must appear
-before the @code{Dot_Replacement} argument, but it
-is also permissible to write these arguments in the opposite order.
-
-As indicated, it is possible to specify different naming schemes for
-bodies, specs, and subunits. Quite often the rule for subunits is the
-same as the rule for bodies, in which case, there is no need to give
-a separate @code{Subunit_File_Name} rule, and in this case the
-@code{Body_File_name} rule is used for subunits as well.
-
-The separate rule for subunits can also be used to implement the rather
-unusual case of a compilation environment (e.g. a single directory) which
-contains a subunit and a child unit with the same unit name. Although
-both units cannot appear in the same partition, the Ada Reference Manual
-allows (but does not require) the possibility of the two units coexisting
-in the same environment.
-
-The file name translation works in the following steps:
-
-@itemize @bullet
-
-@item
-If there is a specific @code{Source_File_Name} pragma for the given unit,
-then this is always used, and any general pattern rules are ignored.
-
-@item
-If there is a pattern type @code{Source_File_Name} pragma that applies to
-the unit, then the resulting file name will be used if the file exists. If
-more than one pattern matches, the latest one will be tried first, and the
-first attempt resulting in a reference to a file that exists will be used.
-
-@item
-If no pattern type @code{Source_File_Name} pragma that applies to the unit
-for which the corresponding file exists, then the standard GNAT default
-naming rules are used.
-
-@end itemize
-
-@noindent
-As an example of the use of this mechanism, consider a commonly used scheme
-in which file names are all lower case, with separating periods copied
-unchanged to the resulting file name, and specs end with ".1.ada", and
-bodies end with ".2.ada". GNAT will follow this scheme if the following
-two pragmas appear:
-
-@smallexample
-pragma Source_File_Name
- (Spec_File_Name => "*.1.ada");
-pragma Source_File_Name
- (Body_File_Name => "*.2.ada");
-@end smallexample
-
-@noindent
-The default GNAT scheme is actually implemented by providing the following
-default pragmas internally:
-
-@smallexample
-pragma Source_File_Name
- (Spec_File_Name => "*.ads", Dot_Replacement => "-");
-pragma Source_File_Name
- (Body_File_Name => "*.adb", Dot_Replacement => "-");
-@end smallexample
-
-@noindent
-Our final example implements a scheme typically used with one of the
-Ada 83 compilers, where the separator character for subunits was "__"
-(two underscores), specs were identified by adding @file{_.ADA}, bodies
-by adding @file{.ADA}, and subunits by
-adding @file{.SEP}. All file names were
-upper case. Child units were not present of course since this was an
-Ada 83 compiler, but it seems reasonable to extend this scheme to use
-the same double underscore separator for child units.
-
-@smallexample
-pragma Source_File_Name
- (Spec_File_Name => "*_.ADA",
- Dot_Replacement => "__",
- Casing = Uppercase);
-pragma Source_File_Name
- (Body_File_Name => "*.ADA",
- Dot_Replacement => "__",
- Casing = Uppercase);
-pragma Source_File_Name
- (Subunit_File_Name => "*.SEP",
- Dot_Replacement => "__",
- Casing = Uppercase);
-@end smallexample
-
-@node Generating Object Files
-@section Generating Object Files
-
-@noindent
-An Ada program consists of a set of source files, and the first step in
-compiling the program is to generate the corresponding object files.
-These are generated by compiling a subset of these source files.
-The files you need to compile are the following:
-
-@itemize @bullet
-@item
-If a package spec has no body, compile the package spec to produce the
-object file for the package.
-
-@item
-If a package has both a spec and a body, compile the body to produce the
-object file for the package. The source file for the package spec need
-not be compiled in this case because there is only one object file, which
-contains the code for both the spec and body of the package.
-
-@item
-For a subprogram, compile the subprogram body to produce the object file
-for the subprogram. The spec, if one is present, is as usual in a
-separate file, and need not be compiled.
-
-@item
-@cindex Subunits
-In the case of subunits, only compile the parent unit. A single object
-file is generated for the entire subunit tree, which includes all the
-subunits.
-
-@item
-Compile child units independently of their parent units
-(though, of course, the spec of all the ancestor unit must be present in order
-to compile a child unit).
-
-@item
-@cindex Generics
-Compile generic units in the same manner as any other units. The object
-files in this case are small dummy files that contain at most the
-flag used for elaboration checking. This is because GNAT always handles generic
-instantiation by means of macro expansion. However, it is still necessary to
-compile generic units, for dependency checking and elaboration purposes.
-@end itemize
-
-@noindent
-The preceding rules describe the set of files that must be compiled to
-generate the object files for a program. Each object file has the same
-name as the corresponding source file, except that the extension is
-@file{.o} as usual.
-
-You may wish to compile other files for the purpose of checking their
-syntactic and semantic correctness. For example, in the case where a
-package has a separate spec and body, you would not normally compile the
-spec. However, it is convenient in practice to compile the spec to make
-sure it is error-free before compiling clients of this spec, because such
-compilations will fail if there is an error in the spec.
-
-GNAT provides an option for compiling such files purely for the
-purposes of checking correctness; such compilations are not required as
-part of the process of building a program. To compile a file in this
-checking mode, use the @option{-gnatc} switch.
-
-@node Source Dependencies
-@section Source Dependencies
-
-@noindent
-A given object file clearly depends on the source file which is compiled
-to produce it. Here we are using @dfn{depends} in the sense of a typical
-@code{make} utility; in other words, an object file depends on a source
-file if changes to the source file require the object file to be
-recompiled.
-In addition to this basic dependency, a given object may depend on
-additional source files as follows:
-
-@itemize @bullet
-@item
-If a file being compiled @code{with}'s a unit @var{X}, the object file
-depends on the file containing the spec of unit @var{X}. This includes
-files that are @code{with}'ed implicitly either because they are parents
-of @code{with}'ed child units or they are run-time units required by the
-language constructs used in a particular unit.
-
-@item
-If a file being compiled instantiates a library level generic unit, the
-object file depends on both the spec and body files for this generic
-unit.
-
-@item
-If a file being compiled instantiates a generic unit defined within a
-package, the object file depends on the body file for the package as
-well as the spec file.
-
-@item
-@findex Inline
-@cindex @option{-gnatn} switch
-If a file being compiled contains a call to a subprogram for which
-pragma @code{Inline} applies and inlining is activated with the
-@option{-gnatn} switch, the object file depends on the file containing the
-body of this subprogram as well as on the file containing the spec. Note
-that for inlining to actually occur as a result of the use of this switch,
-it is necessary to compile in optimizing mode.
-
-@cindex @option{-gnatN} switch
-The use of @option{-gnatN} activates a more extensive inlining optimization
-that is performed by the front end of the compiler. This inlining does
-not require that the code generation be optimized. Like @option{-gnatn},
-the use of this switch generates additional dependencies.
-
-@item
-If an object file O depends on the proper body of a subunit through inlining
-or instantiation, it depends on the parent unit of the subunit. This means that
-any modification of the parent unit or one of its subunits affects the
-compilation of O.
-
-@item
-The object file for a parent unit depends on all its subunit body files.
-
-@item
-The previous two rules meant that for purposes of computing dependencies and
-recompilation, a body and all its subunits are treated as an indivisible whole.
-
-@noindent
-These rules are applied transitively: if unit @code{A} @code{with}'s
-unit @code{B}, whose elaboration calls an inlined procedure in package
-@code{C}, the object file for unit @code{A} will depend on the body of
-@code{C}, in file @file{c.adb}.
-
-The set of dependent files described by these rules includes all the
-files on which the unit is semantically dependent, as described in the
-Ada 95 Language Reference Manual. However, it is a superset of what the
-ARM describes, because it includes generic, inline, and subunit dependencies.
-
-An object file must be recreated by recompiling the corresponding source
-file if any of the source files on which it depends are modified. For
-example, if the @code{make} utility is used to control compilation,
-the rule for an Ada object file must mention all the source files on
-which the object file depends, according to the above definition.
-The determination of the necessary
-recompilations is done automatically when one uses @code{gnatmake}.
-@end itemize
-
-@node The Ada Library Information Files
-@section The Ada Library Information Files
-@cindex Ada Library Information files
-@cindex @file{ali} files
-
-@noindent
-Each compilation actually generates two output files. The first of these
-is the normal object file that has a @file{.o} extension. The second is a
-text file containing full dependency information. It has the same
-name as the source file, but an @file{.ali} extension.
-This file is known as the Ada Library Information (@file{ali}) file.
-The following information is contained in the @file{ali} file.
-
-@itemize @bullet
-@item
-Version information (indicates which version of GNAT was used to compile
-the unit(s) in question)
-
-@item
-Main program information (including priority and time slice settings,
-as well as the wide character encoding used during compilation).
-
-@item
-List of arguments used in the @code{gcc} command for the compilation
-
-@item
-Attributes of the unit, including configuration pragmas used, an indication
-of whether the compilation was successful, exception model used etc.
-
-@item
-A list of relevant restrictions applying to the unit (used for consistency)
-checking.
-
-@item
-Categorization information (e.g. use of pragma @code{Pure}).
-
-@item
-Information on all @code{with}'ed units, including presence of
-@code{Elaborate} or @code{Elaborate_All} pragmas.
-
-@item
-Information from any @code{Linker_Options} pragmas used in the unit
-
-@item
-Information on the use of @code{Body_Version} or @code{Version}
-attributes in the unit.
-
-@item
-Dependency information. This is a list of files, together with
-time stamp and checksum information. These are files on which
-the unit depends in the sense that recompilation is required
-if any of these units are modified.
-
-@item
-Cross-reference data. Contains information on all entities referenced
-in the unit. Used by tools like @code{gnatxref} and @code{gnatfind} to
-provide cross-reference information.
-
-@end itemize
-
-@noindent
-For a full detailed description of the format of the @file{ali} file,
-see the source of the body of unit @code{Lib.Writ}, contained in file
-@file{lib-writ.adb} in the GNAT compiler sources.
-
-@node Binding an Ada Program
-@section Binding an Ada Program
-
-@noindent
-When using languages such as C and C++, once the source files have been
-compiled the only remaining step in building an executable program
-is linking the object modules together. This means that it is possible to
-link an inconsistent version of a program, in which two units have
-included different versions of the same header.
-
-The rules of Ada do not permit such an inconsistent program to be built.
-For example, if two clients have different versions of the same package,
-it is illegal to build a program containing these two clients.
-These rules are enforced by the GNAT binder, which also determines an
-elaboration order consistent with the Ada rules.
-
-The GNAT binder is run after all the object files for a program have
-been created. It is given the name of the main program unit, and from
-this it determines the set of units required by the program, by reading the
-corresponding ALI files. It generates error messages if the program is
-inconsistent or if no valid order of elaboration exists.
-
-If no errors are detected, the binder produces a main program, in Ada by
-default, that contains calls to the elaboration procedures of those
-compilation unit that require them, followed by
-a call to the main program. This Ada program is compiled to generate the
-object file for the main program. The name of
-the Ada file is @file{b~@var{xxx}.adb} (with the corresponding spec
-@file{b~@var{xxx}.ads}) where @var{xxx} is the name of the
-main program unit.
-
-Finally, the linker is used to build the resulting executable program,
-using the object from the main program from the bind step as well as the
-object files for the Ada units of the program.
-
-@node Mixed Language Programming
-@section Mixed Language Programming
-@cindex Mixed Language Programming
-
-@menu
-* Interfacing to C::
-* Calling Conventions::
-@end menu
-
-@node Interfacing to C
-@subsection Interfacing to C
-@noindent
-There are two ways to
-build a program that contains some Ada files and some other language
-files depending on whether the main program is in Ada or not.
-If the main program is in Ada, you should proceed as follows:
-
-@enumerate
-@item
-Compile the other language files to generate object files. For instance:
-@smallexample
-gcc -c file1.c
-gcc -c file2.c
-@end smallexample
-
-@item
-Compile the Ada units to produce a set of object files and ALI
-files. For instance:
-@smallexample
-gnatmake ^-c^/ACTIONS=COMPILE^ my_main.adb
-@end smallexample
-
-@item
-Run the Ada binder on the Ada main program. For instance:
-@smallexample
-gnatbind my_main.ali
-@end smallexample
-
-@item
-Link the Ada main program, the Ada objects and the other language
-objects. For instance:
-@smallexample
-gnatlink my_main.ali file1.o file2.o
-@end smallexample
-@end enumerate
-
-The three last steps can be grouped in a single command:
-@smallexample
-gnatmake my_main.adb -largs file1.o file2.o
-@end smallexample
-
-@cindex Binder output file
-@noindent
-If the main program is in some language other than Ada, Then you may
-have more than one entry point in the Ada subsystem. You must use a
-special option of the binder to generate callable routines to initialize
-and finalize the Ada units (@pxref{Binding with Non-Ada Main Programs}).
-Calls to the initialization and finalization routines must be inserted in
-the main program, or some other appropriate point in the code. The call to
-initialize the Ada units must occur before the first Ada subprogram is
-called, and the call to finalize the Ada units must occur after the last
-Ada subprogram returns. You use the same procedure for building the
-program as described previously. In this case, however, the binder
-only places the initialization and finalization subprograms into file
-@file{b~@var{xxx}.adb} instead of the main program.
-So, if the main program is not in Ada, you should proceed as follows:
-
-@enumerate
-@item
-Compile the other language files to generate object files. For instance:
-@smallexample
-gcc -c file1.c
-gcc -c file2.c
-@end smallexample
-
-@item
-Compile the Ada units to produce a set of object files and ALI
-files. For instance:
-@smallexample
-gnatmake ^-c^/ACTIONS=COMPILE^ entry_point1.adb
-gnatmake ^-c^/ACTIONS=COMPILE^ entry_point2.adb
-@end smallexample
-
-@item
-Run the Ada binder on the Ada main program. For instance:
-@smallexample
-gnatbind ^-n^/NOMAIN^ entry_point1.ali entry_point2.ali
-@end smallexample
-
-@item
-Link the Ada main program, the Ada objects and the other language
-objects. You only need to give the last entry point here. For instance:
-@smallexample
-gnatlink entry_point2.ali file1.o file2.o
-@end smallexample
-@end enumerate
-
-@node Calling Conventions
-@subsection Calling Conventions
-@cindex Foreign Languages
-@cindex Calling Conventions
-GNAT follows standard calling sequence conventions and will thus interface
-to any other language that also follows these conventions. The following
-Convention identifiers are recognized by GNAT:
-
-@itemize @bullet
-@cindex Interfacing to Ada
-@cindex Other Ada compilers
-@cindex Convention Ada
-@item
-Ada. This indicates that the standard Ada calling sequence will be
-used and all Ada data items may be passed without any limitations in the
-case where GNAT is used to generate both the caller and callee. It is also
-possible to mix GNAT generated code and code generated by another Ada
-compiler. In this case, the data types should be restricted to simple
-cases, including primitive types. Whether complex data types can be passed
-depends on the situation. Probably it is safe to pass simple arrays, such
-as arrays of integers or floats. Records may or may not work, depending
-on whether both compilers lay them out identically. Complex structures
-involving variant records, access parameters, tasks, or protected types,
-are unlikely to be able to be passed.
-
-Note that in the case of GNAT running
-on a platform that supports DEC Ada 83, a higher degree of compatibility
-can be guaranteed, and in particular records are layed out in an identical
-manner in the two compilers. Note also that if output from two different
-compilers is mixed, the program is responsible for dealing with elaboration
-issues. Probably the safest approach is to write the main program in the
-version of Ada other than GNAT, so that it takes care of its own elaboration
-requirements, and then call the GNAT-generated adainit procedure to ensure
-elaboration of the GNAT components. Consult the documentation of the other
-Ada compiler for further details on elaboration.
-
-However, it is not possible to mix the tasking run time of GNAT and
-DEC Ada 83, All the tasking operations must either be entirely within
-GNAT compiled sections of the program, or entirely within DEC Ada 83
-compiled sections of the program.
-
-@cindex Interfacing to Assembly
-@cindex Convention Assembler
-@item
-Assembler. Specifies assembler as the convention. In practice this has the
-same effect as convention Ada (but is not equivalent in the sense of being
-considered the same convention).
-
-@cindex Convention Asm
-@findex Asm
-@item
-Asm. Equivalent to Assembler.
-
-@cindex Convention Asm
-@findex Asm
-@item
-Asm. Equivalent to Assembly.
-
-@cindex Interfacing to COBOL
-@cindex Convention COBOL
-@findex COBOL
-@item
-COBOL. Data will be passed according to the conventions described
-in section B.4 of the Ada 95 Reference Manual.
-
-@findex C
-@cindex Interfacing to C
-@cindex Convention C
-@item
-C. Data will be passed according to the conventions described
-in section B.3 of the Ada 95 Reference Manual.
-
-@cindex Convention Default
-@findex Default
-@item
-Default. Equivalent to C.
-
-@cindex Convention External
-@findex External
-@item
-External. Equivalent to C.
-
-@findex C++
-@cindex Interfacing to C++
-@cindex Convention C++
-@item
-CPP. This stands for C++. For most purposes this is identical to C.
-See the separate description of the specialized GNAT pragmas relating to
-C++ interfacing for further details.
-
-@findex Fortran
-@cindex Interfacing to Fortran
-@cindex Convention Fortran
-@item
-Fortran. Data will be passed according to the conventions described
-in section B.5 of the Ada 95 Reference Manual.
-
-@item
-Intrinsic. This applies to an intrinsic operation, as defined in the Ada 95
-Reference Manual. If a a pragma Import (Intrinsic) applies to a subprogram,
-this means that the body of the subprogram is provided by the compiler itself,
-usually by means of an efficient code sequence, and that the user does not
-supply an explicit body for it. In an application program, the pragma can only
-be applied to the following two sets of names, which the GNAT compiler
-recognizes.
-@itemize @bullet
-@item
-Rotate_Left, Rotate_Right, Shift_Left, Shift_Right, Shift_Right_-
-Arithmetic. The corresponding subprogram declaration must have
-two formal parameters. The
-first one must be a signed integer type or a modular type with a binary
-modulus, and the second parameter must be of type Natural.
-The return type must be the same as the type of the first argument. The size
-of this type can only be 8, 16, 32, or 64.
-@item binary arithmetic operators: "+", "-", "*", "/"
-The corresponding operator declaration must have parameters and result type
-that have the same root numeric type (for example, all three are long_float
-types). This simplifies the definition of operations that use type checking
-to perform dimensional checks:
-@smallexample
-type Distance is new Long_Float;
-type Time is new Long_Float;
-type Velocity is new Long_Float;
-function "/" (D : Distance; T : Time)
- return Velocity;
-pragma Import (Intrinsic, "/");
-@end smallexample
-@noindent
-This common idiom is often programmed with a generic definition and an explicit
-body. The pragma makes it simpler to introduce such declarations. It incurs
-no overhead in compilation time or code size, because it is implemented as a
-single machine instruction.
-@end itemize
-@noindent
-
-@findex Stdcall
-@cindex Convention Stdcall
-@item
-Stdcall. This is relevant only to NT/Win95 implementations of GNAT,
-and specifies that the Stdcall calling sequence will be used, as defined
-by the NT API.
-
-@findex DLL
-@cindex Convention DLL
-@item
-DLL. This is equivalent to Stdcall.
-
-@findex Win32
-@cindex Convention Win32
-@item
-Win32. This is equivalent to Stdcall.
-
-@findex Stubbed
-@cindex Convention Stubbed
-@item
-Stubbed. This is a special convention that indicates that the compiler
-should provide a stub body that raises @code{Program_Error}.
-@end itemize
-
-@noindent
-GNAT additionally provides a useful pragma @code{Convention_Identifier}
-that can be used to parametrize conventions and allow additional synonyms
-to be specified. For example if you have legacy code in which the convention
-identifier Fortran77 was used for Fortran, you can use the configuration
-pragma:
-
-@smallexample
- pragma Convention_Identifier (Fortran77, Fortran);
-@end smallexample
-
-@noindent
-And from now on the identifier Fortran77 may be used as a convention
-identifier (for example in an @code{Import} pragma) with the same
-meaning as Fortran.
-
-@node Building Mixed Ada & C++ Programs
-@section Building Mixed Ada & C++ Programs
-
-@noindent
-Building a mixed application containing both Ada and C++ code may be a
-challenge for the unaware programmer. As a matter of fact, this
-interfacing has not been standardized in the Ada 95 reference manual due
-to the immaturity and lack of standard of C++ at the time. This
-section gives a few hints that should make this task easier. In
-particular the first section addresses the differences with
-interfacing with C. The second section looks into the delicate problem
-of linking the complete application from its Ada and C++ parts. The last
-section give some hints on how the GNAT run time can be adapted in order
-to allow inter-language dispatching with a new C++ compiler.
-
-@menu
-* Interfacing to C++::
-* Linking a Mixed C++ & Ada Program::
-* A Simple Example::
-* Adapting the Run Time to a New C++ Compiler::
-@end menu
-
-@node Interfacing to C++
-@subsection Interfacing to C++
-
-@noindent
-GNAT supports interfacing with C++ compilers generating code that is
-compatible with the standard Application Binary Interface of the given
-platform.
-
-@noindent
-Interfacing can be done at 3 levels: simple data, subprograms and
-classes. In the first 2 cases, GNAT offer a specific @var{Convention
-CPP} that behaves exactly like @var{Convention C}. Usually C++ mangle
-names of subprograms and currently GNAT does not provide any help to
-solve the demangling problem. This problem can be addressed in 2 ways:
-@itemize @bullet
-@item
-by modifying the C++ code in order to force a C convention using
-the @var{extern "C"} syntax.
-
-@item
-by figuring out the mangled name and use it as the Link_Name argument of
-the pragma import.
-@end itemize
-
-@noindent
-Interfacing at the class level can be achieved by using the GNAT specific
-pragmas such as @code{CPP_Class} and @code{CPP_Virtual}. See the GNAT
-Reference Manual for additional information.
-
-@node Linking a Mixed C++ & Ada Program
-@subsection Linking a Mixed C++ & Ada Program
-
-@noindent
-Usually the linker of the C++ development system must be used to link
-mixed applications because most C++ systems will resolve elaboration
-issues (such as calling constructors on global class instances)
-transparently during the link phase. GNAT has been adapted to ease the
-use of a foreign linker for the last phase. Three cases can be
-considered:
-@enumerate
-
-@item
-Using GNAT and G++ (GNU C++ compiler) from the same GCC
-installation. The c++ linker can simply be called by using the c++
-specific driver called @code{c++}. Note that this setup is not
-very common because it may request recompiling the whole GCC
-tree from sources and it does not allow to upgrade easily to a new
-version of one compiler for one of the two languages without taking the
-risk of destabilizing the other.
-
-@smallexample
-$ c++ -c file1.C
-$ c++ -c file2.C
-$ gnatmake ada_unit -largs file1.o file2.o --LINK=c++
-@end smallexample
-
-@item
-Using GNAT and G++ from 2 different GCC installations. If both compilers
-are on the PATH, the same method can be used. It is important to be
-aware that environment variables such as C_INCLUDE_PATH,
-GCC_EXEC_PREFIX, BINUTILS_ROOT or GCC_ROOT will affect both compilers at
-the same time and thus may make one of the 2 compilers operate
-improperly if they are set for the other. In particular it is important
-that the link command has access to the proper gcc library @file{libgcc.a},
-that is to say the one that is part of the C++ compiler
-installation. The implicit link command as suggested in the gnatmake
-command from the former example can be replaced by an explicit link
-command with full verbosity in order to verify which library is used:
-@smallexample
-$ gnatbind ada_unit
-$ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++
-@end smallexample
-If there is a problem due to interfering environment variables, it can
-be workaround by using an intermediate script. The following example
-shows the proper script to use when GNAT has not been installed at its
-default location and g++ has been installed at its default location:
-
-@smallexample
-$ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script
-$ cat ./my_script
-#!/bin/sh
-unset BINUTILS_ROOT
-unset GCC_ROOT
-c++ $*
-@end smallexample
-
-@item
-Using a non GNU C++ compiler. The same set of command as previously
-described can be used to insure that the c++ linker is
-used. Nonetheless, you need to add the path to libgcc explicitely, since some
-libraries needed by GNAT are located in this directory:
-
-@smallexample
-
-$ gnatlink ada_unit file1.o file2.o --LINK=./my_script
-$ cat ./my_script
-#!/bin/sh
-CC $* `gcc -print-libgcc-file-name`
-
-@end smallexample
-
-Where CC is the name of the non GNU C++ compiler.
-
-@end enumerate
-
-@node A Simple Example
-@subsection A Simple Example
-@noindent
-The following example, provided as part of the GNAT examples, show how
-to achieve procedural interfacing between Ada and C++ in both
-directions. The C++ class A has 2 methods. The first method is exported
-to Ada by the means of an extern C wrapper function. The second method
-calls an Ada subprogram. On the Ada side, The C++ calls is modelized by
-a limited record with a layout comparable to the C++ class. The Ada
-subprogram, in turn, calls the c++ method. So from the C++ main program
-the code goes back and forth between the 2 languages.
-
-@noindent
-Here are the compilation commands
-@ifclear vxworks
-for native configurations:
-@smallexample
-$ gnatmake -c simple_cpp_interface
-$ c++ -c cpp_main.C
-$ c++ -c ex7.C
-$ gnatbind -n simple_cpp_interface
-$ gnatlink simple_cpp_interface -o cpp_main --LINK=$(CPLUSPLUS)
- -lstdc++ ex7.o cpp_main.o
-@end smallexample
-@end ifclear
-@ifset vxworks
-for a GNAT VxWorks/PowerPC configuration:
-@smallexample
-$ powerpc-wrs-vxworks-gnatmake -c simple_cpp_interface
-$ powerpc-wrs-vxworks-gnatbind -n simple_cpp_interface
-$ gnatlink simple_cpp_interface -o ada_part
-$ c++ppc -c -DCPU=PPC604 -I/usr/windppc/target/h cpp_main.C
-$ c++ppc -c -DCPU=PPC604 -I/usr/windppc/target/h ex7.C
-$ ldppc -r -o my_main my_main.o ex7.o ada_part
-@end smallexample
-@end ifset
-@noindent
-Here are the corresponding sources:
-@smallexample
-
-//cpp_main.C
-
-#include "ex7.h"
-
-extern "C" @{
- void adainit (void);
- void adafinal (void);
- void method1 (A *t);
-@}
-
-void method1 (A *t)
-@{
- t->method1 ();
-@}
-
-int main ()
-@{
- A obj;
- adainit ();
- obj.method2 (3030);
- adafinal ();
-@}
-
-//ex7.h
-
-class Origin @{
- public:
- int o_value;
-@};
-class A : public Origin @{
- public:
- void method1 (void);
- virtual void method2 (int v);
- A();
- int a_value;
-@};
-
-//ex7.C
-
-#include "ex7.h"
-#include <stdio.h>
-
-extern "C" @{ void ada_method2 (A *t, int v);@}
-
-void A::method1 (void)
-@{
- a_value = 2020;
- printf ("in A::method1, a_value = %d \n",a_value);
-
-@}
-
-void A::method2 (int v)
-@{
- ada_method2 (this, v);
- printf ("in A::method2, a_value = %d \n",a_value);
-
-@}
-
-A::A(void)
-@{
- a_value = 1010;
- printf ("in A::A, a_value = %d \n",a_value);
-@}
-
--- Ada sources
-@b{package} @b{body} Simple_Cpp_Interface @b{is}
-
- @b{procedure} Ada_Method2 (This : @b{in} @b{out} A; V : Integer) @b{is}
- @b{begin}
- Method1 (This);
- This.A_Value := V;
- @b{end} Ada_Method2;
-
-@b{end} Simple_Cpp_Interface;
-
-@b{package} Simple_Cpp_Interface @b{is}
- @b{type} A @b{is} @b{limited}
- @b{record}
- O_Value : Integer;
- A_Value : Integer;
- @b{end} @b{record};
- @b{pragma} Convention (C, A);
-
- @b{procedure} Method1 (This : @b{in} @b{out} A);
- @b{pragma} Import (C, Method1);
-
- @b{procedure} Ada_Method2 (This : @b{in} @b{out} A; V : Integer);
- @b{pragma} Export (C, Ada_Method2);
-
-@b{end} Simple_Cpp_Interface;
-@end smallexample
-
-@node Adapting the Run Time to a New C++ Compiler
-@subsection Adapting the Run Time to a New C++ Compiler
-@noindent
-GNAT offers the capability to derive Ada 95 tagged types directly from
-preexisting C++ classes and . See "Interfacing with C++" in the GNAT
-reference manual. The mechanism used by GNAT for achieving such a goal
-has been made user configurable through a GNAT library unit
-@code{Interfaces.CPP}. The default version of this file is adapted to
-the GNU c++ compiler. Internal knowledge of the virtual
-table layout used by the new C++ compiler is needed to configure
-properly this unit. The Interface of this unit is known by the compiler
-and cannot be changed except for the value of the constants defining the
-characteristics of the virtual table: CPP_DT_Prologue_Size, CPP_DT_Entry_Size,
-CPP_TSD_Prologue_Size, CPP_TSD_Entry_Size. Read comments in the source
-of this unit for more details.
-
-@node Comparison between GNAT and C/C++ Compilation Models
-@section Comparison between GNAT and C/C++ Compilation Models
-
-@noindent
-The GNAT model of compilation is close to the C and C++ models. You can
-think of Ada specs as corresponding to header files in C. As in C, you
-don't need to compile specs; they are compiled when they are used. The
-Ada @code{with} is similar in effect to the @code{#include} of a C
-header.
-
-One notable difference is that, in Ada, you may compile specs separately
-to check them for semantic and syntactic accuracy. This is not always
-possible with C headers because they are fragments of programs that have
-less specific syntactic or semantic rules.
-
-The other major difference is the requirement for running the binder,
-which performs two important functions. First, it checks for
-consistency. In C or C++, the only defense against assembling
-inconsistent programs lies outside the compiler, in a makefile, for
-example. The binder satisfies the Ada requirement that it be impossible
-to construct an inconsistent program when the compiler is used in normal
-mode.
-
-@cindex Elaboration order control
-The other important function of the binder is to deal with elaboration
-issues. There are also elaboration issues in C++ that are handled
-automatically. This automatic handling has the advantage of being
-simpler to use, but the C++ programmer has no control over elaboration.
-Where @code{gnatbind} might complain there was no valid order of
-elaboration, a C++ compiler would simply construct a program that
-malfunctioned at run time.
-
-@node Comparison between GNAT and Conventional Ada Library Models
-@section Comparison between GNAT and Conventional Ada Library Models
-
-@noindent
-This section is intended to be useful to Ada programmers who have
-previously used an Ada compiler implementing the traditional Ada library
-model, as described in the Ada 95 Language Reference Manual. If you
-have not used such a system, please go on to the next section.
-
-@cindex GNAT library
-In GNAT, there is no @dfn{library} in the normal sense. Instead, the set of
-source files themselves acts as the library. Compiling Ada programs does
-not generate any centralized information, but rather an object file and
-a ALI file, which are of interest only to the binder and linker.
-In a traditional system, the compiler reads information not only from
-the source file being compiled, but also from the centralized library.
-This means that the effect of a compilation depends on what has been
-previously compiled. In particular:
-
-@itemize @bullet
-@item
-When a unit is @code{with}'ed, the unit seen by the compiler corresponds
-to the version of the unit most recently compiled into the library.
-
-@item
-Inlining is effective only if the necessary body has already been
-compiled into the library.
-
-@item
-Compiling a unit may obsolete other units in the library.
-@end itemize
-
-@noindent
-In GNAT, compiling one unit never affects the compilation of any other
-units because the compiler reads only source files. Only changes to source
-files can affect the results of a compilation. In particular:
-
-@itemize @bullet
-@item
-When a unit is @code{with}'ed, the unit seen by the compiler corresponds
-to the source version of the unit that is currently accessible to the
-compiler.
-
-@item
-@cindex Inlining
-Inlining requires the appropriate source files for the package or
-subprogram bodies to be available to the compiler. Inlining is always
-effective, independent of the order in which units are complied.
-
-@item
-Compiling a unit never affects any other compilations. The editing of
-sources may cause previous compilations to be out of date if they
-depended on the source file being modified.
-@end itemize
-
-@noindent
-The most important result of these differences is that order of compilation
-is never significant in GNAT. There is no situation in which one is
-required to do one compilation before another. What shows up as order of
-compilation requirements in the traditional Ada library becomes, in
-GNAT, simple source dependencies; in other words, there is only a set
-of rules saying what source files must be present when a file is
-compiled.
-
-@node Compiling Using gcc
-@chapter Compiling Using @code{gcc}
-
-@noindent
-This chapter discusses how to compile Ada programs using the @code{gcc}
-command. It also describes the set of switches
-that can be used to control the behavior of the compiler.
-@menu
-* Compiling Programs::
-* Switches for gcc::
-* Search Paths and the Run-Time Library (RTL)::
-* Order of Compilation Issues::
-* Examples::
-@end menu
-
-@node Compiling Programs
-@section Compiling Programs
-
-@noindent
-The first step in creating an executable program is to compile the units
-of the program using the @code{gcc} command. You must compile the
-following files:
-
-@itemize @bullet
-@item
-the body file (@file{.adb}) for a library level subprogram or generic
-subprogram
-
-@item
-the spec file (@file{.ads}) for a library level package or generic
-package that has no body
-
-@item
-the body file (@file{.adb}) for a library level package
-or generic package that has a body
-
-@end itemize
-
-@noindent
-You need @emph{not} compile the following files
-
-@itemize @bullet
-
-@item
-the spec of a library unit which has a body
-
-@item
-subunits
-@end itemize
-
-@noindent
-because they are compiled as part of compiling related units. GNAT
-package specs
-when the corresponding body is compiled, and subunits when the parent is
-compiled.
-@cindex No code generated
-If you attempt to compile any of these files, you will get one of the
-following error messages (where fff is the name of the file you compiled):
-
-@smallexample
-No code generated for file @var{fff} (@var{package spec})
-No code generated for file @var{fff} (@var{subunit})
-@end smallexample
-
-@noindent
-The basic command for compiling a file containing an Ada unit is
-
-@smallexample
-$ gcc -c [@var{switches}] @file{file name}
-@end smallexample
-
-@noindent
-where @var{file name} is the name of the Ada file (usually
-having an extension
-@file{.ads} for a spec or @file{.adb} for a body).
-@ifclear vms
-You specify the
-@code{-c} switch to tell @code{gcc} to compile, but not link, the file.
-@end ifclear
-The result of a successful compilation is an object file, which has the
-same name as the source file but an extension of @file{.o} and an Ada
-Library Information (ALI) file, which also has the same name as the
-source file, but with @file{.ali} as the extension. GNAT creates these
-two output files in the current directory, but you may specify a source
-file in any directory using an absolute or relative path specification
-containing the directory information.
-
-@findex gnat1
-@code{gcc} is actually a driver program that looks at the extensions of
-the file arguments and loads the appropriate compiler. For example, the
-GNU C compiler is @file{cc1}, and the Ada compiler is @file{gnat1}.
-These programs are in directories known to the driver program (in some
-configurations via environment variables you set), but need not be in
-your path. The @code{gcc} driver also calls the assembler and any other
-utilities needed to complete the generation of the required object
-files.
-
-It is possible to supply several file names on the same @code{gcc}
-command. This causes @code{gcc} to call the appropriate compiler for
-each file. For example, the following command lists three separate
-files to be compiled:
-
-@smallexample
-$ gcc -c x.adb y.adb z.c
-@end smallexample
-
-@noindent
-calls @code{gnat1} (the Ada compiler) twice to compile @file{x.adb} and
-@file{y.adb}, and @code{cc1} (the C compiler) once to compile @file{z.c}.
-The compiler generates three object files @file{x.o}, @file{y.o} and
-@file{z.o} and the two ALI files @file{x.ali} and @file{y.ali} from the
-Ada compilations. Any switches apply to all the files ^listed,^listed.^
-@ifclear vms
-except for
-@option{-gnat@var{x}} switches, which apply only to Ada compilations.
-@end ifclear
-
-@node Switches for gcc
-@section Switches for @code{gcc}
-
-@noindent
-The @code{gcc} command accepts switches that control the
-compilation process. These switches are fully described in this section.
-First we briefly list all the switches, in alphabetical order, then we
-describe the switches in more detail in functionally grouped sections.
-
-@menu
-* Output and Error Message Control::
-* Debugging and Assertion Control::
-* Run-Time Checks::
-* Stack Overflow Checking::
-* Run-Time Control::
-* Validity Checking::
-* Style Checking::
-* Using gcc for Syntax Checking::
-* Using gcc for Semantic Checking::
-* Compiling Ada 83 Programs::
-* Character Set Control::
-* File Naming Control::
-* Subprogram Inlining Control::
-* Auxiliary Output Control::
-* Debugging Control::
-* Units to Sources Mapping Files::
-@end menu
-
-@table @code
-@ifclear vms
-@cindex @code{-b} (@code{gcc})
-@item -b @var{target}
-Compile your program to run on @var{target}, which is the name of a
-system configuration. You must have a GNAT cross-compiler built if
-@var{target} is not the same as your host system.
-
-@item -B@var{dir}
-@cindex @code{-B} (@code{gcc})
-Load compiler executables (for example, @code{gnat1}, the Ada compiler)
-from @var{dir} instead of the default location. Only use this switch
-when multiple versions of the GNAT compiler are available. See the
-@code{gcc} manual page for further details. You would normally use the
-@code{-b} or @code{-V} switch instead.
-
-@item -c
-@cindex @code{-c} (@code{gcc})
-Compile. Always use this switch when compiling Ada programs.
-
-Note: for some other languages when using @code{gcc}, notably in
-the case of C and C++, it is possible to use
-use @code{gcc} without a @code{-c} switch to
-compile and link in one step. In the case of GNAT, you
-cannot use this approach, because the binder must be run
-and @code{gcc} cannot be used to run the GNAT binder.
-@end ifclear
-
-@item ^-g^/DEBUG^
-@cindex @code{^-g^/DEBUG^} (@code{gcc})
-Generate debugging information. This information is stored in the object
-file and copied from there to the final executable file by the linker,
-where it can be read by the debugger. You must use the
-@code{^-g^/DEBUG^} switch if you plan on using the debugger.
-
-@item ^-I^/SEARCH=^@var{dir}
-@cindex @code{^-I^/SEARCH^} (@code{gcc})
-@cindex RTL
-Direct GNAT to search the @var{dir} directory for source files needed by
-the current compilation
-(@pxref{Search Paths and the Run-Time Library (RTL)}).
-
-@item ^-I-^/NOCURRENT_DIRECTORY^
-@cindex @code{^-I-^/NOCURRENT_DIRECTORY^} (@code{gcc})
-@cindex RTL
-Except for the source file named in the command line, do not look for source files
-in the directory containing the source file named in the command line
-(@pxref{Search Paths and the Run-Time Library (RTL)}).
-
-@ifclear vms
-@item -o @var{file}
-@cindex @code{-o} (@code{gcc})
-This switch is used in @code{gcc} to redirect the generated object file
-and its associated ALI file. Beware of this switch with GNAT, because it may
-cause the object file and ALI file to have different names which in turn
-may confuse the binder and the linker.
-@end ifclear
-
-@ifclear vms
-@item -O[@var{n}]
-@cindex @code{-O} (@code{gcc})
-@var{n} controls the optimization level.
-
-@table @asis
-@item n = 0
-No optimization, the default setting if no @code{-O} appears
-
-@item n = 1
-Normal optimization, the default if you specify @code{-O} without
-an operand.
-
-@item n = 2
-Extensive optimization
-
-@item n = 3
-Extensive optimization with automatic inlining. This applies only to
-inlining within a unit. For details on control of inter-unit inlining
-see @xref{Subprogram Inlining Control}.
-@end table
-@end ifclear
-
-@ifset vms
-@item /NOOPTIMIZE (default)
-@itemx /OPTIMIZE[=(keyword[,...])]
-Selects the level of optimization for your program. The supported
-keywords are as follows:
-@table @code
-@item ALL (default)
-Perform most optimizations, including those that
-be expensive.
-
-@item NONE
-Do not do any optimizations. Same as @code{/NOOPTIMIZE}.
-
-@item SOME
-Perform some optimizations, but omit ones that are costly.
-
-@item DEVELOPMENT
-Same as @code{SOME}.
-
-@item INLINING
-Full optimization, and also attempt automatic inlining of small
-subprograms within a unit (@pxref{Inlining of Subprograms}).
-
-@item UNROLL_LOOPS
-Try to unroll loops. This keyword may be specified together with
-any keyword above other than @code{NONE}. Loop unrolling
-usually, but not always, improves the performance of programs.
-@end table
-@end ifset
-
-@item --RTS=@var{rts-path}
-@cindex @code{--RTS} (@code{gcc})
-Specifies the default location of the runtime library. Same meaning as the
-equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
-
-@item ^-S^/ASM^
-@cindex @code{^-S^/ASM^} (@code{gcc})
-^Used in place of @code{-c} to^Used to^
-cause the assembler source file to be
-generated, using @file{^.s^.S^} as the extension,
-instead of the object file.
-This may be useful if you need to examine the generated assembly code.
-
-@item ^-v^/VERBOSE^
-@cindex @code{^-v^/VERBOSE^} (@code{gcc})
-Show commands generated by the @code{gcc} driver. Normally used only for
-debugging purposes or if you need to be sure what version of the
-compiler you are executing.
-
-@ifclear vms
-@item -V @var{ver}
-@cindex @code{-V} (@code{gcc})
-Execute @var{ver} version of the compiler. This is the @code{gcc}
-version, not the GNAT version.
-@end ifclear
-
-@item -gnata
-Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be
-activated.
-
-@item -gnatA
-Avoid processing @file{gnat.adc}. If a gnat.adc file is present, it will be ignored.
-
-@item -gnatb
-Generate brief messages to @file{stderr} even if verbose mode set.
-
-@item -gnatc
-Check syntax and semantics only (no code generation attempted).
-
-@item -gnatC
-Compress debug information and external symbol name table entries.
-
-@item -gnatD
-Output expanded source files for source level debugging. This switch
-also suppress generation of cross-reference information (see -gnatx).
-
-@item -gnatec@var{path}
-Specify a configuration pragma file. (see @ref{The Configuration Pragmas Files})
-
-@item -gnatem@var{path}
-Specify a mapping file. (see @ref{Units to Sources Mapping Files})
-
-@item -gnatE
-Full dynamic elaboration checks.
-
-@item -gnatf
-Full errors. Multiple errors per line, all undefined references.
-
-@item -gnatF
-Externals names are folded to all uppercase.
-
-@item -gnatg
-Internal GNAT implementation mode. This should not be used for
-applications programs, it is intended only for use by the compiler
-and its run-time library. For documentation, see the GNAT sources.
-
-@item -gnatG
-List generated expanded code in source form.
-
-@item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
-Identifier character set
-@ifclear vms
-(@var{c}=1/2/3/4/8/9/p/f/n/w).
-@end ifclear
-@ifset vms
-For details of the possible selections for @var{c},
-see @xref{Character Set Control}.
-@end ifset
-
-@item ^-gnath^/HELP^
-Output usage information. The output is written to @file{stdout}.
-
-@item ^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{n}
-Limit file names to @var{n} (1-999) characters ^(@code{k} = krunch)^^.
-
-@item -gnatl
-Output full source listing with embedded error messages.
-
-@item -gnatm^^=^@var{n}
-Limit number of detected errors to @var{n} (1-999).
-
-@item -gnatn
-Activate inlining across unit boundaries for subprograms for which
-pragma @code{inline} is specified.
-
-@item -gnatN
-Activate front end inlining.
-
-@item ^-fno-inline^/INLINE=SUPPRESS^
-Suppresses all inlining, even if other optimization or inlining switches
-are set.
-
-@ifclear vms
-@item -fstack-check
-Activates stack checking. See separate section on stack checking for
-details of the use of this option.
-@end ifclear
-
-@item -gnato
-Enable numeric overflow checking (which is not normally enabled by
-default). Not that division by zero is a separate check that is not
-controlled by this switch (division by zero checking is on by default).
-
-@item -gnatp
-Suppress all checks.
-
-@item -gnatq
-Don't quit; try semantics, even if parse errors.
-
-@item -gnatQ
-Don't quit; generate @file{ali} and tree files even if illegalities.
-
-@item -gnatP
-Enable polling. This is required on some systems (notably Windows NT) to
-obtain asynchronous abort and asynchronous transfer of control capability.
-See the description of pragma Polling in the GNAT Reference Manual for
-full details.
-
-@item -gnatR[0/1/2/3][s]
-Output representation information for declared types and objects.
-
-@item -gnats
-Syntax check only.
-
-@item -gnatt
-Tree output file to be generated.
-
-@item -gnatT nnn
-Set time slice to specified number of microseconds
-
-@item -gnatu
-List units for this compilation.
-
-@item -gnatU
-Tag all error messages with the unique string "error:"
-
-@item -gnatv
-Verbose mode. Full error output with source lines to @file{stdout}.
-
-@item -gnatV
-Control level of validity checking. See separate section describing
-this feature.
-
-@item ^-gnatwxxx^/WARNINGS=^@var{xxx}
-Warning mode where
-@var{xxx} is a string of options describing the exact warnings that
-are enabled or disabled. See separate section on warning control.
-
-@item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
-Wide character encoding method
-@ifclear vms
-(@var{e}=n/h/u/s/e/8).
-@end ifclear
-@ifset vms
-(@var{e}=@code{BRACKETS, NONE, HEX, UPPER, SHIFT_JIS, EUC, UTF8})
-@end ifset
-
-@item -gnatx
-Suppress generation of cross-reference information.
-
-@item ^-gnaty^/STYLE_CHECKS=(option,option..)^
-Enable built-in style checks. See separate section describing this feature.
-
-@item ^-gnatz^/DISTRIBUTION_STUBS=^@var{m}
-Distribution stub generation and compilation
-@ifclear vms
-(@var{m}=r/c for receiver/caller stubs).
-@end ifclear
-@ifset vms
-(@var{m}=@code{RECEIVER} or @code{CALLER} to specify the type of stubs
-to be generated and compiled).
-@end ifset
-
-@item -gnat83
-Enforce Ada 83 restrictions.
-
-@ifclear vms
-@item -pass-exit-codes
-Catch exit codes from the compiler and use the most meaningful as
-exit status.
-@end ifclear
-@end table
-
-@ifclear vms
-You may combine a sequence of GNAT switches into a single switch. For
-example, the combined switch
-
-@cindex Combining GNAT switches
-@smallexample
--gnatofi3
-@end smallexample
-
-@noindent
-is equivalent to specifying the following sequence of switches:
-
-@smallexample
--gnato -gnatf -gnati3
-@end smallexample
-@end ifclear
-
-@noindent
-The following restrictions apply to the combination of switches
-in this manner:
-
-@itemize @bullet
-@item
-The switch @option{-gnatc} if combined with other switches must come
-first in the string.
-
-@item
-The switch @option{-gnats} if combined with other switches must come
-first in the string.
-
-@item
-Once a "y" appears in the string (that is a use of the @option{-gnaty}
-switch), then all further characters in the switch are interpreted
-as style modifiers (see description of @option{-gnaty}).
-
-@item
-Once a "d" appears in the string (that is a use of the @option{-gnatd}
-switch), then all further characters in the switch are interpreted
-as debug flags (see description of @option{-gnatd}).
-
-@item
-Once a "w" appears in the string (that is a use of the @option{-gnatw}
-switch), then all further characters in the switch are interpreted
-as warning mode modifiers (see description of @option{-gnatw}).
-
-@item
-Once a "V" appears in the string (that is a use of the @option{-gnatV}
-switch), then all further characters in the switch are interpreted
-as validity checking options (see description of @option{-gnatV}).
-
-@end itemize
-
-@node Output and Error Message Control
-@subsection Output and Error Message Control
-@findex stderr
-
-@noindent
-The standard default format for error messages is called "brief format."
-Brief format messages are written to @file{stderr} (the standard error
-file) and have the following form:
-
-@smallexample
-@iftex
-@leftskip=.7cm
-@end iftex
-e.adb:3:04: Incorrect spelling of keyword "function"
-e.adb:4:20: ";" should be "is"
-@end smallexample
-
-@noindent
-The first integer after the file name is the line number in the file,
-and the second integer is the column number within the line.
-@code{glide} can parse the error messages
-and point to the referenced character.
-The following switches provide control over the error message
-format:
-
-@table @code
-@item -gnatv
-@cindex @option{-gnatv} (@code{gcc})
-@findex stdout
-@ifclear vms
-The v stands for verbose.
-@end ifclear
-The effect of this setting is to write long-format error
-messages to @file{stdout} (the standard output file.
-The same program compiled with the
-@option{-gnatv} switch would generate:
-
-@smallexample
-@group
-@cartouche
-3. funcion X (Q : Integer)
- |
->>> Incorrect spelling of keyword "function"
-4. return Integer;
- |
->>> ";" should be "is"
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-The vertical bar indicates the location of the error, and the @samp{>>>}
-prefix can be used to search for error messages. When this switch is
-used the only source lines output are those with errors.
-
-@item -gnatl
-@cindex @option{-gnatl} (@code{gcc})
-@ifclear vms
-The @code{l} stands for list.
-@end ifclear
-This switch causes a full listing of
-the file to be generated. The output might look as follows:
-
-@smallexample
-@group
-@cartouche
- 1. procedure E is
- 2. V : Integer;
- 3. funcion X (Q : Integer)
- |
- >>> Incorrect spelling of keyword "function"
- 4. return Integer;
- |
- >>> ";" should be "is"
- 5. begin
- 6. return Q + Q;
- 7. end;
- 8. begin
- 9. V := X + X;
-10.end E;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-@findex stderr
-When you specify the @option{-gnatv} or @option{-gnatl} switches and
-standard output is redirected, a brief summary is written to
-@file{stderr} (standard error) giving the number of error messages and
-warning messages generated.
-
-@item -gnatU
-@cindex @option{-gnatU} (@code{gcc})
-This switch forces all error messages to be preceded by the unique
-string "error:". This means that error messages take a few more
-characters in space, but allows easy searching for and identification
-of error messages.
-
-@item -gnatb
-@cindex @option{-gnatb} (@code{gcc})
-@ifclear vms
-The @code{b} stands for brief.
-@end ifclear
-This switch causes GNAT to generate the
-brief format error messages to @file{stderr} (the standard error
-file) as well as the verbose
-format message or full listing (which as usual is written to
-@file{stdout} (the standard output file).
-
-@item -gnatm^^=^@var{n}
-@cindex @option{-gnatm} (@code{gcc})
-@ifclear vms
-The @code{m} stands for maximum.
-@end ifclear
-@var{n} is a decimal integer in the
-range of 1 to 999 and limits the number of error messages to be
-generated. For example, using @option{-gnatm2} might yield
-
-@smallexample
-@iftex
-@leftskip=.7cm
-@end iftex
-e.adb:3:04: Incorrect spelling of keyword "function"
-e.adb:5:35: missing ".."
-fatal error: maximum errors reached
-compilation abandoned
-@end smallexample
-
-@item -gnatf
-@cindex @option{-gnatf} (@code{gcc})
-@cindex Error messages, suppressing
-@ifclear vms
-The @code{f} stands for full.
-@end ifclear
-Normally, the compiler suppresses error messages that are likely to be
-redundant. This switch causes all error
-messages to be generated. In particular, in the case of
-references to undefined variables. If a given variable is referenced
-several times, the normal format of messages is
-@smallexample
-@iftex
-@leftskip=.7cm
-@end iftex
-e.adb:7:07: "V" is undefined (more references follow)
-@end smallexample
-
-@noindent
-where the parenthetical comment warns that there are additional
-references to the variable @code{V}. Compiling the same program with the
-@option{-gnatf} switch yields
-
-@smallexample
-e.adb:7:07: "V" is undefined
-e.adb:8:07: "V" is undefined
-e.adb:8:12: "V" is undefined
-e.adb:8:16: "V" is undefined
-e.adb:9:07: "V" is undefined
-e.adb:9:12: "V" is undefined
-@end smallexample
-
-@item -gnatq
-@cindex @option{-gnatq} (@code{gcc})
-@ifclear vms
-The @code{q} stands for quit (really "don't quit").
-@end ifclear
-In normal operation mode, the compiler first parses the program and
-determines if there are any syntax errors. If there are, appropriate
-error messages are generated and compilation is immediately terminated.
-This switch tells
-GNAT to continue with semantic analysis even if syntax errors have been
-found. This may enable the detection of more errors in a single run. On
-the other hand, the semantic analyzer is more likely to encounter some
-internal fatal error when given a syntactically invalid tree.
-
-@item -gnatQ
-In normal operation mode, the @file{ali} file is not generated if any
-illegalities are detected in the program. The use of @option{-gnatQ} forces
-generation of the @file{ali} file. This file is marked as being in
-error, so it cannot be used for binding purposes, but it does contain
-reasonably complete cross-reference information, and thus may be useful
-for use by tools (e.g. semantic browsing tools or integrated development
-environments) that are driven from the @file{ali} file.
-
-In addition, if @option{-gnatt} is also specified, then the tree file is
-generated even if there are illegalities. It may be useful in this case
-to also specify @option{-gnatq} to ensure that full semantic processing
-occurs. The resulting tree file can be processed by ASIS, for the purpose
-of providing partial information about illegal units, but if the error
-causes the tree to be badly malformed, then ASIS may crash during the
-analysis.
-
-@end table
-
-@noindent
-In addition to error messages, which correspond to illegalities as defined
-in the Ada 95 Reference Manual, the compiler detects two kinds of warning
-situations.
-
-@cindex Warning messages
-First, the compiler considers some constructs suspicious and generates a
-warning message to alert you to a possible error. Second, if the
-compiler detects a situation that is sure to raise an exception at
-run time, it generates a warning message. The following shows an example
-of warning messages:
-@smallexample
-@iftex
-@leftskip=.2cm
-@end iftex
-e.adb:4:24: warning: creation of object may raise Storage_Error
-e.adb:10:17: warning: static value out of range
-e.adb:10:17: warning: "Constraint_Error" will be raised at run time
-
-@end smallexample
-
-@noindent
-GNAT considers a large number of situations as appropriate
-for the generation of warning messages. As always, warnings are not
-definite indications of errors. For example, if you do an out-of-range
-assignment with the deliberate intention of raising a
-@code{Constraint_Error} exception, then the warning that may be
-issued does not indicate an error. Some of the situations for which GNAT
-issues warnings (at least some of the time) are given in the following
-list, which is not necessarily complete.
-
-@itemize @bullet
-@item
-Possible infinitely recursive calls
-
-@item
-Out-of-range values being assigned
-
-@item
-Possible order of elaboration problems
-
-@item
-Unreachable code
-
-@item
-Fixed-point type declarations with a null range
-
-@item
-Variables that are never assigned a value
-
-@item
-Variables that are referenced before being initialized
-
-@item
-Task entries with no corresponding accept statement
-
-@item
-Duplicate accepts for the same task entry in a select
-
-@item
-Objects that take too much storage
-
-@item
-Unchecked conversion between types of differing sizes
-
-@item
-Missing return statements along some execution paths in a function
-
-@item
-Incorrect (unrecognized) pragmas
-
-@item
-Incorrect external names
-
-@item
-Allocation from empty storage pool
-
-@item
-Potentially blocking operations in protected types
-
-@item
-Suspicious parenthesization of expressions
-
-@item
-Mismatching bounds in an aggregate
-
-@item
-Attempt to return local value by reference
-
-@item
-Unrecognized pragmas
-
-@item
-Premature instantiation of a generic body
-
-@item
-Attempt to pack aliased components
-
-@item
-Out of bounds array subscripts
-
-@item
-Wrong length on string assignment
-
-@item
-Violations of style rules if style checking is enabled
-
-@item
-Unused with clauses
-
-@item
-Bit_Order usage that does not have any effect
-
-@item
-Compile time biased rounding of floating-point constant
-
-@item
-Standard.Duration used to resolve universal fixed expression
-
-@item
-Dereference of possibly null value
-
-@item
-Declaration that is likely to cause storage error
-
-@item
-Internal GNAT unit with'ed by application unit
-
-@item
-Values known to be out of range at compile time
-
-@item
-Unreferenced labels and variables
-
-@item
-Address overlays that could clobber memory
-
-@item
-Unexpected initialization when address clause present
-
-@item
-Bad alignment for address clause
-
-@item
-Useless type conversions
-
-@item
-Redundant assignment statements
-
-@item
-Accidental hiding of name by child unit
-
-@item
-Unreachable code
-
-@item
-Access before elaboration detected at compile time
-
-@item
-A range in a @code{for} loop that is known to be null or might be null
-
-@end itemize
-
-@noindent
-The following switches are available to control the handling of
-warning messages:
-
-@table @code
-@item -gnatwa (activate all optional errors)
-@cindex @option{-gnatwa} (@code{gcc})
-This switch activates most optional warning messages, see remaining list
-in this section for details on optional warning messages that can be
-individually controlled. The warnings that are not turned on by this
-switch are @option{-gnatwb} (biased rounding),
-@option{-gnatwd} (implicit dereferencing),
-and @option{-gnatwh} (hiding). All other optional warnings are
-turned on.
-
-@item -gnatwA (suppress all optional errors)
-@cindex @option{-gnatwA} (@code{gcc})
-This switch suppresses all optional warning messages, see remaining list
-in this section for details on optional warning messages that can be
-individually controlled.
-
-@item -gnatwb (activate warnings on biased rounding)
-@cindex @option{-gnatwb} (@code{gcc})
-@cindex Rounding, biased
-@cindex Biased rounding
-If a static floating-point expression has a value that is exactly half
-way between two adjacent machine numbers, then the rules of Ada
-(Ada Reference Manual, section 4.9(38)) require that this rounding
-be done away from zero, even if the normal unbiased rounding rules
-at run time would require rounding towards zero. This warning message
-alerts you to such instances where compile-time rounding and run-time
-rounding are not equivalent. If it is important to get proper run-time
-rounding, then you can force this by making one of the operands into
-a variable. The default is that such warnings are not generated.
-Note that @option{-gnatwa} does not affect the setting of
-this warning option.
-
-@item -gnatwB (suppress warnings on biased rounding)
-@cindex @option{-gnatwB} (@code{gcc})
-This switch disables warnings on biased rounding.
-
-@item -gnatwc (activate warnings on conditionals)
-@cindex @option{-gnatwc} (@code{gcc})
-@cindex Conditionals, constant
-This switch activates warnings for conditional expressions used in
-tests that are known to be True or False at compile time. The default
-is that such warnings are not generated.
-This warning can also be turned on using @option{-gnatwa}.
-
-@item -gnatwC (suppress warnings on conditionals)
-@cindex @option{-gnatwC} (@code{gcc})
-This switch suppresses warnings for conditional expressions used in
-tests that are known to be True or False at compile time.
-
-@item -gnatwd (activate warnings on implicit dereferencing)
-@cindex @option{-gnatwd} (@code{gcc})
-If this switch is set, then the use of a prefix of an access type
-in an indexed component, slice, or selected component without an
-explicit @code{.all} will generate a warning. With this warning
-enabled, access checks occur only at points where an explicit
-@code{.all} appears in the source code (assuming no warnings are
-generated as a result of this switch). The default is that such
-warnings are not generated.
-Note that @option{-gnatwa} does not affect the setting of
-this warning option.
-
-@item -gnatwD (suppress warnings on implicit dereferencing)
-@cindex @option{-gnatwD} (@code{gcc})
-@cindex Implicit dereferencing
-@cindex Dereferencing, implicit
-This switch suppresses warnings for implicit deferences in
-indexed components, slices, and selected components.
-
-@item -gnatwe (treat warnings as errors)
-@cindex @option{-gnatwe} (@code{gcc})
-@cindex Warnings, treat as error
-This switch causes warning messages to be treated as errors.
-The warning string still appears, but the warning messages are counted
-as errors, and prevent the generation of an object file.
-
-@item -gnatwf (activate warnings on unreferenced formals)
-@cindex @option{-gnatwf} (@code{gcc})
-@cindex Formals, unreferenced
-This switch causes a warning to be generated if a formal parameter
-is not referenced in the body of the subprogram. This warning can
-also be turned on using @option{-gnatwa} or @option{-gnatwu}.
-
-@item -gnatwF (suppress warnings on unreferenced formals)
-@cindex @option{-gnatwF} (@code{gcc})
-This switch suppresses warnings for unreferenced formal
-parameters. Note that the
-combination @option{-gnatwu} followed by @option{-gnatwF} has the
-effect of warning on unreferenced entities other than subprogram
-formals.
-
-@item -gnatwh (activate warnings on hiding)
-@cindex @option{-gnatwh} (@code{gcc})
-@cindex Hiding of Declarations
-This switch activates warnings on hiding declarations.
-A declaration is considered hiding
-if it is for a non-overloadable entity, and it declares an entity with the
-same name as some other entity that is directly or use-visible. The default
-is that such warnings are not generated.
-Note that @option{-gnatwa} does not affect the setting of this warning option.
-
-@item -gnatwH (suppress warnings on hiding)
-@cindex @option{-gnatwH} (@code{gcc})
-This switch suppresses warnings on hiding declarations.
-
-@item -gnatwi (activate warnings on implementation units).
-@cindex @option{-gnatwi} (@code{gcc})
-This switch activates warnings for a @code{with} of an internal GNAT
-implementation unit, defined as any unit from the @code{Ada},
-@code{Interfaces}, @code{GNAT},
-^^@code{DEC},^ or @code{System}
-hierarchies that is not
-documented in either the Ada Reference Manual or the GNAT
-Programmer's Reference Manual. Such units are intended only
-for internal implementation purposes and should not be @code{with}'ed
-by user programs. The default is that such warnings are generated
-This warning can also be turned on using @option{-gnatwa}.
-
-@item -gnatwI (disable warnings on implementation units).
-@cindex @option{-gnatwI} (@code{gcc})
-This switch disables warnings for a @code{with} of an internal GNAT
-implementation unit.
-
-@item -gnatwl (activate warnings on elaboration pragmas)
-@cindex @option{-gnatwl} (@code{gcc})
-@cindex Elaboration, warnings
-This switch activates warnings on missing pragma Elaborate_All statements.
-See the section in this guide on elaboration checking for details on
-when such pragma should be used. The default is that such warnings
-are not generated.
-This warning can also be turned on using @option{-gnatwa}.
-
-@item -gnatwL (suppress warnings on elaboration pragmas)
-@cindex @option{-gnatwL} (@code{gcc})
-This switch suppresses warnings on missing pragma Elaborate_All statements.
-See the section in this guide on elaboration checking for details on
-when such pragma should be used.
-
-@item -gnatwo (activate warnings on address clause overlays)
-@cindex @option{-gnatwo} (@code{gcc})
-@cindex Address Clauses, warnings
-This switch activates warnings for possibly unintended initialization
-effects of defining address clauses that cause one variable to overlap
-another. The default is that such warnings are generated.
-This warning can also be turned on using @option{-gnatwa}.
-
-@item -gnatwO (suppress warnings on address clause overlays)
-@cindex @option{-gnatwO} (@code{gcc})
-This switch suppresses warnings on possibly unintended initialization
-effects of defining address clauses that cause one variable to overlap
-another.
-
-@item -gnatwp (activate warnings on ineffective pragma Inlines)
-@cindex @option{-gnatwp} (@code{gcc})
-@cindex Inlining, warnings
-This switch activates warnings for failure of front end inlining
-(activated by @option{-gnatN}) to inline a particular call. There are
-many reasons for not being able to inline a call, including most
-commonly that the call is too complex to inline.
-This warning can also be turned on using @option{-gnatwa}.
-
-@item -gnatwP (suppress warnings on ineffective pragma Inlines)
-@cindex @option{-gnatwP} (@code{gcc})
-This switch suppresses warnings on ineffective pragma Inlines. If the
-inlining mechanism cannot inline a call, it will simply ignore the
-request silently.
-
-@item -gnatwr (activate warnings on redundant constructs)
-@cindex @option{-gnatwr} (@code{gcc})
-This switch activates warnings for redundant constructs. The following
-is the current list of constructs regarded as redundant:
-This warning can also be turned on using @option{-gnatwa}.
-
-@itemize @bullet
-@item
-Assignment of an item to itself.
-@item
-Type conversion that converts an expression to its own type.
-@item
-Use of the attribute @code{Base} where @code{typ'Base} is the same
-as @code{typ}.
-@item
-Use of pragma @code{Pack} when all components are placed by a record
-representation clause.
-@end itemize
-
-@item -gnatwR (suppress warnings on redundant constructs)
-@cindex @option{-gnatwR} (@code{gcc})
-This switch suppresses warnings for redundant constructs.
-
-@item -gnatws (suppress all warnings)
-@cindex @option{-gnatws} (@code{gcc})
-This switch completely suppresses the
-output of all warning messages from the GNAT front end.
-Note that it does not suppress warnings from the @code{gcc} back end.
-To suppress these back end warnings as well, use the switch @code{-w}
-in addition to @option{-gnatws}.
-
-@item -gnatwu (activate warnings on unused entities)
-@cindex @option{-gnatwu} (@code{gcc})
-This switch activates warnings to be generated for entities that
-are defined but not referenced, and for units that are @code{with}'ed
-and not
-referenced. In the case of packages, a warning is also generated if
-no entities in the package are referenced. This means that if the package
-is referenced but the only references are in @code{use}
-clauses or @code{renames}
-declarations, a warning is still generated. A warning is also generated
-for a generic package that is @code{with}'ed but never instantiated.
-In the case where a package or subprogram body is compiled, and there
-is a @code{with} on the corresponding spec
-that is only referenced in the body,
-a warning is also generated, noting that the
-@code{with} can be moved to the body. The default is that
-such warnings are not generated.
-This switch also activates warnings on unreferenced formals
-(it is includes the effect of @option{-gnatwf}).
-This warning can also be turned on using @option{-gnatwa}.
-
-@item -gnatwU (suppress warnings on unused entities)
-@cindex @option{-gnatwU} (@code{gcc})
-This switch suppresses warnings for unused entities and packages.
-It also turns off warnings on unreferenced formals (and thus includes
-the effect of @option{-gnatwF}).
-
-@noindent
-A string of warning parameters can be used in the same parameter. For example:
-
-@smallexample
--gnatwaLe
-@end smallexample
-
-@noindent
-Would turn on all optional warnings except for elaboration pragma warnings,
-and also specify that warnings should be treated as errors.
-
-@item -w
-@cindex @code{-w}
-This switch suppresses warnings from the @code{gcc} backend. It may be
-used in conjunction with @option{-gnatws} to ensure that all warnings
-are suppressed during the entire compilation process.
-
-@end table
-
-@node Debugging and Assertion Control
-@subsection Debugging and Assertion Control
-
-@table @code
-@item -gnata
-@cindex @option{-gnata} (@code{gcc})
-@findex Assert
-@findex Debug
-@cindex Assertions
-
-@noindent
-The pragmas @code{Assert} and @code{Debug} normally have no effect and
-are ignored. This switch, where @samp{a} stands for assert, causes
-@code{Assert} and @code{Debug} pragmas to be activated.
-
-The pragmas have the form:
-
-@smallexample
-@group
-@cartouche
- @b{pragma} Assert (@var{Boolean-expression} [,
- @var{static-string-expression}])
- @b{pragma} Debug (@var{procedure call})
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-The @code{Assert} pragma causes @var{Boolean-expression} to be tested.
-If the result is @code{True}, the pragma has no effect (other than
-possible side effects from evaluating the expression). If the result is
-@code{False}, the exception @code{Assert_Failure} declared in the package
-@code{System.Assertions} is
-raised (passing @var{static-string-expression}, if present, as the
-message associated with the exception). If no string expression is
-given the default is a string giving the file name and line number
-of the pragma.
-
-The @code{Debug} pragma causes @var{procedure} to be called. Note that
-@code{pragma Debug} may appear within a declaration sequence, allowing
-debugging procedures to be called between declarations.
-
-@ifset vms
-@item /DEBUG[=debug-level]
-@itemx /NODEBUG
-Specifies how much debugging information is to be included in
-the resulting object file where 'debug-level' is one of the following:
-@table @code
-@item TRACEBACK (default)
-Include both debugger symbol records and traceback
-the object file.
-@item ALL
-Include both debugger symbol records and traceback in
-object file.
-@item NONE
-Excludes both debugger symbol records and traceback
-the object file. Same as /NODEBUG.
-@item SYMBOLS
-Includes only debugger symbol records in the object
-file. Note that this doesn't include traceback information.
-@end table
-@end ifset
-@end table
-
-@node Validity Checking
-@subsection Validity Checking
-@findex Validity Checking
-
-@noindent
-The Ada 95 Reference Manual has specific requirements for checking
-for invalid values. In particular, RM 13.9.1 requires that the
-evaluation of invalid values (for example from unchecked conversions),
-not result in erroneous execution. In GNAT, the result of such an
-evaluation in normal default mode is to either use the value
-unmodified, or to raise Constraint_Error in those cases where use
-of the unmodified value would cause erroneous execution. The cases
-where unmodified values might lead to erroneous execution are case
-statements (where a wild jump might result from an invalid value),
-and subscripts on the left hand side (where memory corruption could
-occur as a result of an invalid value).
-
-The @option{-gnatVx} switch allows more control over the validity checking
-mode. The @code{x} argument here is a string of letters which control which
-validity checks are performed in addition to the default checks described
-above.
-
-@itemize @bullet
-@item
-@option{-gnatVc} Validity checks for copies
-
-The right hand side of assignments, and the initializing values of
-object declarations are validity checked.
-
-@item
-@option{-gnatVd} Default (RM) validity checks
-
-Some validity checks are done by default following normal Ada semantics
-(RM 13.9.1 (9-11)).
-A check is done in case statements that the expression is within the range
-of the subtype. If it is not, Constraint_Error is raised.
-For assignments to array components, a check is done that the expression used
-as index is within the range. If it is not, Constraint_Error is raised.
-Both these validity checks may be turned off using switch @option{-gnatVD}.
-They are turned on by default. If @option{-gnatVD} is specified, a subsequent
-switch @option{-gnatVd} will leave the checks turned on.
-Switch @option{-gnatVD} should be used only if you are sure that all such
-expressions have valid values. If you use this switch and invalid values
-are present, then the program is erroneous, and wild jumps or memory
-overwriting may occur.
-
-@item
-@option{-gnatVi} Validity checks for @code{in} mode parameters
-
-Arguments for parameters of mode @code{in} are validity checked in function
-and procedure calls at the point of call.
-
-@item
-@option{-gnatVm} Validity checks for @code{in out} mode parameters
-
-Arguments for parameters of mode @code{in out} are validity checked in
-procedure calls at the point of call. The @code{'m'} here stands for
-modify, since this concerns parameters that can be modified by the call.
-Note that there is no specific option to test @code{out} parameters,
-but any reference within the subprogram will be tested in the usual
-manner, and if an invalid value is copied back, any reference to it
-will be subject to validity checking.
-
-@item
-@option{-gnatVo} Validity checks for operator and attribute operands
-
-Arguments for predefined operators and attributes are validity checked.
-This includes all operators in package @code{Standard},
-the shift operators defined as intrinsic in package @code{Interfaces}
-and operands for attributes such as @code{Pos}.
-
-@item
-@option{-gnatVr} Validity checks for function returns
-
-The expression in @code{return} statements in functions is validity
-checked.
-
-@item
-@option{-gnatVs} Validity checks for subscripts
-
-All subscripts expressions are checked for validity, whether they appear
-on the right side or left side (in default mode only left side subscripts
-are validity checked).
-
-@item
-@option{-gnatVt} Validity checks for tests
-
-Expressions used as conditions in @code{if}, @code{while} or @code{exit}
-statements are checked, as well as guard expressions in entry calls.
-
-@item
-@option{-gnatVf} Validity checks for floating-point values
-
-In the absence of this switch, validity checking occurs only for discrete
-values. If @option{-gnatVf} is specified, then validity checking also applies
-for floating-point values, and NaN's and infinities are considered invalid,
-as well as out of range values for constrained types. Note that this means
-that standard @code{IEEE} infinity mode is not allowed. The exact contexts
-in which floating-point values are checked depends on the setting of other
-options. For example @option{-gnatVif} or @option{-gnatVfi} (the order does
-not matter) specifies that floating-point parameters of mode @code{in} should
-be validity checked.
-
-@item
-@option{-gnatVa} All validity checks
-
-All the above validity checks are turned on. That is @option{-gnatVa} is
-equivalent to @code{gnatVcdfimorst}.
-
-@item
-@option{-gnatVn} No validity checks
-
-This switch turns off all validity checking, including the default checking
-for case statements and left hand side subscripts. Note that the use of
-the switch @option{-gnatp} supresses all run-time checks, including
-validity checks, and thus implies @option{-gnatVn}.
-
-@end itemize
-
-The @option{-gnatV} switch may be followed by a string of letters to turn on
-a series of validity checking options. For example, @option{-gnatVcr} specifies
-that in addition to the default validity checking, copies and function
-return expressions be validity checked. In order to make it easier to specify
-a set of options, the upper case letters @code{CDFIMORST} may be used to turn
-off the corresponding lower case option, so for example @option{-gnatVaM} turns
-on all validity checking options except for checking of @code{in out}
-procedure arguments.
-
-The specification of additional validity checking generates extra code (and
-in the case of @option{-gnatva} the code expansion can be substantial. However,
-these additional checks can be very useful in smoking out cases of
-uninitialized variables, incorrect use of unchecked conversion, and other
-errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
-is useful in conjunction with the extra validity checking, since this
-ensures that wherever possible uninitialized variables have invalid values.
-
-See also the pragma @code{Validity_Checks} which allows modification of
-the validity checking mode at the program source level, and also allows for
-temporary disabling of validity checks.
-
-@node Style Checking
-@subsection Style Checking
-@findex Style checking
-
-@noindent
-The -gnaty@var{^x^(option,option,..)^} switch causes the compiler to
-enforce specified style rules. A limited set of style rules has been used
-in writing the GNAT sources themselves. This switch allows user programs
-to activate all or some of these checks. If the source program fails a
-specified style check, an appropriate warning message is given, preceded by
-the character sequence "(style)".
-@ifset vms
-(OPTION,OPTION,..) is a sequence of keywords
-@end ifset
-@ifclear vms
-The string @var{x} is a sequence of letters or digits
-@end ifclear
-indicating the particular style
-checks to be performed. The following checks are defined:
-
-@table @code
-@item 1-9 (specify indentation level)
-If a digit from 1-9 appears in the string after @option{-gnaty} then proper
-indentation is checked, with the digit indicating the indentation level
-required. The general style of required indentation is as specified by
-the examples in the Ada Reference Manual. Full line comments must be
-aligned with the @code{--} starting on a column that is a multiple of
-the alignment level.
-
-@item ^a^ATTRIBUTE^ (check attribute casing)
-If the ^letter a^word ATTRIBUTE^ appears in the string after @option{-gnaty} then
-attribute names, including the case of keywords such as @code{digits}
-used as attributes names, must be written in mixed case, that is, the
-initial letter and any letter following an underscore must be uppercase.
-All other letters must be lowercase.
-
-@item ^b^BLANKS^ (blanks not allowed at statement end)
-If the ^letter b^word BLANKS^ appears in the string after @option{-gnaty} then
-trailing blanks are not allowed at the end of statements. The purpose of this
-rule, together with h (no horizontal tabs), is to enforce a canonical format
-for the use of blanks to separate source tokens.
-
-@item ^c^COMMENTS^ (check comments)
-If the ^letter c^word COMMENTS^ appears in the string after @option{-gnaty} then
-comments must meet the following set of rules:
-
-@itemize @bullet
-
-@item
-The "--" that starts the column must either start in column one, or else
-at least one blank must precede this sequence.
-
-@item
-Comments that follow other tokens on a line must have at least one blank
-following the "--" at the start of the comment.
-
-@item
-Full line comments must have two blanks following the "--" that starts
-the comment, with the following exceptions.
-
-@item
-A line consisting only of the "--" characters, possibly preceded by blanks
-is permitted.
-
-@item
-A comment starting with "--x" where x is a special character is permitted.
-This alows proper processing of the output generated by specialized tools
-including @code{gnatprep} (where --! is used) and the SPARK annnotation
-language (where --# is used). For the purposes of this rule, a special
-character is defined as being in one of the ASCII ranges
-16#21#..16#2F# or 16#3A#..16#3F#.
-
-@item
-A line consisting entirely of minus signs, possibly preceded by blanks, is
-permitted. This allows the construction of box comments where lines of minus
-signs are used to form the top and bottom of the box.
-
-@item
-If a comment starts and ends with "--" is permitted as long as at least
-one blank follows the initial "--". Together with the preceding rule,
-this allows the construction of box comments, as shown in the following
-example:
-@smallexample
----------------------------
--- This is a box comment --
--- with two text lines. --
----------------------------
-@end smallexample
-@end itemize
-
-@item ^e^END^ (check end/exit labels)
-If the ^letter e^word END^ appears in the string after @option{-gnaty} then
-optional labels on @code{end} statements ending subprograms and on
-@code{exit} statements exiting named loops, are required to be present.
-
-@item ^f^VTABS^ (no form feeds or vertical tabs)
-If the ^letter f^word VTABS^ appears in the string after @option{-gnaty} then
-neither form feeds nor vertical tab characters are not permitted
-in the source text.
-
-@item ^h^HTABS^ (no horizontal tabs)
-If the ^letter h^word HTABS^ appears in the string after @option{-gnaty} then
-horizontal tab characters are not permitted in the source text.
-Together with the b (no blanks at end of line) check, this
-enforces a canonical form for the use of blanks to separate
-source tokens.
-
-@item ^i^IF_THEN^ (check if-then layout)
-If the ^letter i^word IF_THEN^ appears in the string after @option{-gnaty},
-then the keyword @code{then} must appear either on the same
-line as corresponding @code{if}, or on a line on its own, lined
-up under the @code{if} with at least one non-blank line in between
-containing all or part of the condition to be tested.
-
-@item ^k^KEYWORD^ (check keyword casing)
-If the ^letter k^word KEYWORD^ appears in the string after @option{-gnaty} then
-all keywords must be in lower case (with the exception of keywords
-such as @code{digits} used as attribute names to which this check
-does not apply).
-
-@item ^l^LAYOUT^ (check layout)
-If the ^letter l^word LAYOUT^ appears in the string after @option{-gnaty} then
-layout of statement and declaration constructs must follow the
-recommendations in the Ada Reference Manual, as indicated by the
-form of the syntax rules. For example an @code{else} keyword must
-be lined up with the corresponding @code{if} keyword.
-
-There are two respects in which the style rule enforced by this check
-option are more liberal than those in the Ada Reference Manual. First
-in the case of record declarations, it is permissible to put the
-@code{record} keyword on the same line as the @code{type} keyword, and
-then the @code{end} in @code{end record} must line up under @code{type}.
-For example, either of the following two layouts is acceptable:
-
-@smallexample
-@group
-@cartouche
-@b{type} q @b{is record}
- a : integer;
- b : integer;
-@b{end record};
-
-@b{type} q @b{is}
- @b{record}
- a : integer;
- b : integer;
- @b{end record};
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-Second, in the case of a block statement, a permitted alternative
-is to put the block label on the same line as the @code{declare} or
-@code{begin} keyword, and then line the @code{end} keyword up under
-the block label. For example both the following are permitted:
-
-@smallexample
-@group
-@cartouche
-Block : @b{declare}
- A : Integer := 3;
-@b{begin}
- Proc (A, A);
-@b{end} Block;
-
-Block :
- @b{declare}
- A : Integer := 3;
- @b{begin}
- Proc (A, A);
- @b{end} Block;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-The same alternative format is allowed for loops. For example, both of
-the following are permitted:
-
-@smallexample
-@group
-@cartouche
-Clear : @b{while} J < 10 @b{loop}
- A (J) := 0;
-@b{end loop} Clear;
-
-Clear :
- @b{while} J < 10 @b{loop}
- A (J) := 0;
- @b{end loop} Clear;
-@end cartouche
-@end group
-@end smallexample
-
-@item ^m^LINE_LENGTH^ (check maximum line length)
-If the ^letter m^word LINE_LENGTH^ appears in the string after @option{-gnaty}
-then the length of source lines must not exceed 79 characters, including
-any trailing blanks. The value of 79 allows convenient display on an
-80 character wide device or window, allowing for possible special
-treatment of 80 character lines.
-
-@item ^Mnnn^MAX_LENGTH=nnn^ (set maximum line length)
-If the sequence ^M^MAX_LENGTH=^nnn, where nnn is a decimal number, appears in
-the string after @option{-gnaty} then the length of lines must not exceed the
-given value.
-
-@item ^n^STANDARD_CASING^ (check casing of entities in Standard)
-If the ^letter n^word STANDARD_CASING^ appears in the string
-after @option{-gnaty} then any identifier from Standard must be cased
-to match the presentation in the Ada Reference Manual (for example,
-@code{Integer} and @code{ASCII.NUL}).
-
-@item ^o^ORDERED_SUBPROGRAMS^ (check order of subprogram bodies)
-If the ^letter o^word ORDERED_SUBPROGRAMS^ appears in the string
-after @option{-gnaty} then all subprogram bodies in a given scope
-(e.g. a package body) must be in alphabetical order. The ordering
-rule uses normal Ada rules for comparing strings, ignoring casing
-of letters, except that if there is a trailing numeric suffix, then
-the value of this suffix is used in the ordering (e.g. Junk2 comes
-before Junk10).
-
-@item ^p^PRAGMA^ (check pragma casing)
-If the ^letter p^word PRAGMA^ appears in the string after @option{-gnaty} then
-pragma names must be written in mixed case, that is, the
-initial letter and any letter following an underscore must be uppercase.
-All other letters must be lowercase.
-
-@item ^r^REFERENCES^ (check references)
-If the ^letter r^word REFERENCES^ appears in the string after @option{-gnaty}
-then all identifier references must be cased in the same way as the
-corresponding declaration. No specific casing style is imposed on
-identifiers. The only requirement is for consistency of references
-with declarations.
-
-@item ^s^SPECS^ (check separate specs)
-If the ^letter s^word SPECS^ appears in the string after @option{-gnaty} then
-separate declarations ("specs") are required for subprograms (a
-body is not allowed to serve as its own declaration). The only
-exception is that parameterless library level procedures are
-not required to have a separate declaration. This exception covers
-the most frequent form of main program procedures.
-
-@item ^t^TOKEN^ (check token spacing)
-If the ^letter t^word TOKEN^ appears in the string after @option{-gnaty} then
-the following token spacing rules are enforced:
-
-@itemize @bullet
-
-@item
-The keywords @code{abs} and @code{not} must be followed by a space.
-
-@item
-The token @code{=>} must be surrounded by spaces.
-
-@item
-The token @code{<>} must be preceded by a space or a left parenthesis.
-
-@item
-Binary operators other than @code{**} must be surrounded by spaces.
-There is no restriction on the layout of the @code{**} binary operator.
-
-@item
-Colon must be surrounded by spaces.
-
-@item
-Colon-equal (assignment) must be surrounded by spaces.
-
-@item
-Comma must be the first non-blank character on the line, or be
-immediately preceded by a non-blank character, and must be followed
-by a space.
-
-@item
-If the token preceding a left paren ends with a letter or digit, then
-a space must separate the two tokens.
-
-@item
-A right parenthesis must either be the first non-blank character on
-a line, or it must be preceded by a non-blank character.
-
-@item
-A semicolon must not be preceded by a space, and must not be followed by
-a non-blank character.
-
-@item
-A unary plus or minus may not be followed by a space.
-
-@item
-A vertical bar must be surrounded by spaces.
-@end itemize
-
-@noindent
-In the above rules, appearing in column one is always permitted, that is,
-counts as meeting either a requirement for a required preceding space,
-or as meeting a requirement for no preceding space.
-
-Appearing at the end of a line is also always permitted, that is, counts
-as meeting either a requirement for a following space, or as meeting
-a requirement for no following space.
-
-@end table
-
-@noindent
-If any of these style rules is violated, a message is generated giving
-details on the violation. The initial characters of such messages are
-always "(style)". Note that these messages are treated as warning
-messages, so they normally do not prevent the generation of an object
-file. The @option{-gnatwe} switch can be used to treat warning messages,
-including style messages, as fatal errors.
-
-@noindent
-The switch
-^@option{-gnaty} on its own (that is not followed by any letters or digits),^/STYLE_CHECKS=ALL_BUILTIN^
-is equivalent to ^@code{gnaty3abcefhiklmprst}, that is^^ all checking
-options ^are^^ enabled with
-the exception of ^-gnatyo^ORDERED_SUBPROGRAMS^,
-with an indentation level of 3. This is the standard
-checking option that is used for the GNAT sources.
-
-@node Run-Time Checks
-@subsection Run-Time Checks
-@cindex Division by zero
-@cindex Access before elaboration
-@cindex Checks, division by zero
-@cindex Checks, access before elaboration
-
-@noindent
-If you compile with the default options, GNAT will insert many run-time
-checks into the compiled code, including code that performs range
-checking against constraints, but not arithmetic overflow checking for
-integer operations (including division by zero) or checks for access
-before elaboration on subprogram calls. All other run-time checks, as
-required by the Ada 95 Reference Manual, are generated by default.
-The following @code{gcc} switches refine this default behavior:
-
-@table @code
-@item -gnatp
-@cindex @option{-gnatp} (@code{gcc})
-@cindex Suppressing checks
-@cindex Checks, suppressing
-@findex Suppress
-Suppress all run-time checks as though @code{pragma Suppress (all_checks})
-had been present in the source. Validity checks are also suppressed (in
-other words @option{-gnatp} also implies @option{-gnatVn}.
-Use this switch to improve the performance
-of the code at the expense of safety in the presence of invalid data or
-program bugs.
-
-@item -gnato
-@cindex @option{-gnato} (@code{gcc})
-@cindex Overflow checks
-@cindex Check, overflow
-Enables overflow checking for integer operations.
-This causes GNAT to generate slower and larger executable
-programs by adding code to check for overflow (resulting in raising
-@code{Constraint_Error} as required by standard Ada
-semantics). These overflow checks correspond to situations in which
-the true value of the result of an operation may be outside the base
-range of the result type. The following example shows the distinction:
-
-@smallexample
-X1 : Integer := Integer'Last;
-X2 : Integer range 1 .. 5 := 5;
-...
-X1 := X1 + 1; -- @option{-gnato} required to catch the Constraint_Error
-X2 := X2 + 1; -- range check, @option{-gnato} has no effect here
-@end smallexample
-
-@noindent
-Here the first addition results in a value that is outside the base range
-of Integer, and hence requires an overflow check for detection of the
-constraint error. The second increment operation results in a violation
-of the explicit range constraint, and such range checks are always
-performed. Basically the compiler can assume that in the absence of
-the @option{-gnato} switch that any value of type @code{xxx} is
-in range of the base type of @code{xxx}.
-
-@findex Machine_Overflows
-Note that the @option{-gnato} switch does not affect the code generated
-for any floating-point operations; it applies only to integer
-semantics).
-For floating-point, GNAT has the @code{Machine_Overflows}
-attribute set to @code{False} and the normal mode of operation is to
-generate IEEE NaN and infinite values on overflow or invalid operations
-(such as dividing 0.0 by 0.0).
-
-The reason that we distinguish overflow checking from other kinds of
-range constraint checking is that a failure of an overflow check can
-generate an incorrect value, but cannot cause erroneous behavior. This
-is unlike the situation with a constraint check on an array subscript,
-where failure to perform the check can result in random memory description,
-or the range check on a case statement, where failure to perform the check
-can cause a wild jump.
-
-Note again that @option{-gnato} is off by default, so overflow checking is
-not performed in default mode. This means that out of the box, with the
-default settings, GNAT does not do all the checks expected from the
-language description in the Ada Reference Manual. If you want all constraint
-checks to be performed, as described in this Manual, then you must
-explicitly use the -gnato switch either on the @code{gnatmake} or
-@code{gcc} command.
-
-@item -gnatE
-@cindex @option{-gnatE} (@code{gcc})
-@cindex Elaboration checks
-@cindex Check, elaboration
-Enables dynamic checks for access-before-elaboration
-on subprogram calls and generic instantiations.
-For full details of the effect and use of this switch,
-@xref{Compiling Using gcc}.
-@end table
-
-@findex Unsuppress
-@noindent
-The setting of these switches only controls the default setting of the
-checks. You may modify them using either @code{Suppress} (to remove
-checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
-the program source.
-
-@node Stack Overflow Checking
-@subsection Stack Overflow Checking
-@cindex Stack Overflow Checking
-@cindex -fstack-check
-
-@noindent
-For most operating systems, @code{gcc} does not perform stack overflow
-checking by default. This means that if the main environment task or
-some other task exceeds the available stack space, then unpredictable
-behavior will occur.
-
-To activate stack checking, compile all units with the gcc option
-@code{-fstack-check}. For example:
-
-@smallexample
-gcc -c -fstack-check package1.adb
-@end smallexample
-
-@noindent
-Units compiled with this option will generate extra instructions to check
-that any use of the stack (for procedure calls or for declaring local
-variables in declare blocks) do not exceed the available stack space.
-If the space is exceeded, then a @code{Storage_Error} exception is raised.
-
-For declared tasks, the stack size is always controlled by the size
-given in an applicable @code{Storage_Size} pragma (or is set to
-the default size if no pragma is used.
-
-For the environment task, the stack size depends on
-system defaults and is unknown to the compiler. The stack
-may even dynamically grow on some systems, precluding the
-normal Ada semantics for stack overflow. In the worst case,
-unbounded stack usage, causes unbounded stack expansion
-resulting in the system running out of virtual memory.
-
-The stack checking may still work correctly if a fixed
-size stack is allocated, but this cannot be guaranteed.
-To ensure that a clean exception is signalled for stack
-overflow, set the environment variable
-@code{GNAT_STACK_LIMIT} to indicate the maximum
-stack area that can be used, as in:
-@cindex GNAT_STACK_LIMIT
-
-@smallexample
-SET GNAT_STACK_LIMIT 1600
-@end smallexample
-
-@noindent
-The limit is given in kilobytes, so the above declaration would
-set the stack limit of the environment task to 1.6 megabytes.
-Note that the only purpose of this usage is to limit the amount
-of stack used by the environment task. If it is necessary to
-increase the amount of stack for the environment task, then this
-is an operating systems issue, and must be addressed with the
-appropriate operating systems commands.
-
-@node Run-Time Control
-@subsection Run-Time Control
-
-@table @code
-@item -gnatT nnn
-@cindex @option{-gnatT} (@code{gcc})
-@cindex Time Slicing
-
-@noindent
-The @code{gnatT} switch can be used to specify the time-slicing value
-to be used for task switching between equal priority tasks. The value
-@code{nnn} is given in microseconds as a decimal integer.
-
-Setting the time-slicing value is only effective if the underlying thread
-control system can accommodate time slicing. Check the documentation of
-your operating system for details. Note that the time-slicing value can
-also be set by use of pragma @code{Time_Slice} or by use of the
-@code{t} switch in the gnatbind step. The pragma overrides a command
-line argument if both are present, and the @code{t} switch for gnatbind
-overrides both the pragma and the @code{gcc} command line switch.
-@end table
-
-@node Using gcc for Syntax Checking
-@subsection Using @code{gcc} for Syntax Checking
-@table @code
-@item -gnats
-@cindex @option{-gnats} (@code{gcc})
-@ifclear vms
-
-@noindent
-The @code{s} stands for syntax.
-@end ifclear
-
-Run GNAT in syntax checking only mode. For
-example, the command
-
-@smallexample
-$ gcc -c -gnats x.adb
-@end smallexample
-
-@noindent
-compiles file @file{x.adb} in syntax-check-only mode. You can check a
-series of files in a single command
-@ifclear vms
-, and can use wild cards to specify such a group of files.
-Note that you must specify the @code{-c} (compile
-only) flag in addition to the @option{-gnats} flag.
-@end ifclear
-.
-
-You may use other switches in conjunction with @option{-gnats}. In
-particular, @option{-gnatl} and @option{-gnatv} are useful to control the
-format of any generated error messages.
-
-The output is simply the error messages, if any. No object file or ALI
-file is generated by a syntax-only compilation. Also, no units other
-than the one specified are accessed. For example, if a unit @code{X}
-@code{with}'s a unit @code{Y}, compiling unit @code{X} in syntax
-check only mode does not access the source file containing unit
-@code{Y}.
-
-@cindex Multiple units, syntax checking
-Normally, GNAT allows only a single unit in a source file. However, this
-restriction does not apply in syntax-check-only mode, and it is possible
-to check a file containing multiple compilation units concatenated
-together. This is primarily used by the @code{gnatchop} utility
-(@pxref{Renaming Files Using gnatchop}).
-@end table
-
-@node Using gcc for Semantic Checking
-@subsection Using @code{gcc} for Semantic Checking
-@table @code
-@item -gnatc
-@cindex @option{-gnatc} (@code{gcc})
-
-@ifclear vms
-@noindent
-The @code{c} stands for check.
-@end ifclear
-Causes the compiler to operate in semantic check mode,
-with full checking for all illegalities specified in the
-Ada 95 Reference Manual, but without generation of any object code
-(no object file is generated).
-
-Because dependent files must be accessed, you must follow the GNAT
-semantic restrictions on file structuring to operate in this mode:
-
-@itemize @bullet
-@item
-The needed source files must be accessible
-(@pxref{Search Paths and the Run-Time Library (RTL)}).
-
-@item
-Each file must contain only one compilation unit.
-
-@item
-The file name and unit name must match (@pxref{File Naming Rules}).
-@end itemize
-
-The output consists of error messages as appropriate. No object file is
-generated. An @file{ALI} file is generated for use in the context of
-cross-reference tools, but this file is marked as not being suitable
-for binding (since no object file is generated).
-The checking corresponds exactly to the notion of
-legality in the Ada 95 Reference Manual.
-
-Any unit can be compiled in semantics-checking-only mode, including
-units that would not normally be compiled (subunits,
-and specifications where a separate body is present).
-@end table
-
-@node Compiling Ada 83 Programs
-@subsection Compiling Ada 83 Programs
-@table @code
-@cindex Ada 83 compatibility
-@item -gnat83
-@cindex @option{-gnat83} (@code{gcc})
-@cindex ACVC, Ada 83 tests
-
-@noindent
-Although GNAT is primarily an Ada 95 compiler, it accepts this switch to
-specify that an Ada 83 program is to be compiled in Ada83 mode. If you specify
-this switch, GNAT rejects most Ada 95 extensions and applies Ada 83 semantics
-where this can be done easily.
-It is not possible to guarantee this switch does a perfect
-job; for example, some subtle tests, such as are
-found in earlier ACVC tests (that have been removed from the ACVC suite for Ada
-95), may not compile correctly. However, for most purposes, using
-this switch should help to ensure that programs that compile correctly
-under the @option{-gnat83} switch can be ported easily to an Ada 83
-compiler. This is the main use of the switch.
-
-With few exceptions (most notably the need to use @code{<>} on
-@cindex Generic formal parameters
-unconstrained generic formal parameters, the use of the new Ada 95
-keywords, and the use of packages
-with optional bodies), it is not necessary to use the
-@option{-gnat83} switch when compiling Ada 83 programs, because, with rare
-exceptions, Ada 95 is upwardly compatible with Ada 83. This
-means that a correct Ada 83 program is usually also a correct Ada 95
-program.
-
-@end table
-
-@node Character Set Control
-@subsection Character Set Control
-@table @code
-@item ^-gnati^/IDENTIFIER_CHARACTER_SET=^@var{c}
-@cindex @code{^-gnati^/IDENTIFIER_CHARACTER_SET^} (@code{gcc})
-
-@noindent
-Normally GNAT recognizes the Latin-1 character set in source program
-identifiers, as described in the Ada 95 Reference Manual.
-This switch causes
-GNAT to recognize alternate character sets in identifiers. @var{c} is a
-single character ^^or word^ indicating the character set, as follows:
-
-@table @code
-@item 1
-Latin-1 identifiers
-
-@item 2
-Latin-2 letters allowed in identifiers
-
-@item 3
-Latin-3 letters allowed in identifiers
-
-@item 4
-Latin-4 letters allowed in identifiers
-
-@item 5
-Latin-5 (Cyrillic) letters allowed in identifiers
-
-@item 9
-Latin-9 letters allowed in identifiers
-
-@item ^p^PC^
-IBM PC letters (code page 437) allowed in identifiers
-
-@item ^8^PC850^
-IBM PC letters (code page 850) allowed in identifiers
-
-@item ^f^FULL_UPPER^
-Full upper-half codes allowed in identifiers
-
-@item ^n^NO_UPPER^
-No upper-half codes allowed in identifiers
-
-@item ^w^WIDE^
-Wide-character codes (that is, codes greater than 255)
-allowed in identifiers
-@end table
-
-@xref{Foreign Language Representation}, for full details on the
-implementation of these character sets.
-
-@item ^-gnatW^/WIDE_CHARACTER_ENCODING=^@var{e}
-@cindex @code{^-gnatW^/WIDE_CHARACTER_ENCODING^} (@code{gcc})
-Specify the method of encoding for wide characters.
-@var{e} is one of the following:
-
-@table @code
-
-@item ^h^HEX^
-Hex encoding (brackets coding also recognized)
-
-@item ^u^UPPER^
-Upper half encoding (brackets encoding also recognized)
-
-@item ^s^SHIFT_JIS^
-Shift/JIS encoding (brackets encoding also recognized)
-
-@item ^e^EUC^
-EUC encoding (brackets encoding also recognized)
-
-@item ^8^UTF8^
-UTF-8 encoding (brackets encoding also recognized)
-
-@item ^b^BRACKETS^
-Brackets encoding only (default value)
-@end table
-For full details on the these encoding
-methods see @xref{Wide Character Encodings}.
-Note that brackets coding is always accepted, even if one of the other
-options is specified, so for example @option{-gnatW8} specifies that both
-brackets and @code{UTF-8} encodings will be recognized. The units that are
-with'ed directly or indirectly will be scanned using the specified
-representation scheme, and so if one of the non-brackets scheme is
-used, it must be used consistently throughout the program. However,
-since brackets encoding is always recognized, it may be conveniently
-used in standard libraries, allowing these libraries to be used with
-any of the available coding schemes.
-scheme. If no @option{-gnatW?} parameter is present, then the default
-representation is Brackets encoding only.
-
-Note that the wide character representation that is specified (explicitly
-or by default) for the main program also acts as the default encoding used
-for Wide_Text_IO files if not specifically overridden by a WCEM form
-parameter.
-
-@end table
-@node File Naming Control
-@subsection File Naming Control
-
-@table @code
-@item ^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{n}
-@cindex @option{-gnatk} (@code{gcc})
-Activates file name "krunching". @var{n}, a decimal integer in the range
-1-999, indicates the maximum allowable length of a file name (not
-including the @file{.ads} or @file{.adb} extension). The default is not
-to enable file name krunching.
-
-For the source file naming rules, @xref{File Naming Rules}.
-@end table
-
-@node Subprogram Inlining Control
-@subsection Subprogram Inlining Control
-
-@table @code
-@item -gnatn
-@cindex @option{-gnatn} (@code{gcc})
-@ifclear vms
-The @code{n} here is intended to suggest the first syllable of the
-word "inline".
-@end ifclear
-GNAT recognizes and processes @code{Inline} pragmas. However, for the
-inlining to actually occur, optimization must be enabled. To enable
-inlining across unit boundaries, this is, inlining a call in one unit of
-a subprogram declared in a @code{with}'ed unit, you must also specify
-this switch.
-In the absence of this switch, GNAT does not attempt
-inlining across units and does not need to access the bodies of
-subprograms for which @code{pragma Inline} is specified if they are not
-in the current unit.
-
-If you specify this switch the compiler will access these bodies,
-creating an extra source dependency for the resulting object file, and
-where possible, the call will be inlined.
-For further details on when inlining is possible
-see @xref{Inlining of Subprograms}.
-
-@item -gnatN
-@cindex @option{-gnatN} (@code{gcc})
-The front end inlining activated by this switch is generally more extensive,
-and quite often more effective than the standard @option{-gnatn} inlining mode.
-It will also generate additional dependencies.
-
-@end table
-
-@node Auxiliary Output Control
-@subsection Auxiliary Output Control
-
-@table @code
-@item -gnatt
-@cindex @option{-gnatt} (@code{gcc})
-@cindex Writing internal trees
-@cindex Internal trees, writing to file
-Causes GNAT to write the internal tree for a unit to a file (with the
-extension @file{.adt}.
-This not normally required, but is used by separate analysis tools.
-Typically
-these tools do the necessary compilations automatically, so you should
-not have to specify this switch in normal operation.
-
-@item -gnatu
-@cindex @option{-gnatu} (@code{gcc})
-Print a list of units required by this compilation on @file{stdout}.
-The listing includes all units on which the unit being compiled depends
-either directly or indirectly.
-
-@ifclear vms
-@item -pass-exit-codes
-@cindex @code{-pass-exit-codes} (@code{gcc})
-If this switch is not used, the exit code returned by @code{gcc} when
-compiling multiple files indicates whether all source files have
-been successfully used to generate object files or not.
-
-When @code{-pass-exit-codes} is used, @code{gcc} exits with an extended
-exit status and allows an integrated development environment to better
-react to a compilation failure. Those exit status are:
-
-@table @asis
-@item 5
-There was an error in at least one source file.
-@item 3
-At least one source file did not generate an object file.
-@item 2
-The compiler died unexpectedly (internal error for example).
-@item 0
-An object file has been generated for every source file.
-@end table
-@end ifclear
-@end table
-
-@node Debugging Control
-@subsection Debugging Control
-
-@table @code
-@cindex Debugging options
-@ifclear vms
-@item -gnatd@var{x}
-Activate internal debugging switches. @var{x} is a letter or digit, or
-string of letters or digits, which specifies the type of debugging
-outputs desired. Normally these are used only for internal development
-or system debugging purposes. You can find full documentation for these
-switches in the body of the @code{Debug} unit in the compiler source
-file @file{debug.adb}.
-@end ifclear
-
-@item -gnatG
-@cindex @option{-gnatG} (@code{gcc})
-This switch causes the compiler to generate auxiliary output containing
-a pseudo-source listing of the generated expanded code. Like most Ada
-compilers, GNAT works by first transforming the high level Ada code into
-lower level constructs. For example, tasking operations are transformed
-into calls to the tasking run-time routines. A unique capability of GNAT
-is to list this expanded code in a form very close to normal Ada source.
-This is very useful in understanding the implications of various Ada
-usage on the efficiency of the generated code. There are many cases in
-Ada (e.g. the use of controlled types), where simple Ada statements can
-generate a lot of run-time code. By using @option{-gnatG} you can identify
-these cases, and consider whether it may be desirable to modify the coding
-approach to improve efficiency.
-
-The format of the output is very similar to standard Ada source, and is
-easily understood by an Ada programmer. The following special syntactic
-additions correspond to low level features used in the generated code that
-do not have any exact analogies in pure Ada source form. The following
-is a partial list of these special constructions. See the specification
-of package @code{Sprint} in file @file{sprint.ads} for a full list.
-
-@table @code
-@item new @var{xxx} [storage_pool = @var{yyy}]
-Shows the storage pool being used for an allocator.
-
-@item at end @var{procedure-name};
-Shows the finalization (cleanup) procedure for a scope.
-
-@item (if @var{expr} then @var{expr} else @var{expr})
-Conditional expression equivalent to the @code{x?y:z} construction in C.
-
-@item @var{target}^^^(@var{source})
-A conversion with floating-point truncation instead of rounding.
-
-@item @var{target}?(@var{source})
-A conversion that bypasses normal Ada semantic checking. In particular
-enumeration types and fixed-point types are treated simply as integers.
-
-@item @var{target}?^^^(@var{source})
-Combines the above two cases.
-
-@item @var{x} #/ @var{y}
-@itemx @var{x} #mod @var{y}
-@itemx @var{x} #* @var{y}
-@itemx @var{x} #rem @var{y}
-A division or multiplication of fixed-point values which are treated as
-integers without any kind of scaling.
-
-@item free @var{expr} [storage_pool = @var{xxx}]
-Shows the storage pool associated with a @code{free} statement.
-
-@item freeze @var{typename} [@var{actions}]
-Shows the point at which @var{typename} is frozen, with possible
-associated actions to be performed at the freeze point.
-
-@item reference @var{itype}
-Reference (and hence definition) to internal type @var{itype}.
-
-@item @var{function-name}! (@var{arg}, @var{arg}, @var{arg})
-Intrinsic function call.
-
-@item @var{labelname} : label
-Declaration of label @var{labelname}.
-
-@item @var{expr} && @var{expr} && @var{expr} ... && @var{expr}
-A multiple concatenation (same effect as @var{expr} & @var{expr} &
-@var{expr}, but handled more efficiently).
-
-@item [constraint_error]
-Raise the @code{Constraint_Error} exception.
-
-@item @var{expression}'reference
-A pointer to the result of evaluating @var{expression}.
-
-@item @var{target-type}!(@var{source-expression})
-An unchecked conversion of @var{source-expression} to @var{target-type}.
-
-@item [@var{numerator}/@var{denominator}]
-Used to represent internal real literals (that) have no exact
-representation in base 2-16 (for example, the result of compile time
-evaluation of the expression 1.0/27.0).
-
-@item -gnatD
-@cindex @option{-gnatD} (@code{gcc})
-This switch is used in conjunction with @option{-gnatG} to cause the expanded
-source, as described above to be written to files with names
-@file{^xxx.dg^XXX_DG^}, where @file{xxx} is the normal file name,
-for example, if the source file name is @file{hello.adb},
-then a file @file{^hello.adb.dg^HELLO.ADB_DG^} will be written.
-The debugging information generated
-by the @code{gcc} @code{^-g^/DEBUG^} switch will refer to the generated
-@file{^xxx.dg^XXX_DG^} file. This allows you to do source level debugging using
-the generated code which is sometimes useful for complex code, for example
-to find out exactly which part of a complex construction raised an
-exception. This switch also suppress generation of cross-reference
-information (see -gnatx).
-
-@item -gnatC
-@cindex @option{-gnatE} (@code{gcc})
-In the generated debugging information, and also in the case of long external
-names, the compiler uses a compression mechanism if the name is very long.
-This compression method uses a checksum, and avoids trouble on some operating
-systems which have difficulty with very long names. The @option{-gnatC} switch
-forces this compression approach to be used on all external names and names
-in the debugging information tables. This reduces the size of the generated
-executable, at the expense of making the naming scheme more complex. The
-compression only affects the qualification of the name. Thus a name in
-the source:
-
-@smallexample
-Very_Long_Package.Very_Long_Inner_Package.Var
-@end smallexample
-
-@noindent
-would normally appear in these tables as:
-
-@smallexample
-very_long_package__very_long_inner_package__var
-@end smallexample
-
-@noindent
-but if the @option{-gnatC} switch is used, then the name appears as
-
-@smallexample
-XCb7e0c705__var
-@end smallexample
-
-@noindent
-Here b7e0c705 is a compressed encoding of the qualification prefix.
-The GNAT Ada aware version of GDB understands these encoded prefixes, so if this
-debugger is used, the encoding is largely hidden from the user of the compiler.
-
-@end table
-
-@item -gnatR[0|1|2|3][s]
-@cindex @option{-gnatR} (@code{gcc})
-This switch controls output from the compiler of a listing showing
-representation information for declared types and objects. For
-@option{-gnatR0}, no information is output (equivalent to omitting
-the @option{-gnatR} switch). For @option{-gnatR1} (which is the default,
-so @option{-gnatR} with no parameter has the same effect), size and alignment
-information is listed for declared array and record types. For
-@option{-gnatR2}, size and alignment information is listed for all
-expression information for values that are computed at run time for
-variant records. These symbolic expressions have a mostly obvious
-format with #n being used to represent the value of the n'th
-discriminant. See source files @file{repinfo.ads/adb} in the
-@code{GNAT} sources for full detalis on the format of @option{-gnatR3}
-output. If the switch is followed by an s (e.g. @option{-gnatR2s}), then
-the output is to a file with the name @file{^file.rep^file_REP^} where
-file is the name of the corresponding source file.
-
-@item -gnatx
-@cindex @option{-gnatx} (@code{gcc})
-Normally the compiler generates full cross-referencing information in
-the @file{ALI} file. This information is used by a number of tools,
-including @code{gnatfind} and @code{gnatxref}. The -gnatx switch
-suppresses this information. This saves some space and may slightly
-speed up compilation, but means that these tools cannot be used.
-@end table
-
-@node Units to Sources Mapping Files
-@subsection Units to Sources Mapping Files
-
-@table @code
-
-@item -gnatem@var{path}
-@cindex @option{-gnatem} (@code{gcc})
-A mapping file is a way to communicate to the compiler two mappings:
-from unit names to file names (without any directory information) and from
-file names to path names (with full directory information). These mappings
-are used by the compiler to short-circuit the path search.
-
-A mapping file is a sequence of sets of three lines. In each set,
-the first line is the unit name, in lower case, with "%s" appended for
-specifications and "%b" appended for bodies; the second line is the file
-name; and the third line is the path name.
-
-Example:
-@smallexample
- main%b
- main.2.ada
- /gnat/project1/sources/main.2.ada
-@end smallexample
-
-When the switch @option{-gnatem} is specified, the compiler will create
-in memory the two mappings from the specified file. If there is any problem
-(non existent file, truncated file or duplicate entries), no mapping
-will be created.
-
-Several @option{-gnatem} switches may be specified; however, only the last
-one on the command line will be taken into account.
-
-When using a project file, @code{gnatmake} create a temporary mapping file
-and communicates it to the compiler using this switch.
-
-@end table
-
-@node Search Paths and the Run-Time Library (RTL)
-@section Search Paths and the Run-Time Library (RTL)
-
-@noindent
-With the GNAT source-based library system, the compiler must be able to
-find source files for units that are needed by the unit being compiled.
-Search paths are used to guide this process.
-
-The compiler compiles one source file whose name must be given
-explicitly on the command line. In other words, no searching is done
-for this file. To find all other source files that are needed (the most
-common being the specs of units), the compiler examines the following
-directories, in the following order:
-
-@enumerate
-@item
-The directory containing the source file of the main unit being compiled
-(the file name on the command line).
-
-@item
-Each directory named by an @code{^-I^/SOURCE_SEARCH^} switch given on the @code{gcc}
-command line, in the order given.
-
-@item
-@findex ADA_INCLUDE_PATH
-Each of the directories listed in the value of the
-@code{ADA_INCLUDE_PATH} ^environment variable^logical name^.
-@ifclear vms
-Construct this value
-exactly as the @code{PATH} environment variable: a list of directory
-names separated by colons (semicolons when working with the NT version).
-@end ifclear
-@ifset vms
-Normally, define this value as a logical name containing a comma separated
-list of directory names.
-
-This variable can also be defined by means of an environment string
-(an argument to the DEC C exec* set of functions).
-
-Logical Name:
-@smallexample
-DEFINE ANOTHER_PATH FOO:[BAG]
-DEFINE ADA_INCLUDE_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
-@end smallexample
-
-By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
-first, followed by the standard Ada 95
-libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADAINCLUDE].
-If this is not redefined, the user will obtain the DEC Ada83 IO packages
-(Text_IO, Sequential_IO, etc)
-instead of the Ada95 packages. Thus, in order to get the Ada 95
-packages by default, ADA_INCLUDE_PATH must be redefined.
-@end ifset
-@item
-The content of the "ada_source_path" file which is part of the GNAT
-installation tree and is used to store standard libraries such as the
-GNAT Run Time Library (RTL) source files.
-@ifclear vms
-@ref{Installing an Ada Library}
-@end ifclear
-@end enumerate
-
-@noindent
-Specifying the switch @code{^-I-^/NOCURRENT_DIRECTORY^}
-inhibits the use of the directory
-containing the source file named in the command line. You can still
-have this directory on your search path, but in this case it must be
-explicitly requested with a @code{^-I^/SOURCE_SEARCH^} switch.
-
-Specifying the switch @code{-nostdinc}
-inhibits the search of the default location for the GNAT Run Time
-Library (RTL) source files.
-
-The compiler outputs its object files and ALI files in the current
-working directory.
-@ifclear vms
-Caution: The object file can be redirected with the @code{-o} switch;
-however, @code{gcc} and @code{gnat1} have not been coordinated on this
-so the ALI file will not go to the right place. Therefore, you should
-avoid using the @code{-o} switch.
-@end ifclear
-
-@findex System.IO
-The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
-children make up the GNAT RTL, together with the simple @code{System.IO}
-package used in the "Hello World" example. The sources for these units
-are needed by the compiler and are kept together in one directory. Not
-all of the bodies are needed, but all of the sources are kept together
-anyway. In a normal installation, you need not specify these directory
-names when compiling or binding. Either the environment variables or
-the built-in defaults cause these files to be found.
-
-In addition to the language-defined hierarchies (System, Ada and
-Interfaces), the GNAT distribution provides a fourth hierarchy,
-consisting of child units of GNAT. This is a collection of generally
-useful routines. See the GNAT Reference Manual for further details.
-
-Besides simplifying access to the RTL, a major use of search paths is
-in compiling sources from multiple directories. This can make
-development environments much more flexible.
-
-@node Order of Compilation Issues
-@section Order of Compilation Issues
-
-@noindent
-If, in our earlier example, there was a spec for the @code{hello}
-procedure, it would be contained in the file @file{hello.ads}; yet this
-file would not have to be explicitly compiled. This is the result of the
-model we chose to implement library management. Some of the consequences
-of this model are as follows:
-
-@itemize @bullet
-@item
-There is no point in compiling specs (except for package
-specs with no bodies) because these are compiled as needed by clients. If
-you attempt a useless compilation, you will receive an error message.
-It is also useless to compile subunits because they are compiled as needed
-by the parent.
-
-@item
-There are no order of compilation requirements: performing a
-compilation never obsoletes anything. The only way you can obsolete
-something and require recompilations is to modify one of the
-source files on which it depends.
-
-@item
-There is no library as such, apart from the ALI files
-(@pxref{The Ada Library Information Files}, for information on the format of these
-files). For now we find it convenient to create separate ALI files, but
-eventually the information therein may be incorporated into the object
-file directly.
-
-@item
-When you compile a unit, the source files for the specs of all units
-that it @code{with}'s, all its subunits, and the bodies of any generics it
-instantiates must be available (reachable by the search-paths mechanism
-described above), or you will receive a fatal error message.
-@end itemize
-
-@node Examples
-@section Examples
-
-@noindent
-The following are some typical Ada compilation command line examples:
-
-@table @code
-@item $ gcc -c xyz.adb
-Compile body in file @file{xyz.adb} with all default options.
-
-@ifclear vms
-@item $ gcc -c -O2 -gnata xyz-def.adb
-@end ifclear
-@ifset vms
-@item $ GNAT COMPILE /OPTIMIZE=ALL -gnata xyz-def.adb
-@end ifset
-
-Compile the child unit package in file @file{xyz-def.adb} with extensive
-optimizations, and pragma @code{Assert}/@code{Debug} statements
-enabled.
-
-@item $ gcc -c -gnatc abc-def.adb
-Compile the subunit in file @file{abc-def.adb} in semantic-checking-only
-mode.
-@end table
-
-@node Binding Using gnatbind
-@chapter Binding Using @code{gnatbind}
-@findex gnatbind
-
-@menu
-* Running gnatbind::
-* Generating the Binder Program in C::
-* Consistency-Checking Modes::
-* Binder Error Message Control::
-* Elaboration Control::
-* Output Control::
-* Binding with Non-Ada Main Programs::
-* Binding Programs with No Main Subprogram::
-* Summary of Binder Switches::
-* Command-Line Access::
-* Search Paths for gnatbind::
-* Examples of gnatbind Usage::
-@end menu
-
-@noindent
-This chapter describes the GNAT binder, @code{gnatbind}, which is used
-to bind compiled GNAT objects. The @code{gnatbind} program performs
-four separate functions:
-
-@enumerate
-@item
-Checks that a program is consistent, in accordance with the rules in
-Chapter 10 of the Ada 95 Reference Manual. In particular, error
-messages are generated if a program uses inconsistent versions of a
-given unit.
-
-@item
-Checks that an acceptable order of elaboration exists for the program
-and issues an error message if it cannot find an order of elaboration
-that satisfies the rules in Chapter 10 of the Ada 95 Language Manual.
-
-@item
-Generates a main program incorporating the given elaboration order.
-This program is a small Ada package (body and spec) that
-must be subsequently compiled
-using the GNAT compiler. The necessary compilation step is usually
-performed automatically by @code{gnatlink}. The two most important
-functions of this program
-are to call the elaboration routines of units in an appropriate order
-and to call the main program.
-
-@item
-Determines the set of object files required by the given main program.
-This information is output in the forms of comments in the generated program,
-to be read by the @code{gnatlink} utility used to link the Ada application.
-@end enumerate
-
-@node Running gnatbind
-@section Running @code{gnatbind}
-
-@noindent
-The form of the @code{gnatbind} command is
-
-@smallexample
-$ gnatbind [@var{switches}] @var{mainprog}[.ali] [@var{switches}]
-@end smallexample
-
-@noindent
-where @var{mainprog}.adb is the Ada file containing the main program
-unit body. If no switches are specified, @code{gnatbind} constructs an Ada
-package in two files which names are
-@file{b~@var{ada_main}.ads}, and @file{b~@var{ada_main}.adb}.
-For example, if given the
-parameter @samp{hello.ali}, for a main program contained in file
-@file{hello.adb}, the binder output files would be @file{b~hello.ads}
-and @file{b~hello.adb}.
-
-When doing consistency checking, the binder takes into consideration
-any source files it can locate. For example, if the binder determines
-that the given main program requires the package @code{Pack}, whose
-@file{.ali}
-file is @file{pack.ali} and whose corresponding source spec file is
-@file{pack.ads}, it attempts to locate the source file @file{pack.ads}
-(using the same search path conventions as previously described for the
-@code{gcc} command). If it can locate this source file, it checks that
-the time stamps
-or source checksums of the source and its references to in @file{ali} files
-match. In other words, any @file{ali} files that mentions this spec must have
-resulted from compiling this version of the source file (or in the case
-where the source checksums match, a version close enough that the
-difference does not matter).
-
-@cindex Source files, use by binder
-The effect of this consistency checking, which includes source files, is
-that the binder ensures that the program is consistent with the latest
-version of the source files that can be located at bind time. Editing a
-source file without compiling files that depend on the source file cause
-error messages to be generated by the binder.
-
-For example, suppose you have a main program @file{hello.adb} and a
-package @code{P}, from file @file{p.ads} and you perform the following
-steps:
-
-@enumerate
-@item
-Enter @code{gcc -c hello.adb} to compile the main program.
-
-@item
-Enter @code{gcc -c p.ads} to compile package @code{P}.
-
-@item
-Edit file @file{p.ads}.
-
-@item
-Enter @code{gnatbind hello}.
-@end enumerate
-
-At this point, the file @file{p.ali} contains an out-of-date time stamp
-because the file @file{p.ads} has been edited. The attempt at binding
-fails, and the binder generates the following error messages:
-
-@smallexample
-error: "hello.adb" must be recompiled ("p.ads" has been modified)
-error: "p.ads" has been modified and must be recompiled
-@end smallexample
-
-@noindent
-Now both files must be recompiled as indicated, and then the bind can
-succeed, generating a main program. You need not normally be concerned
-with the contents of this file, but it is similar to the following which
-is the binder file generated for a simple "hello world" program.
-
-@smallexample
-@iftex
-@leftskip=0cm
-@end iftex
--- The package is called Ada_Main unless this name is actually used
--- as a unit name in the partition, in which case some other unique
--- name is used.
-
-with System;
-package ada_main is
-
- Elab_Final_Code : Integer;
- pragma Import (C, Elab_Final_Code, "__gnat_inside_elab_final_code");
-
- -- The main program saves the parameters (argument count,
- -- argument values, environment pointer) in global variables
- -- for later access by other units including
- -- Ada.Command_Line.
-
- gnat_argc : Integer;
- gnat_argv : System.Address;
- gnat_envp : System.Address;
-
- -- The actual variables are stored in a library routine. This
- -- is useful for some shared library situations, where there
- -- are problems if variables are not in the library.
-
- pragma Import (C, gnat_argc);
- pragma Import (C, gnat_argv);
- pragma Import (C, gnat_envp);
-
- -- The exit status is similarly an external location
-
- gnat_exit_status : Integer;
- pragma Import (C, gnat_exit_status);
-
- GNAT_Version : constant String :=
- "GNAT Version: 3.15w (20010315)";
- pragma Export (C, GNAT_Version, "__gnat_version");
-
- -- This is the generated adafinal routine that performs
- -- finalization at the end of execution. In the case where
- -- Ada is the main program, this main program makes a call
- -- to adafinal at program termination.
-
- procedure adafinal;
- pragma Export (C, adafinal, "adafinal");
-
- -- This is the generated adainit routine that performs
- -- initialization at the start of execution. In the case
- -- where Ada is the main program, this main program makes
- -- a call to adainit at program startup.
-
- procedure adainit;
- pragma Export (C, adainit, "adainit");
-
- -- This routine is called at the start of execution. It is
- -- a dummy routine that is used by the debugger to breakpoint
- -- at the start of execution.
-
- procedure Break_Start;
- pragma Import (C, Break_Start, "__gnat_break_start");
-
- -- This is the actual generated main program (it would be
- -- suppressed if the no main program switch were used). As
- -- required by standard system conventions, this program has
- -- the external name main.
-
- function main
- (argc : Integer;
- argv : System.Address;
- envp : System.Address)
- return Integer;
- pragma Export (C, main, "main");
-
- -- The following set of constants give the version
- -- identification values for every unit in the bound
- -- partition. This identification is computed from all
- -- dependent semantic units, and corresponds to the
- -- string that would be returned by use of the
- -- Body_Version or Version attributes.
-
- type Version_32 is mod 2 ** 32;
- u00001 : constant Version_32 := 16#7880BEB3#;
- u00002 : constant Version_32 := 16#0D24CBD0#;
- u00003 : constant Version_32 := 16#3283DBEB#;
- u00004 : constant Version_32 := 16#2359F9ED#;
- u00005 : constant Version_32 := 16#664FB847#;
- u00006 : constant Version_32 := 16#68E803DF#;
- u00007 : constant Version_32 := 16#5572E604#;
- u00008 : constant Version_32 := 16#46B173D8#;
- u00009 : constant Version_32 := 16#156A40CF#;
- u00010 : constant Version_32 := 16#033DABE0#;
- u00011 : constant Version_32 := 16#6AB38FEA#;
- u00012 : constant Version_32 := 16#22B6217D#;
- u00013 : constant Version_32 := 16#68A22947#;
- u00014 : constant Version_32 := 16#18CC4A56#;
- u00015 : constant Version_32 := 16#08258E1B#;
- u00016 : constant Version_32 := 16#367D5222#;
- u00017 : constant Version_32 := 16#20C9ECA4#;
- u00018 : constant Version_32 := 16#50D32CB6#;
- u00019 : constant Version_32 := 16#39A8BB77#;
- u00020 : constant Version_32 := 16#5CF8FA2B#;
- u00021 : constant Version_32 := 16#2F1EB794#;
- u00022 : constant Version_32 := 16#31AB6444#;
- u00023 : constant Version_32 := 16#1574B6E9#;
- u00024 : constant Version_32 := 16#5109C189#;
- u00025 : constant Version_32 := 16#56D770CD#;
- u00026 : constant Version_32 := 16#02F9DE3D#;
- u00027 : constant Version_32 := 16#08AB6B2C#;
- u00028 : constant Version_32 := 16#3FA37670#;
- u00029 : constant Version_32 := 16#476457A0#;
- u00030 : constant Version_32 := 16#731E1B6E#;
- u00031 : constant Version_32 := 16#23C2E789#;
- u00032 : constant Version_32 := 16#0F1BD6A1#;
- u00033 : constant Version_32 := 16#7C25DE96#;
- u00034 : constant Version_32 := 16#39ADFFA2#;
- u00035 : constant Version_32 := 16#571DE3E7#;
- u00036 : constant Version_32 := 16#5EB646AB#;
- u00037 : constant Version_32 := 16#4249379B#;
- u00038 : constant Version_32 := 16#0357E00A#;
- u00039 : constant Version_32 := 16#3784FB72#;
- u00040 : constant Version_32 := 16#2E723019#;
- u00041 : constant Version_32 := 16#623358EA#;
- u00042 : constant Version_32 := 16#107F9465#;
- u00043 : constant Version_32 := 16#6843F68A#;
- u00044 : constant Version_32 := 16#63305874#;
- u00045 : constant Version_32 := 16#31E56CE1#;
- u00046 : constant Version_32 := 16#02917970#;
- u00047 : constant Version_32 := 16#6CCBA70E#;
- u00048 : constant Version_32 := 16#41CD4204#;
- u00049 : constant Version_32 := 16#572E3F58#;
- u00050 : constant Version_32 := 16#20729FF5#;
- u00051 : constant Version_32 := 16#1D4F93E8#;
- u00052 : constant Version_32 := 16#30B2EC3D#;
- u00053 : constant Version_32 := 16#34054F96#;
- u00054 : constant Version_32 := 16#5A199860#;
- u00055 : constant Version_32 := 16#0E7F912B#;
- u00056 : constant Version_32 := 16#5760634A#;
- u00057 : constant Version_32 := 16#5D851835#;
-
- -- The following Export pragmas export the version numbers
- -- with symbolic names ending in B (for body) or S
- -- (for spec) so that they can be located in a link. The
- -- information provided here is sufficient to track down
- -- the exact versions of units used in a given build.
-
- pragma Export (C, u00001, "helloB");
- pragma Export (C, u00002, "system__standard_libraryB");
- pragma Export (C, u00003, "system__standard_libraryS");
- pragma Export (C, u00004, "adaS");
- pragma Export (C, u00005, "ada__text_ioB");
- pragma Export (C, u00006, "ada__text_ioS");
- pragma Export (C, u00007, "ada__exceptionsB");
- pragma Export (C, u00008, "ada__exceptionsS");
- pragma Export (C, u00009, "gnatS");
- pragma Export (C, u00010, "gnat__heap_sort_aB");
- pragma Export (C, u00011, "gnat__heap_sort_aS");
- pragma Export (C, u00012, "systemS");
- pragma Export (C, u00013, "system__exception_tableB");
- pragma Export (C, u00014, "system__exception_tableS");
- pragma Export (C, u00015, "gnat__htableB");
- pragma Export (C, u00016, "gnat__htableS");
- pragma Export (C, u00017, "system__exceptionsS");
- pragma Export (C, u00018, "system__machine_state_operationsB");
- pragma Export (C, u00019, "system__machine_state_operationsS");
- pragma Export (C, u00020, "system__machine_codeS");
- pragma Export (C, u00021, "system__storage_elementsB");
- pragma Export (C, u00022, "system__storage_elementsS");
- pragma Export (C, u00023, "system__secondary_stackB");
- pragma Export (C, u00024, "system__secondary_stackS");
- pragma Export (C, u00025, "system__parametersB");
- pragma Export (C, u00026, "system__parametersS");
- pragma Export (C, u00027, "system__soft_linksB");
- pragma Export (C, u00028, "system__soft_linksS");
- pragma Export (C, u00029, "system__stack_checkingB");
- pragma Export (C, u00030, "system__stack_checkingS");
- pragma Export (C, u00031, "system__tracebackB");
- pragma Export (C, u00032, "system__tracebackS");
- pragma Export (C, u00033, "ada__streamsS");
- pragma Export (C, u00034, "ada__tagsB");
- pragma Export (C, u00035, "ada__tagsS");
- pragma Export (C, u00036, "system__string_opsB");
- pragma Export (C, u00037, "system__string_opsS");
- pragma Export (C, u00038, "interfacesS");
- pragma Export (C, u00039, "interfaces__c_streamsB");
- pragma Export (C, u00040, "interfaces__c_streamsS");
- pragma Export (C, u00041, "system__file_ioB");
- pragma Export (C, u00042, "system__file_ioS");
- pragma Export (C, u00043, "ada__finalizationB");
- pragma Export (C, u00044, "ada__finalizationS");
- pragma Export (C, u00045, "system__finalization_rootB");
- pragma Export (C, u00046, "system__finalization_rootS");
- pragma Export (C, u00047, "system__finalization_implementationB");
- pragma Export (C, u00048, "system__finalization_implementationS");
- pragma Export (C, u00049, "system__string_ops_concat_3B");
- pragma Export (C, u00050, "system__string_ops_concat_3S");
- pragma Export (C, u00051, "system__stream_attributesB");
- pragma Export (C, u00052, "system__stream_attributesS");
- pragma Export (C, u00053, "ada__io_exceptionsS");
- pragma Export (C, u00054, "system__unsigned_typesS");
- pragma Export (C, u00055, "system__file_control_blockS");
- pragma Export (C, u00056, "ada__finalization__list_controllerB");
- pragma Export (C, u00057, "ada__finalization__list_controllerS");
-
- -- BEGIN ELABORATION ORDER
- -- ada (spec)
- -- gnat (spec)
- -- gnat.heap_sort_a (spec)
- -- gnat.heap_sort_a (body)
- -- gnat.htable (spec)
- -- gnat.htable (body)
- -- interfaces (spec)
- -- system (spec)
- -- system.machine_code (spec)
- -- system.parameters (spec)
- -- system.parameters (body)
- -- interfaces.c_streams (spec)
- -- interfaces.c_streams (body)
- -- system.standard_library (spec)
- -- ada.exceptions (spec)
- -- system.exception_table (spec)
- -- system.exception_table (body)
- -- ada.io_exceptions (spec)
- -- system.exceptions (spec)
- -- system.storage_elements (spec)
- -- system.storage_elements (body)
- -- system.machine_state_operations (spec)
- -- system.machine_state_operations (body)
- -- system.secondary_stack (spec)
- -- system.stack_checking (spec)
- -- system.soft_links (spec)
- -- system.soft_links (body)
- -- system.stack_checking (body)
- -- system.secondary_stack (body)
- -- system.standard_library (body)
- -- system.string_ops (spec)
- -- system.string_ops (body)
- -- ada.tags (spec)
- -- ada.tags (body)
- -- ada.streams (spec)
- -- system.finalization_root (spec)
- -- system.finalization_root (body)
- -- system.string_ops_concat_3 (spec)
- -- system.string_ops_concat_3 (body)
- -- system.traceback (spec)
- -- system.traceback (body)
- -- ada.exceptions (body)
- -- system.unsigned_types (spec)
- -- system.stream_attributes (spec)
- -- system.stream_attributes (body)
- -- system.finalization_implementation (spec)
- -- system.finalization_implementation (body)
- -- ada.finalization (spec)
- -- ada.finalization (body)
- -- ada.finalization.list_controller (spec)
- -- ada.finalization.list_controller (body)
- -- system.file_control_block (spec)
- -- system.file_io (spec)
- -- system.file_io (body)
- -- ada.text_io (spec)
- -- ada.text_io (body)
- -- hello (body)
- -- END ELABORATION ORDER
-
-end ada_main;
-
--- The following source file name pragmas allow the generated file
--- names to be unique for different main programs. They are needed
--- since the package name will always be Ada_Main.
-
-pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
-pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
-
--- Generated package body for Ada_Main starts here
-
-package body ada_main is
-
- -- The actual finalization is performed by calling the
- -- library routine in System.Standard_Library.Adafinal
-
- procedure Do_Finalize;
- pragma Import (C, Do_Finalize, "system__standard_library__adafinal");
-
- -------------
- -- adainit --
- -------------
-
-@findex adainit
- procedure adainit is
-
- -- These booleans are set to True once the associated unit has
- -- been elaborated. It is also used to avoid elaborating the
- -- same unit twice.
-
- E040 : Boolean; pragma Import (Ada, E040, "interfaces__c_streams_E");
- E008 : Boolean; pragma Import (Ada, E008, "ada__exceptions_E");
- E014 : Boolean; pragma Import (Ada, E014, "system__exception_table_E");
- E053 : Boolean; pragma Import (Ada, E053, "ada__io_exceptions_E");
- E017 : Boolean; pragma Import (Ada, E017, "system__exceptions_E");
- E024 : Boolean; pragma Import (Ada, E024, "system__secondary_stack_E");
- E030 : Boolean; pragma Import (Ada, E030, "system__stack_checking_E");
- E028 : Boolean; pragma Import (Ada, E028, "system__soft_links_E");
- E035 : Boolean; pragma Import (Ada, E035, "ada__tags_E");
- E033 : Boolean; pragma Import (Ada, E033, "ada__streams_E");
- E046 : Boolean; pragma Import (Ada, E046, "system__finalization_root_E");
- E048 : Boolean; pragma Import (Ada, E048, "system__finalization_implementation_E");
- E044 : Boolean; pragma Import (Ada, E044, "ada__finalization_E");
- E057 : Boolean; pragma Import (Ada, E057, "ada__finalization__list_controller_E");
- E055 : Boolean; pragma Import (Ada, E055, "system__file_control_block_E");
- E042 : Boolean; pragma Import (Ada, E042, "system__file_io_E");
- E006 : Boolean; pragma Import (Ada, E006, "ada__text_io_E");
-
- -- Set_Globals is a library routine that stores away the
- -- value of the indicated set of global values in global
- -- variables within the library.
-
- procedure Set_Globals
- (Main_Priority : Integer;
- Time_Slice_Value : Integer;
- WC_Encoding : Character;
- Locking_Policy : Character;
- Queuing_Policy : Character;
- Task_Dispatching_Policy : Character;
- Adafinal : System.Address;
- Unreserve_All_Interrupts : Integer;
- Exception_Tracebacks : Integer);
-@findex __gnat_set_globals
- pragma Import (C, Set_Globals, "__gnat_set_globals");
-
- -- SDP_Table_Build is a library routine used to build the
- -- exception tables. See unit Ada.Exceptions in files
- -- a-except.ads/adb for full details of how zero cost
- -- exception handling works. This procedure, the call to
- -- it, and the two following tables are all omitted if the
- -- build is in longjmp/setjump exception mode.
-
-@findex SDP_Table_Build
-@findex Zero Cost Exceptions
- procedure SDP_Table_Build
- (SDP_Addresses : System.Address;
- SDP_Count : Natural;
- Elab_Addresses : System.Address;
- Elab_Addr_Count : Natural);
- pragma Import (C, SDP_Table_Build, "__gnat_SDP_Table_Build");
-
- -- Table of Unit_Exception_Table addresses. Used for zero
- -- cost exception handling to build the top level table.
-
- ST : aliased constant array (1 .. 23) of System.Address := (
- Hello'UET_Address,
- Ada.Text_Io'UET_Address,
- Ada.Exceptions'UET_Address,
- Gnat.Heap_Sort_A'UET_Address,
- System.Exception_Table'UET_Address,
- System.Machine_State_Operations'UET_Address,
- System.Secondary_Stack'UET_Address,
- System.Parameters'UET_Address,
- System.Soft_Links'UET_Address,
- System.Stack_Checking'UET_Address,
- System.Traceback'UET_Address,
- Ada.Streams'UET_Address,
- Ada.Tags'UET_Address,
- System.String_Ops'UET_Address,
- Interfaces.C_Streams'UET_Address,
- System.File_Io'UET_Address,
- Ada.Finalization'UET_Address,
- System.Finalization_Root'UET_Address,
- System.Finalization_Implementation'UET_Address,
- System.String_Ops_Concat_3'UET_Address,
- System.Stream_Attributes'UET_Address,
- System.File_Control_Block'UET_Address,
- Ada.Finalization.List_Controller'UET_Address);
-
- -- Table of addresses of elaboration routines. Used for
- -- zero cost exception handling to make sure these
- -- addresses are included in the top level procedure
- -- address table.
-
- EA : aliased constant array (1 .. 23) of System.Address := (
- adainit'Code_Address,
- Do_Finalize'Code_Address,
- Ada.Exceptions'Elab_Spec'Address,
- System.Exceptions'Elab_Spec'Address,
- Interfaces.C_Streams'Elab_Spec'Address,
- System.Exception_Table'Elab_Body'Address,
- Ada.Io_Exceptions'Elab_Spec'Address,
- System.Stack_Checking'Elab_Spec'Address,
- System.Soft_Links'Elab_Body'Address,
- System.Secondary_Stack'Elab_Body'Address,
- Ada.Tags'Elab_Spec'Address,
- Ada.Tags'Elab_Body'Address,
- Ada.Streams'Elab_Spec'Address,
- System.Finalization_Root'Elab_Spec'Address,
- Ada.Exceptions'Elab_Body'Address,
- System.Finalization_Implementation'Elab_Spec'Address,
- System.Finalization_Implementation'Elab_Body'Address,
- Ada.Finalization'Elab_Spec'Address,
- Ada.Finalization.List_Controller'Elab_Spec'Address,
- System.File_Control_Block'Elab_Spec'Address,
- System.File_Io'Elab_Body'Address,
- Ada.Text_Io'Elab_Spec'Address,
- Ada.Text_Io'Elab_Body'Address);
-
- -- Start of processing for adainit
-
- begin
-
- -- Call SDP_Table_Build to build the top level procedure
- -- table for zero cost exception handling (omitted in
- -- longjmp/setjump mode).
-
- SDP_Table_Build (ST'Address, 23, EA'Address, 23);
-
- -- Call Set_Globals to record various information for
- -- this partition. The values are derived by the binder
- -- from information stored in the ali files by the compiler.
-
-@findex __gnat_set_globals
- Set_Globals
- (Main_Priority => -1,
- -- Priority of main program, -1 if no pragma Priority used
-
- Time_Slice_Value => -1,
- -- Time slice from Time_Slice pragma, -1 if none used
-
- WC_Encoding => 'b',
- -- Wide_Character encoding used, default is brackets
-
- Locking_Policy => ' ',
- -- Locking_Policy used, default of space means not
- -- specified, otherwise it is the first character of
- -- the policy name.
-
- Queuing_Policy => ' ',
- -- Queuing_Policy used, default of space means not
- -- specified, otherwise it is the first character of
- -- the policy name.
-
- Task_Dispatching_Policy => ' ',
- -- Task_Dispatching_Policy used, default of space means
- -- not specified, otherwise first character of the
- -- policy name.
-
- Adafinal => System.Null_Address,
- -- Address of Adafinal routine, not used anymore
-
- Unreserve_All_Interrupts => 0,
- -- Set true if pragma Unreserve_All_Interrupts was used
-
- Exception_Tracebacks => 0);
- -- Indicates if exception tracebacks are enabled
-
- Elab_Final_Code := 1;
-
- -- Now we have the elaboration calls for all units in the partition.
- -- The Elab_Spec and Elab_Body attributes generate references to the
- -- implicit elaboration procedures generated by the compiler for
- -- each unit that requires elaboration.
-
- if not E040 then
- Interfaces.C_Streams'Elab_Spec;
- end if;
- E040 := True;
- if not E008 then
- Ada.Exceptions'Elab_Spec;
- end if;
- if not E014 then
- System.Exception_Table'Elab_Body;
- E014 := True;
- end if;
- if not E053 then
- Ada.Io_Exceptions'Elab_Spec;
- E053 := True;
- end if;
- if not E017 then
- System.Exceptions'Elab_Spec;
- E017 := True;
- end if;
- if not E030 then
- System.Stack_Checking'Elab_Spec;
- end if;
- if not E028 then
- System.Soft_Links'Elab_Body;
- E028 := True;
- end if;
- E030 := True;
- if not E024 then
- System.Secondary_Stack'Elab_Body;
- E024 := True;
- end if;
- if not E035 then
- Ada.Tags'Elab_Spec;
- end if;
- if not E035 then
- Ada.Tags'Elab_Body;
- E035 := True;
- end if;
- if not E033 then
- Ada.Streams'Elab_Spec;
- E033 := True;
- end if;
- if not E046 then
- System.Finalization_Root'Elab_Spec;
- end if;
- E046 := True;
- if not E008 then
- Ada.Exceptions'Elab_Body;
- E008 := True;
- end if;
- if not E048 then
- System.Finalization_Implementation'Elab_Spec;
- end if;
- if not E048 then
- System.Finalization_Implementation'Elab_Body;
- E048 := True;
- end if;
- if not E044 then
- Ada.Finalization'Elab_Spec;
- end if;
- E044 := True;
- if not E057 then
- Ada.Finalization.List_Controller'Elab_Spec;
- end if;
- E057 := True;
- if not E055 then
- System.File_Control_Block'Elab_Spec;
- E055 := True;
- end if;
- if not E042 then
- System.File_Io'Elab_Body;
- E042 := True;
- end if;
- if not E006 then
- Ada.Text_Io'Elab_Spec;
- end if;
- if not E006 then
- Ada.Text_Io'Elab_Body;
- E006 := True;
- end if;
-
- Elab_Final_Code := 0;
- end adainit;
-
- --------------
- -- adafinal --
- --------------
-
-@findex adafinal
- procedure adafinal is
- begin
- Do_Finalize;
- end adafinal;
-
- ----------
- -- main --
- ----------
-
- -- main is actually a function, as in the ANSI C standard,
- -- defined to return the exit status. The three parameters
- -- are the argument count, argument values and environment
- -- pointer.
-
-@findex Main Program
- function main
- (argc : Integer;
- argv : System.Address;
- envp : System.Address)
- return Integer
- is
- -- The initialize routine performs low level system
- -- initialization using a standard library routine which
- -- sets up signal handling and performs any other
- -- required setup. The routine can be found in file
- -- a-init.c.
-
-@findex __gnat_initialize
- procedure initialize;
- pragma Import (C, initialize, "__gnat_initialize");
-
- -- The finalize routine performs low level system
- -- finalization using a standard library routine. The
- -- routine is found in file a-final.c and in the standard
- -- distribution is a dummy routine that does nothing, so
- -- really this is a hook for special user finalization.
-
-@findex __gnat_finalize
- procedure finalize;
- pragma Import (C, finalize, "__gnat_finalize");
-
- -- We get to the main program of the partition by using
- -- pragma Import because if we try to with the unit and
- -- call it Ada style, then not only do we waste time
- -- recompiling it, but also, we don't really know the right
- -- switches (e.g. identifier character set) to be used
- -- to compile it.
-
- procedure Ada_Main_Program;
- pragma Import (Ada, Ada_Main_Program, "_ada_hello");
-
- -- Start of processing for main
-
- begin
- -- Save global variables
-
- gnat_argc := argc;
- gnat_argv := argv;
- gnat_envp := envp;
-
- -- Call low level system initialization
-
- Initialize;
-
- -- Call our generated Ada initialization routine
-
- adainit;
-
- -- This is the point at which we want the debugger to get
- -- control
-
- Break_Start;
-
- -- Now we call the main program of the partition
-
- Ada_Main_Program;
-
- -- Perform Ada finalization
-
- adafinal;
-
- -- Perform low level system finalization
-
- Finalize;
-
- -- Return the proper exit status
- return (gnat_exit_status);
- end;
-
--- This section is entirely comments, so it has no effect on the
--- compilation of the Ada_Main package. It provides the list of
--- object files and linker options, as well as some standard
--- libraries needed for the link. The gnatlink utility parses
--- this b~hello.adb file to read these comment lines to generate
--- the appropriate command line arguments for the call to the
--- system linker. The BEGIN/END lines are used for sentinels for
--- this parsing operation.
-
--- The exact file names will of course depend on the environment,
--- host/target and location of files on the host system.
-
-@findex Object file list
--- BEGIN Object file/option list
- -- ./hello.o
- -- -L./
- -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
- -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
--- END Object file/option list
-
-end ada_main;
-
-@end smallexample
-
-@noindent
-The Ada code in the above example is exactly what is generated by the
-binder. We have added comments to more clearly indicate the function
-of each part of the generated @code{Ada_Main} package.
-
-The code is standard Ada in all respects, and can be processed by any
-tools that handle Ada. In particular, it is possible to use the debugger
-in Ada mode to debug the generated Ada_Main package. For example, suppose
-that for reasons that you do not understand, your program is blowing up
-during elaboration of the body of @code{Ada.Text_IO}. To chase this bug
-down, you can place a breakpoint on the call:
-
-@smallexample
-Ada.Text_Io'Elab_Body;
-@end smallexample
-
-@noindent
-and trace the elaboration routine for this package to find out where
-the problem might be (more usually of course you would be debugging
-elaboration code in your own application).
-
-@node Generating the Binder Program in C
-@section Generating the Binder Program in C
-@noindent
-In most normal usage, the default mode of @code{gnatbind} which is to
-generate the main package in Ada, as described in the previous section.
-In particular, this means that any Ada programmer can read and understand
-the generated main program. It can also be debugged just like any other
-Ada code provided the @code{-g} switch is used for @code{gnatbind}
-and @code{gnatlink}.
-
-However for some purposes it may be convenient to generate the main
-program in C rather than Ada. This may for example be helpful when you
-are generating a mixed language program with the main program in C. The
-GNAT compiler itself is an example. The use of the @code{-C} switch
-for both @code{gnatbind} and @code{gnatlink} will cause the program to
-be generated in C (and compiled using the gnu C compiler). The
-following shows the C code generated for the same "Hello World"
-program:
-
-@smallexample
-
-#ifdef __STDC__
-#define PARAMS(paramlist) paramlist
-#else
-#define PARAMS(paramlist) ()
-#endif
-
-extern void __gnat_set_globals
- PARAMS ((int, int, int, int, int, int,
- void (*) PARAMS ((void)), int, int));
-extern void adafinal PARAMS ((void));
-extern void adainit PARAMS ((void));
-extern void system__standard_library__adafinal PARAMS ((void));
-extern int main PARAMS ((int, char **, char **));
-extern void exit PARAMS ((int));
-extern void __gnat_break_start PARAMS ((void));
-extern void _ada_hello PARAMS ((void));
-extern void __gnat_initialize PARAMS ((void));
-extern void __gnat_finalize PARAMS ((void));
-
-extern void ada__exceptions___elabs PARAMS ((void));
-extern void system__exceptions___elabs PARAMS ((void));
-extern void interfaces__c_streams___elabs PARAMS ((void));
-extern void system__exception_table___elabb PARAMS ((void));
-extern void ada__io_exceptions___elabs PARAMS ((void));
-extern void system__stack_checking___elabs PARAMS ((void));
-extern void system__soft_links___elabb PARAMS ((void));
-extern void system__secondary_stack___elabb PARAMS ((void));
-extern void ada__tags___elabs PARAMS ((void));
-extern void ada__tags___elabb PARAMS ((void));
-extern void ada__streams___elabs PARAMS ((void));
-extern void system__finalization_root___elabs PARAMS ((void));
-extern void ada__exceptions___elabb PARAMS ((void));
-extern void system__finalization_implementation___elabs PARAMS ((void));
-extern void system__finalization_implementation___elabb PARAMS ((void));
-extern void ada__finalization___elabs PARAMS ((void));
-extern void ada__finalization__list_controller___elabs PARAMS ((void));
-extern void system__file_control_block___elabs PARAMS ((void));
-extern void system__file_io___elabb PARAMS ((void));
-extern void ada__text_io___elabs PARAMS ((void));
-extern void ada__text_io___elabb PARAMS ((void));
-
-extern int __gnat_inside_elab_final_code;
-
-extern int gnat_argc;
-extern char **gnat_argv;
-extern char **gnat_envp;
-extern int gnat_exit_status;
-
-char __gnat_version[] = "GNAT Version: 3.15w (20010315)";
-void adafinal () @{
- system__standard_library__adafinal ();
-@}
-
-void adainit ()
-@{
- extern char ada__exceptions_E;
- extern char system__exceptions_E;
- extern char interfaces__c_streams_E;
- extern char system__exception_table_E;
- extern char ada__io_exceptions_E;
- extern char system__secondary_stack_E;
- extern char system__stack_checking_E;
- extern char system__soft_links_E;
- extern char ada__tags_E;
- extern char ada__streams_E;
- extern char system__finalization_root_E;
- extern char system__finalization_implementation_E;
- extern char ada__finalization_E;
- extern char ada__finalization__list_controller_E;
- extern char system__file_control_block_E;
- extern char system__file_io_E;
- extern char ada__text_io_E;
-
- extern void *__gnat_hello__SDP;
- extern void *__gnat_ada__text_io__SDP;
- extern void *__gnat_ada__exceptions__SDP;
- extern void *__gnat_gnat__heap_sort_a__SDP;
- extern void *__gnat_system__exception_table__SDP;
- extern void *__gnat_system__machine_state_operations__SDP;
- extern void *__gnat_system__secondary_stack__SDP;
- extern void *__gnat_system__parameters__SDP;
- extern void *__gnat_system__soft_links__SDP;
- extern void *__gnat_system__stack_checking__SDP;
- extern void *__gnat_system__traceback__SDP;
- extern void *__gnat_ada__streams__SDP;
- extern void *__gnat_ada__tags__SDP;
- extern void *__gnat_system__string_ops__SDP;
- extern void *__gnat_interfaces__c_streams__SDP;
- extern void *__gnat_system__file_io__SDP;
- extern void *__gnat_ada__finalization__SDP;
- extern void *__gnat_system__finalization_root__SDP;
- extern void *__gnat_system__finalization_implementation__SDP;
- extern void *__gnat_system__string_ops_concat_3__SDP;
- extern void *__gnat_system__stream_attributes__SDP;
- extern void *__gnat_system__file_control_block__SDP;
- extern void *__gnat_ada__finalization__list_controller__SDP;
-
- void **st[23] = @{
- &__gnat_hello__SDP,
- &__gnat_ada__text_io__SDP,
- &__gnat_ada__exceptions__SDP,
- &__gnat_gnat__heap_sort_a__SDP,
- &__gnat_system__exception_table__SDP,
- &__gnat_system__machine_state_operations__SDP,
- &__gnat_system__secondary_stack__SDP,
- &__gnat_system__parameters__SDP,
- &__gnat_system__soft_links__SDP,
- &__gnat_system__stack_checking__SDP,
- &__gnat_system__traceback__SDP,
- &__gnat_ada__streams__SDP,
- &__gnat_ada__tags__SDP,
- &__gnat_system__string_ops__SDP,
- &__gnat_interfaces__c_streams__SDP,
- &__gnat_system__file_io__SDP,
- &__gnat_ada__finalization__SDP,
- &__gnat_system__finalization_root__SDP,
- &__gnat_system__finalization_implementation__SDP,
- &__gnat_system__string_ops_concat_3__SDP,
- &__gnat_system__stream_attributes__SDP,
- &__gnat_system__file_control_block__SDP,
- &__gnat_ada__finalization__list_controller__SDP@};
-
- extern void ada__exceptions___elabs ();
- extern void system__exceptions___elabs ();
- extern void interfaces__c_streams___elabs ();
- extern void system__exception_table___elabb ();
- extern void ada__io_exceptions___elabs ();
- extern void system__stack_checking___elabs ();
- extern void system__soft_links___elabb ();
- extern void system__secondary_stack___elabb ();
- extern void ada__tags___elabs ();
- extern void ada__tags___elabb ();
- extern void ada__streams___elabs ();
- extern void system__finalization_root___elabs ();
- extern void ada__exceptions___elabb ();
- extern void system__finalization_implementation___elabs ();
- extern void system__finalization_implementation___elabb ();
- extern void ada__finalization___elabs ();
- extern void ada__finalization__list_controller___elabs ();
- extern void system__file_control_block___elabs ();
- extern void system__file_io___elabb ();
- extern void ada__text_io___elabs ();
- extern void ada__text_io___elabb ();
-
- void (*ea[23]) () = @{
- adainit,
- system__standard_library__adafinal,
- ada__exceptions___elabs,
- system__exceptions___elabs,
- interfaces__c_streams___elabs,
- system__exception_table___elabb,
- ada__io_exceptions___elabs,
- system__stack_checking___elabs,
- system__soft_links___elabb,
- system__secondary_stack___elabb,
- ada__tags___elabs,
- ada__tags___elabb,
- ada__streams___elabs,
- system__finalization_root___elabs,
- ada__exceptions___elabb,
- system__finalization_implementation___elabs,
- system__finalization_implementation___elabb,
- ada__finalization___elabs,
- ada__finalization__list_controller___elabs,
- system__file_control_block___elabs,
- system__file_io___elabb,
- ada__text_io___elabs,
- ada__text_io___elabb@};
-
- __gnat_SDP_Table_Build (&st, 23, ea, 23);
- __gnat_set_globals (
- -1, /* Main_Priority */
- -1, /* Time_Slice_Value */
- 'b', /* WC_Encoding */
- ' ', /* Locking_Policy */
- ' ', /* Queuing_Policy */
- ' ', /* Tasking_Dispatching_Policy */
- 0, /* Finalization routine address, not used anymore */
- 0, /* Unreserve_All_Interrupts */
- 0); /* Exception_Tracebacks */
-
- __gnat_inside_elab_final_code = 1;
-
- if (ada__exceptions_E == 0) @{
- ada__exceptions___elabs ();
- @}
- if (system__exceptions_E == 0) @{
- system__exceptions___elabs ();
- system__exceptions_E++;
- @}
- if (interfaces__c_streams_E == 0) @{
- interfaces__c_streams___elabs ();
- @}
- interfaces__c_streams_E = 1;
- if (system__exception_table_E == 0) @{
- system__exception_table___elabb ();
- system__exception_table_E++;
- @}
- if (ada__io_exceptions_E == 0) @{
- ada__io_exceptions___elabs ();
- ada__io_exceptions_E++;
- @}
- if (system__stack_checking_E == 0) @{
- system__stack_checking___elabs ();
- @}
- if (system__soft_links_E == 0) @{
- system__soft_links___elabb ();
- system__soft_links_E++;
- @}
- system__stack_checking_E = 1;
- if (system__secondary_stack_E == 0) @{
- system__secondary_stack___elabb ();
- system__secondary_stack_E++;
- @}
- if (ada__tags_E == 0) @{
- ada__tags___elabs ();
- @}
- if (ada__tags_E == 0) @{
- ada__tags___elabb ();
- ada__tags_E++;
- @}
- if (ada__streams_E == 0) @{
- ada__streams___elabs ();
- ada__streams_E++;
- @}
- if (system__finalization_root_E == 0) @{
- system__finalization_root___elabs ();
- @}
- system__finalization_root_E = 1;
- if (ada__exceptions_E == 0) @{
- ada__exceptions___elabb ();
- ada__exceptions_E++;
- @}
- if (system__finalization_implementation_E == 0) @{
- system__finalization_implementation___elabs ();
- @}
- if (system__finalization_implementation_E == 0) @{
- system__finalization_implementation___elabb ();
- system__finalization_implementation_E++;
- @}
- if (ada__finalization_E == 0) @{
- ada__finalization___elabs ();
- @}
- ada__finalization_E = 1;
- if (ada__finalization__list_controller_E == 0) @{
- ada__finalization__list_controller___elabs ();
- @}
- ada__finalization__list_controller_E = 1;
- if (system__file_control_block_E == 0) @{
- system__file_control_block___elabs ();
- system__file_control_block_E++;
- @}
- if (system__file_io_E == 0) @{
- system__file_io___elabb ();
- system__file_io_E++;
- @}
- if (ada__text_io_E == 0) @{
- ada__text_io___elabs ();
- @}
- if (ada__text_io_E == 0) @{
- ada__text_io___elabb ();
- ada__text_io_E++;
- @}
-
- __gnat_inside_elab_final_code = 0;
-@}
-int main (argc, argv, envp)
- int argc;
- char **argv;
- char **envp;
-@{
- gnat_argc = argc;
- gnat_argv = argv;
- gnat_envp = envp;
-
- __gnat_initialize ();
- adainit ();
- __gnat_break_start ();
-
- _ada_hello ();
-
- system__standard_library__adafinal ();
- __gnat_finalize ();
- exit (gnat_exit_status);
-@}
-unsigned helloB = 0x7880BEB3;
-unsigned system__standard_libraryB = 0x0D24CBD0;
-unsigned system__standard_libraryS = 0x3283DBEB;
-unsigned adaS = 0x2359F9ED;
-unsigned ada__text_ioB = 0x47C85FC4;
-unsigned ada__text_ioS = 0x496FE45C;
-unsigned ada__exceptionsB = 0x74F50187;
-unsigned ada__exceptionsS = 0x6736945B;
-unsigned gnatS = 0x156A40CF;
-unsigned gnat__heap_sort_aB = 0x033DABE0;
-unsigned gnat__heap_sort_aS = 0x6AB38FEA;
-unsigned systemS = 0x0331C6FE;
-unsigned system__exceptionsS = 0x20C9ECA4;
-unsigned system__exception_tableB = 0x68A22947;
-unsigned system__exception_tableS = 0x394BADD5;
-unsigned gnat__htableB = 0x08258E1B;
-unsigned gnat__htableS = 0x367D5222;
-unsigned system__machine_state_operationsB = 0x4F3B7492;
-unsigned system__machine_state_operationsS = 0x182F5CF4;
-unsigned system__storage_elementsB = 0x2F1EB794;
-unsigned system__storage_elementsS = 0x102C83C7;
-unsigned system__secondary_stackB = 0x1574B6E9;
-unsigned system__secondary_stackS = 0x708E260A;
-unsigned system__parametersB = 0x56D770CD;
-unsigned system__parametersS = 0x237E39BE;
-unsigned system__soft_linksB = 0x08AB6B2C;
-unsigned system__soft_linksS = 0x1E2491F3;
-unsigned system__stack_checkingB = 0x476457A0;
-unsigned system__stack_checkingS = 0x5299FCED;
-unsigned system__tracebackB = 0x2971EBDE;
-unsigned system__tracebackS = 0x2E9C3122;
-unsigned ada__streamsS = 0x7C25DE96;
-unsigned ada__tagsB = 0x39ADFFA2;
-unsigned ada__tagsS = 0x769A0464;
-unsigned system__string_opsB = 0x5EB646AB;
-unsigned system__string_opsS = 0x63CED018;
-unsigned interfacesS = 0x0357E00A;
-unsigned interfaces__c_streamsB = 0x3784FB72;
-unsigned interfaces__c_streamsS = 0x2E723019;
-unsigned system__file_ioB = 0x623358EA;
-unsigned system__file_ioS = 0x31F873E6;
-unsigned ada__finalizationB = 0x6843F68A;
-unsigned ada__finalizationS = 0x63305874;
-unsigned system__finalization_rootB = 0x31E56CE1;
-unsigned system__finalization_rootS = 0x23169EF3;
-unsigned system__finalization_implementationB = 0x6CCBA70E;
-unsigned system__finalization_implementationS = 0x604AA587;
-unsigned system__string_ops_concat_3B = 0x572E3F58;
-unsigned system__string_ops_concat_3S = 0x01F57876;
-unsigned system__stream_attributesB = 0x1D4F93E8;
-unsigned system__stream_attributesS = 0x30B2EC3D;
-unsigned ada__io_exceptionsS = 0x34054F96;
-unsigned system__unsigned_typesS = 0x7B9E7FE3;
-unsigned system__file_control_blockS = 0x2FF876A8;
-unsigned ada__finalization__list_controllerB = 0x5760634A;
-unsigned ada__finalization__list_controllerS = 0x5D851835;
-
-/* BEGIN ELABORATION ORDER
-ada (spec)
-gnat (spec)
-gnat.heap_sort_a (spec)
-gnat.htable (spec)
-gnat.htable (body)
-interfaces (spec)
-system (spec)
-system.parameters (spec)
-system.standard_library (spec)
-ada.exceptions (spec)
-system.exceptions (spec)
-system.parameters (body)
-gnat.heap_sort_a (body)
-interfaces.c_streams (spec)
-interfaces.c_streams (body)
-system.exception_table (spec)
-system.exception_table (body)
-ada.io_exceptions (spec)
-system.storage_elements (spec)
-system.storage_elements (body)
-system.machine_state_operations (spec)
-system.machine_state_operations (body)
-system.secondary_stack (spec)
-system.stack_checking (spec)
-system.soft_links (spec)
-system.soft_links (body)
-system.stack_checking (body)
-system.secondary_stack (body)
-system.standard_library (body)
-system.string_ops (spec)
-system.string_ops (body)
-ada.tags (spec)
-ada.tags (body)
-ada.streams (spec)
-system.finalization_root (spec)
-system.finalization_root (body)
-system.string_ops_concat_3 (spec)
-system.string_ops_concat_3 (body)
-system.traceback (spec)
-system.traceback (body)
-ada.exceptions (body)
-system.unsigned_types (spec)
-system.stream_attributes (spec)
-system.stream_attributes (body)
-system.finalization_implementation (spec)
-system.finalization_implementation (body)
-ada.finalization (spec)
-ada.finalization (body)
-ada.finalization.list_controller (spec)
-ada.finalization.list_controller (body)
-system.file_control_block (spec)
-system.file_io (spec)
-system.file_io (body)
-ada.text_io (spec)
-ada.text_io (body)
-hello (body)
- END ELABORATION ORDER */
-
-/* BEGIN Object file/option list
-./hello.o
--L./
--L/usr/local/gnat/lib/gcc-lib/alpha-dec-osf5.1/2.8.1/adalib/
-/usr/local/gnat/lib/gcc-lib/alpha-dec-osf5.1/2.8.1/adalib/libgnat.a
--lexc
- END Object file/option list */
-
-@end smallexample
-
-@noindent
-Here again, the C code is exactly what is generated by the binder. The
-functions of the various parts of this code correspond in an obvious
-manner with the commented Ada code shown in the example in the previous
-section.
-
-@node Consistency-Checking Modes
-@section Consistency-Checking Modes
-
-@noindent
-As described in the previous section, by default @code{gnatbind} checks
-that object files are consistent with one another and are consistent
-with any source files it can locate. The following switches control binder
-access to sources.
-
-@table @code
-@item ^-s^/READ_SOURCES=ALL^
-@cindex @code{^-s^/READ_SOURCES=ALL^} (@code{gnatbind})
-Require source files to be present. In this mode, the binder must be
-able to locate all source files that are referenced, in order to check
-their consistency. In normal mode, if a source file cannot be located it
-is simply ignored. If you specify this switch, a missing source
-file is an error.
-
-@item ^-x^/READ_SOURCES=NONE^
-@cindex @code{^-x^/READ_SOURCES=NONE^} (@code{gnatbind})
-Exclude source files. In this mode, the binder only checks that ALI
-files are consistent with one another. Source files are not accessed.
-The binder runs faster in this mode, and there is still a guarantee that
-the resulting program is self-consistent.
-If a source file has been edited since it was last compiled, and you
-specify this switch, the binder will not detect that the object
-file is out of date with respect to the source file. Note that this is the
-mode that is automatically used by @code{gnatmake} because in this
-case the checking against sources has already been performed by
-@code{gnatmake} in the course of compilation (i.e. before binding).
-
-@ifset vms
-@item /READ_SOURCES=AVAILABLE
-This is the default mode in which source files are checked if they are
-available, and ignored if they are not available.
-@end ifset
-@end table
-
-@node Binder Error Message Control
-@section Binder Error Message Control
-
-@noindent
-The following switches provide control over the generation of error
-messages from the binder:
-
-@table @code
-@item ^-v^/REPORT_ERRORS=VERBOSE^
-@cindex @code{^-v^/REPORT_ERRORS=VERBOSE^} (@code{gnatbind})
-Verbose mode. In the normal mode, brief error messages are generated to
-@file{stderr}. If this switch is present, a header is written
-to @file{stdout} and any error messages are directed to @file{stdout}.
-All that is written to @file{stderr} is a brief summary message.
-
-@item ^-b^/REPORT_ERRORS=BRIEF^
-@cindex @code{^-b^/REPORT_ERRORS=BRIEF^} (@code{gnatbind})
-Generate brief error messages to @file{stderr} even if verbose mode is
-specified. This is relevant only when used with the
-@code{^-v^/REPORT_ERRORS=VERBOSE^} switch.
-
-@ifclear vms
-@item -m@var{n}
-@cindex @code{-m} (@code{gnatbind})
-Limits the number of error messages to @var{n}, a decimal integer in the
-range 1-999. The binder terminates immediately if this limit is reached.
-
-@item -M@var{xxx}
-@cindex @code{-M} (@code{gnatbind})
-Renames the generated main program from @code{main} to @code{xxx}.
-This is useful in the case of some cross-building environments, where
-the actual main program is separate from the one generated
-by @code{gnatbind}.
-@end ifclear
-
-@item ^-ws^/WARNINGS=SUPPRESS^
-@cindex @code{^-ws^/WARNINGS=SUPPRESS^} (@code{gnatbind})
-@cindex Warnings
-Suppress all warning messages.
-
-@item ^-we^/WARNINGS=ERROR^
-@cindex @code{^-we^/WARNINGS=ERROR^} (@code{gnatbind})
-Treat any warning messages as fatal errors.
-
-@ifset vms
-@item /WARNINGS=NORMAL
-Standard mode with warnings generated, but warnings do not get treated
-as errors.
-@end ifset
-
-@item ^-t^/NOTIME_STAMP_CHECK^
-@cindex @code{^-t^/NOTIME_STAMP_CHECK^} (@code{gnatbind})
-@cindex Time stamp checks, in binder
-@cindex Binder consistency checks
-@cindex Consistency checks, in binder
-The binder performs a number of consistency checks including:
-
-@itemize @bullet
-@item
-Check that time stamps of a given source unit are consistent
-@item
-Check that checksums of a given source unit are consistent
-@item
-Check that consistent versions of @code{GNAT} were used for compilation
-@item
-Check consistency of configuration pragmas as required
-@end itemize
-
-@noindent
-Normally failure of such checks, in accordance with the consistency
-requirements of the Ada Reference Manual, causes error messages to be
-generated which abort the binder and prevent the output of a binder
-file and subsequent link to obtain an executable.
-
-The @code{^-t^/NOTIME_STAMP_CHECK^} switch converts these error messages
-into warnings, so that
-binding and linking can continue to completion even in the presence of such
-errors. The result may be a failed link (due to missing symbols), or a
-non-functional executable which has undefined semantics.
-@emph{This means that
-@code{^-t^/NOTIME_STAMP_CHECK^} should be used only in unusual situations,
-with extreme care.}
-@end table
-
-@node Elaboration Control
-@section Elaboration Control
-
-@noindent
-The following switches provide additional control over the elaboration
-order. For full details see @xref{Elaboration Order Handling in GNAT}.
-
-@table @code
-@item ^-p^/PESSIMISTIC_ELABORATION^
-@cindex @code{^-h^/PESSIMISTIC_ELABORATION^} (@code{gnatbind})
-Normally the binder attempts to choose an elaboration order that is
-likely to minimize the likelihood of an elaboration order error resulting
-in raising a @code{Program_Error} exception. This switch reverses the
-action of the binder, and requests that it deliberately choose an order
-that is likely to maximize the likelihood of an elaboration error.
-This is useful in ensuring portability and avoiding dependence on
-accidental fortuitous elaboration ordering.
-
-Normally it only makes sense to use the @code{-p} switch if dynamic
-elaboration checking is used (@option{-gnatE} switch used for compilation).
-This is because in the default static elaboration mode, all necessary
-@code{Elaborate_All} pragmas are implicitly inserted. These implicit
-pragmas are still respected by the binder in @code{-p} mode, so a
-safe elaboration order is assured.
-@end table
-
-@node Output Control
-@section Output Control
-
-@noindent
-The following switches allow additional control over the output
-generated by the binder.
-
-@table @code
-
-@item ^-A^/BIND_FILE=ADA^
-@cindex @code{^-A^/BIND_FILE=ADA^} (@code{gnatbind})
-Generate binder program in Ada (default). The binder program is named
-@file{b~@var{mainprog}.adb} by default. This can be changed with
-@code{-o} @code{gnatbind} option.
-
-@item ^-c^/NOOUTPUT^
-@cindex @code{^-c^/NOOUTPUT^} (@code{gnatbind})
-Check only. Do not generate the binder output file. In this mode the
-binder performs all error checks but does not generate an output file.
-
-@item ^-C^/BIND_FILE=C^
-@cindex @code{^-C^/BIND_FILE=C^} (@code{gnatbind})
-Generate binder program in C. The binder program is named
-@file{b_@var{mainprog}.c}. This can be changed with @code{-o} @code{gnatbind}
-option.
-
-@item ^-e^/ELABORATION_DEPENDENCIES^
-@cindex @code{^-e^/ELABORATION_DEPENDENCIES^} (@code{gnatbind})
-Output complete list of elaboration-order dependencies, showing the
-reason for each dependency. This output can be rather extensive but may
-be useful in diagnosing problems with elaboration order. The output is
-written to @file{stdout}.
-
-@item ^-h^/HELP^
-@cindex @code{^-h^/HELP^} (@code{gnatbind})
-Output usage information. The output is written to @file{stdout}.
-
-@item ^-K^/LINKER_OPTION_LIST^
-@cindex @code{^-K^/LINKER_OPTION_LIST^} (@code{gnatbind})
-Output linker options to @file{stdout}. Includes library search paths,
-contents of pragmas Ident and Linker_Options, and libraries added
-by @code{gnatbind}.
-
-@item ^-l^/ORDER_OF_ELABORATION^
-@cindex @code{^-l^/ORDER_OF_ELABORATION^} (@code{gnatbind})
-Output chosen elaboration order. The output is written to @file{stdout}.
-
-@item ^-O^/OBJECT_LIST^
-@cindex @code{^-O^/OBJECT_LIST^} (@code{gnatbind})
-Output full names of all the object files that must be linked to provide
-the Ada component of the program. The output is written to @file{stdout}.
-This list includes the files explicitly supplied and referenced by the user
-as well as implicitly referenced run-time unit files. The latter are
-omitted if the corresponding units reside in shared libraries. The
-directory names for the run-time units depend on the system configuration.
-
-@item ^-o ^/OUTPUT=^@var{file}
-@cindex @code{^-o^/OUTPUT^} (@code{gnatbind})
-Set name of output file to @var{file} instead of the normal
-@file{b~@var{mainprog}.adb} default. Note that @var{file} denote the Ada
-binder generated body filename. In C mode you would normally give
-@var{file} an extension of @file{.c} because it will be a C source program.
-Note that if this option is used, then linking must be done manually.
-It is not possible to use gnatlink in this case, since it cannot locate
-the binder file.
-
-@item ^-r^/RESTRICTION_LIST^
-@cindex @code{^-r^/RESTRICTION_LIST^} (@code{gnatbind})
-Generate list of @code{pragma Rerstrictions} that could be applied to
-the current unit. This is useful for code audit purposes, and also may
-be used to improve code generation in some cases.
-
-@end table
-
-@node Binding with Non-Ada Main Programs
-@section Binding with Non-Ada Main Programs
-
-@noindent
-In our description so far we have assumed that the main
-program is in Ada, and that the task of the binder is to generate a
-corresponding function @code{main} that invokes this Ada main
-program. GNAT also supports the building of executable programs where
-the main program is not in Ada, but some of the called routines are
-written in Ada and compiled using GNAT (@pxref{Mixed Language Programming}).
-The following switch is used in this situation:
-
-@table @code
-@item ^-n^/NOMAIN^
-@cindex @code{^-n^/NOMAIN^} (@code{gnatbind})
-No main program. The main program is not in Ada.
-@end table
-
-@noindent
-In this case, most of the functions of the binder are still required,
-but instead of generating a main program, the binder generates a file
-containing the following callable routines:
-
-@table @code
-@item adainit
-@findex adainit
-You must call this routine to initialize the Ada part of the program by
-calling the necessary elaboration routines. A call to @code{adainit} is
-required before the first call to an Ada subprogram.
-
-Note that it is assumed that the basic execution environment must be setup
-to be appropriate for Ada execution at the point where the first Ada
-subprogram is called. In particular, if the Ada code will do any
-floating-point operations, then the FPU must be setup in an appropriate
-manner. For the case of the x86, for example, full precision mode is
-required. The procedure GNAT.Float_Control.Reset may be used to ensure
-that the FPU is in the right state.
-
-@item adafinal
-@findex adafinal
-You must call this routine to perform any library-level finalization
-required by the Ada subprograms. A call to @code{adafinal} is required
-after the last call to an Ada subprogram, and before the program
-terminates.
-@end table
-
-@noindent
-If the @code{^-n^/NOMAIN^} switch
-@cindex Binder, multiple input files
-is given, more than one ALI file may appear on
-the command line for @code{gnatbind}. The normal @dfn{closure}
-calculation is performed for each of the specified units. Calculating
-the closure means finding out the set of units involved by tracing
-@code{with} references. The reason it is necessary to be able to
-specify more than one ALI file is that a given program may invoke two or
-more quite separate groups of Ada units.
-
-The binder takes the name of its output file from the last specified ALI
-file, unless overridden by the use of the @code{^-o file^/OUTPUT=file^}.
-The output is an Ada unit in source form that can
-be compiled with GNAT unless the -C switch is used in which case the
-output is a C source file, which must be compiled using the C compiler.
-This compilation occurs automatically as part of the @code{gnatlink}
-processing.
-
-Currently the GNAT run time requires a FPU using 80 bits mode
-precision. Under targets where this is not the default it is required to
-call GNAT.Float_Control.Reset before using floating point numbers (this
-include float computation, float input and output) in the Ada code. A
-side effect is that this could be the wrong mode for the foreign code
-where floating point computation could be broken after this call.
-
-@node Binding Programs with No Main Subprogram
-@section Binding Programs with No Main Subprogram
-
-@noindent
-It is possible to have an Ada program which does not have a main
-subprogram. This program will call the elaboration routines of all the
-packages, then the finalization routines.
-
-The following switch is used to bind programs organized in this manner:
-
-@table @code
-@item ^-z^/ZERO_MAIN^
-@cindex @code{^-z^/ZERO_MAIN^} (@code{gnatbind})
-Normally the binder checks that the unit name given on the command line
-corresponds to a suitable main subprogram. When this switch is used,
-a list of ALI files can be given, and the execution of the program
-consists of elaboration of these units in an appropriate order.
-@end table
-
-@node Summary of Binder Switches
-@section Summary of Binder Switches
-
-@noindent
-The following are the switches available with @code{gnatbind}:
-
-@table @code
-@item ^-aO^/OBJECT_SEARCH^
-Specify directory to be searched for ALI files.
-
-@item ^-aI^/SOURCE_SEARCH^
-Specify directory to be searched for source file.
-
-@item ^-A^/BIND_FILE=ADA^
-Generate binder program in Ada (default)
-
-@item ^-b^/REPORT_ERRORS=BRIEF^
-Generate brief messages to @file{stderr} even if verbose mode set.
-
-@item ^-c^/NOOUTPUT^
-Check only, no generation of binder output file.
-
-@item ^-C^/BIND_FILE=C^
-Generate binder program in C
-
-@item ^-e^/ELABORATION_DEPENDENCIES^
-Output complete list of elaboration-order dependencies.
-
-@item -E
-Store tracebacks in exception occurrences when the target supports it.
-This is the default with the zero cost exception mechanism.
-This option is currently supported on the following targets:
-all x86 ports, Solaris, Windows, HP-UX, AIX, PowerPC VxWorks and Alpha VxWorks.
-See also the packages @code{GNAT.Traceback} and
-@code{GNAT.Traceback.Symbolic} for more information.
-Note that on x86 ports, you must not use @code{-fomit-frame-pointer}
-@code{gcc} option.
-
-@item -h
-Output usage (help) information
-
-@item ^-I^/SEARCH^
-Specify directory to be searched for source and ALI files.
-
-@item ^-I-^/NOCURRENT_DIRECTORY^
-Do not look for sources in the current directory where @code{gnatbind} was
-invoked, and do not look for ALI files in the directory containing the
-ALI file named in the @code{gnatbind} command line.
-
-@item ^-l^/ORDER_OF_ELABORATION^
-Output chosen elaboration order.
-
-@item -Lxxx
-Binds the units for library building. In this case the adainit and
-adafinal procedures (See @pxref{Binding with Non-Ada Main Programs})
-are renamed to xxxinit and xxxfinal. Implies -n.
-@ifclear vms
-See @pxref{GNAT and Libraries} for more details.
-@end ifclear
-
-@item -Mxyz
-Rename generated main program from main to xyz
-
-@item ^-m^/ERROR_LIMIT=^@var{n}
-Limit number of detected errors to @var{n} (1-999).
-@ifset wnt
-Furthermore, under Windows, the sources pointed to by the libraries path
-set in the registry are not searched for.
-@end ifset
-
-@item ^-n^/NOMAIN^
-No main program.
-
-@item -nostdinc
-Do not look for sources in the system default directory.
-
-@item -nostdlib
-Do not look for library files in the system default directory.
-
-@item --RTS=@var{rts-path}
-@cindex @code{--RTS} (@code{gnatbind})
-Specifies the default location of the runtime library. Same meaning as the
-equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
-
-@item ^-o ^/OUTPUT=^@var{file}
-Name the output file @var{file} (default is @file{b~@var{xxx}.adb}).
-Note that if this option is used, then linking must be done manually,
-gnatlink cannot be used.
-
-@item ^-O^/OBJECT_LIST^
-Output object list.
-
-@item -p
-Pessimistic (worst-case) elaboration order
-
-@item ^-s^/READ_SOURCES=ALL^
-Require all source files to be present.
-
-@ifclear vms
-@item -static
-Link against a static GNAT run time.
-
-@item -shared
-Link against a shared GNAT run time when available.
-@end ifclear
-
-@item ^-t^/NOTIME_STAMP_CHECK^
-Tolerate time stamp and other consistency errors
-
-@item -T@var{n}
-Set the time slice value to n microseconds. A value of zero means no time
-slicing and also indicates to the tasking run time to match as close as
-possible to the annex D requirements of the RM.
-
-@item ^-v^/REPORT_ERRORS=VERBOSE^
-Verbose mode. Write error messages, header, summary output to
-@file{stdout}.
-
-@ifclear vms
-@item -w@var{x}
-Warning mode (@var{x}=s/e for suppress/treat as error)
-@end ifclear
-
-@ifset vms
-@item /WARNINGS=NORMAL
-Normal warnings mode. Warnings are issued but ignored
-
-@item /WARNINGS=SUPPRESS
-All warning messages are suppressed
-
-@item /WARNINGS=ERROR
-Warning messages are treated as fatal errors
-@end ifset
-
-@item ^-x^/READ_SOURCES=NONE^
-Exclude source files (check object consistency only).
-
-@ifset vms
-@item /READ_SOURCES=AVAILABLE
-Default mode, in which sources are checked for consistency only if
-they are available.
-@end ifset
-
-@item ^-z^/ZERO_MAIN^
-No main subprogram.
-
-@end table
-
-@ifclear vms
-You may obtain this listing by running the program @code{gnatbind} with
-no arguments.
-@end ifclear
-
-@node Command-Line Access
-@section Command-Line Access
-
-@noindent
-The package @code{Ada.Command_Line} provides access to the command-line
-arguments and program name. In order for this interface to operate
-correctly, the two variables
-
-@smallexample
-@group
-@cartouche
-int gnat_argc;
-char **gnat_argv;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-@findex gnat_argv
-@findex gnat_argc
-are declared in one of the GNAT library routines. These variables must
-be set from the actual @code{argc} and @code{argv} values passed to the
-main program. With no @code{^n^/NOMAIN^} present, @code{gnatbind}
-generates the C main program to automatically set these variables.
-If the @code{^n^/NOMAIN^} switch is used, there is no automatic way to
-set these variables. If they are not set, the procedures in
-@code{Ada.Command_Line} will not be available, and any attempt to use
-them will raise @code{Constraint_Error}. If command line access is
-required, your main program must set @code{gnat_argc} and
-@code{gnat_argv} from the @code{argc} and @code{argv} values passed to
-it.
-
-@node Search Paths for gnatbind
-@section Search Paths for @code{gnatbind}
-
-@noindent
-The binder takes the name of an ALI file as its argument and needs to
-locate source files as well as other ALI files to verify object consistency.
-
-For source files, it follows exactly the same search rules as @code{gcc}
-(@pxref{Search Paths and the Run-Time Library (RTL)}). For ALI files the
-directories searched are:
-
-@enumerate
-@item
-The directory containing the ALI file named in the command line, unless
-the switch @code{^-I-^/NOCURRENT_DIRECTORY^} is specified.
-
-@item
-All directories specified by @code{^-I^/SEARCH^}
-switches on the @code{gnatbind}
-command line, in the order given.
-
-@item
-@findex ADA_OBJECTS_PATH
-Each of the directories listed in the value of the
-@code{ADA_OBJECTS_PATH} ^environment variable^logical name^.
-@ifclear vms
-Construct this value
-exactly as the @code{PATH} environment variable: a list of directory
-names separated by colons (semicolons when working with the NT version
-of GNAT).
-@end ifclear
-@ifset vms
-Normally, define this value as a logical name containing a comma separated
-list of directory names.
-
-This variable can also be defined by means of an environment string
-(an argument to the DEC C exec* set of functions).
-
-Logical Name:
-@smallexample
-DEFINE ANOTHER_PATH FOO:[BAG]
-DEFINE ADA_OBJECTS_PATH ANOTHER_PATH,FOO:[BAM],FOO:[BAR]
-@end smallexample
-
-By default, the path includes GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
-first, followed by the standard Ada 95
-libraries in GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB].
-If this is not redefined, the user will obtain the DEC Ada83 IO packages
-(Text_IO, Sequential_IO, etc)
-instead of the Ada95 packages. Thus, in order to get the Ada 95
-packages by default, ADA_OBJECTS_PATH must be redefined.
-@end ifset
-
-@item
-The content of the "ada_object_path" file which is part of the GNAT
-installation tree and is used to store standard libraries such as the
-GNAT Run Time Library (RTL) unless the switch @code{-nostdlib} is
-specified.
-@ifclear vms
-@ref{Installing an Ada Library}
-@end ifclear
-@end enumerate
-
-@noindent
-In the binder the switch @code{^-I^/SEARCH^}
-is used to specify both source and
-library file paths. Use @code{^-aI^/SOURCE_SEARCH^}
-instead if you want to specify
-source paths only, and @code{^-aO^/LIBRARY_SEARCH^}
-if you want to specify library paths
-only. This means that for the binder
-@code{^-I^/SEARCH=^}@var{dir} is equivalent to
-@code{^-aI^/SOURCE_SEARCH=^}@var{dir}
-@code{^-aO^/OBJECT_SEARCH=^}@var{dir}.
-The binder generates the bind file (a C language source file) in the
-current working directory.
-
-@findex Ada
-@findex System
-@findex Interfaces
-@findex GNAT
-The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
-children make up the GNAT Run-Time Library, together with the package
-GNAT and its children, which contain a set of useful additional
-library functions provided by GNAT. The sources for these units are
-needed by the compiler and are kept together in one directory. The ALI
-files and object files generated by compiling the RTL are needed by the
-binder and the linker and are kept together in one directory, typically
-different from the directory containing the sources. In a normal
-installation, you need not specify these directory names when compiling
-or binding. Either the environment variables or the built-in defaults
-cause these files to be found.
-
-Besides simplifying access to the RTL, a major use of search paths is
-in compiling sources from multiple directories. This can make
-development environments much more flexible.
-
-@node Examples of gnatbind Usage
-@section Examples of @code{gnatbind} Usage
-
-@noindent
-This section contains a number of examples of using the GNAT binding
-utility @code{gnatbind}.
-
-@table @code
-@item gnatbind hello
-The main program @code{Hello} (source program in @file{hello.adb}) is
-bound using the standard switch settings. The generated main program is
-@file{b~hello.adb}. This is the normal, default use of the binder.
-
-@ifclear vms
-@item gnatbind hello -o mainprog.adb
-@end ifclear
-@ifset vms
-@item gnatbind HELLO.ALI /OUTPUT=Mainprog.ADB
-@end ifset
-The main program @code{Hello} (source program in @file{hello.adb}) is
-bound using the standard switch settings. The generated main program is
-@file{mainprog.adb} with the associated spec in
-@file{mainprog.ads}. Note that you must specify the body here not the
-spec, in the case where the output is in Ada. Note that if this option
-is used, then linking must be done manually, since gnatlink will not
-be able to find the generated file.
-
-@ifclear vms
-@item gnatbind main -C -o mainprog.c -x
-@end ifclear
-@ifset vms
-@item gnatbind MAIN.ALI /BIND_FILE=C /OUTPUT=Mainprog.C /READ_SOURCES=NONE
-@end ifset
-The main program @code{Main} (source program in
-@file{main.adb}) is bound, excluding source files from the
-consistency checking, generating
-the file @file{mainprog.c}.
-
-@ifclear vms
-@item gnatbind -x main_program -C -o mainprog.c
-This command is exactly the same as the previous example. Switches may
-appear anywhere in the command line, and single letter switches may be
-combined into a single switch.
-@end ifclear
-
-@ifclear vms
-@item gnatbind -n math dbase -C -o ada-control.c
-@end ifclear
-@ifset vms
-@item gnatbind /NOMAIN math dbase /BIND_FILE=C /OUTPUT=ada-control.c
-@end ifset
-The main program is in a language other than Ada, but calls to
-subprograms in packages @code{Math} and @code{Dbase} appear. This call
-to @code{gnatbind} generates the file @file{ada-control.c} containing
-the @code{adainit} and @code{adafinal} routines to be called before and
-after accessing the Ada units.
-@end table
-
-@node Linking Using gnatlink
-@chapter Linking Using @code{gnatlink}
-@findex gnatlink
-
-@noindent
-This chapter discusses @code{gnatlink}, a utility program used to link
-Ada programs and build an executable file. This is a simple program
-that invokes the Unix linker (via the @code{gcc}
-command) with a correct list of object files and library references.
-@code{gnatlink} automatically determines the list of files and
-references for the Ada part of a program. It uses the binder file
-generated by the binder to determine this list.
-
-@menu
-* Running gnatlink::
-* Switches for gnatlink::
-* Setting Stack Size from gnatlink::
-* Setting Heap Size from gnatlink::
-@end menu
-
-@node Running gnatlink
-@section Running @code{gnatlink}
-
-@noindent
-The form of the @code{gnatlink} command is
-
-@smallexample
-$ gnatlink [@var{switches}] @var{mainprog}[.ali] [@var{non-Ada objects}]
- [@var{linker options}]
-@end smallexample
-
-@noindent
-@file{@var{mainprog}.ali} references the ALI file of the main program.
-The @file{.ali} extension of this file can be omitted. From this
-reference, @code{gnatlink} locates the corresponding binder file
-@file{b~@var{mainprog}.adb} and, using the information in this file along
-with the list of non-Ada objects and linker options, constructs a Unix
-linker command file to create the executable.
-
-The arguments following @file{@var{mainprog}.ali} are passed to the
-linker uninterpreted. They typically include the names of object files
-for units written in other languages than Ada and any library references
-required to resolve references in any of these foreign language units,
-or in @code{pragma Import} statements in any Ada units.
-
-@var{linker options} is an optional list of linker specific
-switches. The default linker called by gnatlink is @var{gcc} which in
-turn calls the appropriate system linker usually called
-@var{ld}. Standard options for the linker such as @code{-lmy_lib} or
-@code{-Ldir} can be added as is. For options that are not recognized by
-@var{gcc} as linker options, the @var{gcc} switches @code{-Xlinker} or
-@code{-Wl,} shall be used. Refer to the GCC documentation for
-details. Here is an example showing how to generate a linker map
-assuming that the underlying linker is GNU ld:
-
-@smallexample
-$ gnatlink my_prog -Wl,-Map,MAPFILE
-@end smallexample
-
-Using @var{linker options} it is possible to set the program stack and
-heap size. See @pxref{Setting Stack Size from gnatlink} and
-@pxref{Setting Heap Size from gnatlink}.
-
-@code{gnatlink} determines the list of objects required by the Ada
-program and prepends them to the list of objects passed to the linker.
-@code{gnatlink} also gathers any arguments set by the use of
-@code{pragma Linker_Options} and adds them to the list of arguments
-presented to the linker.
-
-@ifset vms
-@code{gnatlink} accepts the following types of extra files on the command
-line: objects (.OBJ), libraries (.OLB), shareable images (.EXE), and
-options files (.OPT). These are recognized and handled according to their
-extension.
-@end ifset
-
-@node Switches for gnatlink
-@section Switches for @code{gnatlink}
-
-@noindent
-The following switches are available with the @code{gnatlink} utility:
-
-@table @code
-
-@item ^-A^/BIND_FILE=ADA^
-@cindex @code{^-A^/BIND_FILE=ADA^} (@code{gnatlink})
-The binder has generated code in Ada. This is the default.
-
-@item ^-C^/BIND_FILE=C^
-@cindex @code{^-C^/BIND_FILE=C^} (@code{gnatlink})
-If instead of generating a file in Ada, the binder has generated one in
-C, then the linker needs to know about it. Use this switch to signal
-to @code{gnatlink} that the binder has generated C code rather than
-Ada code.
-
-@item -f
-@cindex Command line length
-@cindex @code{-f} (@code{gnatlink})
-On some targets, the command line length is limited, and @code{gnatlink}
-will generate a separate file for the linker if the list of object files
-is too long. The @code{-f} flag forces this file to be generated even if
-the limit is not exceeded. This is useful in some cases to deal with
-special situations where the command line length is exceeded.
-
-@item ^-g^/DEBUG^
-@cindex Debugging information, including
-@cindex @code{^-g^/DEBUG^} (@code{gnatlink})
-The option to include debugging information causes the Ada bind file (in
-other words, @file{b~@var{mainprog}.adb}) to be compiled with
-@code{^-g^/DEBUG^}.
-In addition, the binder does not delete the @file{b~@var{mainprog}.adb},
-@file{b~@var{mainprog}.o} and @file{b~@var{mainprog}.ali} files.
-Without @code{^-g^/DEBUG^}, the binder removes these files by
-default. The same procedure apply if a C bind file was generated using
-@code{^-C^/BIND_FILE=C^} @code{gnatbind} option, in this case the filenames are
-@file{b_@var{mainprog}.c} and @file{b_@var{mainprog}.o}.
-
-@ifclear vms
-@item -n
-@cindex @code{-n} (@code{gnatlink})
-Do not compile the file generated by the binder. This may be used when
-a link is rerun with different options, but there is no need to recompile
-the binder file.
-@end ifclear
-
-@item ^-v^/VERBOSE^
-@cindex @code{^-v^/VERBOSE^} (@code{gnatlink})
-Causes additional information to be output, including a full list of the
-included object files. This switch option is most useful when you want
-to see what set of object files are being used in the link step.
-
-@ifclear vms
-@item -v -v
-@cindex @code{-v -v} (@code{gnatlink})
-Very verbose mode. Requests that the compiler operate in verbose mode when
-it compiles the binder file, and that the system linker run in verbose mode.
-@end ifclear
-
-@item ^-o ^/EXECUTABLE=^@var{exec-name}
-@cindex @code{^-o^/EXECUTABLE^} (@code{gnatlink})
-@var{exec-name} specifies an alternate name for the generated
-executable program. If this switch is omitted, the executable has the same
-name as the main unit. For example, @code{gnatlink try.ali} creates
-an executable called @file{^try^TRY.EXE^}.
-
-@ifclear vms
-@item -b @var{target}
-@cindex @code{-b} (@code{gnatlink})
-Compile your program to run on @var{target}, which is the name of a
-system configuration. You must have a GNAT cross-compiler built if
-@var{target} is not the same as your host system.
-
-@item -B@var{dir}
-@cindex @code{-B} (@code{gnatlink})
-Load compiler executables (for example, @code{gnat1}, the Ada compiler)
-from @var{dir} instead of the default location. Only use this switch
-when multiple versions of the GNAT compiler are available. See the
-@code{gcc} manual page for further details. You would normally use the
-@code{-b} or @code{-V} switch instead.
-
-@item --GCC=@var{compiler_name}
-@cindex @code{--GCC=compiler_name} (@code{gnatlink})
-Program used for compiling the binder file. The default is
-`@code{gcc}'. You need to use quotes around @var{compiler_name} if
-@code{compiler_name} contains spaces or other separator characters. As
-an example @code{--GCC="foo -x -y"} will instruct @code{gnatlink} to use
-@code{foo -x -y} as your compiler. Note that switch @code{-c} is always
-inserted after your command name. Thus in the above example the compiler
-command that will be used by @code{gnatlink} will be @code{foo -c -x -y}.
-If several @code{--GCC=compiler_name} are used, only the last
-@var{compiler_name} is taken into account. However, all the additional
-switches are also taken into account. Thus,
-@code{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
-@code{--GCC="bar -x -y -z -t"}.
-
-@item --LINK=@var{name}
-@cindex @code{--LINK=} (@code{gnatlink})
-@var{name} is the name of the linker to be invoked. This is especially
-useful in mixed language programs since languages such as c++ require
-their own linker to be used. When this switch is omitted, the default
-name for the linker is (@file{gcc}). When this switch is used, the
-specified linker is called instead of (@file{gcc}) with exactly the same
-parameters that would have been passed to (@file{gcc}) so if the desired
-linker requires different parameters it is necessary to use a wrapper
-script that massages the parameters before invoking the real linker. It
-may be useful to control the exact invocation by using the verbose
-switch.
-
-@end ifclear
-
-@ifset vms
-@item /DEBUG=TRACEBACK
-@cindex @code{/DEBUG=TRACEBACK} (@code{gnatlink})
-This qualifier causes sufficient information to be included in the
-executable file to allow a traceback, but does not include the full
-symbol information needed by the debugger.
-
-@item /IDENTIFICATION="<string>"
-"<string>" specifies the string to be stored in the image file identification
-field in the image header. It overrides any pragma Ident specified string.
-
-@item /NOINHIBIT-EXEC
-Generate the executable file even if there are linker warnings.
-
-@item /NOSTART_FILES
-Don't link in the object file containing the "main" transfer address.
-Used when linking with a foreign language main program compiled with a
-Digital compiler.
-
-@item /STATIC
-Prefer linking with object libraries over shareable images, even without
-/DEBUG.
-@end ifset
-
-@end table
-
-@node Setting Stack Size from gnatlink
-@section Setting Stack Size from @code{gnatlink}
-
-@noindent
-It is possible to specify the program stack size from @code{gnatlink}.
-Assuming that the underlying linker is GNU ld there is two ways to do so:
-
-@itemize @bullet
-
-@item using @code{-Xlinker} linker option
-
-@smallexample
-$ gnatlink hello -Xlinker --stack=0x10000,0x1000
-@end smallexample
-
-This set the stack reserve size to 0x10000 bytes and the stack commit
-size to 0x1000 bytes.
-
-@item using @code{-Wl} linker option
-
-@smallexample
-$ gnatlink hello -Wl,--stack=0x1000000
-@end smallexample
-
-This set the stack reserve size to 0x1000000 bytes. Note that with
-@code{-Wl} option it is not possible to set the stack commit size
-because the coma is a separator for this option.
-
-@end itemize
-
-@node Setting Heap Size from gnatlink
-@section Setting Heap Size from @code{gnatlink}
-
-@noindent
-It is possible to specify the program heap size from @code{gnatlink}.
-Assuming that the underlying linker is GNU ld there is two ways to do so:
-
-@itemize @bullet
-
-@item using @code{-Xlinker} linker option
-
-@smallexample
-$ gnatlink hello -Xlinker --heap=0x10000,0x1000
-@end smallexample
-
-This set the heap reserve size to 0x10000 bytes and the heap commit
-size to 0x1000 bytes.
-
-@item using @code{-Wl} linker option
-
-@smallexample
-$ gnatlink hello -Wl,--heap=0x1000000
-@end smallexample
-
-This set the heap reserve size to 0x1000000 bytes. Note that with
-@code{-Wl} option it is not possible to set the heap commit size
-because the coma is a separator for this option.
-
-@end itemize
-
-@node The GNAT Make Program gnatmake
-@chapter The GNAT Make Program @code{gnatmake}
-@findex gnatmake
-
-@menu
-* Running gnatmake::
-* Switches for gnatmake::
-* Mode Switches for gnatmake::
-* Notes on the Command Line::
-* How gnatmake Works::
-* Examples of gnatmake Usage::
-@end menu
-@noindent
-A typical development cycle when working on an Ada program consists of
-the following steps:
-
-@enumerate
-@item
-Edit some sources to fix bugs.
-
-@item
-Add enhancements.
-
-@item
-Compile all sources affected.
-
-@item
-Rebind and relink.
-
-@item
-Test.
-@end enumerate
-
-@noindent
-The third step can be tricky, because not only do the modified files
-@cindex Dependency rules
-have to be compiled, but any files depending on these files must also be
-recompiled. The dependency rules in Ada can be quite complex, especially
-in the presence of overloading, @code{use} clauses, generics and inlined
-subprograms.
-
-@code{gnatmake} automatically takes care of the third and fourth steps
-of this process. It determines which sources need to be compiled,
-compiles them, and binds and links the resulting object files.
-
-Unlike some other Ada make programs, the dependencies are always
-accurately recomputed from the new sources. The source based approach of
-the GNAT compilation model makes this possible. This means that if
-changes to the source program cause corresponding changes in
-dependencies, they will always be tracked exactly correctly by
-@code{gnatmake}.
-
-@node Running gnatmake
-@section Running @code{gnatmake}
-
-@noindent
-The usual form of the @code{gnatmake} command is
-
-@smallexample
-$ gnatmake [@var{switches}] @var{file_name} [@var{file_names}] [@var{mode_switches}]
-@end smallexample
-
-@noindent
-The only required argument is one @var{file_name}, which specifies
-a compilation unit that is a main program. Several @var{file_names} can be
-specified: this will result in several executables being built.
-If @code{switches} are present, they can be placed before the first
-@var{file_name}, between @var{file_names} or after the last @var{file_name}.
-If @var{mode_switches} are present, they must always be placed after
-the last @var{file_name} and all @code{switches}.
-
-If you are using standard file extensions (.adb and .ads), then the
-extension may be omitted from the @var{file_name} arguments. However, if
-you are using non-standard extensions, then it is required that the
-extension be given. A relative or absolute directory path can be
-specified in a @var{file_name}, in which case, the input source file will
-be searched for in the specified directory only. Otherwise, the input
-source file will first be searched in the directory where
-@code{gnatmake} was invoked and if it is not found, it will be search on
-the source path of the compiler as described in
-@ref{Search Paths and the Run-Time Library (RTL)}.
-
-When several @var{file_names} are specified, if an executable needs to be
-rebuilt and relinked, all subsequent executables will be rebuilt and
-relinked, even if this would not be absolutely necessary.
-
-All @code{gnatmake} output (except when you specify
-@code{^-M^/DEPENDENCIES_LIST^}) is to
-@file{stderr}. The output produced by the
-@code{^-M^/DEPENDENCIES_LIST^} switch is send to
-@file{stdout}.
-
-@node Switches for gnatmake
-@section Switches for @code{gnatmake}
-
-@noindent
-You may specify any of the following switches to @code{gnatmake}:
-
-@table @code
-@ifclear vms
-@item --GCC=@var{compiler_name}
-@cindex @code{--GCC=compiler_name} (@code{gnatmake})
-Program used for compiling. The default is `@code{gcc}'. You need to use
-quotes around @var{compiler_name} if @code{compiler_name} contains
-spaces or other separator characters. As an example @code{--GCC="foo -x
--y"} will instruct @code{gnatmake} to use @code{foo -x -y} as your
-compiler. Note that switch @code{-c} is always inserted after your
-command name. Thus in the above example the compiler command that will
-be used by @code{gnatmake} will be @code{foo -c -x -y}.
-If several @code{--GCC=compiler_name} are used, only the last
-@var{compiler_name} is taken into account. However, all the additional
-switches are also taken into account. Thus,
-@code{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
-@code{--GCC="bar -x -y -z -t"}.
-
-@item --GNATBIND=@var{binder_name}
-@cindex @code{--GNATBIND=binder_name} (@code{gnatmake})
-Program used for binding. The default is `@code{gnatbind}'. You need to
-use quotes around @var{binder_name} if @var{binder_name} contains spaces
-or other separator characters. As an example @code{--GNATBIND="bar -x
--y"} will instruct @code{gnatmake} to use @code{bar -x -y} as your
-binder. Binder switches that are normally appended by @code{gnatmake} to
-`@code{gnatbind}' are now appended to the end of @code{bar -x -y}.
-
-@item --GNATLINK=@var{linker_name}
-@cindex @code{--GNATLINK=linker_name} (@code{gnatmake})
-Program used for linking. The default is `@code{gnatlink}'. You need to
-use quotes around @var{linker_name} if @var{linker_name} contains spaces
-or other separator characters. As an example @code{--GNATLINK="lan -x
--y"} will instruct @code{gnatmake} to use @code{lan -x -y} as your
-linker. Linker switches that are normally appended by @code{gnatmake} to
-`@code{gnatlink}' are now appended to the end of @code{lan -x -y}.
-
-@end ifclear
-
-@item ^-a^/ALL_FILES^
-@cindex @code{^-a^/ALL_FILES^} (@code{gnatmake})
-Consider all files in the make process, even the GNAT internal system
-files (for example, the predefined Ada library files), as well as any
-locked files. Locked files are files whose ALI file is write-protected.
-By default,
-@code{gnatmake} does not check these files,
-because the assumption is that the GNAT internal files are properly up
-to date, and also that any write protected ALI files have been properly
-installed. Note that if there is an installation problem, such that one
-of these files is not up to date, it will be properly caught by the
-binder.
-You may have to specify this switch if you are working on GNAT
-itself. @code{^-a^/ALL_FILES^} is also useful in conjunction with
-@code{^-f^/FORCE_COMPILE^}
-if you need to recompile an entire application,
-including run-time files, using special configuration pragma settings,
-such as a non-standard @code{Float_Representation} pragma.
-By default
-@code{gnatmake ^-a^/ALL_FILES^} compiles all GNAT
-internal files with
-@ifclear vms
-@code{gcc -c -gnatpg} rather than @code{gcc -c}.
-@end ifclear
-@ifset vms
-the @code{/CHECKS=SUPPRESS_ALL /STYLE_CHECKS=GNAT} switch.
-@end ifset
-
-@item ^-b^/ACTIONS=BIND^
-@cindex @code{^-b^/ACTIONS=BIND^} (@code{gnatmake})
-Bind only. Can be combined with @code{^-c^/ACTIONS=COMPILE^} to do compilation
-and binding, but no link. Can be combined with @code{^-l^/ACTIONS=LINK^}
-to do binding and linking. When not combined with @code{^-c^/ACTIONS=COMPILE^}
-all the units in the closure of the main program must have been previously
-compiled and must be up to date. The root unit specified by @var{file_name}
-may be given without extension, with the source extension or, if no GNAT
-Project File is specified, with the ALI file extension.
-
-@item ^-c^/ACTIONS=COMPILE^
-@cindex @code{^-c^/ACTIONS=COMPILE^} (@code{gnatmake})
-Compile only. Do not perform binding, except when @code{^-b^/ACTIONS=BIND^}
-is also specified. Do not perform linking, except if both
-@code{^-b^/ACTIONS=BIND^} and
- @code{^-l^/ACTIONS=LINK^} are also specified.
-If the root unit specified by @var{file_name} is not a main unit, this is the
-default. Otherwise @code{gnatmake} will attempt binding and linking
-unless all objects are up to date and the executable is more recent than
-the objects.
-
-@item ^-C^/MAPPING^
-@cindex @code{^-C^/MAPPING^} (@code{gnatmake})
-Use a mapping file. A mapping file is a way to communicate to the compiler
-two mappings: from unit names to file names (without any directory information)
-and from file names to path names (with full directory information).
-These mappings are used by the compiler to short-circuit the path search.
-When @code{gnatmake} is invoked with this switch, it will create a mapping
-file, initially populated by the project manager, if @code{-P} is used,
-otherwise initially empty. Each invocation of the compiler will add the newly
-accessed sources to the mapping file. This will improve the source search
-during the next invocation of the compiler.
-
-@item ^-f^/FORCE_COMPILE^
-@cindex @code{^-f^/FORCE_COMPILE^} (@code{gnatmake})
-Force recompilations. Recompile all sources, even though some object
-files may be up to date, but don't recompile predefined or GNAT internal
-files or locked files (files with a write-protected ALI file),
-unless the @code{^-a^/ALL_FILES^} switch is also specified.
-
-@item
-@item ^-i^/IN_PLACE^
-@cindex @code{^-i^/IN_PLACE^} (@code{gnatmake})
-In normal mode, @code{gnatmake} compiles all object files and ALI files
-into the current directory. If the @code{^-i^/IN_PLACE^} switch is used,
-then instead object files and ALI files that already exist are overwritten
-in place. This means that once a large project is organized into separate
-directories in the desired manner, then @code{gnatmake} will automatically
-maintain and update this organization. If no ALI files are found on the
-Ada object path (@ref{Search Paths and the Run-Time Library (RTL)}),
-the new object and ALI files are created in the
-directory containing the source being compiled. If another organization
-is desired, where objects and sources are kept in different directories,
-a useful technique is to create dummy ALI files in the desired directories.
-When detecting such a dummy file, @code{gnatmake} will be forced to recompile
-the corresponding source file, and it will be put the resulting object
-and ALI files in the directory where it found the dummy file.
-
-@item ^-j^/PROCESSES=^@var{n}
-@cindex @code{^-j^/PROCESSES^} (@code{gnatmake})
-@cindex Parallel make
-Use @var{n} processes to carry out the (re)compilations. On a
-multiprocessor machine compilations will occur in parallel. In the
-event of compilation errors, messages from various compilations might
-get interspersed (but @code{gnatmake} will give you the full ordered
-list of failing compiles at the end). If this is problematic, rerun
-the make process with n set to 1 to get a clean list of messages.
-
-@item ^-k^/CONTINUE_ON_ERROR^
-@cindex @code{^-k^/CONTINUE_ON_ERROR^} (@code{gnatmake})
-Keep going. Continue as much as possible after a compilation error. To
-ease the programmer's task in case of compilation errors, the list of
-sources for which the compile fails is given when @code{gnatmake}
-terminates.
-
-If @code{gnatmake} is invoked with several @file{file_names} and with this
-switch, if there are compilation errors when building an executable,
-@code{gnatmake} will not attempt to build the following executables.
-
-@item ^-l^/ACTIONS=LINK^
-@cindex @code{^-l^/ACTIONS=LINK^} (@code{gnatmake})
-Link only. Can be combined with @code{^-b^/ACTIONS=BIND^} to binding
-and linking. Linking will not be performed if combined with
-@code{^-c^/ACTIONS=COMPILE^}
-but not with @code{^-b^/ACTIONS=BIND^}.
-When not combined with @code{^-b^/ACTIONS=BIND^}
-all the units in the closure of the main program must have been previously
-compiled and must be up to date, and the main program need to have been bound.
-The root unit specified by @var{file_name}
-may be given without extension, with the source extension or, if no GNAT
-Project File is specified, with the ALI file extension.
-
-@item ^-m^/MINIMAL_RECOMPILATION^
-@cindex @code{^-m^/MINIMAL_RECOMPILATION^} (@code{gnatmake})
-Specifies that the minimum necessary amount of recompilations
-be performed. In this mode @code{gnatmake} ignores time
-stamp differences when the only
-modifications to a source file consist in adding/removing comments,
-empty lines, spaces or tabs. This means that if you have changed the
-comments in a source file or have simply reformatted it, using this
-switch will tell gnatmake not to recompile files that depend on it
-(provided other sources on which these files depend have undergone no
-semantic modifications). Note that the debugging information may be
-out of date with respect to the sources if the @code{-m} switch causes
-a compilation to be switched, so the use of this switch represents a
-trade-off between compilation time and accurate debugging information.
-
-@item ^-M^/DEPENDENCIES_LIST^
-@cindex Dependencies, producing list
-@cindex @code{^-M^/DEPENDENCIES_LIST^} (@code{gnatmake})
-Check if all objects are up to date. If they are, output the object
-dependences to @file{stdout} in a form that can be directly exploited in
-a @file{Makefile}. By default, each source file is prefixed with its
-(relative or absolute) directory name. This name is whatever you
-specified in the various @code{^-aI^/SOURCE_SEARCH^}
-and @code{^-I^/SEARCH^} switches. If you use
-@code{gnatmake ^-M^/DEPENDENCIES_LIST^}
-@code{^-q^/QUIET^}
-(see below), only the source file names,
-without relative paths, are output. If you just specify the
-@code{^-M^/DEPENDENCIES_LIST^}
-switch, dependencies of the GNAT internal system files are omitted. This
-is typically what you want. If you also specify
-the @code{^-a^/ALL_FILES^} switch,
-dependencies of the GNAT internal files are also listed. Note that
-dependencies of the objects in external Ada libraries (see switch
-@code{^-aL^/SKIP_MISSING=^}@var{dir} in the following list) are never reported.
-
-@item ^-n^/DO_OBJECT_CHECK^
-@cindex @code{^-n^/DO_OBJECT_CHECK^} (@code{gnatmake})
-Don't compile, bind, or link. Checks if all objects are up to date.
-If they are not, the full name of the first file that needs to be
-recompiled is printed.
-Repeated use of this option, followed by compiling the indicated source
-file, will eventually result in recompiling all required units.
-
-@item ^-o ^/EXECUTABLE=^@var{exec_name}
-@cindex @code{^-o^/EXECUTABLE^} (@code{gnatmake})
-Output executable name. The name of the final executable program will be
-@var{exec_name}. If the @code{^-o^/EXECUTABLE^} switch is omitted the default
-name for the executable will be the name of the input file in appropriate form
-for an executable file on the host system.
-
-This switch cannot be used when invoking @code{gnatmake} with several
-@file{file_names}.
-
-@item ^-q^/QUIET^
-@cindex @code{^-q^/QUIET^} (@code{gnatmake})
-Quiet. When this flag is not set, the commands carried out by
-@code{gnatmake} are displayed.
-
-@item ^-s^/SWITCH_CHECK/^
-@cindex @code{^-s^/SWITCH_CHECK^} (@code{gnatmake})
-Recompile if compiler switches have changed since last compilation.
-All compiler switches but -I and -o are taken into account in the
-following way:
-orders between different ``first letter'' switches are ignored, but
-orders between same switches are taken into account. For example,
-@code{-O -O2} is different than @code{-O2 -O}, but @code{-g -O} is equivalent
-to @code{-O -g}.
-
-@item ^-u^/UNIQUE^
-@cindex @code{^-u^/UNIQUE^} (@code{gnatmake})
-Unique. Recompile at most the main file. It implies -c. Combined with
--f, it is equivalent to calling the compiler directly.
-
-@item ^-v^/REASONS^
-@cindex @code{^-v^/REASONS^} (@code{gnatmake})
-Verbose. Displays the reason for all recompilations @code{gnatmake}
-decides are necessary.
-
-@item ^-z^/NOMAIN^
-@cindex @code{^-z^/NOMAIN^} (@code{gnatmake})
-No main subprogram. Bind and link the program even if the unit name
-given on the command line is a package name. The resulting executable
-will execute the elaboration routines of the package and its closure,
-then the finalization routines.
-
-@item @code{gcc} @asis{switches}
-@ifclear vms
-The switch @code{-g} or any uppercase switch (other than @code{-A},
-@code{-L} or
-@code{-S}) or any switch that is more than one character is passed to
-@code{gcc} (e.g. @code{-O}, @option{-gnato,} etc.)
-@end ifclear
-@ifset vms
-Any qualifier that cannot be recognized as a qualifier for @code{GNAT MAKE}
-but is recognizable as a valid qualifier for @code{GNAT COMPILE} is
-automatically treated as a compiler switch, and passed on to all
-compilations that are carried out.
-@end ifset
-@end table
-
-@noindent
-Source and library search path switches:
-
-@table @code
-@item ^-aI^/SOURCE_SEARCH=^@var{dir}
-@cindex @code{^-aI^/SOURCE_SEARCH^} (@code{gnatmake})
-When looking for source files also look in directory @var{dir}.
-The order in which source files search is undertaken is
-described in @ref{Search Paths and the Run-Time Library (RTL)}.
-
-@item ^-aL^/SKIP_MISSING=^@var{dir}
-@cindex @code{^-aL^/SKIP_MISSING^} (@code{gnatmake})
-Consider @var{dir} as being an externally provided Ada library.
-Instructs @code{gnatmake} to skip compilation units whose @file{.ali}
-files have been located in directory @var{dir}. This allows you to have
-missing bodies for the units in @var{dir} and to ignore out of date bodies
-for the same units. You still need to specify
-the location of the specs for these units by using the switches
-@code{^-aI^/SOURCE_SEARCH=^@var{dir}}
-or @code{^-I^/SEARCH=^@var{dir}}.
-Note: this switch is provided for compatibility with previous versions
-of @code{gnatmake}. The easier method of causing standard libraries
-to be excluded from consideration is to write-protect the corresponding
-ALI files.
-
-@item ^-aO^/OBJECT_SEARCH=^@var{dir}
-@cindex @code{^-aO^/OBJECT_SEARCH^} (@code{gnatmake})
-When searching for library and object files, look in directory
-@var{dir}. The order in which library files are searched is described in
-@ref{Search Paths for gnatbind}.
-
-@item ^-A^/CONDITIONAL_SOURCE_SEARCH=^@var{dir}
-@cindex Search paths, for @code{gnatmake}
-@cindex @code{^-A^/CONDITIONAL_SOURCE_SEARCH^} (@code{gnatmake})
-Equivalent to @code{^-aL^/SKIP_MISSING=^@var{dir}
-^-aI^/SOURCE_SEARCH=^@var{dir}}.
-
-@item ^-I^/SEARCH=^@var{dir}
-@cindex @code{^-I^/SEARCH^} (@code{gnatmake})
-Equivalent to @code{^-aO^/OBJECT_SEARCH=^@var{dir}
-^-aI^/SOURCE_SEARCH=^@var{dir}}.
-
-@item ^-I-^/NOCURRENT_DIRECTORY^
-@cindex @code{^-I-^/NOCURRENT_DIRECTORY^} (@code{gnatmake})
-@cindex Source files, suppressing search
-Do not look for source files in the directory containing the source
-file named in the command line.
-Do not look for ALI or object files in the directory
-where @code{gnatmake} was invoked.
-
-@item ^-L^/LIBRARY_SEARCH=^@var{dir}
-@cindex @code{^-L^/LIBRARY_SEARCH^} (@code{gnatmake})
-@cindex Linker libraries
-Add directory @var{dir} to the list of directories in which the linker
-@ifset wnt
-Furthermore, under Windows, the sources pointed to by the libraries path
-set in the registry are not searched for.
-@end ifset
-will search for libraries. This is equivalent to
-@code{-largs ^-L^/LIBRARY_SEARCH=^}@var{dir}.
-
-@item -nostdinc
-@cindex @code{-nostdinc} (@code{gnatmake})
-Do not look for source files in the system default directory.
-
-@item -nostdlib
-@cindex @code{-nostdlib} (@code{gnatmake})
-Do not look for library files in the system default directory.
-
-@item --RTS=@var{rts-path}
-@cindex @code{--RTS} (@code{gnatmake})
-Specifies the default location of the runtime library. We look for the runtime
-in the following directories, and stop as soon as a valid runtime is found
-("adainclude" or "ada_source_path", and "adalib" or "ada_object_path" present):
-
-@itemize @bullet
-@item <current directory>/$rts_path
-
-@item <default-search-dir>/$rts_path
-
-@item <default-search-dir>/rts-$rts_path
-@end itemize
-
-@noindent
-The selected path is handled like a normal RTS path.
-
-@end table
-
-@node Mode Switches for gnatmake
-@section Mode Switches for @code{gnatmake}
-
-@noindent
-The mode switches (referred to as @code{mode_switches}) allow the
-inclusion of switches that are to be passed to the compiler itself, the
-binder or the linker. The effect of a mode switch is to cause all
-subsequent switches up to the end of the switch list, or up to the next
-mode switch, to be interpreted as switches to be passed on to the
-designated component of GNAT.
-
-@table @code
-@item -cargs @var{switches}
-@cindex @code{-cargs} (@code{gnatmake})
-Compiler switches. Here @var{switches} is a list of switches
-that are valid switches for @code{gcc}. They will be passed on to
-all compile steps performed by @code{gnatmake}.
-
-@item -bargs @var{switches}
-@cindex @code{-bargs} (@code{gnatmake})
-Binder switches. Here @var{switches} is a list of switches
-that are valid switches for @code{gcc}. They will be passed on to
-all bind steps performed by @code{gnatmake}.
-
-@item -largs @var{switches}
-@cindex @code{-largs} (@code{gnatmake})
-Linker switches. Here @var{switches} is a list of switches
-that are valid switches for @code{gcc}. They will be passed on to
-all link steps performed by @code{gnatmake}.
-@end table
-
-@node Notes on the Command Line
-@section Notes on the Command Line
-
-@noindent
-This section contains some additional useful notes on the operation
-of the @code{gnatmake} command.
-
-@itemize @bullet
-@item
-@cindex Recompilation, by @code{gnatmake}
-If @code{gnatmake} finds no ALI files, it recompiles the main program
-and all other units required by the main program.
-This means that @code{gnatmake}
-can be used for the initial compile, as well as during subsequent steps of
-the development cycle.
-
-@item
-If you enter @code{gnatmake @var{file}.adb}, where @file{@var{file}.adb}
-is a subunit or body of a generic unit, @code{gnatmake} recompiles
-@file{@var{file}.adb} (because it finds no ALI) and stops, issuing a
-warning.
-
-@item
-In @code{gnatmake} the switch @code{^-I^/SEARCH^}
-is used to specify both source and
-library file paths. Use @code{^-aI^/SOURCE_SEARCH^}
-instead if you just want to specify
-source paths only and @code{^-aO^/OBJECT_SEARCH^}
-if you want to specify library paths
-only.
-
-@item
-@code{gnatmake} examines both an ALI file and its corresponding object file
-for consistency. If an ALI is more recent than its corresponding object,
-or if the object file is missing, the corresponding source will be recompiled.
-Note that @code{gnatmake} expects an ALI and the corresponding object file
-to be in the same directory.
-
-@item
-@code{gnatmake} will ignore any files whose ALI file is write-protected.
-This may conveniently be used to exclude standard libraries from
-consideration and in particular it means that the use of the
-@code{^-f^/FORCE_COMPILE^} switch will not recompile these files
-unless @code{^-a^/ALL_FILES^} is also specified.
-
-@item
-@code{gnatmake} has been designed to make the use of Ada libraries
-particularly convenient. Assume you have an Ada library organized
-as follows: @var{^obj-dir^[OBJ_DIR]^} contains the objects and ALI files for
-of your Ada compilation units,
-whereas @var{^include-dir^[INCLUDE_DIR]^} contains the
-specs of these units, but no bodies. Then to compile a unit
-stored in @code{main.adb}, which uses this Ada library you would just type
-
-@smallexample
-@ifclear vms
-$ gnatmake -aI@var{include-dir} -aL@var{obj-dir} main
-@end ifclear
-@ifset vms
-$ gnatmake /SOURCE_SEARCH=@var{[INCLUDE_DIR]}
- /SKIP_MISSING=@var{[OBJ_DIR]} main
-@end ifset
-@end smallexample
-
-@item
-Using @code{gnatmake} along with the
-@code{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}
-switch provides a mechanism for avoiding unnecessary rcompilations. Using
-this switch,
-you can update the comments/format of your
-source files without having to recompile everything. Note, however, that
-adding or deleting lines in a source files may render its debugging
-info obsolete. If the file in question is a spec, the impact is rather
-limited, as that debugging info will only be useful during the
-elaboration phase of your program. For bodies the impact can be more
-significant. In all events, your debugger will warn you if a source file
-is more recent than the corresponding object, and alert you to the fact
-that the debugging information may be out of date.
-@end itemize
-
-@node How gnatmake Works
-@section How @code{gnatmake} Works
-
-@noindent
-Generally @code{gnatmake} automatically performs all necessary
-recompilations and you don't need to worry about how it works. However,
-it may be useful to have some basic understanding of the @code{gnatmake}
-approach and in particular to understand how it uses the results of
-previous compilations without incorrectly depending on them.
-
-First a definition: an object file is considered @dfn{up to date} if the
-corresponding ALI file exists and its time stamp predates that of the
-object file and if all the source files listed in the
-dependency section of this ALI file have time stamps matching those in
-the ALI file. This means that neither the source file itself nor any
-files that it depends on have been modified, and hence there is no need
-to recompile this file.
-
-@code{gnatmake} works by first checking if the specified main unit is up
-to date. If so, no compilations are required for the main unit. If not,
-@code{gnatmake} compiles the main program to build a new ALI file that
-reflects the latest sources. Then the ALI file of the main unit is
-examined to find all the source files on which the main program depends,
-and @code{gnatmake} recursively applies the above procedure on all these files.
-
-This process ensures that @code{gnatmake} only trusts the dependencies
-in an existing ALI file if they are known to be correct. Otherwise it
-always recompiles to determine a new, guaranteed accurate set of
-dependencies. As a result the program is compiled "upside down" from what may
-be more familiar as the required order of compilation in some other Ada
-systems. In particular, clients are compiled before the units on which
-they depend. The ability of GNAT to compile in any order is critical in
-allowing an order of compilation to be chosen that guarantees that
-@code{gnatmake} will recompute a correct set of new dependencies if
-necessary.
-
-When invoking @code{gnatmake} with several @var{file_names}, if a unit is
-imported by several of the executables, it will be recompiled at most once.
-
-@node Examples of gnatmake Usage
-@section Examples of @code{gnatmake} Usage
-
-@table @code
-@item gnatmake hello.adb
-Compile all files necessary to bind and link the main program
-@file{hello.adb} (containing unit @code{Hello}) and bind and link the
-resulting object files to generate an executable file @file{^hello^HELLO.EXE^}.
-
-@item gnatmake main1 main2 main3
-Compile all files necessary to bind and link the main programs
-@file{main1.adb} (containing unit @code{Main1}), @file{main2.adb}
-(containing unit @code{Main2}) and @file{main3.adb}
-(containing unit @code{Main3}) and bind and link the resulting object files
-to generate three executable files @file{^main1^MAIN1.EXE^},
-@file{^main2^MAIN2.EXE^}
-and @file{^main3^MAIN3.EXE^}.
-
-@ifclear vms
-@item gnatmake -q Main_Unit -cargs -O2 -bargs -l
-@end ifclear
-
-@ifset vms
-@item gnatmake Main_Unit /QUIET /COMPILER_QUALIFIERS /OPTIMIZE=ALL /BINDER_QUALIFIERS /ORDER_OF_ELABORATION
-@end ifset
-Compile all files necessary to bind and link the main program unit
-@code{Main_Unit} (from file @file{main_unit.adb}). All compilations will
-be done with optimization level 2 and the order of elaboration will be
-listed by the binder. @code{gnatmake} will operate in quiet mode, not
-displaying commands it is executing.
-@end table
-
-@node Renaming Files Using gnatchop
-@chapter Renaming Files Using @code{gnatchop}
-@findex gnatchop
-
-@noindent
-This chapter discusses how to handle files with multiple units by using
-the @code{gnatchop} utility. This utility is also useful in renaming
-files to meet the standard GNAT default file naming conventions.
-
-@menu
-* Handling Files with Multiple Units::
-* Operating gnatchop in Compilation Mode::
-* Command Line for gnatchop::
-* Switches for gnatchop::
-* Examples of gnatchop Usage::
-@end menu
-
-@node Handling Files with Multiple Units
-@section Handling Files with Multiple Units
-
-@noindent
-The basic compilation model of GNAT requires that a file submitted to the
-compiler have only one unit and there be a strict correspondence
-between the file name and the unit name.
-
-The @code{gnatchop} utility allows both of these rules to be relaxed,
-allowing GNAT to process files which contain multiple compilation units
-and files with arbitrary file names. @code{gnatchop}
-reads the specified file and generates one or more output files,
-containing one unit per file. The unit and the file name correspond,
-as required by GNAT.
-
-If you want to permanently restructure a set of "foreign" files so that
-they match the GNAT rules, and do the remaining development using the
-GNAT structure, you can simply use @code{gnatchop} once, generate the
-new set of files and work with them from that point on.
-
-Alternatively, if you want to keep your files in the "foreign" format,
-perhaps to maintain compatibility with some other Ada compilation
-system, you can set up a procedure where you use @code{gnatchop} each
-time you compile, regarding the source files that it writes as temporary
-files that you throw away.
-
-@node Operating gnatchop in Compilation Mode
-@section Operating gnatchop in Compilation Mode
-
-@noindent
-The basic function of @code{gnatchop} is to take a file with multiple units
-and split it into separate files. The boundary between files is reasonably
-clear, except for the issue of comments and pragmas. In default mode, the
-rule is that any pragmas between units belong to the previous unit, except
-that configuration pragmas always belong to the following unit. Any comments
-belong to the following unit. These rules
-almost always result in the right choice of
-the split point without needing to mark it explicitly and most users will
-find this default to be what they want. In this default mode it is incorrect to
-submit a file containing only configuration pragmas, or one that ends in
-configuration pragmas, to @code{gnatchop}.
-
-However, using a special option to activate "compilation mode",
-@code{gnatchop}
-can perform another function, which is to provide exactly the semantics
-required by the RM for handling of configuration pragmas in a compilation.
-In the absence of configuration pragmas (at the main file level), this
-option has no effect, but it causes such configuration pragmas to be handled
-in a quite different manner.
-
-First, in compilation mode, if @code{gnatchop} is given a file that consists of
-only configuration pragmas, then this file is appended to the
-@file{gnat.adc} file in the current directory. This behavior provides
-the required behavior described in the RM for the actions to be taken
-on submitting such a file to the compiler, namely that these pragmas
-should apply to all subsequent compilations in the same compilation
-environment. Using GNAT, the current directory, possibly containing a
-@file{gnat.adc} file is the representation
-of a compilation environment. For more information on the
-@file{gnat.adc} file, see the section on handling of configuration
-pragmas @pxref{Handling of Configuration Pragmas}.
-
-Second, in compilation mode, if @code{gnatchop}
-is given a file that starts with
-configuration pragmas, and contains one or more units, then these
-configuration pragmas are prepended to each of the chopped files. This
-behavior provides the required behavior described in the RM for the
-actions to be taken on compiling such a file, namely that the pragmas
-apply to all units in the compilation, but not to subsequently compiled
-units.
-
-Finally, if configuration pragmas appear between units, they are appended
-to the previous unit. This results in the previous unit being illegal,
-since the compiler does not accept configuration pragmas that follow
-a unit. This provides the required RM behavior that forbids configuration
-pragmas other than those preceding the first compilation unit of a
-compilation.
-
-For most purposes, @code{gnatchop} will be used in default mode. The
-compilation mode described above is used only if you need exactly
-accurate behavior with respect to compilations, and you have files
-that contain multiple units and configuration pragmas. In this
-circumstance the use of @code{gnatchop} with the compilation mode
-switch provides the required behavior, and is for example the mode
-in which GNAT processes the ACVC tests.
-
-@node Command Line for gnatchop
-@section Command Line for @code{gnatchop}
-
-@noindent
-The @code{gnatchop} command has the form:
-
-@smallexample
-$ gnatchop switches @var{file name} [@var{file name} @var{file name} ...]
- [@var{directory}]
-@end smallexample
-
-@noindent
-The only required argument is the file name of the file to be chopped.
-There are no restrictions on the form of this file name. The file itself
-contains one or more Ada units, in normal GNAT format, concatenated
-together. As shown, more than one file may be presented to be chopped.
-
-When run in default mode, @code{gnatchop} generates one output file in
-the current directory for each unit in each of the files.
-
-@var{directory}, if specified, gives the name of the directory to which
-the output files will be written. If it is not specified, all files are
-written to the current directory.
-
-For example, given a
-file called @file{hellofiles} containing
-
-@smallexample
-@group
-@cartouche
-@b{procedure} hello;
-
-@b{with} Text_IO; @b{use} Text_IO;
-@b{procedure} hello @b{is}
-@b{begin}
- Put_Line ("Hello");
-@b{end} hello;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-the command
-
-@smallexample
-$ gnatchop ^hellofiles^HELLOFILES.^
-@end smallexample
-
-@noindent
-generates two files in the current directory, one called
-@file{hello.ads} containing the single line that is the procedure spec,
-and the other called @file{hello.adb} containing the remaining text. The
-original file is not affected. The generated files can be compiled in
-the normal manner.
-
-@node Switches for gnatchop
-@section Switches for @code{gnatchop}
-
-@noindent
-@code{gnatchop} recognizes the following switches:
-
-@table @code
-
-@item ^-c^/COMPILATION^
-@cindex @code{^-c^/COMPILATION^} (@code{gnatchop})
-Causes @code{gnatchop} to operate in compilation mode, in which
-configuration pragmas are handled according to strict RM rules. See
-previous section for a full description of this mode.
-
-@ifclear vms
-@item -gnatxxx
-This passes the given @option{-gnatxxx} switch to @code{gnat} which is
-used to parse the given file. Not all @code{xxx} options make sense,
-but for example, the use of @option{-gnati2} allows @code{gnatchop} to
-process a source file that uses Latin-2 coding for identifiers.
-@end ifclear
-
-@item ^-h^/HELP^
-Causes @code{gnatchop} to generate a brief help summary to the standard
-output file showing usage information.
-
-@item ^-k@var{mm}^/FILE_NAME_MAX_LENGTH=@var{mm}^
-@cindex @code{^-k^/FILE_NAME_MAX_LENGTH^} (@code{gnatchop})
-Limit generated file names to the specified number @code{mm}
-of characters.
-This is useful if the
-resulting set of files is required to be interoperable with systems
-which limit the length of file names.
-@ifset vms
-If no value is given, or
-if no @code{/FILE_NAME_MAX_LENGTH} qualifier is given,
-a default of 39, suitable for OpenVMS Alpha
-Systems, is assumed
-@end ifset
-@ifclear vms
-No space is allowed between the @code{-k} and the numeric value. The numeric
-value may be omitted in which case a default of @code{-k8},
-suitable for use
-with DOS-like file systems, is used. If no @code{-k} switch
-is present then
-there is no limit on the length of file names.
-@end ifclear
-
-@item ^-p^/PRESERVE^
-@cindex @code{^-p^/PRESERVE^} (@code{gnatchop})
-Causes the file ^modification^creation^ time stamp of the input file to be
-preserved and used for the time stamp of the output file(s). This may be
-useful for preserving coherency of time stamps in an enviroment where
-@code{gnatchop} is used as part of a standard build process.
-
-@item ^-q^/QUIET^
-@cindex @code{^-q^/QUIET^} (@code{gnatchop})
-Causes output of informational messages indicating the set of generated
-files to be suppressed. Warnings and error messages are unaffected.
-
-@item ^-r^/REFERENCE^
-@cindex @code{^-r^/REFERENCE^} (@code{gnatchop})
-@findex Source_Reference
-Generate @code{Source_Reference} pragmas. Use this switch if the output
-files are regarded as temporary and development is to be done in terms
-of the original unchopped file. This switch causes
-@code{Source_Reference} pragmas to be inserted into each of the
-generated files to refers back to the original file name and line number.
-The result is that all error messages refer back to the original
-unchopped file.
-In addition, the debugging information placed into the object file (when
-the @code{^-g^/DEBUG^} switch of @code{gcc} or @code{gnatmake} is specified) also
-refers back to this original file so that tools like profilers and
-debuggers will give information in terms of the original unchopped file.
-
-If the original file to be chopped itself contains
-a @code{Source_Reference}
-pragma referencing a third file, then gnatchop respects
-this pragma, and the generated @code{Source_Reference} pragmas
-in the chopped file refer to the original file, with appropriate
-line numbers. This is particularly useful when @code{gnatchop}
-is used in conjunction with @code{gnatprep} to compile files that
-contain preprocessing statements and multiple units.
-
-@item ^-v^/VERBOSE^
-@cindex @code{^-v^/VERBOSE^} (@code{gnatchop})
-Causes @code{gnatchop} to operate in verbose mode. The version
-number and copyright notice are output, as well as exact copies of
-the gnat1 commands spawned to obtain the chop control information.
-
-@item ^-w^/OVERWRITE^
-@cindex @code{^-w^/OVERWRITE^} (@code{gnatchop})
-Overwrite existing file names. Normally @code{gnatchop} regards it as a
-fatal error if there is already a file with the same name as a
-file it would otherwise output, in other words if the files to be
-chopped contain duplicated units. This switch bypasses this
-check, and causes all but the last instance of such duplicated
-units to be skipped.
-
-@ifclear vms
-@item --GCC=xxxx
-@cindex @code{--GCC=} (@code{gnatchop})
-Specify the path of the GNAT parser to be used. When this switch is used,
-no attempt is made to add the prefix to the GNAT parser executable.
-@end ifclear
-@end table
-
-@node Examples of gnatchop Usage
-@section Examples of @code{gnatchop} Usage
-
-@table @code
-@ifset vms
-@item gnatchop /OVERWRITE HELLO_S.ADA [ICHBIAH.FILES]
-@end ifset
-@ifclear vms
-@item gnatchop -w hello_s.ada ichbiah/files
-@end ifclear
-
-Chops the source file @file{hello_s.ada}. The output files will be
-placed in the directory @file{^ichbiah/files^[ICHBIAH.FILES]^},
-overwriting any
-files with matching names in that directory (no files in the current
-directory are modified).
-
-@item gnatchop ^archive^ARCHIVE.^
-Chops the source file @file{^archive^ARCHIVE.^}
-into the current directory. One
-useful application of @code{gnatchop} is in sending sets of sources
-around, for example in email messages. The required sources are simply
-concatenated (for example, using a ^Unix @code{cat}^VMS @code{APPEND/NEW}^
-command), and then
-@code{gnatchop} is used at the other end to reconstitute the original
-file names.
-
-@item gnatchop file1 file2 file3 direc
-Chops all units in files @file{file1}, @file{file2}, @file{file3}, placing
-the resulting files in the directory @file{direc}. Note that if any units
-occur more than once anywhere within this set of files, an error message
-is generated, and no files are written. To override this check, use the
-@code{^-w^/OVERWRITE^} switch,
-in which case the last occurrence in the last file will
-be the one that is output, and earlier duplicate occurrences for a given
-unit will be skipped.
-@end table
-
-@node Configuration Pragmas
-@chapter Configuration Pragmas
-@cindex Configuration pragmas
-@cindex Pragmas, configuration
-
-@noindent
-In Ada 95, configuration pragmas include those pragmas described as
-such in the Ada 95 Reference Manual, as well as
-implementation-dependent pragmas that are configuration pragmas. See the
-individual descriptions of pragmas in the GNAT Reference Manual for
-details on these additional GNAT-specific configuration pragmas. Most
-notably, the pragma @code{Source_File_Name}, which allows
-specifying non-default names for source files, is a configuration
-pragma. The following is a complete list of configuration pragmas
-recognized by @code{GNAT}:
-
-@smallexample
- Ada_83
- Ada_95
- C_Pass_By_Copy
- Component_Alignment
- Discard_Names
- Elaboration_Checks
- Eliminate
- Extend_System
- Extensions_Allowed
- External_Name_Casing
- Float_Representation
- Initialize_Scalars
- License
- Locking_Policy
- Long_Float
- No_Run_Time
- Normalize_Scalars
- Polling
- Propagate_Exceptions
- Queuing_Policy
- Ravenscar
- Restricted_Run_Time
- Restrictions
- Reviewable
- Source_File_Name
- Style_Checks
- Suppress
- Task_Dispatching_Policy
- Unsuppress
- Use_VADS_Size
- Warnings
- Validity_Checks
-@end smallexample
-
-@menu
-* Handling of Configuration Pragmas::
-* The Configuration Pragmas Files::
-@end menu
-
-@node Handling of Configuration Pragmas
-@section Handling of Configuration Pragmas
-
-Configuration pragmas may either appear at the start of a compilation
-unit, in which case they apply only to that unit, or they may apply to
-all compilations performed in a given compilation environment.
-
-GNAT also provides the @code{gnatchop} utility to provide an automatic
-way to handle configuration pragmas following the semantics for
-compilations (that is, files with multiple units), described in the RM.
-See section @pxref{Operating gnatchop in Compilation Mode} for details.
-However, for most purposes, it will be more convenient to edit the
-@file{gnat.adc} file that contains configuration pragmas directly,
-as described in the following section.
-
-@node The Configuration Pragmas Files
-@section The Configuration Pragmas Files
-@cindex @file{gnat.adc}
-
-@noindent
-In GNAT a compilation environment is defined by the current
-directory at the time that a compile command is given. This current
-directory is searched for a file whose name is @file{gnat.adc}. If
-this file is present, it is expected to contain one or more
-configuration pragmas that will be applied to the current compilation.
-However, if the switch @option{-gnatA} is used, @file{gnat.adc} is not
-considered.
-
-Configuration pragmas may be entered into the @file{gnat.adc} file
-either by running @code{gnatchop} on a source file that consists only of
-configuration pragmas, or more conveniently by
-direct editing of the @file{gnat.adc} file, which is a standard format
-source file.
-
-In addition to @file{gnat.adc}, one additional file containing configuration
-pragmas may be applied to the current compilation using the switch
-@option{-gnatec}@var{path}. @var{path} must designate an existing file that
-contains only configuration pragmas. These configuration pragmas are
-in addition to those found in @file{gnat.adc} (provided @file{gnat.adc}
-is present and switch @option{-gnatA} is not used).
-
-It is allowed to specify several switches @option{-gnatec}, however only
-the last one on the command line will be taken into account.
-
-@ifset vms
-Of special interest to GNAT OpenVMS Alpha is the following configuration pragma:
-
-@smallexample
-@cartouche
-@b{pragma} Extend_System (Aux_DEC);
-@end cartouche
-@end smallexample
-
-@noindent
-In the presence of this pragma, GNAT adds to the definition of the
-predefined package SYSTEM all the additional types and subprograms that are
-defined in DEC Ada. See @pxref{Compatibility with DEC Ada} for details.
-@end ifset
-
-@node Handling Arbitrary File Naming Conventions Using gnatname
-@chapter Handling Arbitrary File Naming Conventions Using @code{gnatname}
-@cindex Arbitrary File Naming Conventions
-
-@menu
-* Arbitrary File Naming Conventions::
-* Running gnatname::
-* Switches for gnatname::
-* Examples of gnatname Usage::
-@end menu
-
-@node Arbitrary File Naming Conventions
-@section Arbitrary File Naming Conventions
-
-@noindent
-The GNAT compiler must be able to know the source file name of a compilation unit.
-When using the standard GNAT default file naming conventions (@code{.ads} for specs,
-@code{.adb} for bodies), the GNAT compiler does not need additional information.
-
-@noindent
-When the source file names do not follow the standard GNAT default file naming
-conventions, the GNAT compiler must be given additional information through
-a configuration pragmas file (see @ref{Configuration Pragmas}) or a project file.
-When the non standard file naming conventions are well-defined, a small number of
-pragmas @code{Source_File_Name} specifying a naming pattern
-(see @ref{Alternative File Naming Schemes}) may be sufficient. However,
-if the file naming conventions are irregular or arbitrary, a number
-of pragma @code{Source_File_Name} for individual compilation units must be defined.
-To help maintain the correspondence between compilation unit names and
-source file names within the compiler,
-GNAT provides a tool @code{gnatname} to generate the required pragmas for a
-set of files.
-
-@node Running gnatname
-@section Running @code{gnatname}
-
-@noindent
-The usual form of the @code{gnatname} command is
-
-@smallexample
-$ gnatname [@var{switches}] @var{naming_pattern} [@var{naming_patterns}]
-@end smallexample
-
-@noindent
-All of the arguments are optional. If invoked without any argument,
-@code{gnatname} will display its usage.
-
-@noindent
-When used with at least one naming pattern, @code{gnatname} will attempt to
-find all the compilation units in files that follow at least one of the
-naming patterns. To find these compilation units,
-@code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
-regular files.
-
-@noindent
-One or several Naming Patterns may be given as arguments to @code{gnatname}.
-Each Naming Pattern is enclosed between double quotes.
-A Naming Pattern is a regular expression similar to the wildcard patterns
-used in file names by the Unix shells or the DOS prompt.
-
-@noindent
-Examples of Naming Patterns are
-
-@smallexample
- "*.[12].ada"
- "*.ad[sb]*"
- "body_*" "spec_*"
-@end smallexample
-
-@noindent
-For a more complete description of the syntax of Naming Patterns, see the second kind
-of regular expressions described in @file{g-regexp.ads} (the "Glob" regular
-expressions).
-
-@noindent
-When invoked with no switches, @code{gnatname} will create a configuration
-pragmas file @file{gnat.adc} in the current working directory, with pragmas
-@code{Source_File_Name} for each file that contains a valid Ada unit.
-
-@node Switches for gnatname
-@section Switches for @code{gnatname}
-
-@noindent
-Switches for @code{gnatname} must precede any specified Naming Pattern.
-
-@noindent
-You may specify any of the following switches to @code{gnatname}:
-
-@table @code
-
-@item -c@file{file}
-@cindex @code{-c} (@code{gnatname})
-Create a configuration pragmas file @file{file} (instead of the default
-@file{gnat.adc}). There may be zero, one or more space between @code{-c} and
-@file{file}. @file{file} may include directory information. @file{file} must be
-writeable. There may be only one switch @code{-c}. When a switch @code{-c} is
-specified, no switch @code{-P} may be specified (see below).
-
-@item -d@file{dir}
-@cindex @code{-d} (@code{gnatname})
-Look for source files in directory @file{dir}. There may be zero, one or more spaces
-between @code{-d} and @file{dir}. When a switch @code{-d} is specified,
-the current working directory will not be searched for source files, unless it
-is explictly
-specified with a @code{-d} or @code{-D} switch. Several switches @code{-d} may be
-specified. If @file{dir} is a relative path, it is relative to the directory of
-the configuration pragmas file specified with switch @code{-c}, or to the directory
-of the project file specified with switch @code{-P} or, if neither switch @code{-c}
-nor switch @code{-P} are specified, it is relative to the current working
-directory. The directory
-specified with switch @code{-c} must exist and be readable.
-
-@item -D@file{file}
-@cindex @code{-D} (@code{gnatname})
-Look for source files in all directories listed in text file @file{file}. There may be
-zero, one or more spaces between @code{-d} and @file{dir}. @file{file}
-must be an existing, readable text file. Each non empty line in @file{file} must be
-a directory. Specifying switch @code{-D} is equivalent to specifying as many switches
-@code{-d} as there are non empty lines in @file{file}.
-
-@item -h
-@cindex @code{-h} (@code{gnatname})
-Output usage (help) information. The output is written to @file{stdout}.
-
-@item -P@file{proj}
-@cindex @code{-P} (@code{gnatname})
-Create or update project file @file{proj}. There may be zero, one or more space
-between @code{-P} and @file{proj}. @file{proj} may include directory information.
-@file{proj} must be writeable. There may be only one switch @code{-P}.
-When a switch @code{-P} is specified, no switch @code{-c} may be specified.
-
-@item -v
-@cindex @code{-v} (@code{gnatname})
-Verbose mode. Output detailed explanation of behavior to @file{stdout}. This includes
-name of the file written, the name of the directories to search and, for each file
-in those directories whose name matches at least one of the Naming Patterns, an
-indication of whether the file contains a unit, and if so the name of the unit.
-
-@item -v -v
-Very Verbose mode. In addition to the output produced in verbose mode, for each file
-in the searched directories whose name matches none of the Naming Patterns, an
-indication is given that there is no match.
-
-@item -x@file{pattern}
-Excluded patterns. Using this switch, it is possible to exclude some files
-that would match the name patterns. For example,
-@code{"gnatname -x "*_nt.ada" "*.ada"} will look for Ada units in all files
-with the @file{.ada} extension, except those whose names end with
-@file{_nt.ada}.
-
-@end table
-
-@node Examples of gnatname Usage
-@section Examples of @code{gnatname} Usage
-
-@smallexample
-$ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
-@end smallexample
-
-In this example, the directory @file{/home/me} must already exist and be
-writeable. In addition, the directory @file{/home/me/sources} (specified by
-@code{-d sources}) must exist and be readable. Note the optional spaces after
-@code{-c} and @code{-d}.
-
-@smallexample
-$ gnatname -P/home/me/proj -x "*_nt_body.ada" -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
-@end smallexample
-
-Note that several switches @code{-d} may be used, even in conjunction with one
-or several switches @code{-D}. Several Naming Patterns and one excluded pattern
-are used in this example.
-
-
-@c *****************************************
-@c * G N A T P r o j e c t M a n a g e r *
-@c *****************************************
-@node GNAT Project Manager
-@chapter GNAT Project Manager
-
-@menu
-* Introduction::
-* Examples of Project Files::
-* Project File Syntax::
-* Objects and Sources in Project Files::
-* Importing Projects::
-* Project Extension::
-* External References in Project Files::
-* Packages in Project Files::
-* Variables from Imported Projects::
-* Naming Schemes::
-* Library Projects::
-* Switches Related to Project Files::
-* Tools Supporting Project Files::
-* An Extended Example::
-* Project File Complete Syntax::
-@end menu
-
-
-@c ****************
-@c * Introduction *
-@c ****************
-
-@node Introduction
-@section Introduction
-
-@noindent
-This chapter describes GNAT's @emph{Project Manager}, a facility that
-lets you configure various properties for a collection of source files. In
-particular, you can specify:
-@itemize @bullet
-@item
-The directory or set of directories containing the source files, and/or the
-names of the specific source files themselves
-@item
-The directory in which the compiler's output
-(@file{ALI} files, object files, tree files) will be placed
-@item
-The directory in which the executable programs will be placed
-@item
-Switch settings for any of the project-enabled tools (@command{gnatmake},
-compiler, binder, linker, @code{gnatls}, @code{gnatxref}, @code{gnatfind});
-you can apply these settings either globally or to individual units
-@item
-The source files containing the main subprogram(s) to be built
-@item
-The source programming language(s) (currently Ada and/or C)
-@item
-Source file naming conventions; you can specify these either globally or for
-individual units
-@end itemize
-
-@menu
-* Project Files::
-@end menu
-
-@node Project Files
-@subsection Project Files
-
-@noindent
-A @dfn{project} is a specific set of values for these properties. You can
-define a project's settings in a @dfn{project file}, a text file with an
-Ada-like syntax; a property value is either a string or a list of strings.
-Properties that are not explicitly set receive default values. A project
-file may interrogate the values of @dfn{external variables} (user-defined
-command-line switches or environment variables), and it may specify property
-settings conditionally, based on the value of such variables.
-
-In simple cases, a project's source files depend only on other source files
-in the same project, or on the predefined libraries. ("Dependence" is in
-the technical sense; for example, one Ada unit "with"ing another.) However,
-the Project Manager also allows much more sophisticated arrangements,
-with the source files in one project depending on source files in other
-projects:
-@itemize @bullet
-@item
-One project can @emph{import} other projects containing needed source files.
-@item
-You can organize GNAT projects in a hierarchy: a @emph{child} project
-can extend a @emph{parent} project, inheriting the parent's source files and
-optionally overriding any of them with alternative versions
-@end itemize
-
-@noindent
-More generally, the Project Manager lets you structure large development
-efforts into hierarchical subsystems, with build decisions deferred to the
-subsystem level and thus different compilation environments (switch settings)
-used for different subsystems.
-
-The Project Manager is invoked through the @option{-P@emph{projectfile}}
-switch to @command{gnatmake} or to the @command{gnat} front driver.
-If you want to define (on the command line) an external variable that is
-queried by the project file, additionally use the
-@option{-X@emph{vbl}=@emph{value}} switch.
-The Project Manager parses and interprets the project file, and drives the
-invoked tool based on the project settings.
-
-The Project Manager supports a wide range of development strategies,
-for systems of all sizes. Some typical practices that are easily handled:
-@itemize @bullet
-@item
-Using a common set of source files, but generating object files in different
-directories via different switch settings
-@item
-Using a mostly-shared set of source files, but with different versions of
-some unit or units
-@end itemize
-
-@noindent
-The destination of an executable can be controlled inside a project file
-using the @option{-o} switch. In the absence of such a switch either inside
-the project file or on the command line, any executable files generated by
-@command{gnatmake} will be placed in the directory @code{Exec_Dir} specified
-in the project file. If no @code{Exec_Dir} is specified, they will be placed
-in the object directory of the project.
-
-You can use project files to achieve some of the effects of a source
-versioning system (for example, defining separate projects for
-the different sets of sources that comprise different releases) but the
-Project Manager is independent of any source configuration management tools
-that might be used by the developers.
-
-The next section introduces the main features of GNAT's project facility
-through a sequence of examples; subsequent sections will present the syntax
-and semantics in more detail.
-
-
-@c *****************************
-@c * Examples of Project Files *
-@c *****************************
-
-@node Examples of Project Files
-@section Examples of Project Files
-@noindent
-This section illustrates some of the typical uses of project files and
-explains their basic structure and behavior.
-
-@menu
-* Common Sources with Different Switches and Different Output Directories::
-* Using External Variables::
-* Importing Other Projects::
-* Extending a Project::
-@end menu
-
-@node Common Sources with Different Switches and Different Output Directories
-@subsection Common Sources with Different Switches and Different Output Directories
-
-@menu
-* Source Files::
-* Specifying the Object Directory::
-* Specifying the Exec Directory::
-* Project File Packages::
-* Specifying Switch Settings::
-* Main Subprograms::
-* Source File Naming Conventions::
-* Source Language(s)::
-@end menu
-
-@noindent
-Assume that the Ada source files @file{pack.ads}, @file{pack.adb}, and
-@file{proc.adb} are in the @file{/common} directory. The file
-@file{proc.adb} contains an Ada main subprogram @code{Proc} that "with"s
-package @code{Pack}. We want to compile these source files under two sets
-of switches:
-@itemize @bullet
-@item
-When debugging, we want to pass the @option{-g} switch to @command{gnatmake},
-and the @option{-gnata}, @option{-gnato}, and @option{-gnatE} switches to the
-compiler; the compiler's output is to appear in @file{/common/debug}
-@item
-When preparing a release version, we want to pass the @option{-O2} switch to
-the compiler; the compiler's output is to appear in @file{/common/release}
-@end itemize
-
-@noindent
-The GNAT project files shown below, respectively @file{debug.gpr} and
-@file{release.gpr} in the @file{/common} directory, achieve these effects.
-
-Diagrammatically:
-@smallexample
-@group
-/common
- debug.gpr
- release.gpr
- pack.ads
- pack.adb
- proc.adb
-@end group
-@group
-/common/debug @{-g, -gnata, -gnato, -gnatE@}
- proc.ali, proc.o
- pack.ali, pack.o
-@end group
-@group
-/common/release @{-O2@}
- proc.ali, proc.o
- pack.ali, pack.o
-@end group
-@end smallexample
-Here are the project files:
-@smallexample
-@group
-project Debug is
- for Object_Dir use "debug";
- for Main use ("proc");
-
- package Builder is
- for Default_Switches ("Ada") use ("-g");
- end Builder;
-@end group
-
-@group
- package Compiler is
- for Default_Switches ("Ada")
- use ("-fstack-check", "-gnata", "-gnato", "-gnatE");
- end Compiler;
-end Debug;
-@end group
-@end smallexample
-
-@smallexample
-@group
-project Release is
- for Object_Dir use "release";
- for Exec_Dir use ".";
- for Main use ("proc");
-
- package Compiler is
- for Default_Switches ("Ada") use ("-O2");
- end Compiler;
-end Release;
-@end group
-@end smallexample
-
-@noindent
-The name of the project defined by @file{debug.gpr} is @code{"Debug"} (case
-insensitive), and analogously the project defined by @file{release.gpr} is
-@code{"Release"}. For consistency the file should have the same name as the
-project, and the project file's extension should be @code{"gpr"}. These
-conventions are not required, but a warning is issued if they are not followed.
-
-If the current directory is @file{/temp}, then the command
-@smallexample
-gnatmake -P/common/debug.gpr
-@end smallexample
-
-@noindent
-generates object and ALI files in @file{/common/debug}, and the @code{proc}
-executable also in @file{/common/debug}, using the switch settings defined in
-the project file.
-
-Likewise, the command
-@smallexample
-gnatmake -P/common/release.gpr
-@end smallexample
-
-@noindent
-generates object and ALI files in @file{/common/release}, and the @code{proc}
-executable in @file{/common}, using the switch settings from the project file.
-
-@node Source Files
-@unnumberedsubsubsec Source Files
-
-@noindent
-If a project file does not explicitly specify a set of source directories or
-a set of source files, then by default the project's source files are the
-Ada source files in the project file directory. Thus @file{pack.ads},
-@file{pack.adb}, and @file{proc.adb} are the source files for both projects.
-
-@node Specifying the Object Directory
-@unnumberedsubsubsec Specifying the Object Directory
-
-@noindent
-Several project properties are modeled by Ada-style @emph{attributes};
-you define the property by supplying the equivalent of an Ada attribute
-definition clause in the project file.
-A project's object directory is such a property; the corresponding
-attribute is @code{Object_Dir}, and its value is a string expression. A
-directory may be specified either as absolute or as relative; in the latter
-case, it is relative to the project file directory. Thus the compiler's
-output is directed to @file{/common/debug} (for the @code{Debug} project)
-and to @file{/common/release} (for the @code{Release} project). If
-@code{Object_Dir} is not specified, then the default is the project file
-directory.
-
-@node Specifying the Exec Directory
-@unnumberedsubsubsec Specifying the Exec Directory
-
-@noindent
-A project's exec directory is another property; the corresponding
-attribute is @code{Exec_Dir}, and its value is also a string expression,
-either specified as relative or absolute. If @code{Exec_Dir} is not specified,
-then the default is the object directory (which may also be the project file
-directory if attribute @code{Object_Dir} is not specified). Thus the executable
-is placed in @file{/common/debug} for the @code{Debug} project (attribute
-@code{Exec_Dir} not specified) and in @file{/common} for the @code{Release}
-project.
-
-@node Project File Packages
-@unnumberedsubsubsec Project File Packages
-
-@noindent
-A GNAT tool integrated with the Project Manager is modeled by a
-corresponding package in the project file.
-The @code{Debug} project defines the packages @code{Builder}
-(for @command{gnatmake}) and @code{Compiler};
-the @code{Release} project defines only the @code{Compiler} package.
-
-The Ada package syntax is not to be taken literally. Although packages in
-project files bear a surface resemblance to packages in Ada source code, the
-notation is simply a way to convey a grouping of properties for a named
-entity. Indeed, the package names permitted in project files are restricted
-to a predefined set, corresponding to the project-aware tools, and the contents
-of packages are limited to a small set of constructs.
-The packages in the example above contain attribute definitions.
-
-
-@node Specifying Switch Settings
-@unnumberedsubsubsec Specifying Switch Settings
-
-@noindent
-Switch settings for a project-aware tool can be specified through attributes
-in the package corresponding to the tool.
-The example above illustrates one of the relevant attributes,
-@code{Default_Switches}, defined in the packages in both project files.
-Unlike simple attributes like @code{Source_Dirs}, @code{Default_Switches} is
-known as an @emph{associative array}. When you define this attribute, you must
-supply an "index" (a literal string), and the effect of the attribute
-definition is to set the value of the "array" at the specified "index".
-For the @code{Default_Switches} attribute, the index is a programming
-language (in our case, Ada) , and the value specified (after @code{use})
-must be a list of string expressions.
-
-The attributes permitted in project files are restricted to a predefined set.
-Some may appear at project level, others in packages.
-For any attribute that is an associate array, the index must always be a
-literal string, but the restrictions on this string (e.g., a file name or a
-language name) depend on the individual attribute.
-Also depending on the attribute, its specified value will need to be either a
-string or a string list.
-
-In the @code{Debug} project, we set the switches for two tools,
-@command{gnatmake} and the compiler, and thus we include corresponding
-packages, with each package defining the @code{Default_Switches} attribute
-with index @code{"Ada"}.
-Note that the package corresponding to
-@command{gnatmake} is named @code{Builder}. The @code{Release} project is
-similar, but with just the @code{Compiler} package.
-
-In project @code{Debug} above the switches starting with @option{-gnat} that
-are specified in package @code{Compiler} could have been placed in package
-@code{Builder}, since @command{gnatmake} transmits all such switches to the
-compiler.
-
-@node Main Subprograms
-@unnumberedsubsubsec Main Subprograms
-
-@noindent
-One of the properties of a project is its list of main subprograms (actually
-a list of names of source files containing main subprograms, with the file
-extension optional. This property is captured in the @code{Main} attribute,
-whose value is a list of strings. If a project defines the @code{Main}
-attribute, then you do not need to identify the main subprogram(s) when
-invoking @command{gnatmake} (see @ref{gnatmake and Project Files}).
-
-@node Source File Naming Conventions
-@unnumberedsubsubsec Source File Naming Conventions
-
-@noindent
-Since the project files do not specify any source file naming conventions,
-the GNAT defaults are used. The mechanism for defining source file naming
-conventions -- a package named @code{Naming} -- will be described below
-(@pxref{Naming Schemes}).
-
-@node Source Language(s)
-@unnumberedsubsubsec Source Language(s)
-
-@noindent
-Since the project files do not specify a @code{Languages} attribute, by
-default the GNAT tools assume that the language of the project file is Ada.
-More generally, a project can comprise source files
-in Ada, C, and/or other languages.
-
-@node Using External Variables
-@subsection Using External Variables
-
-@noindent
-Instead of supplying different project files for debug and release, we can
-define a single project file that queries an external variable (set either
-on the command line or via an environment variable) in order to
-conditionally define the appropriate settings. Again, assume that the
-source files @file{pack.ads}, @file{pack.adb}, and @file{proc.adb} are
-located in directory @file{/common}. The following project file,
-@file{build.gpr}, queries the external variable named @code{STYLE} and
-defines an object directory and switch settings based on whether the value
-is @code{"deb"} (debug) or @code{"rel"} (release), where the default is
-@code{"deb"}.
-
-@smallexample
-@group
-project Build is
- for Main use ("proc");
-
- type Style_Type is ("deb", "rel");
- Style : Style_Type := external ("STYLE", "deb");
-
- case Style is
- when "deb" =>
- for Object_Dir use "debug";
-
- when "rel" =>
- for Object_Dir use "release";
- for Exec_Dir use ".";
- end case;
-@end group
-
-@group
- package Builder is
-
- case Style is
- when "deb" =>
- for Default_Switches ("Ada") use ("-g");
- end case;
-
- end Builder;
-@end group
-
-@group
- package Compiler is
-
- case Style is
- when "deb" =>
- for Default_Switches ("Ada") use ("-gnata", "-gnato", "-gnatE");
-
- when "rel" =>
- for Default_Switches ("Ada") use ("-O2");
- end case;
-
- end Compiler;
-
-end Build;
-@end group
-@end smallexample
-
-@noindent
-@code{Style_Type} is an example of a @emph{string type}, which is the project
-file analog of an Ada enumeration type but containing string literals rather
-than identifiers. @code{Style} is declared as a variable of this type.
-
-The form @code{external("STYLE", "deb")} is known as an
-@emph{external reference}; its first argument is the name of an
-@emph{external variable}, and the second argument is a default value to be
-used if the external variable doesn't exist. You can define an external
-variable on the command line via the @option{-X} switch, or you can use an
-environment variable as an external variable.
-
-Each @code{case} construct is expanded by the Project Manager based on the
-value of @code{Style}. Thus the command
-@smallexample
-gnatmake -P/common/build.gpr -XSTYLE=deb
-@end smallexample
-
-@noindent
-is equivalent to the @command{gnatmake} invocation using the project file
-@file{debug.gpr} in the earlier example. So is the command
-@smallexample
-gnatmake -P/common/build.gpr
-@end smallexample
-
-@noindent
-since @code{"deb"} is the default for @code{STYLE}.
-
-Analogously,
-@smallexample
-gnatmake -P/common/build.gpr -XSTYLE=rel
-@end smallexample
-
-@noindent
-is equivalent to the @command{gnatmake} invocation using the project file
-@file{release.gpr} in the earlier example.
-
-
-@node Importing Other Projects
-@subsection Importing Other Projects
-
-@noindent
-A compilation unit in a source file in one project may depend on compilation
-units in source files in other projects. To obtain this behavior, the
-dependent project must @emph{import} the projects containing the needed source
-files. This effect is embodied in syntax similar to an Ada @code{with} clause,
-but the "with"ed entities are strings denoting project files.
-
-As an example, suppose that the two projects @code{GUI_Proj} and
-@code{Comm_Proj} are defined in the project files @file{gui_proj.gpr} and
-@file{comm_proj.gpr} in directories @file{/gui} and @file{/comm},
-respectively. Assume that the source files for @code{GUI_Proj} are
-@file{gui.ads} and @file{gui.adb}, and that the source files for
-@code{Comm_Proj} are @file{comm.ads} and @file{comm.adb}, with each set of
-files located in its respective project file directory. Diagrammatically:
-
-@smallexample
-@group
-/gui
- gui_proj.gpr
- gui.ads
- gui.adb
-@end group
-
-@group
-/comm
- comm_proj.gpr
- comm.ads
- comm.adb
-@end group
-@end smallexample
-
-@noindent
-We want to develop an application in directory @file{/app} that "with"s the
-packages @code{GUI} and @code{Comm}, using the properties of the
-corresponding project files (e.g. the switch settings and object directory).
-Skeletal code for a main procedure might be something like the following:
-
-@smallexample
-@group
-with GUI, Comm;
-procedure App_Main is
- ...
-begin
- ...
-end App_Main;
-@end group
-@end smallexample
-
-@noindent
-Here is a project file, @file{app_proj.gpr}, that achieves the desired
-effect:
-
-@smallexample
-@group
-with "/gui/gui_proj", "/comm/comm_proj";
-project App_Proj is
- for Main use ("app_main");
-end App_Proj;
-@end group
-@end smallexample
-
-@noindent
-Building an executable is achieved through the command:
-@smallexample
-gnatmake -P/app/app_proj
-@end smallexample
-@noindent
-which will generate the @code{app_main} executable in the directory where
-@file{app_proj.gpr} resides.
-
-If an imported project file uses the standard extension (@code{gpr}) then
-(as illustrated above) the @code{with} clause can omit the extension.
-
-Our example specified an absolute path for each imported project file.
-Alternatively, you can omit the directory if either
-@itemize @bullet
-@item
-The imported project file is in the same directory as the importing project
-file, or
-@item
-You have defined an environment variable @code{ADA_PROJECT_PATH} that
-includes the directory containing the needed project file.
-@end itemize
-
-@noindent
-Thus, if we define @code{ADA_PROJECT_PATH} to include @file{/gui} and
-@file{/comm}, then our project file @file{app_proj.gpr} could be written as
-follows:
-
-@smallexample
-@group
-with "gui_proj", "comm_proj";
-project App_Proj is
- for Main use ("app_main");
-end App_Proj;
-@end group
-@end smallexample
-
-@noindent
-Importing other projects raises the possibility of ambiguities. For
-example, the same unit might be present in different imported projects, or
-it might be present in both the importing project and an imported project.
-Both of these conditions are errors. Note that in the current version of
-the Project Manager, it is illegal to have an ambiguous unit even if the
-unit is never referenced by the importing project. This restriction may be
-relaxed in a future release.
-
-@node Extending a Project
-@subsection Extending a Project
-
-@noindent
-A common situation in large software systems is to have multiple
-implementations for a common interface; in Ada terms, multiple versions of a
-package body for the same specification. For example, one implementation
-might be safe for use in tasking programs, while another might only be used
-in sequential applications. This can be modeled in GNAT using the concept
-of @emph{project extension}. If one project (the "child") @emph{extends}
-another project (the "parent") then by default all source files of the
-parent project are inherited by the child, but the child project can
-override any of the parent's source files with new versions, and can also
-add new files. This facility is the project analog of extension in
-Object-Oriented Programming. Project hierarchies are permitted (a child
-project may be the parent of yet another project), and a project that
-inherits one project can also import other projects.
-
-As an example, suppose that directory @file{/seq} contains the project file
-@file{seq_proj.gpr} and the source files @file{pack.ads}, @file{pack.adb},
-and @file{proc.adb}:
-
-@smallexample
-@group
-/seq
- pack.ads
- pack.adb
- proc.adb
- seq_proj.gpr
-@end group
-@end smallexample
-
-@noindent
-Note that the project file can simply be empty (that is, no attribute or
-package is defined):
-
-@smallexample
-@group
-project Seq_Proj is
-end Seq_Proj;
-@end group
-@end smallexample
-
-@noindent
-implying that its source files are all the Ada source files in the project
-directory.
-
-Suppose we want to supply an alternate version of @file{pack.adb}, in
-directory @file{/tasking}, but use the existing versions of @file{pack.ads}
-and @file{proc.adb}. We can define a project @code{Tasking_Proj} that
-inherits @code{Seq_Proj}:
-
-@smallexample
-@group
-/tasking
- pack.adb
- tasking_proj.gpr
-@end group
-
-@group
-project Tasking_Proj extends "/seq/seq_proj" is
-end Tasking_Proj;
-@end group
-@end smallexample
-
-@noindent
-The version of @file{pack.adb} used in a build depends on which project file
-is specified.
-
-Note that we could have designed this using project import rather than
-project inheritance; a @code{base} project would contain the sources for
-@file{pack.ads} and @file{proc.adb}, a sequential project would import
-@code{base} and add @file{pack.adb}, and likewise a tasking project would
-import @code{base} and add a different version of @file{pack.adb}. The
-choice depends on whether other sources in the original project need to be
-overridden. If they do, then project extension is necessary, otherwise,
-importing is sufficient.
-
-
-@c ***********************
-@c * Project File Syntax *
-@c ***********************
-
-@node Project File Syntax
-@section Project File Syntax
-
-@menu
-* Basic Syntax::
-* Packages::
-* Expressions::
-* String Types::
-* Variables::
-* Attributes::
-* Associative Array Attributes::
-* case Constructions::
-@end menu
-
-@noindent
-This section describes the structure of project files.
-
-A project may be an @emph{independent project}, entirely defined by a single
-project file. Any Ada source file in an independent project depends only
-on the predefined library and other Ada source files in the same project.
-
-@noindent
-A project may also @dfn{depend on} other projects, in either or both of the following ways:
-@itemize @bullet
-@item It may import any number of projects
-@item It may extend at most one other project
-@end itemize
-
-@noindent
-The dependence relation is a directed acyclic graph (the subgraph reflecting
-the "extends" relation is a tree).
-
-A project's @dfn{immediate sources} are the source files directly defined by
-that project, either implicitly by residing in the project file's directory,
-or explicitly through any of the source-related attributes described below.
-More generally, a project @var{proj}'s @dfn{sources} are the immediate sources
-of @var{proj} together with the immediate sources (unless overridden) of any
-project on which @var{proj} depends (either directly or indirectly).
-
-@node Basic Syntax
-@subsection Basic Syntax
-
-@noindent
-As seen in the earlier examples, project files have an Ada-like syntax.
-The minimal project file is:
-@smallexample
-@group
-project Empty is
-
-end Empty;
-@end group
-@end smallexample
-
-@noindent
-The identifier @code{Empty} is the name of the project.
-This project name must be present after the reserved
-word @code{end} at the end of the project file, followed by a semi-colon.
-
-Any name in a project file, such as the project name or a variable name,
-has the same syntax as an Ada identifier.
-
-The reserved words of project files are the Ada reserved words plus
-@code{extends}, @code{external}, and @code{project}. Note that the only Ada
-reserved words currently used in project file syntax are:
-
-@itemize @bullet
-@item
-@code{case}
-@item
-@code{end}
-@item
-@code{for}
-@item
-@code{is}
-@item
-@code{others}
-@item
-@code{package}
-@item
-@code{renames}
-@item
-@code{type}
-@item
-@code{use}
-@item
-@code{when}
-@item
-@code{with}
-@end itemize
-
-@noindent
-Comments in project files have the same syntax as in Ada, two consecutives
-hyphens through the end of the line.
-
-@node Packages
-@subsection Packages
-
-@noindent
-A project file may contain @emph{packages}. The name of a package must be one
-of the identifiers (case insensitive) from a predefined list, and a package
-with a given name may only appear once in a project file. The predefined list
-includes the following packages:
-
-@itemize @bullet
-@item
-@code{Naming}
-@item
-@code{Builder}
-@item
-@code{Compiler}
-@item
-@code{Binder}
-@item
-@code{Linker}
-@item
-@code{Finder}
-@item
-@code{Cross_Reference}
-@item
-@code{gnatls}
-@end itemize
-
-@noindent
-(The complete list of the package names and their attributes can be found
-in file @file{prj-attr.adb}).
-
-@noindent
-In its simplest form, a package may be empty:
-
-@smallexample
-@group
-project Simple is
- package Builder is
- end Builder;
-end Simple;
-@end group
-@end smallexample
-
-@noindent
-A package may contain @emph{attribute declarations},
-@emph{variable declarations} and @emph{case constructions}, as will be
-described below.
-
-When there is ambiguity between a project name and a package name,
-the name always designates the project. To avoid possible confusion, it is
-always a good idea to avoid naming a project with one of the
-names allowed for packages or any name that starts with @code{gnat}.
-
-
-@node Expressions
-@subsection Expressions
-
-@noindent
-An @emph{expression} is either a @emph{string expression} or a
-@emph{string list expression}.
-
-A @emph{string expression} is either a @emph{simple string expression} or a
-@emph{compound string expression}.
-
-A @emph{simple string expression} is one of the following:
-@itemize @bullet
-@item A literal string; e.g.@code{"comm/my_proj.gpr"}
-@item A string-valued variable reference (see @ref{Variables})
-@item A string-valued attribute reference (see @ref{Attributes})
-@item An external reference (see @ref{External References in Project Files})
-@end itemize
-
-@noindent
-A @emph{compound string expression} is a concatenation of string expressions,
-using @code{"&"}
-@smallexample
- Path & "/" & File_Name & ".ads"
-@end smallexample
-
-@noindent
-A @emph{string list expression} is either a
-@emph{simple string list expression} or a
-@emph{compound string list expression}.
-
-A @emph{simple string list expression} is one of the following:
-@itemize @bullet
-@item A parenthesized list of zero or more string expressions, separated by commas
-@smallexample
- File_Names := (File_Name, "gnat.adc", File_Name & ".orig");
- Empty_List := ();
-@end smallexample
-@item A string list-valued variable reference
-@item A string list-valued attribute reference
-@end itemize
-
-@noindent
-A @emph{compound string list expression} is the concatenation (using
-@code{"&"}) of a simple string list expression and an expression. Note that
-each term in a compound string list expression, except the first, may be
-either a string expression or a string list expression.
-
-@smallexample
-@group
- File_Name_List := () & File_Name; -- One string in this list
- Extended_File_Name_List := File_Name_List & (File_Name & ".orig");
- -- Two strings
- Big_List := File_Name_List & Extended_File_Name_List;
- -- Concatenation of two string lists: three strings
- Illegal_List := "gnat.adc" & Extended_File_Name_List;
- -- Illegal: must start with a string list
-@end group
-@end smallexample
-
-
-@node String Types
-@subsection String Types
-
-@noindent
-The value of a variable may be restricted to a list of string literals.
-The restricted list of string literals is given in a
-@emph{string type declaration}.
-
-Here is an example of a string type declaration:
-
-@smallexample
- type OS is ("NT, "nt", "Unix", "Linux", "other OS");
-@end smallexample
-
-@noindent
-Variables of a string type are called @emph{typed variables}; all other
-variables are called @emph{untyped variables}. Typed variables are
-particularly useful in @code{case} constructions
-(see @ref{case Constructions}).
-
-A string type declaration starts with the reserved word @code{type}, followed
-by the name of the string type (case-insensitive), followed by the reserved
-word @code{is}, followed by a parenthesized list of one or more string literals
-separated by commas, followed by a semicolon.
-
-The string literals in the list are case sensitive and must all be different.
-They may include any graphic characters allowed in Ada, including spaces.
-
-A string type may only be declared at the project level, not inside a package.
-
-A string type may be referenced by its name if it has been declared in the same
-project file, or by its project name, followed by a dot,
-followed by the string type name.
-
-
-@node Variables
-@subsection Variables
-
-@noindent
-A variable may be declared at the project file level, or in a package.
-Here are some examples of variable declarations:
-
-@smallexample
-@group
- This_OS : OS := external ("OS"); -- a typed variable declaration
- That_OS := "Linux"; -- an untyped variable declaration
-@end group
-@end smallexample
-
-@noindent
-A @emph{typed variable declaration} includes the variable name, followed by a colon,
-followed by the name of a string type, followed by @code{:=}, followed by
-a simple string expression.
-
-An @emph{untyped variable declaration} includes the variable name,
-followed by @code{:=}, followed by an expression. Note that, despite the
-terminology, this form of "declaration" resembles more an assignment
-than a declaration in Ada. It is a declaration in several senses:
-@itemize @bullet
-@item
-The variable name does not need to be defined previously
-@item
-The declaration establishes the @emph{kind} (string versus string list) of the
-variable, and later declarations of the same variable need to be consistent
-with this
-@end itemize
-
-@noindent
-A string variable declaration (typed or untyped) declares a variable
-whose value is a string. This variable may be used as a string expression.
-@smallexample
- File_Name := "readme.txt";
- Saved_File_Name := File_Name & ".saved";
-@end smallexample
-
-@noindent
-A string list variable declaration declares a variable whose value is a list
-of strings. The list may contain any number (zero or more) of strings.
-
-@smallexample
- Empty_List := ();
- List_With_One_Element := ("-gnaty");
- List_With_Two_Elements := List_With_One_Element & "-gnatg";
- Long_List := ("main.ada", "pack1_.ada", "pack1.ada", "pack2_.ada"
- "pack2.ada", "util_.ada", "util.ada");
-@end smallexample
-
-@noindent
-The same typed variable may not be declared more than once at project level, and it may not be declared more than once in any package; it is in effect a constant or a readonly variable.
-
-The same untyped variable may be declared several times.
-In this case, the new value replaces the old one,
-and any subsequent reference to the variable uses the new value.
-However, as noted above, if a variable has been declared as a string, all subsequent
-declarations must give it a string value. Similarly, if a variable has
-been declared as a string list, all subsequent declarations
-must give it a string list value.
-
-A @emph{variable reference} may take several forms:
-
-@itemize @bullet
-@item The simple variable name, for a variable in the current package (if any) or in the current project
-@item A context name, followed by a dot, followed by the variable name.
-@end itemize
-
-@noindent
-A @emph{context} may be one of the following:
-
-@itemize @bullet
-@item The name of an existing package in the current project
-@item The name of an imported project of the current project
-@item The name of an ancestor project (i.e., a project extended by the current project, either directly or indirectly)
-@item An imported/parent project name, followed by a dot, followed by a package name
-@end itemize
-
-@noindent
-A variable reference may be used in an expression.
-
-
-@node Attributes
-@subsection Attributes
-
-@noindent
-A project (and its packages) may have @emph{attributes} that define the project's properties.
-Some attributes have values that are strings;
-others have values that are string lists.
-
-There are two categories of attributes: @emph{simple attributes} and @emph{associative arrays}
-(see @ref{Associative Array Attributes}).
-
-The names of the attributes are restricted; there is a list of project
-attributes, and a list of package attributes for each package.
-The names are not case sensitive.
-
-The project attributes are as follows (all are simple attributes):
-
-@multitable @columnfractions .4 .3
-@item @emph{Attribute Name}
-@tab @emph{Value}
-@item @code{Source_Files}
-@tab string list
-@item @code{Source_Dirs}
-@tab string list
-@item @code{Source_List_File}
-@tab string
-@item @code{Object_Dir}
-@tab string
-@item @code{Exec_Dir}
-@tab string
-@item @code{Main}
-@tab string list
-@item @code{Languages}
-@tab string list
-@item @code{Library_Dir}
-@tab string
-@item @code{Library_Name}
-@tab string
-@item @code{Library_Kind}
-@tab string
-@item @code{Library_Elaboration}
-@tab string
-@item @code{Library_Version}
-@tab string
-@end multitable
-
-@noindent
-The attributes for package @code{Naming} are as follows
-(see @ref{Naming Schemes}):
-
-@multitable @columnfractions .4 .2 .2 .2
-@item Attribute Name @tab Category @tab Index @tab Value
-@item @code{Specification_Suffix}
-@tab associative array
-@tab language name
-@tab string
-@item @code{Implementation_Suffix}
-@tab associative array
-@tab language name
-@tab string
-@item @code{Separate_Suffix}
-@tab simple attribute
-@tab n/a
-@tab string
-@item @code{Casing}
-@tab simple attribute
-@tab n/a
-@tab string
-@item @code{Dot_Replacement}
-@tab simple attribute
-@tab n/a
-@tab string
-@item @code{Specification}
-@tab associative array
-@tab Ada unit name
-@tab string
-@item @code{Implementation}
-@tab associative array
-@tab Ada unit name
-@tab string
-@item @code{Specification_Exceptions}
-@tab associative array
-@tab language name
-@tab string list
-@item @code{Implementation_Exceptions}
-@tab associative array
-@tab language name
-@tab string list
-@end multitable
-
-@noindent
-The attributes for package @code{Builder}, @code{Compiler}, @code{Binder},
-@code{Linker}, @code{Cross_Reference}, and @code{Finder}
-are as follows (see @ref{Switches and Project Files}).
-
-@multitable @columnfractions .4 .2 .2 .2
-@item Attribute Name @tab Category @tab Index @tab Value
-@item @code{Default_Switches}
-@tab associative array
-@tab language name
-@tab string list
-@item @code{Switches}
-@tab associative array
-@tab file name
-@tab string list
-@end multitable
-
-@noindent
-In addition, package @code{Builder} has a single string attribute
-@code{Local_Configuration_Pragmas} and package @code{Builder} has a single
-string attribute @code{Global_Configuration_Pragmas}.
-
-@noindent
-The attribute for package @code{Glide} are not documented: they are for
-internal use only.
-
-@noindent
-Each simple attribute has a default value: the empty string (for string-valued
-attributes) and the empty list (for string list-valued attributes).
-
-Similar to variable declarations, an attribute declaration defines a new value
-for an attribute.
-
-Examples of simple attribute declarations:
-
-@smallexample
- for Object_Dir use "objects";
- for Source_Dirs use ("units", "test/drivers");
-@end smallexample
-
-@noindent
-A @dfn{simple attribute declaration} starts with the reserved word @code{for},
-followed by the name of the attribute, followed by the reserved word
-@code{use}, followed by an expression (whose kind depends on the attribute),
-followed by a semicolon.
-
-Attributes may be referenced in expressions.
-The general form for such a reference is @code{<entity>'<attribute>}:
-the entity for which the attribute is defined,
-followed by an apostrophe, followed by the name of the attribute.
-For associative array attributes, a litteral string between parentheses
-need to be supplied as index.
-
-Examples are:
-
-@smallexample
- project'Object_Dir
- Naming'Dot_Replacement
- Imported_Project'Source_Dirs
- Imported_Project.Naming'Casing
- Builder'Default_Switches("Ada")
-@end smallexample
-
-@noindent
-The entity may be:
-@itemize @bullet
-@item @code{project} for an attribute of the current project
-@item The name of an existing package of the current project
-@item The name of an imported project
-@item The name of a parent project (extended by the current project)
-@item An imported/parent project name, followed by a dot,
- followed by a package name
-@end itemize
-
-@noindent
-Example:
-@smallexample
-@group
- project Prj is
- for Source_Dirs use project'Source_Dirs & "units";
- for Source_Dirs use project'Source_Dirs & "test/drivers"
- end Prj;
-@end group
-@end smallexample
-
-@noindent
-In the first attribute declaration, initially the attribute @code{Source_Dirs}
-has the default value: an empty string list. After this declaration,
-@code{Source_Dirs} is a string list of one element: "units".
-After the second attribute declaration @code{Source_Dirs} is a string list of
-two elements: "units" and "test/drivers".
-
-Note: this example is for illustration only. In practice,
-the project file would contain only one attribute declaration:
-
-@smallexample
- for Source_Dirs use ("units", "test/drivers");
-@end smallexample
-
-
-@node Associative Array Attributes
-@subsection Associative Array Attributes
-
-@noindent
-Some attributes are defined as @emph{associative arrays}. An associative
-array may be regarded as a function that takes a string as a parameter
-and delivers a string or string list value as its result.
-
-Here are some examples of associative array attribute declarations:
-
-@smallexample
- for Implementation ("main") use "Main.ada";
- for Switches ("main.ada") use ("-v", "-gnatv");
- for Switches ("main.ada") use Builder'Switches ("main.ada") & "-g";
-@end smallexample
-
-@noindent
-Like untyped variables and simple attributes, associative array attributes may be declared several times. Each declaration supplies a new value for the
-attribute, replacing the previous setting.
-
-
-@node case Constructions
-@subsection @code{case} Constructions
-
-@noindent
-A @code{case} construction is used in a project file to effect conditional
-behavior.
-Here is a typical example:
-
-@smallexample
-@group
-project MyProj is
- type OS_Type is ("Linux", "Unix", "NT", "VMS");
-
- OS : OS_Type := external ("OS", "Linux");
-@end group
-
-@group
- package Compiler is
- case OS is
- when "Linux" | "Unix" =>
- for Default_Switches ("Ada") use ("-gnath");
- when "NT" =>
- for Default_Switches ("Ada") use ("-gnatP");
- when others =>
- end case;
- end Compiler;
-end MyProj;
-@end group
-@end smallexample
-
-@noindent
-The syntax of a @code{case} construction is based on the Ada case statement
-(although there is no @code{null} construction for empty alternatives).
-
-Following the reserved word @code{case} there is the case variable (a typed
-string variable), the reserved word @code{is}, and then a sequence of one or
-more alternatives.
-Each alternative comprises the reserved word @code{when}, either a list of
-literal strings separated by the @code{"|"} character or the reserved word
-@code{others}, and the @code{"=>"} token.
-Each literal string must belong to the string type that is the type of the
-case variable.
-An @code{others} alternative, if present, must occur last.
-The @code{end case;} sequence terminates the case construction.
-
-After each @code{=>}, there are zero or more constructions. The only
-constructions allowed in a case construction are other case constructions and
-attribute declarations. String type declarations, variable declarations and
-package declarations are not allowed.
-
-The value of the case variable is often given by an external reference
-(see @ref{External References in Project Files}).
-
-
-@c ****************************************
-@c * Objects and Sources in Project Files *
-@c ****************************************
-
-@node Objects and Sources in Project Files
-@section Objects and Sources in Project Files
-
-@menu
-* Object Directory::
-* Exec Directory::
-* Source Directories::
-* Source File Names::
-@end menu
-
-@noindent
-Each project has exactly one object directory and one or more source
-directories. The source directories must contain at least one source file,
-unless the project file explicitly specifies that no source files are present
-(see @ref{Source File Names}).
-
-
-@node Object Directory
-@subsection Object Directory
-
-@noindent
-The object directory for a project is the directory containing the compiler's
-output (such as @file{ALI} files and object files) for the project's immediate
-sources. Note that for inherited sources (when extending a parent project) the
-parent project's object directory is used.
-
-The object directory is given by the value of the attribute @code{Object_Dir}
-in the project file.
-
-@smallexample
- for Object_Dir use "objects";
-@end smallexample
-
-@noindent
-The attribute @var{Object_Dir} has a string value, the path name of the object
-directory. The path name may be absolute or relative to the directory of the
-project file. This directory must already exist, and be readable and writable.
-
-By default, when the attribute @code{Object_Dir} is not given an explicit value
-or when its value is the empty string, the object directory is the same as the
-directory containing the project file.
-
-
-@node Exec Directory
-@subsection Exec Directory
-
-@noindent
-The exec directory for a project is the directory containing the executables
-for the project's main subprograms.
-
-The exec directory is given by the value of the attribute @code{Exec_Dir}
-in the project file.
-
-@smallexample
- for Exec_Dir use "executables";
-@end smallexample
-
-@noindent
-The attribute @var{Exec_Dir} has a string value, the path name of the exec
-directory. The path name may be absolute or relative to the directory of the
-project file. This directory must already exist, and be writable.
-
-By default, when the attribute @code{Exec_Dir} is not given an explicit value
-or when its value is the empty string, the exec directory is the same as the
-object directory of the project file.
-
-
-@node Source Directories
-@subsection Source Directories
-
-@noindent
-The source directories of a project are specified by the project file
-attribute @code{Source_Dirs}.
-
-This attribute's value is a string list. If the attribute is not given an
-explicit value, then there is only one source directory, the one where the
-project file resides.
-
-A @code{Source_Dirs} attribute that is explicitly defined to be the empty list,
-as in
-
-@smallexample
- for Source_Dirs use ();
-@end smallexample
-
-@noindent
-indicates that the project contains no source files.
-
-Otherwise, each string in the string list designates one or more
-source directories.
-
-@smallexample
- for Source_Dirs use ("sources", "test/drivers");
-@end smallexample
-
-@noindent
-If a string in the list ends with @code{"/**"}, then the directory whose path
-name precedes the two asterisks, as well as all its subdirectories
-(recursively), are source directories.
-
-@smallexample
- for Source_Dirs use ("/system/sources/**");
-@end smallexample
-
-@noindent
-Here the directory @code{/system/sources} and all of its subdirectories
-(recursively) are source directories.
-
-To specify that the source directories are the directory of the project file
-and all of its subdirectories, you can declare @code{Source_Dirs} as follows:
-@smallexample
- for Source_Dirs use ("./**");
-@end smallexample
-
-@noindent
-Each of the source directories must exist and be readable.
-
-
-@node Source File Names
-@subsection Source File Names
-
-@noindent
-In a project that contains source files, their names may be specified by the
-attributes @code{Source_Files} (a string list) or @code{Source_List_File}
-(a string). Source file names never include any directory information.
-
-If the attribute @code{Source_Files} is given an explicit value, then each
-element of the list is a source file name.
-
-@smallexample
- for Source_Files use ("main.adb");
- for Source_Files use ("main.adb", "pack1.ads", "pack2.adb");
-@end smallexample
-
-@noindent
-If the attribute @code{Source_Files} is not given an explicit value,
-but the attribute @code{Source_List_File} is given a string value,
-then the source file names are contained in the text file whose path name
-(absolute or relative to the directory of the project file) is the
-value of the attribute @code{Source_List_File}.
-
-Each line in the file that is not empty or is not a comment
-contains a source file name. A comment line starts with two hyphens.
-
-@smallexample
- for Source_List_File use "source_list.txt";
-@end smallexample
-
-@noindent
-By default, if neither the attribute @code{Source_Files} nor the attribute
-@code{Source_List_File} is given an explicit value, then each file in the
-source directories that conforms to the project's naming scheme
-(see @ref{Naming Schemes}) is an immediate source of the project.
-
-A warning is issued if both attributes @code{Source_Files} and
-@code{Source_List_File} are given explicit values. In this case, the attribute
-@code{Source_Files} prevails.
-
-Each source file name must be the name of one and only one existing source file
-in one of the source directories.
-
-A @code{Source_Files} attribute defined with an empty list as its value
-indicates that there are no source files in the project.
-
-Except for projects that are clearly specified as containing no Ada source
-files (@code{Source_Dirs} or @code{Source_Files} specified as an empty list,
-or @code{Languages} specified without @code{"Ada"} in the list)
-@smallexample
- for Source_Dirs use ();
- for Source_Files use ();
- for Languages use ("C", "C++");
-@end smallexample
-
-@noindent
-a project must contain at least one immediate source.
-
-Projects with no source files are useful as template packages
-(see @ref{Packages in Project Files}) for other projects; in particular to
-define a package @code{Naming} (see @ref{Naming Schemes}).
-
-
-@c ****************************
-@c * Importing Projects *
-@c ****************************
-
-@node Importing Projects
-@section Importing Projects
-
-@noindent
-An immediate source of a project P may depend on source files that
-are neither immediate sources of P nor in the predefined library.
-To get this effect, P must @emph{import} the projects that contain the needed
-source files.
-
-@smallexample
-@group
- with "project1", "utilities.gpr";
- with "/namings/apex.gpr";
- project Main is
- ...
-@end group
-@end smallexample
-
-@noindent
-As can be seen in this example, the syntax for importing projects is similar
-to the syntax for importing compilation units in Ada. However, project files
-use literal strings instead of names, and the @code{with} clause identifies
-project files rather than packages.
-
-Each literal string is the file name or path name (absolute or relative) of a
-project file. If a string is simply a file name, with no path, then its
-location is determined by the @emph{project path}:
-
-@itemize @bullet
-@item
-If the environment variable @env{ADA_PROJECT_PATH} exists, then the project
-path includes all the directories in this environment variable, plus the
-directory of the project file.
-
-@item
-If the environment variable @env{ADA_PROJECT_PATH} does not exist,
-then the project path contains only one directory, namely the one where
-the project file is located.
-@end itemize
-
-@noindent
-If a relative pathname is used as in
-
-@smallexample
- with "tests/proj";
-@end smallexample
-
-@noindent
-then the path is relative to the directory where the importing project file is
-located. Any symbolic link will be fully resolved in the directory
-of the importing project file before the imported project file is looked up.
-
-When the @code{with}'ed project file name does not have an extension,
-the default is @file{.gpr}. If a file with this extension is not found, then
-the file name as specified in the @code{with} clause (no extension) will be
-used. In the above example, if a file @code{project1.gpr} is found, then it
-will be used; otherwise, if a file @code{project1} exists then it will be used;
-if neither file exists, this is an error.
-
-A warning is issued if the name of the project file does not match the
-name of the project; this check is case insensitive.
-
-Any source file that is an immediate source of the imported project can be
-used by the immediate sources of the importing project, and recursively. Thus
-if @code{A} imports @code{B}, and @code{B} imports @code{C}, the immediate
-sources of @code{A} may depend on the immediate sources of @code{C}, even if
-@code{A} does not import @code{C} explicitly. However, this is not recommended,
-because if and when @code{B} ceases to import @code{C}, some sources in
-@code{A} will no longer compile.
-
-A side effect of this capability is that cyclic dependences are not permitted:
-if @code{A} imports @code{B} (directly or indirectly) then @code{B} is not
-allowed to import @code{A}.
-
-
-@c *********************
-@c * Project Extension *
-@c *********************
-
-@node Project Extension
-@section Project Extension
-
-@noindent
-During development of a large system, it is sometimes necessary to use
-modified versions of some of the source files without changing the original
-sources. This can be achieved through a facility known as
-@emph{project extension}.
-
-@smallexample
- project Modified_Utilities extends "/baseline/utilities.gpr" is ...
-@end smallexample
-
-@noindent
-The project file for the project being extended (the @emph{parent}) is
-identified by the literal string that follows the reserved word @code{extends},
-which itself follows the name of the extending project (the @emph{child}).
-
-By default, a child project inherits all the sources of its parent.
-However, inherited sources can be overridden: a unit with the same name as one
-in the parent will hide the original unit.
-Inherited sources are considered to be sources (but not immediate sources)
-of the child project; see @ref{Project File Syntax}.
-
-An inherited source file retains any switches specified in the parent project.
-
-For example if the project @code{Utilities} contains the specification and the
-body of an Ada package @code{Util_IO}, then the project
-@code{Modified_Utilities} can contain a new body for package @code{Util_IO}.
-The original body of @code{Util_IO} will not be considered in program builds.
-However, the package specification will still be found in the project
-@code{Utilities}.
-
-A child project can have only one parent but it may import any number of other
-projects.
-
-A project is not allowed to import directly or indirectly at the same time a
-child project and any of its ancestors.
-
-
-@c ****************************************
-@c * External References in Project Files *
-@c ****************************************
-
-@node External References in Project Files
-@section External References in Project Files
-
-@noindent
-A project file may contain references to external variables; such references
-are called @emph{external references}.
-
-An external variable is either defined as part of the environment (an
-environment variable in Unix, for example) or else specified on the command
-line via the @option{-X@emph{vbl}=@emph{value}} switch. If both, then the
-command line value is used.
-
-An external reference is denoted by the built-in function
-@code{external}, which returns a string value. This function has two forms:
-@itemize @bullet
-@item @code{external (external_variable_name)}
-@item @code{external (external_variable_name, default_value)}
-@end itemize
-
-@noindent
-Each parameter must be a string literal. For example:
-
-@smallexample
- external ("USER")
- external ("OS", "Linux")
-@end smallexample
-
-@noindent
-In the form with one parameter, the function returns the value of
-the external variable given as parameter. If this name is not present in the
-environment, then the returned value is an empty string.
-
-In the form with two string parameters, the second parameter is
-the value returned when the variable given as the first parameter is not
-present in the environment. In the example above, if @code{"OS"} is not
-the name of an environment variable and is not passed on the command line,
-then the returned value will be @code{"Linux"}.
-
-An external reference may be part of a string expression or of a string
-list expression, to define variables or attributes.
-
-@smallexample
-@group
- type Mode_Type is ("Debug", "Release");
- Mode : Mode_Type := external ("MODE");
- case Mode is
- when "Debug" =>
- ...
-@end group
-@end smallexample
-
-
-@c *****************************
-@c * Packages in Project Files *
-@c *****************************
-
-@node Packages in Project Files
-@section Packages in Project Files
-
-@noindent
-The @emph{package} is the project file feature that defines the settings for
-project-aware tools.
-For each such tool you can declare a corresponding package; the names for these
-packages are preset (see @ref{Packages}) but are not case sensitive.
-A package may contain variable declarations, attribute declarations, and case
-constructions.
-
-@smallexample
-@group
- project Proj is
- package Builder is -- used by gnatmake
- for Default_Switches ("Ada") use ("-v", "-g");
- end Builder;
- end Proj;
-@end group
-@end smallexample
-
-@noindent
-A package declaration starts with the reserved word @code{package},
-followed by the package name (case insensitive), followed by the reserved word
-@code{is}. It ends with the reserved word @code{end}, followed by the package
-name, finally followed by a semi-colon.
-
-Most of the packages have an attribute @code{Default_Switches}.
-This attribute is an associative array, and its value is a string list.
-The index of the associative array is the name of a programming language (case
-insensitive). This attribute indicates the switch or switches to be used
-with the corresponding tool.
-
-Some packages also have another attribute, @code{Switches}, an associative
-array whose value is a string list. The index is the name of a source file.
-This attribute indicates the switch or switches to be used by the corresponding
-tool when dealing with this specific file.
-
-Further information on these switch-related attributes is found in
-@ref{Switches and Project Files}.
-
-A package may be declared as a @emph{renaming} of another package; e.g., from
-the project file for an imported project.
-
-@smallexample
-@group
- with "/global/apex.gpr";
- project Example is
- package Naming renames Apex.Naming;
- ...
- end Example;
-@end group
-@end smallexample
-
-@noindent
-Packages that are renamed in other project files often come from project files
-that have no sources: they are just used as templates. Any modification in the
-template will be reflected automatically in all the project files that rename
-a package from the template.
-
-In addition to the tool-oriented packages, you can also declare a package
-named @code{Naming} to establish specialized source file naming conventions
-(see @ref{Naming Schemes}).
-
-
-@c ************************************
-@c * Variables from Imported Projects *
-@c ************************************
-
-@node Variables from Imported Projects
-@section Variables from Imported Projects
-
-@noindent
-An attribute or variable defined in an imported or parent project can
-be used in expressions in the importing / extending project.
-Such an attribute or variable is prefixed with the name of the project
-and (if relevant) the name of package where it is defined.
-
-@smallexample
-@group
- with "imported";
- project Main extends "base" is
- Var1 := Imported.Var;
- Var2 := Base.Var & ".new";
-@end group
-
-@group
- package Builder is
- for Default_Switches ("Ada") use Imported.Builder.Ada_Switches &
- "-gnatg" & "-v";
- end Builder;
-@end group
-
-@group
- package Compiler is
- for Default_Switches ("Ada") use Base.Compiler.Ada_Switches;
- end Compiler;
- end Main;
-@end group
-@end smallexample
-
-@noindent
-In this example:
-
-@itemize @bullet
-@item
-@code{Var1} is a copy of the variable @code{Var} defined in the project file
-@file{"imported.gpr"}
-@item
-the value of @code{Var2} is a copy of the value of variable @code{Var}
-defined in the project file @file{base.gpr}, concatenated with @code{".new"}
-@item
-attribute @code{Default_Switches ("Ada")} in package @code{Builder}
-is a string list that includes in its value a copy of variable
-@code{Ada_Switches} defined in the @code{Builder} package in project file
-@file{imported.gpr} plus two new elements: @option{"-gnatg"} and @option{"-v"};
-@item
-attribute @code{Default_Switches ("Ada")} in package @code{Compiler}
-is a copy of the variable @code{Ada_Switches} defined in the @code{Compiler}
-package in project file @file{base.gpr}, the project being extended.
-@end itemize
-
-
-@c ******************
-@c * Naming Schemes *
-@c ******************
-
-@node Naming Schemes
-@section Naming Schemes
-
-@noindent
-Sometimes an Ada software system is ported from a foreign compilation
-environment to GNAT, with file names that do not use the default GNAT
-conventions. Instead of changing all the file names (which for a variety of
-reasons might not be possible), you can define the relevant file naming scheme
-in the @code{Naming} package in your project file. For example, the following
-package models the Apex file naming rules:
-
-@smallexample
-@group
- package Naming is
- for Casing use "lowercase";
- for Dot_Replacement use ".";
- for Specification_Suffix ("Ada") use ".1.ada";
- for Implementation_Suffix ("Ada") use ".2.ada";
- end Naming;
-@end group
-@end smallexample
-
-@noindent
-You can define the following attributes in package @code{Naming}:
-
-@table @code
-
-@item @var{Casing}
-This must be a string with one of the three values @code{"lowercase"},
-@code{"uppercase"} or @code{"mixedcase"}; these strings are case insensitive.
-
-@noindent
-If @var{Casing} is not specified, then the default is @code{"lowercase"}.
-
-@item @var{Dot_Replacement}
-This must be a string whose value satisfies the following conditions:
-
-@itemize @bullet
-@item It must not be empty
-@item It cannot start or end with an alphanumeric character
-@item It cannot be a single underscore
-@item It cannot start with an underscore followed by an alphanumeric
-@item It cannot contain a dot @code{'.'} except if it the entire string is @code{"."}
-@end itemize
-
-@noindent
-If @code{Dot_Replacement} is not specified, then the default is @code{"-"}.
-
-@item @var{Specification_Suffix}
-This is an associative array (indexed by the programming language name, case
-insensitive) whose value is a string that must satisfy the following
-conditions:
-
-@itemize @bullet
-@item It must not be empty
-@item It cannot start with an alphanumeric character
-@item It cannot start with an underscore followed by an alphanumeric character
-@end itemize
-@noindent
-If @code{Specification_Suffix ("Ada")} is not specified, then the default is
-@code{".ads"}.
-
-@item @var{Implementation_Suffix}
-This is an associative array (indexed by the programming language name, case
-insensitive) whose value is a string that must satisfy the following
-conditions:
-
-@itemize @bullet
-@item It must not be empty
-@item It cannot start with an alphanumeric character
-@item It cannot start with an underscore followed by an alphanumeric character
-@item It cannot be a suffix of @code{Specification_Suffix}
-@end itemize
-@noindent
-If @code{Implementation_Suffix ("Ada")} is not specified, then the default is
-@code{".adb"}.
-
-@item @var{Separate_Suffix}
-This must be a string whose value satisfies the same conditions as
-@code{Implementation_Suffix}.
-
-@noindent
-If @code{Separate_Suffix ("Ada")} is not specified, then it defaults to same
-value as @code{Implementation_Suffix ("Ada")}.
-
-@item @var{Specification}
-@noindent
-You can use the @code{Specification} attribute, an associative array, to define
-the source file name for an individual Ada compilation unit's spec. The array
-index must be a string literal that identifies the Ada unit (case insensitive).
-The value of this attribute must be a string that identifies the file that
-contains this unit's spec (case sensitive or insensitive depending on the
-operating system).
-
-@smallexample
- for Specification ("MyPack.MyChild") use "mypack.mychild.spec";
-@end smallexample
-
-@item @var{Implementation}
-
-You can use the @code{Implementation} attribute, an associative array, to
-define the source file name for an individual Ada compilation unit's body
-(possibly a subunit). The array index must be a string literal that identifies
-the Ada unit (case insensitive). The value of this attribute must be a string
-that identifies the file that contains this unit's body or subunit (case
-sensitive or insensitive depending on the operating system).
-
-@smallexample
- for Implementation ("MyPack.MyChild") use "mypack.mychild.body";
-@end smallexample
-@end table
-
-
-@c ********************
-@c * Library Projects *
-@c ********************
-
-@node Library Projects
-@section Library Projects
-
-@noindent
-@emph{Library projects} are projects whose object code is placed in a library.
-(Note that this facility is not yet supported on all platforms)
-
-To create a library project, you need to define in its project file
-two project-level attributes: @code{Library_Name} and @code{Library_Dir}.
-Additionally, you may define the library-related attributes
-@code{Library_Kind}, @code{Library_Version} and @code{Library_Elaboration}.
-
-The @code{Library_Name} attribute has a string value that must start with a
-letter and include only letters and digits.
-
-The @code{Library_Dir} attribute has a string value that designates the path
-(absolute or relative) of the directory where the library will reside.
-It must designate an existing directory, and this directory needs to be
-different from the project's object directory. It also needs to be writable.
-
-If both @code{Library_Name} and @code{Library_Dir} are specified and
-are legal, then the project file defines a library project. The optional
-library-related attributes are checked only for such project files.
-
-The @code{Library_Kind} attribute has a string value that must be one of the
-following (case insensitive): @code{"static"}, @code{"dynamic"} or
-@code{"relocatable"}. If this attribute is not specified, the library is a
-static library. Otherwise, the library may be dynamic or relocatable.
-Depending on the operating system, there may or may not be a distinction
-between dynamic and relocatable libraries. For example, on Unix there is no
-such distinction.
-
-The @code{Library_Version} attribute has a string value whose interpretation
-is platform dependent. On Unix, it is used only for dynamic/relocatable
-libraries as the internal name of the library (the @code{"soname"}). If the
-library file name (built from the @code{Library_Name}) is different from the
-@code{Library_Version}, then the library file will be a symbolic link to the
-actual file whose name will be @code{Library_Version}.
-
-Example (on Unix):
-
-@smallexample
-@group
-project Plib is
-
- Version := "1";
-
- for Library_Dir use "lib_dir";
- for Library_Name use "dummy";
- for Library_Kind use "relocatable";
- for Library_Version use "libdummy.so." & Version;
-
-end Plib;
-@end group
-@end smallexample
-
-@noindent
-Directory @file{lib_dir} will contain the internal library file whose name
-will be @file{libdummy.so.1}, and @file{libdummy.so} will be a symbolic link to
-@file{libdummy.so.1}.
-
-When @command{gnatmake} detects that a project file (not the main project file)
-is a library project file, it will check all immediate sources of the project
-and rebuild the library if any of the sources have been recompiled.
-All @file{ALI} files will also be copied from the object directory to the
-library directory. To build executables, @command{gnatmake} will use the
-library rather than the individual object files.
-
-
-@c *************************************
-@c * Switches Related to Project Files *
-@c *************************************
-@node Switches Related to Project Files
-@section Switches Related to Project Files
-
-@noindent
-The following switches are used by GNAT tools that support project files:
-
-@table @code
-
-@item @option{-P@var{project}}
-Indicates the name of a project file. This project file will be parsed with
-the verbosity indicated by @option{-vP@emph{x}}, if any, and using the external
-references indicated by @option{-X} switches, if any.
-
-@noindent
-There must be only one @option{-P} switch on the command line.
-
-@noindent
-Since the Project Manager parses the project file only after all the switches
-on the command line are checked, the order of the switches @option{-P},
-@option{-Vp@emph{x}} or @option{-X} is not significant.
-
-@item @option{-X@var{name=value}}
-Indicates that external variable @var{name} has the value @var{value}.
-The Project Manager will use this value for occurrences of
-@code{external(name)} when parsing the project file.
-
-@noindent
-If @var{name} or @var{value} includes a space, then @var{name=value} should be
-put between quotes.
-@smallexample
- -XOS=NT
- -X"user=John Doe"
-@end smallexample
-
-@noindent
-Several @option{-X} switches can be used simultaneously.
-If several @option{-X} switches specify the same @var{name}, only the last one
-is used.
-
-@noindent
-An external variable specified with a @option{-X} switch takes precedence
-over the value of the same name in the environment.
-
-@item @option{-vP@emph{x}}
-Indicates the verbosity of the parsing of GNAT project files.
-@option{-vP0} means Default (no output for syntactically correct project
-files);
-@option{-vP1} means Medium;
-@option{-vP2} means High.
-@noindent
-The default is Default.
-@noindent
-If several @option{-vP@emph{x}} switches are present, only the last one is
-used.
-
-@end table
-
-
-@c **********************************
-@c * Tools Supporting Project Files *
-@c **********************************
-
-@node Tools Supporting Project Files
-@section Tools Supporting Project Files
-
-@menu
-* gnatmake and Project Files::
-* The GNAT Driver and Project Files::
-@ifclear vms
-* Glide and Project Files::
-@end ifclear
-@end menu
-
-@node gnatmake and Project Files
-@subsection gnatmake and Project Files
-
-@noindent
-This section covers two topics related to @command{gnatmake} and project files:
-defining switches for @command{gnatmake} and for the tools that it invokes;
-and the use of the @code{Main} attribute.
-
-@menu
-* Switches and Project Files::
-* Project Files and Main Subprograms::
-@end menu
-
-@node Switches and Project Files
-@subsubsection Switches and Project Files
-
-@noindent
-For each of the packages @code{Builder}, @code{Compiler}, @code{Binder}, and
-@code{Linker}, you can specify a @code{Default_Switches} attribute, a
-@code{Switches} attribute, or both; as their names imply, these switch-related
-attributes affect which switches are used for which files when
-@command{gnatmake} is invoked. As will be explained below, these
-package-contributed switches precede the switches passed on the
-@command{gnatmake} command line.
-
-The @code{Default_Switches} attribute is an associative array indexed by
-language name (case insensitive) and returning a string list. For example:
-
-@smallexample
-@group
-package Compiler is
- for Default_Switches ("Ada") use ("-gnaty", "-v");
-end Compiler;
-@end group
-@end smallexample
-
-@noindent
-The @code{Switches} attribute is also an associative array, indexed by a file
-name (which may or may not be case sensitive, depending on the operating
-system) and returning a string list. For example:
-
-@smallexample
-@group
-package Builder is
- for Switches ("main1.adb") use ("-O2");
- for Switches ("main2.adb") use ("-g");
-end Builder;
-@end group
-@end smallexample
-
-@noindent
-For the @code{Builder} package, the file names should designate source files
-for main subprograms. For the @code{Binder} and @code{Linker} packages, the
-file names should designate @file{ALI} or source files for main subprograms.
-In each case just the file name (without explicit extension) is acceptable.
-
-For each tool used in a program build (@command{gnatmake}, the compiler, the
-binder, and the linker), its corresponding package @dfn{contributes} a set of
-switches for each file on which the tool is invoked, based on the
-switch-related attributes defined in the package. In particular, the switches
-that each of these packages contributes for a given file @var{f} comprise:
-
-@itemize @bullet
-@item
-the value of attribute @code{Switches (@var{f})}, if it is specified in the
-package for the given file,
-@item
-otherwise, the value of @code{Default_Switches ("Ada")}, if it is specified in
-the package.
-@end itemize
-
-@noindent
-If neither of these attributes is defined in the package, then the package does
-not contribute any switches for the given file.
-
-When @command{gnatmake} is invoked on a file, the switches comprise two sets,
-in the following order: those contributed for the file by the @code{Builder}
-package; and the switches passed on the command line.
-
-When @command{gnatmake} invokes a tool (compiler, binder, linker) on a file,
-the switches passed to the tool comprise three sets, in the following order:
-
-@enumerate
-@item
-the applicable switches contributed for the file by the @code{Builder} package
-in the project file supplied on the command line;
-
-@item
-those contributed for the file by the package (in the relevant project file --
-see below) corresponding to the tool; and
-
-@item
-the applicable switches passed on the command line.
-@end enumerate
-
-@noindent
-The term @emph{applicable switches} reflects the fact that @command{gnatmake}
-switches may or may not be passed to individual tools, depending on the
-individual switch.
-
-@command{gnatmake} may invoke the compiler on source files from different
-projects. The Project Manager will use the appropriate project file to
-determine the @code{Compiler} package for each source file being compiled.
-Likewise for the @code{Binder} and @code{Linker} packages.
-
-As an example, consider the following package in a project file:
-
-@smallexample
-@group
-project Proj1 is
- package Compiler is
- for Default_Switches ("Ada") use ("-g");
- for Switches ("a.adb") use ("-O1");
- for Switches ("b.adb") use ("-O2", "-gnaty");
- end Compiler;
-end Proj1;
-@end group
-@end smallexample
-
-@noindent
-If @command{gnatmake} is invoked with this project file, and it needs to
-compile, say, the files @file{a.adb}, @file{b.adb}, and @file{c.adb}, then
-@file{a.adb} will be compiled with the switch @option{-O1}, @file{b.adb}
-with switches @option{-O2} and @option{-gnaty}, and @file{c.adb} with
-@option{-g}.
-
-Another example illustrates the ordering of the switches contributed by
-different packages:
-
-@smallexample
-@group
-project Proj2 is
- package Builder is
- for Switches ("main.adb") use ("-g", "-O1", "-f");
- end Builder;
-@end group
-
-@group
- package Compiler is
- for Switches ("main.adb") use ("-O2");
- end Compiler;
-end Proj2;
-@end group
-@end smallexample
-
-@noindent
-If you issue the command:
-
-@smallexample
- gnatmake -PProj2 -O0 main
-@end smallexample
-
-@noindent
-then the compiler will be invoked on @file{main.adb} with the following sequence of switches
-
-@smallexample
- -g -O1 -O2 -O0
-@end smallexample
-
-with the last @option{-O} switch having precedence over the earlier ones;
-several other switches (such as @option{-c}) are added implicitly.
-
-The switches @option{-g} and @option{-O1} are contributed by package
-@code{Builder}, @option{-O2} is contributed by the package @code{Compiler}
-and @option{-O0} comes from the command line.
-
-The @option{-g} switch will also be passed in the invocation of
-@command{gnatlink.}
-
-A final example illustrates switch contributions from packages in different
-project files:
-
-@smallexample
-@group
-project Proj3 is
- for Source_Files use ("pack.ads", "pack.adb");
- package Compiler is
- for Default_Switches ("Ada") use ("-gnata");
- end Compiler;
-end Proj3;
-@end group
-
-@group
-with "Proj3";
-project Proj4 is
- for Source_Files use ("foo_main.adb", "bar_main.adb");
- package Builder is
- for Switches ("foo_main.adb") use ("-s", "-g");
- end Builder;
-end Proj4;
-@end group
-
-@group
--- Ada source file:
-with Pack;
-procedure Foo_Main is
- ...
-end Foo_Main;
-@end group
-@end smallexample
-
-If the command is
-@smallexample
-gnatmake -PProj4 foo_main.adb -cargs -gnato
-@end smallexample
-
-@noindent
-then the switches passed to the compiler for @file{foo_main.adb} are
-@option{-g} (contributed by the package @code{Proj4.Builder}) and
-@option{-gnato} (passed on the command line).
-When the imported package @code{Pack} is compiled, the switches used are
-@option{-g} from @code{Proj4.Builder}, @option{-gnata} (contributed from
-package @code{Proj3.Compiler}, and @option{-gnato} from the command line.
-
-
-@node Project Files and Main Subprograms
-@subsubsection Project Files and Main Subprograms
-
-@noindent
-When using a project file, you can invoke @command{gnatmake}
-with several main subprograms, by specifying their source files on the command
-line. Each of these needs to be an immediate source file of the project.
-
-@smallexample
- gnatmake -Pprj main1 main2 main3
-@end smallexample
-
-@noindent
-When using a project file, you can also invoke @command{gnatmake} without
-explicitly specifying any main, and the effect depends on whether you have
-defined the @code{Main} attribute. This attribute has a string list value,
-where each element in the list is the name of a source file (the file
-extension is optional) containing a main subprogram.
-
-If the @code{Main} attribute is defined in a project file as a non-empty
-string list and the switch @option{-u} is not used on the command line, then
-invoking @command{gnatmake} with this project file but without any main on the
-command line is equivalent to invoking @command{gnatmake} with all the file
-names in the @code{Main} attribute on the command line.
-
-Example:
-@smallexample
-@group
- project Prj is
- for Main use ("main1", "main2", "main3");
- end Prj;
-@end group
-@end smallexample
-
-@noindent
-With this project file, @code{"gnatmake -Pprj"} is equivalent to
-@code{"gnatmake -Pprj main1 main2 main3"}.
-
-When the project attribute @code{Main} is not specified, or is specified
-as an empty string list, or when the switch @option{-u} is used on the command
-line, then invoking @command{gnatmake} with no main on the command line will
-result in all immediate sources of the project file being checked, and
-potentially recompiled. Depending on the presence of the switch @option{-u},
-sources from other project files on which the immediate sources of the main
-project file depend are also checked and potentially recompiled. In other
-words, the @option{-u} switch is applied to all of the immediate sources of themain project file.
-
-
-@node The GNAT Driver and Project Files
-@subsection The GNAT Driver and Project Files
-
-@noindent
-A number of GNAT tools, other than @command{gnatmake} are project-aware:
-@command{gnatbind}, @command{gnatfind}, @command{gnatlink}, @command{gnatls}
-and @command{gnatxref}. However, none of these tools can be invoked directly
-with a project file switch (@code{-P}). They need to be invoke through the
-@command{gnat} driver.
-
-The @command{gnat} driver is a front-end that accepts a number of commands and
-call the corresponding tool. It has been designed initially for VMS to convert
-VMS style qualifiers to Unix style switches, but it is now available to all
-the GNAT supported platforms.
-
-On non VMS platforms, the @command{gnat} driver accepts the following commands
-(case insensitive):
-
-@itemize @bullet
-@item
-BIND to invoke @command{gnatbind}
-@item
-CHOP to invoke @command{gnatchop}
-@item
-COMP or COMPILE to invoke the compiler
-@item
-ELIM to invoke @command{gnatelim}
-@item
-FIND to invoke @command{gnatfind}
-@item
-KR or KRUNCH to invoke @command{gnatkr}
-@item
-LINK to invoke @command{gnatlink}
-@item
-LS or LIST to invoke @command{gnatls}
-@item
-MAKE to invoke @command{gnatmake}
-@item
-NAME to invoke @command{gnatname}
-@item
-PREP or PREPROCESS to invoke @command{gnatprep}
-@item
-PSTA or STANDARD to invoke @command{gnatpsta}
-@item
-STUB to invoke @command{gnatstub}
-@item
-XREF to invoke @command{gnatxref}
-@end itemize
-
-@noindent
-Note that the compiler is invoked using the command @command{gnatmake -f -u}.
-
-@noindent
-Following the command, you may put switches and arguments for the invoked
-tool.
-
-@smallexample
- gnat bind -C main.ali
- gnat ls -a main
- gnat chop foo.txt
-@end smallexample
-
-@noindent
-In addition, for command BIND, FIND, LS or LIST, LINK and XREF, the project
-file related switches (@code{-P}, @code{-X} and @code{-vPx}) may be used in
-addition to the switches of the invoking tool.
-
-@noindent
-For each of these command, there is possibly a package in the main project that
-corresponds to the invoked tool.
-
-@itemize @bullet
-@item
-package @code{Binder} for command BIND (invoking @code{gnatbind})
-
-@item
-package @code{Finder} for command FIND (invoking @code{gnatfind})
-
-@item
-package @code{Gnatls} for command LS or LIST (invoking @code{gnatls})
-
-@item
-package @code{Linker} for command LINK (invoking @code{gnatlink})
-
-@item
-package @code{Cross_Reference} for command XREF (invoking @code{gnatlink})
-
-@end itemize
-
-@noindent
-Package @code{Gnatls} has a unique attribute @code{Switches}, a simple variable
-with a string list value. It contains switches for the invocation of
-@code{gnatls}.
-
-@smallexample
-@group
-project Proj1 is
- package gnatls is
- for Switches use ("-a", "-v");
- end gnatls;
-end Proj1;
-@end group
-@end smallexample
-
-@noindent
-All other packages contains a switch @code{Default_Switches}, an associative
-array, indexed by the programming language (case insensitive) and having a
-string list value. @code{Default_Switches ("Ada")} contains the switches for
-the invocation of the tool corresponding to the package.
-
-@smallexample
-@group
-project Proj is
-
- for Source_Dirs use ("./**");
-
- package gnatls is
- for Switches use ("-a", "-v");
- end gnatls;
-@end group
-@group
-
- package Binder is
- for Default_Switches ("Ada") use ("-C", "-e");
- end Binder;
-@end group
-@group
-
- package Linker is
- for Default_Switches ("Ada") use ("-C");
- end Linker;
-@end group
-@group
-
- package Finder is
- for Default_Switches ("Ada") use ("-a", "-f");
- end Finder;
-@end group
-@group
-
- package Cross_Reference is
- for Default_Switches ("Ada") use ("-a", "-f", "-d", "-u");
- end Cross_Reference;
-end Proj;
-@end group
-@end smallexample
-
-@noindent
-With the above project file, commands such as
-
-@smallexample
- gnat ls -Pproj main
- gnat xref -Pproj main
- gnat bind -Pproj main.ali
-@end smallexample
-
-@noindent
-will set up the environment properly and invoke the tool with the switches
-found in the package corresponding to the tool.
-
-
-@ifclear vms
-@node Glide and Project Files
-@subsection Glide and Project Files
-
-@noindent
-Glide will automatically recognize the @file{.gpr} extension for
-project files, and will
-convert them to its own internal format automatically. However, it
-doesn't provide a syntax-oriented editor for modifying these
-files.
-The project file will be loaded as text when you select the menu item
-@code{Ada} @result{} @code{Project} @result{} @code{Edit}.
-You can edit this text and save the @file{gpr} file;
-when you next select this project file in Glide it
-will be automatically reloaded.
-
-@ifset vxworks
-Glide uses the @code{gnatlist} attribute in the @code{Ide} package, whose value
-is something like @code{powerpc-wrs-vxworks-gnatls}, to compute the
-cross-prefix. From this information the correct location for the
-GNAT runtime, and thus also the correct cross-references, can be
-determined.
-@end ifset
-@end ifclear
-
-
-@node An Extended Example
-@section An Extended Example
-
-@noindent
-Suppose that we have two programs, @var{prog1} and @var{prog2}, with the sources
-in the respective directories. We would like to build them with a single
-@command{gnatmake} command, and we would like to place their object files into
-@file{.build} subdirectories of the source directories. Furthermore, we would
-like to have to have two separate subdirectories in @file{.build} --
-@file{release} and @file{debug} -- which will contain the object files compiled with
-different set of compilation flags.
-
-In other words, we have the following structure:
-
-@smallexample
-@group
- main
- |- prog1
- | |- .build
- | | debug
- | | release
- |- prog2
- |- .build
- | debug
- | release
-@end group
-@end smallexample
-
-@noindent
-Here are the project files that we need to create in a directory @file{main}
-to maintain this structure:
-
-@enumerate
-
-@item We create a @code{Common} project with a package @code{Compiler} that
-specifies the compilation switches:
-
-@smallexample
-File "common.gpr":
-@group
-@b{project} Common @b{is}
-
- @b{for} Source_Dirs @b{use} (); -- No source files
-@end group
-
-@group
- @b{type} Build_Type @b{is} ("release", "debug");
- Build : Build_Type := External ("BUILD", "debug");
-@end group
-@group
- @b{package} Compiler @b{is}
- @b{case} Build @b{is}
- @b{when} "release" =>
- @b{for} Default_Switches ("Ada") @b{use} ("-O2");
- @b{when} "debug" =>
- @b{for} Default_Switches ("Ada") @b{use} ("-g");
- @b{end case};
- @b{end} Compiler;
-
-@b{end} Common;
-@end group
-@end smallexample
-
-@item We create separate projects for the two programs:
-
-@smallexample
-@group
-File "prog1.gpr":
-
-@b{with} "common";
-@b{project} Prog1 @b{is}
-
- @b{for} Source_Dirs @b{use} ("prog1");
- @b{for} Object_Dir @b{use} "prog1/.build/" & Common.Build;
-
- @b{package} Compiler @b{renames} Common.Compiler;
-
-@b{end} Prog1;
-@end group
-@end smallexample
-
-@smallexample
-@group
-File "prog2.gpr":
-
-@b{with} "common";
-@b{project} Prog2 @b{is}
-
- @b{for} Source_Dirs @b{use} ("prog2");
- @b{for} Object_Dir @b{use} "prog2/.build/" & Common.Build;
-
- @b{package} Compiler @b{renames} Common.Compiler;
-
-@end group
-@b{end} Prog2;
-@end smallexample
-
-@item We create a wrapping project @var{Main}:
-
-@smallexample
-@group
-File "main.gpr":
-
-@b{with} "common";
-@b{with} "prog1";
-@b{with} "prog2";
-@b{project} Main @b{is}
-
- @b{package} Compiler @b{renames} Common.Compiler;
-
-@b{end} Main;
-@end group
-@end smallexample
-
-@item Finally we need to create a dummy procedure that @code{with}s (either
-explicitly or implicitly) all the sources of our two programs.
-
-@end enumerate
-
-@noindent
-Now we can build the programs using the command
-
-@smallexample
- gnatmake -Pmain dummy
-@end smallexample
-
-@noindent
-for the Debug mode, or
-
-@smallexample
- gnatmake -Pmain -XBUILD=release
-@end smallexample
-
-@noindent
-for the Release mode.
-
-
-@c ********************************
-@c * Project File Complete Syntax *
-@c ********************************
-
-@node Project File Complete Syntax
-@section Project File Complete Syntax
-
-@smallexample
-project ::=
- context_clause project_declaration
-
-context_clause ::=
- @{with_clause@}
-
-with_clause ::=
- @b{with} literal_string @{ , literal_string @} ;
-
-project_declaration ::=
- @b{project} <project_>simple_name [ @b{extends} literal_string ] @b{is}
- @{declarative_item@}
- @b{end} <project_>simple_name;
-
-declarative_item ::=
- package_declaration |
- typed_string_declaration |
- other_declarative_item
-
-package_declaration ::=
- @b{package} <package_>simple_name package_completion
-
-package_completion ::=
- package_body | package_renaming
-
-package body ::=
- @b{is}
- @{other_declarative_item@}
- @b{end} <package_>simple_name ;
-
-package_renaming ::==
- @b{renames} <project_>simple_name.<package_>simple_name ;
-
-typed_string_declaration ::=
- @b{type} <typed_string_>_simple_name @b{is}
- ( literal_string @{, literal_string@} );
-
-other_declarative_item ::=
- attribute_declaration |
- typed_variable_declaration |
- variable_declaration |
- case_construction
-
-attribute_declaration ::=
- @b{for} attribute @b{use} expression ;
-
-attribute ::=
- <simple_attribute_>simple_name |
- <associative_array_attribute_>simple_name ( literal_string )
-
-typed_variable_declaration ::=
- <typed_variable_>simple_name : <typed_string_>name := string_expression ;
-
-variable_declaration ::=
- <variable_>simple_name := expression;
-
-expression ::=
- term @{& term@}
-
-term ::=
- literal_string |
- string_list |
- <variable_>name |
- external_value |
- attribute_reference
-
-literal_string ::=
- (same as Ada)
-
-string_list ::=
- ( <string_>expression @{ , <string_>expression @} )
-
-external_value ::=
- @b{external} ( literal_string [, literal_string] )
-
-attribute_reference ::=
- attribute_parent ' <simple_attribute_>simple_name [ ( literal_string ) ]
-
-attribute_parent ::=
- @b{project} |
- <project_or_package>simple_name |
- <project_>simple_name . <package_>simple_name
-
-case_construction ::=
- @b{case} <typed_variable_>name @b{is}
- @{case_item@}
- @b{end case} ;
-
-case_item ::=
- @b{when} discrete_choice_list => @{case_construction | attribute_declaration@}
-
-discrete_choice_list ::=
- literal_string @{| literal_string@}
-
-name ::=
- simple_name @{. simple_name@}
-
-simple_name ::=
- identifier (same as Ada)
-
-@end smallexample
-
-
-@node Elaboration Order Handling in GNAT
-@chapter Elaboration Order Handling in GNAT
-@cindex Order of elaboration
-@cindex Elaboration control
-
-@menu
-* Elaboration Code in Ada 95::
-* Checking the Elaboration Order in Ada 95::
-* Controlling the Elaboration Order in Ada 95::
-* Controlling Elaboration in GNAT - Internal Calls::
-* Controlling Elaboration in GNAT - External Calls::
-* Default Behavior in GNAT - Ensuring Safety::
-* Elaboration Issues for Library Tasks::
-* Mixing Elaboration Models::
-* What to Do If the Default Elaboration Behavior Fails::
-* Elaboration for Access-to-Subprogram Values::
-* Summary of Procedures for Elaboration Control::
-* Other Elaboration Order Considerations::
-@end menu
-
-@noindent
-This chapter describes the handling of elaboration code in Ada 95 and
-in GNAT, and discusses how the order of elaboration of program units can
-be controlled in GNAT, either automatically or with explicit programming
-features.
-
-@node Elaboration Code in Ada 95
-@section Elaboration Code in Ada 95
-
-@noindent
-Ada 95 provides rather general mechanisms for executing code at elaboration
-time, that is to say before the main program starts executing. Such code arises
-in three contexts:
-
-@table @asis
-@item Initializers for variables.
-Variables declared at the library level, in package specs or bodies, can
-require initialization that is performed at elaboration time, as in:
-@smallexample
-@cartouche
-Sqrt_Half : Float := Sqrt (0.5);
-@end cartouche
-@end smallexample
-
-@item Package initialization code
-Code in a @code{BEGIN-END} section at the outer level of a package body is
-executed as part of the package body elaboration code.
-
-@item Library level task allocators
-Tasks that are declared using task allocators at the library level
-start executing immediately and hence can execute at elaboration time.
-@end table
-
-@noindent
-Subprogram calls are possible in any of these contexts, which means that
-any arbitrary part of the program may be executed as part of the elaboration
-code. It is even possible to write a program which does all its work at
-elaboration time, with a null main program, although stylistically this
-would usually be considered an inappropriate way to structure
-a program.
-
-An important concern arises in the context of elaboration code:
-we have to be sure that it is executed in an appropriate order. What we
-have is a series of elaboration code sections, potentially one section
-for each unit in the program. It is important that these execute
-in the correct order. Correctness here means that, taking the above
-example of the declaration of @code{Sqrt_Half},
-if some other piece of
-elaboration code references @code{Sqrt_Half},
-then it must run after the
-section of elaboration code that contains the declaration of
-@code{Sqrt_Half}.
-
-There would never be any order of elaboration problem if we made a rule
-that whenever you @code{with} a unit, you must elaborate both the spec and body
-of that unit before elaborating the unit doing the @code{with}'ing:
-
-@smallexample
-@group
-@cartouche
-@b{with} Unit_1;
-@b{package} Unit_2 @b{is} ...
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-would require that both the body and spec of @code{Unit_1} be elaborated
-before the spec of @code{Unit_2}. However, a rule like that would be far too
-restrictive. In particular, it would make it impossible to have routines
-in separate packages that were mutually recursive.
-
-You might think that a clever enough compiler could look at the actual
-elaboration code and determine an appropriate correct order of elaboration,
-but in the general case, this is not possible. Consider the following
-example.
-
-In the body of @code{Unit_1}, we have a procedure @code{Func_1}
-that references
-the variable @code{Sqrt_1}, which is declared in the elaboration code
-of the body of @code{Unit_1}:
-
-@smallexample
-@cartouche
-Sqrt_1 : Float := Sqrt (0.1);
-@end cartouche
-@end smallexample
-
-@noindent
-The elaboration code of the body of @code{Unit_1} also contains:
-
-@smallexample
-@group
-@cartouche
-@b{if} expression_1 = 1 @b{then}
- Q := Unit_2.Func_2;
-@b{end if};
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-@code{Unit_2} is exactly parallel,
-it has a procedure @code{Func_2} that references
-the variable @code{Sqrt_2}, which is declared in the elaboration code of
-the body @code{Unit_2}:
-
-@smallexample
-@cartouche
-Sqrt_2 : Float := Sqrt (0.1);
-@end cartouche
-@end smallexample
-
-@noindent
-The elaboration code of the body of @code{Unit_2} also contains:
-
-@smallexample
-@group
-@cartouche
-@b{if} expression_2 = 2 @b{then}
- Q := Unit_1.Func_1;
-@b{end if};
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-Now the question is, which of the following orders of elaboration is
-acceptable:
-
-@smallexample
-@group
-Spec of Unit_1
-Spec of Unit_2
-Body of Unit_1
-Body of Unit_2
-@end group
-@end smallexample
-
-@noindent
-or
-
-@smallexample
-@group
-Spec of Unit_2
-Spec of Unit_1
-Body of Unit_2
-Body of Unit_1
-@end group
-@end smallexample
-
-@noindent
-If you carefully analyze the flow here, you will see that you cannot tell
-at compile time the answer to this question.
-If @code{expression_1} is not equal to 1,
-and @code{expression_2} is not equal to 2,
-then either order is acceptable, because neither of the function calls is
-executed. If both tests evaluate to true, then neither order is acceptable
-and in fact there is no correct order.
-
-If one of the two expressions is true, and the other is false, then one
-of the above orders is correct, and the other is incorrect. For example,
-if @code{expression_1} = 1 and @code{expression_2} /= 2,
-then the call to @code{Func_2}
-will occur, but not the call to @code{Func_1.}
-This means that it is essential
-to elaborate the body of @code{Unit_1} before
-the body of @code{Unit_2}, so the first
-order of elaboration is correct and the second is wrong.
-
-By making @code{expression_1} and @code{expression_2}
-depend on input data, or perhaps
-the time of day, we can make it impossible for the compiler or binder
-to figure out which of these expressions will be true, and hence it
-is impossible to guarantee a safe order of elaboration at run time.
-
-@node Checking the Elaboration Order in Ada 95
-@section Checking the Elaboration Order in Ada 95
-
-@noindent
-In some languages that involve the same kind of elaboration problems,
-e.g. Java and C++, the programmer is expected to worry about these
-ordering problems himself, and it is common to
-write a program in which an incorrect elaboration order gives
-surprising results, because it references variables before they
-are initialized.
-Ada 95 is designed to be a safe language, and a programmer-beware approach is
-clearly not sufficient. Consequently, the language provides three lines
-of defense:
-
-@table @asis
-@item Standard rules
-Some standard rules restrict the possible choice of elaboration
-order. In particular, if you @code{with} a unit, then its spec is always
-elaborated before the unit doing the @code{with}. Similarly, a parent
-spec is always elaborated before the child spec, and finally
-a spec is always elaborated before its corresponding body.
-
-@item Dynamic elaboration checks
-@cindex Elaboration checks
-@cindex Checks, elaboration
-Dynamic checks are made at run time, so that if some entity is accessed
-before it is elaborated (typically by means of a subprogram call)
-then the exception (@code{Program_Error}) is raised.
-
-@item Elaboration control
-Facilities are provided for the programmer to specify the desired order
-of elaboration.
-@end table
-
-Let's look at these facilities in more detail. First, the rules for
-dynamic checking. One possible rule would be simply to say that the
-exception is raised if you access a variable which has not yet been
-elaborated. The trouble with this approach is that it could require
-expensive checks on every variable reference. Instead Ada 95 has two
-rules which are a little more restrictive, but easier to check, and
-easier to state:
-
-@table @asis
-@item Restrictions on calls
-A subprogram can only be called at elaboration time if its body
-has been elaborated. The rules for elaboration given above guarantee
-that the spec of the subprogram has been elaborated before the
-call, but not the body. If this rule is violated, then the
-exception @code{Program_Error} is raised.
-
-@item Restrictions on instantiations
-A generic unit can only be instantiated if the body of the generic
-unit has been elaborated. Again, the rules for elaboration given above
-guarantee that the spec of the generic unit has been elaborated
-before the instantiation, but not the body. If this rule is
-violated, then the exception @code{Program_Error} is raised.
-@end table
-
-@noindent
-The idea is that if the body has been elaborated, then any variables
-it references must have been elaborated; by checking for the body being
-elaborated we guarantee that none of its references causes any
-trouble. As we noted above, this is a little too restrictive, because a
-subprogram that has no non-local references in its body may in fact be safe
-to call. However, it really would be unsafe to rely on this, because
-it would mean that the caller was aware of details of the implementation
-in the body. This goes against the basic tenets of Ada.
-
-A plausible implementation can be described as follows.
-A Boolean variable is associated with each subprogram
-and each generic unit. This variable is initialized to False, and is set to
-True at the point body is elaborated. Every call or instantiation checks the
-variable, and raises @code{Program_Error} if the variable is False.
-
-Note that one might think that it would be good enough to have one Boolean
-variable for each package, but that would not deal with cases of trying
-to call a body in the same package as the call
-that has not been elaborated yet.
-Of course a compiler may be able to do enough analysis to optimize away
-some of the Boolean variables as unnecessary, and @code{GNAT} indeed
-does such optimizations, but still the easiest conceptual model is to
-think of there being one variable per subprogram.
-
-@node Controlling the Elaboration Order in Ada 95
-@section Controlling the Elaboration Order in Ada 95
-
-@noindent
-In the previous section we discussed the rules in Ada 95 which ensure
-that @code{Program_Error} is raised if an incorrect elaboration order is
-chosen. This prevents erroneous executions, but we need mechanisms to
-specify a correct execution and avoid the exception altogether.
-To achieve this, Ada 95 provides a number of features for controlling
-the order of elaboration. We discuss these features in this section.
-
-First, there are several ways of indicating to the compiler that a given
-unit has no elaboration problems:
-
-@table @asis
-@item packages that do not require a body
-In Ada 95, a library package that does not require a body does not permit
-a body. This means that if we have a such a package, as in:
-
-@smallexample
-@group
-@cartouche
-@b{package} Definitions @b{is}
- @b{generic}
- @b{type} m @b{is new} integer;
- @b{package} Subp @b{is}
- @b{type} a @b{is array} (1 .. 10) @b{of} m;
- @b{type} b @b{is array} (1 .. 20) @b{of} m;
- @b{end} Subp;
-@b{end} Definitions;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-A package that @code{with}'s @code{Definitions} may safely instantiate
-@code{Definitions.Subp} because the compiler can determine that there
-definitely is no package body to worry about in this case
-
-@item pragma Pure
-@cindex pragma Pure
-@findex Pure
-Places sufficient restrictions on a unit to guarantee that
-no call to any subprogram in the unit can result in an
-elaboration problem. This means that the compiler does not need
-to worry about the point of elaboration of such units, and in
-particular, does not need to check any calls to any subprograms
-in this unit.
-
-@item pragma Preelaborate
-@findex Preelaborate
-@cindex pragma Preelaborate
-This pragma places slightly less stringent restrictions on a unit than
-does pragma Pure,
-but these restrictions are still sufficient to ensure that there
-are no elaboration problems with any calls to the unit.
-
-@item pragma Elaborate_Body
-@findex Elaborate_Body
-@cindex pragma Elaborate_Body
-This pragma requires that the body of a unit be elaborated immediately
-after its spec. Suppose a unit @code{A} has such a pragma,
-and unit @code{B} does
-a @code{with} of unit @code{A}. Recall that the standard rules require
-the spec of unit @code{A}
-to be elaborated before the @code{with}'ing unit; given the pragma in
-@code{A}, we also know that the body of @code{A}
-will be elaborated before @code{B}, so
-that calls to @code{A} are safe and do not need a check.
-@end table
-
-@noindent
-Note that,
-unlike pragma @code{Pure} and pragma @code{Preelaborate},
-the use of
-@code{Elaborate_Body} does not guarantee that the program is
-free of elaboration problems, because it may not be possible
-to satisfy the requested elaboration order.
-Let's go back to the example with @code{Unit_1} and @code{Unit_2}.
-If a programmer
-marks @code{Unit_1} as @code{Elaborate_Body},
-and not @code{Unit_2,} then the order of
-elaboration will be:
-
-@smallexample
-@group
-Spec of Unit_2
-Spec of Unit_1
-Body of Unit_1
-Body of Unit_2
-@end group
-@end smallexample
-
-@noindent
-Now that means that the call to @code{Func_1} in @code{Unit_2}
-need not be checked,
-it must be safe. But the call to @code{Func_2} in
-@code{Unit_1} may still fail if
-@code{Expression_1} is equal to 1,
-and the programmer must still take
-responsibility for this not being the case.
-
-If all units carry a pragma @code{Elaborate_Body}, then all problems are
-eliminated, except for calls entirely within a body, which are
-in any case fully under programmer control. However, using the pragma
-everywhere is not always possible.
-In particular, for our @code{Unit_1}/@code{Unit_2} example, if
-we marked both of them as having pragma @code{Elaborate_Body}, then
-clearly there would be no possible elaboration order.
-
-The above pragmas allow a server to guarantee safe use by clients, and
-clearly this is the preferable approach. Consequently a good rule in
-Ada 95 is to mark units as @code{Pure} or @code{Preelaborate} if possible,
-and if this is not possible,
-mark them as @code{Elaborate_Body} if possible.
-As we have seen, there are situations where neither of these
-three pragmas can be used.
-So we also provide methods for clients to control the
-order of elaboration of the servers on which they depend:
-
-@table @asis
-@item pragma Elaborate (unit)
-@findex Elaborate
-@cindex pragma Elaborate
-This pragma is placed in the context clause, after a @code{with} clause,
-and it requires that the body of the named unit be elaborated before
-the unit in which the pragma occurs. The idea is to use this pragma
-if the current unit calls at elaboration time, directly or indirectly,
-some subprogram in the named unit.
-
-@item pragma Elaborate_All (unit)
-@findex Elaborate_All
-@cindex pragma Elaborate_All
-This is a stronger version of the Elaborate pragma. Consider the
-following example:
-
-@smallexample
-Unit A @code{with}'s unit B and calls B.Func in elab code
-Unit B @code{with}'s unit C, and B.Func calls C.Func
-@end smallexample
-
-@noindent
-Now if we put a pragma @code{Elaborate (B)}
-in unit @code{A}, this ensures that the
-body of @code{B} is elaborated before the call, but not the
-body of @code{C}, so
-the call to @code{C.Func} could still cause @code{Program_Error} to
-be raised.
-
-The effect of a pragma @code{Elaborate_All} is stronger, it requires
-not only that the body of the named unit be elaborated before the
-unit doing the @code{with}, but also the bodies of all units that the
-named unit uses, following @code{with} links transitively. For example,
-if we put a pragma @code{Elaborate_All (B)} in unit @code{A},
-then it requires
-not only that the body of @code{B} be elaborated before @code{A},
-but also the
-body of @code{C}, because @code{B} @code{with}'s @code{C}.
-@end table
-
-@noindent
-We are now in a position to give a usage rule in Ada 95 for avoiding
-elaboration problems, at least if dynamic dispatching and access to
-subprogram values are not used. We will handle these cases separately
-later.
-
-The rule is simple. If a unit has elaboration code that can directly or
-indirectly make a call to a subprogram in a @code{with}'ed unit, or instantiate
-a generic unit in a @code{with}'ed unit,
-then if the @code{with}'ed unit does not have
-pragma @code{Pure} or @code{Preelaborate}, then the client should have
-a pragma @code{Elaborate_All}
-for the @code{with}'ed unit. By following this rule a client is
-assured that calls can be made without risk of an exception.
-If this rule is not followed, then a program may be in one of four
-states:
-
-@table @asis
-@item No order exists
-No order of elaboration exists which follows the rules, taking into
-account any @code{Elaborate}, @code{Elaborate_All},
-or @code{Elaborate_Body} pragmas. In
-this case, an Ada 95 compiler must diagnose the situation at bind
-time, and refuse to build an executable program.
-
-@item One or more orders exist, all incorrect
-One or more acceptable elaboration orders exists, and all of them
-generate an elaboration order problem. In this case, the binder
-can build an executable program, but @code{Program_Error} will be raised
-when the program is run.
-
-@item Several orders exist, some right, some incorrect
-One or more acceptable elaboration orders exists, and some of them
-work, and some do not. The programmer has not controlled
-the order of elaboration, so the binder may or may not pick one of
-the correct orders, and the program may or may not raise an
-exception when it is run. This is the worst case, because it means
-that the program may fail when moved to another compiler, or even
-another version of the same compiler.
-
-@item One or more orders exists, all correct
-One ore more acceptable elaboration orders exist, and all of them
-work. In this case the program runs successfully. This state of
-affairs can be guaranteed by following the rule we gave above, but
-may be true even if the rule is not followed.
-@end table
-
-@noindent
-Note that one additional advantage of following our Elaborate_All rule
-is that the program continues to stay in the ideal (all orders OK) state
-even if maintenance
-changes some bodies of some subprograms. Conversely, if a program that does
-not follow this rule happens to be safe at some point, this state of affairs
-may deteriorate silently as a result of maintenance changes.
-
-You may have noticed that the above discussion did not mention
-the use of @code{Elaborate_Body}. This was a deliberate omission. If you
-@code{with} an @code{Elaborate_Body} unit, it still may be the case that
-code in the body makes calls to some other unit, so it is still necessary
-to use @code{Elaborate_All} on such units.
-
-@node Controlling Elaboration in GNAT - Internal Calls
-@section Controlling Elaboration in GNAT - Internal Calls
-
-@noindent
-In the case of internal calls, i.e. calls within a single package, the
-programmer has full control over the order of elaboration, and it is up
-to the programmer to elaborate declarations in an appropriate order. For
-example writing:
-
-@smallexample
-@group
-@cartouche
-@b{function} One @b{return} Float;
-
-Q : Float := One;
-
-@b{function} One @b{return} Float @b{is}
-@b{begin}
- return 1.0;
-@b{end} One;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-will obviously raise @code{Program_Error} at run time, because function
-One will be called before its body is elaborated. In this case GNAT will
-generate a warning that the call will raise @code{Program_Error}:
-
-@smallexample
-@group
-@cartouche
- 1. procedure y is
- 2. function One return Float;
- 3.
- 4. Q : Float := One;
- |
- >>> warning: cannot call "One" before body is elaborated
- >>> warning: Program_Error will be raised at run time
-
- 5.
- 6. function One return Float is
- 7. begin
- 8. return 1.0;
- 9. end One;
-10.
-11. begin
-12. null;
-13. end;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-Note that in this particular case, it is likely that the call is safe, because
-the function @code{One} does not access any global variables.
-Nevertheless in Ada 95, we do not want the validity of the check to depend on
-the contents of the body (think about the separate compilation case), so this
-is still wrong, as we discussed in the previous sections.
-
-The error is easily corrected by rearranging the declarations so that the
-body of One appears before the declaration containing the call
-(note that in Ada 95,
-declarations can appear in any order, so there is no restriction that
-would prevent this reordering, and if we write:
-
-@smallexample
-@group
-@cartouche
-@b{function} One @b{return} Float;
-
-@b{function} One @b{return} Float @b{is}
-@b{begin}
- return 1.0;
-@b{end} One;
-
-Q : Float := One;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-then all is well, no warning is generated, and no
-@code{Program_Error} exception
-will be raised.
-Things are more complicated when a chain of subprograms is executed:
-
-@smallexample
-@group
-@cartouche
-@b{function} A @b{return} Integer;
-@b{function} B @b{return} Integer;
-@b{function} C @b{return} Integer;
-
-@b{function} B @b{return} Integer @b{is begin return} A; @b{end};
-@b{function} C @b{return} Integer @b{is begin return} B; @b{end};
-
-X : Integer := C;
-
-@b{function} A @b{return} Integer @b{is begin return} 1; @b{end};
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-Now the call to @code{C}
-at elaboration time in the declaration of @code{X} is correct, because
-the body of @code{C} is already elaborated,
-and the call to @code{B} within the body of
-@code{C} is correct, but the call
-to @code{A} within the body of @code{B} is incorrect, because the body
-of @code{A} has not been elaborated, so @code{Program_Error}
-will be raised on the call to @code{A}.
-In this case GNAT will generate a
-warning that @code{Program_Error} may be
-raised at the point of the call. Let's look at the warning:
-
-@smallexample
-@group
-@cartouche
- 1. procedure x is
- 2. function A return Integer;
- 3. function B return Integer;
- 4. function C return Integer;
- 5.
- 6. function B return Integer is begin return A; end;
- |
- >>> warning: call to "A" before body is elaborated may
- raise Program_Error
- >>> warning: "B" called at line 7
- >>> warning: "C" called at line 9
-
- 7. function C return Integer is begin return B; end;
- 8.
- 9. X : Integer := C;
-10.
-11. function A return Integer is begin return 1; end;
-12.
-13. begin
-14. null;
-15. end;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-Note that the message here says "may raise", instead of the direct case,
-where the message says "will be raised". That's because whether
-@code{A} is
-actually called depends in general on run-time flow of control.
-For example, if the body of @code{B} said
-
-@smallexample
-@group
-@cartouche
-@b{function} B @b{return} Integer @b{is}
-@b{begin}
- @b{if} some-condition-depending-on-input-data @b{then}
- @b{return} A;
- @b{else}
- @b{return} 1;
- @b{end if};
-@b{end} B;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-then we could not know until run time whether the incorrect call to A would
-actually occur, so @code{Program_Error} might
-or might not be raised. It is possible for a compiler to
-do a better job of analyzing bodies, to
-determine whether or not @code{Program_Error}
-might be raised, but it certainly
-couldn't do a perfect job (that would require solving the halting problem
-and is provably impossible), and because this is a warning anyway, it does
-not seem worth the effort to do the analysis. Cases in which it
-would be relevant are rare.
-
-In practice, warnings of either of the forms given
-above will usually correspond to
-real errors, and should be examined carefully and eliminated.
-In the rare case where a warning is bogus, it can be suppressed by any of
-the following methods:
-
-@itemize @bullet
-@item
-Compile with the @option{-gnatws} switch set
-
-@item
-Suppress @code{Elaboration_Checks} for the called subprogram
-
-@item
-Use pragma @code{Warnings_Off} to turn warnings off for the call
-@end itemize
-
-@noindent
-For the internal elaboration check case,
-GNAT by default generates the
-necessary run-time checks to ensure
-that @code{Program_Error} is raised if any
-call fails an elaboration check. Of course this can only happen if a
-warning has been issued as described above. The use of pragma
-@code{Suppress (Elaboration_Checks)} may (but is not guaranteed to) suppress
-some of these checks, meaning that it may be possible (but is not
-guaranteed) for a program to be able to call a subprogram whose body
-is not yet elaborated, without raising a @code{Program_Error} exception.
-
-@node Controlling Elaboration in GNAT - External Calls
-@section Controlling Elaboration in GNAT - External Calls
-
-@noindent
-The previous section discussed the case in which the execution of a
-particular thread of elaboration code occurred entirely within a
-single unit. This is the easy case to handle, because a programmer
-has direct and total control over the order of elaboration, and
-furthermore, checks need only be generated in cases which are rare
-and which the compiler can easily detect.
-The situation is more complex when separate compilation is taken into account.
-Consider the following:
-
-@smallexample
-@cartouche
-@group
-@b{package} Math @b{is}
- @b{function} Sqrt (Arg : Float) @b{return} Float;
-@b{end} Math;
-
-@b{package body} Math @b{is}
- @b{function} Sqrt (Arg : Float) @b{return} Float @b{is}
- @b{begin}
- ...
- @b{end} Sqrt;
-@b{end} Math;
-@end group
-@group
-@b{with} Math;
-@b{package} Stuff @b{is}
- X : Float := Math.Sqrt (0.5);
-@b{end} Stuff;
-
-@b{with} Stuff;
-@b{procedure} Main @b{is}
-@b{begin}
- ...
-@b{end} Main;
-@end group
-@end cartouche
-@end smallexample
-
-@noindent
-where @code{Main} is the main program. When this program is executed, the
-elaboration code must first be executed, and one of the jobs of the
-binder is to determine the order in which the units of a program are
-to be elaborated. In this case we have four units: the spec and body
-of @code{Math},
-the spec of @code{Stuff} and the body of @code{Main}).
-In what order should the four separate sections of elaboration code
-be executed?
-
-There are some restrictions in the order of elaboration that the binder
-can choose. In particular, if unit U has a @code{with}
-for a package @code{X}, then you
-are assured that the spec of @code{X}
-is elaborated before U , but you are
-not assured that the body of @code{X}
-is elaborated before U.
-This means that in the above case, the binder is allowed to choose the
-order:
-
-@smallexample
-spec of Math
-spec of Stuff
-body of Math
-body of Main
-@end smallexample
-
-@noindent
-but that's not good, because now the call to @code{Math.Sqrt}
-that happens during
-the elaboration of the @code{Stuff}
-spec happens before the body of @code{Math.Sqrt} is
-elaborated, and hence causes @code{Program_Error} exception to be raised.
-At first glance, one might say that the binder is misbehaving, because
-obviously you want to elaborate the body of something you @code{with}
-first, but
-that is not a general rule that can be followed in all cases. Consider
-
-@smallexample
-@group
-@cartouche
-@b{package} X @b{is} ...
-
-@b{package} Y @b{is} ...
-
-@b{with} X;
-@b{package body} Y @b{is} ...
-
-@b{with} Y;
-@b{package body} X @b{is} ...
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-This is a common arrangement, and, apart from the order of elaboration
-problems that might arise in connection with elaboration code, this works fine.
-A rule that says that you must first elaborate the body of anything you
-@code{with} cannot work in this case:
-the body of @code{X} @code{with}'s @code{Y},
-which means you would have to
-elaborate the body of @code{Y} first, but that @code{with}'s @code{X},
-which means
-you have to elaborate the body of @code{X} first, but ... and we have a
-loop that cannot be broken.
-
-It is true that the binder can in many cases guess an order of elaboration
-that is unlikely to cause a @code{Program_Error}
-exception to be raised, and it tries to do so (in the
-above example of @code{Math/Stuff/Spec}, the GNAT binder will
-by default
-elaborate the body of @code{Math} right after its spec, so all will be well).
-
-However, a program that blindly relies on the binder to be helpful can
-get into trouble, as we discussed in the previous sections, so
-GNAT
-provides a number of facilities for assisting the programmer in
-developing programs that are robust with respect to elaboration order.
-
-@node Default Behavior in GNAT - Ensuring Safety
-@section Default Behavior in GNAT - Ensuring Safety
-
-@noindent
-The default behavior in GNAT ensures elaboration safety. In its
-default mode GNAT implements the
-rule we previously described as the right approach. Let's restate it:
-
-@itemize
-@item
-@emph{If a unit has elaboration code that can directly or indirectly make a
-call to a subprogram in a @code{with}'ed unit, or instantiate a generic unit
-in a @code{with}'ed unit, then if the @code{with}'ed unit
-does not have pragma @code{Pure} or
-@code{Preelaborate}, then the client should have an
-@code{Elaborate_All} for the @code{with}'ed unit.}
-@end itemize
-
-@noindent
-By following this rule a client
-is assured that calls and instantiations can be made without risk of an exception.
-
-In this mode GNAT traces all calls that are potentially made from
-elaboration code, and puts in any missing implicit @code{Elaborate_All}
-pragmas.
-The advantage of this approach is that no elaboration problems
-are possible if the binder can find an elaboration order that is
-consistent with these implicit @code{Elaborate_All} pragmas. The
-disadvantage of this approach is that no such order may exist.
-
-If the binder does not generate any diagnostics, then it means that it
-has found an elaboration order that is guaranteed to be safe. However,
-the binder may still be relying on implicitly generated
-@code{Elaborate_All} pragmas so portability to other compilers than
-GNAT is not guaranteed.
-
-If it is important to guarantee portability, then the compilations should
-use the
-@option{-gnatwl}
-(warn on elaboration problems) switch. This will cause warning messages
-to be generated indicating the missing @code{Elaborate_All} pragmas.
-Consider the following source program:
-
-@smallexample
-@group
-@cartouche
-@b{with} k;
-@b{package} j @b{is}
- m : integer := k.r;
-@b{end};
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-where it is clear that there
-should be a pragma @code{Elaborate_All}
-for unit @code{k}. An implicit pragma will be generated, and it is
-likely that the binder will be able to honor it. However,
-it is safer to include the pragma explicitly in the source. If this
-unit is compiled with the
-@option{-gnatwl}
-switch, then the compiler outputs a warning:
-
-@smallexample
-@group
-@cartouche
-1. with k;
-2. package j is
-3. m : integer := k.r;
- |
- >>> warning: call to "r" may raise Program_Error
- >>> warning: missing pragma Elaborate_All for "k"
-
-4. end;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-and these warnings can be used as a guide for supplying manually
-the missing pragmas.
-
-This default mode is more restrictive than the Ada Reference
-Manual, and it is possible to construct programs which will compile
-using the dynamic model described there, but will run into a
-circularity using the safer static model we have described.
-
-Of course any Ada compiler must be able to operate in a mode
-consistent with the requirements of the Ada Reference Manual,
-and in particular must have the capability of implementing the
-standard dynamic model of elaboration with run-time checks.
-
-In GNAT, this standard mode can be achieved either by the use of
-the @option{-gnatE} switch on the compiler (@code{gcc} or @code{gnatmake})
-command, or by the use of the configuration pragma:
-
-@smallexample
-pragma Elaboration_Checks (RM);
-@end smallexample
-
-@noindent
-Either approach will cause the unit affected to be compiled using the
-standard dynamic run-time elaboration checks described in the Ada
-Reference Manual. The static model is generally preferable, since it
-is clearly safer to rely on compile and link time checks rather than
-run-time checks. However, in the case of legacy code, it may be
-difficult to meet the requirements of the static model. This
-issue is further discussed in
-@ref{What to Do If the Default Elaboration Behavior Fails}.
-
-Note that the static model provides a strict subset of the allowed
-behavior and programs of the Ada Reference Manual, so if you do
-adhere to the static model and no circularities exist,
-then you are assured that your program will
-work using the dynamic model.
-
-@node Elaboration Issues for Library Tasks
-@section Elaboration Issues for Library Tasks
-@cindex Library tasks, elaboration issues
-@cindex Elaboration of library tasks
-
-@noindent
-In this section we examine special elaboration issues that arise for
-programs that declare library level tasks.
-
-Generally the model of execution of an Ada program is that all units are
-elaborated, and then execution of the program starts. However, the
-declaration of library tasks definitely does not fit this model. The
-reason for this is that library tasks start as soon as they are declared
-(more precisely, as soon as the statement part of the enclosing package
-body is reached), that is to say before elaboration
-of the program is complete. This means that if such a task calls a
-subprogram, or an entry in another task, the callee may or may not be
-elaborated yet, and in the standard
-Reference Manual model of dynamic elaboration checks, you can even
-get timing dependent Program_Error exceptions, since there can be
-a race between the elaboration code and the task code.
-
-The static model of elaboration in GNAT seeks to avoid all such
-dynamic behavior, by being conservative, and the conservative
-approach in this particular case is to assume that all the code
-in a task body is potentially executed at elaboration time if
-a task is declared at the library level.
-
-This can definitely result in unexpected circularities. Consider
-the following example
-
-@smallexample
-package Decls is
- task Lib_Task is
- entry Start;
- end Lib_Task;
-
- type My_Int is new Integer;
-
- function Ident (M : My_Int) return My_Int;
-end Decls;
-
-with Utils;
-package body Decls is
- task body Lib_Task is
- begin
- accept Start;
- Utils.Put_Val (2);
- end Lib_Task;
-
- function Ident (M : My_Int) return My_Int is
- begin
- return M;
- end Ident;
-end Decls;
-
-with Decls;
-package Utils is
- procedure Put_Val (Arg : Decls.My_Int);
-end Utils;
-
-with Text_IO;
-package body Utils is
- procedure Put_Val (Arg : Decls.My_Int) is
- begin
- Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
- end Put_Val;
-end Utils;
-
-with Decls;
-procedure Main is
-begin
- Decls.Lib_Task.Start;
-end;
-@end smallexample
-
-@noindent
-If the above example is compiled in the default static elaboration
-mode, then a circularity occurs. The circularity comes from the call
-@code{Utils.Put_Val} in the task body of @code{Decls.Lib_Task}. Since
-this call occurs in elaboration code, we need an implicit pragma
-@code{Elaborate_All} for @code{Utils}. This means that not only must
-the spec and body of @code{Utils} be elaborated before the body
-of @code{Decls}, but also the spec and body of any unit that is
-@code{with'ed} by the body of @code{Utils} must also be elaborated before
-the body of @code{Decls}. This is the transitive implication of
-pragma @code{Elaborate_All} and it makes sense, because in general
-the body of @code{Put_Val} might have a call to something in a
-@code{with'ed} unit.
-
-In this case, the body of Utils (actually its spec) @code{with's}
-@code{Decls}. Unfortunately this means that the body of @code{Decls}
-must be elaborated before itself, in case there is a call from the
-body of @code{Utils}.
-
-Here is the exact chain of events we are worrying about:
-
-@enumerate
-@item
-In the body of @code{Decls} a call is made from within the body of a library
-task to a subprogram in the package @code{Utils}. Since this call may
-occur at elaboration time (given that the task is activated at elaboration
-time), we have to assume the worst, i.e. that the
-call does happen at elaboration time.
-
-@item
-This means that the body and spec of @code{Util} must be elaborated before
-the body of @code{Decls} so that this call does not cause an access before
-elaboration.
-
-@item
-Within the body of @code{Util}, specifically within the body of
-@code{Util.Put_Val} there may be calls to any unit @code{with}'ed
-by this package.
-
-@item
-One such @code{with}'ed package is package @code{Decls}, so there
-might be a call to a subprogram in @code{Decls} in @code{Put_Val}.
-In fact there is such a call in this example, but we would have to
-assume that there was such a call even if it were not there, since
-we are not supposed to write the body of @code{Decls} knowing what
-is in the body of @code{Utils}; certainly in the case of the
-static elaboration model, the compiler does not know what is in
-other bodies and must assume the worst.
-
-@item
-This means that the spec and body of @code{Decls} must also be
-elaborated before we elaborate the unit containing the call, but
-that unit is @code{Decls}! This means that the body of @code{Decls}
-must be elaborated before itself, and that's a circularity.
-@end enumerate
-
-@noindent
-Indeed, if you add an explicit pragma Elaborate_All for @code{Utils} in
-the body of @code{Decls} you will get a true Ada Reference Manual
-circularity that makes the program illegal.
-
-In practice, we have found that problems with the static model of
-elaboration in existing code often arise from library tasks, so
-we must address this particular situation.
-
-Note that if we compile and run the program above, using the dynamic model of
-elaboration (that is to say use the @option{-gnatE} switch),
-then it compiles, binds,
-links, and runs, printing the expected result of 2. Therefore in some sense
-the circularity here is only apparent, and we need to capture
-the properties of this program that distinguish it from other library-level
-tasks that have real elaboration problems.
-
-We have four possible answers to this question:
-
-@itemize @bullet
-
-@item
-Use the dynamic model of elaboration.
-
-If we use the @option{-gnatE} switch, then as noted above, the program works.
-Why is this? If we examine the task body, it is apparent that the task cannot
-proceed past the
-@code{accept} statement until after elaboration has been completed, because
-the corresponding entry call comes from the main program, not earlier.
-This is why the dynamic model works here. But that's really giving
-up on a precise analysis, and we prefer to take this approach only if we cannot
-solve the
-problem in any other manner. So let us examine two ways to reorganize
-the program to avoid the potential elaboration problem.
-
-@item
-Split library tasks into separate packages.
-
-Write separate packages, so that library tasks are isolated from
-other declarations as much as possible. Let us look at a variation on
-the above program.
-
-@smallexample
-package Decls1 is
- task Lib_Task is
- entry Start;
- end Lib_Task;
-end Decls1;
-
-with Utils;
-package body Decls1 is
- task body Lib_Task is
- begin
- accept Start;
- Utils.Put_Val (2);
- end Lib_Task;
-end Decls1;
-
-package Decls2 is
- type My_Int is new Integer;
- function Ident (M : My_Int) return My_Int;
-end Decls2;
-
-with Utils;
-package body Decls2 is
- function Ident (M : My_Int) return My_Int is
- begin
- return M;
- end Ident;
-end Decls2;
-
-with Decls2;
-package Utils is
- procedure Put_Val (Arg : Decls2.My_Int);
-end Utils;
-
-with Text_IO;
-package body Utils is
- procedure Put_Val (Arg : Decls2.My_Int) is
- begin
- Text_IO.Put_Line (Decls2.My_Int'Image (Decls2.Ident (Arg)));
- end Put_Val;
-end Utils;
-
-with Decls1;
-procedure Main is
-begin
- Decls1.Lib_Task.Start;
-end;
-@end smallexample
-
-@noindent
-All we have done is to split @code{Decls} into two packages, one
-containing the library task, and one containing everything else. Now
-there is no cycle, and the program compiles, binds, links and executes
-using the default static model of elaboration.
-
-@item
-Declare separate task types.
-
-A significant part of the problem arises because of the use of the
-single task declaration form. This means that the elaboration of
-the task type, and the elaboration of the task itself (i.e. the
-creation of the task) happen at the same time. A good rule
-of style in Ada 95 is to always create explicit task types. By
-following the additional step of placing task objects in separate
-packages from the task type declaration, many elaboration problems
-are avoided. Here is another modified example of the example program:
-
-@smallexample
-package Decls is
- task type Lib_Task_Type is
- entry Start;
- end Lib_Task_Type;
-
- type My_Int is new Integer;
-
- function Ident (M : My_Int) return My_Int;
-end Decls;
-
-with Utils;
-package body Decls is
- task body Lib_Task_Type is
- begin
- accept Start;
- Utils.Put_Val (2);
- end Lib_Task_Type;
-
- function Ident (M : My_Int) return My_Int is
- begin
- return M;
- end Ident;
-end Decls;
-
-with Decls;
-package Utils is
- procedure Put_Val (Arg : Decls.My_Int);
-end Utils;
-
-with Text_IO;
-package body Utils is
- procedure Put_Val (Arg : Decls.My_Int) is
- begin
- Text_IO.Put_Line (Decls.My_Int'Image (Decls.Ident (Arg)));
- end Put_Val;
-end Utils;
-
-with Decls;
-package Declst is
- Lib_Task : Decls.Lib_Task_Type;
-end Declst;
-
-with Declst;
-procedure Main is
-begin
- Declst.Lib_Task.Start;
-end;
-@end smallexample
-
-@noindent
-What we have done here is to replace the @code{task} declaration in
-package @code{Decls} with a @code{task type} declaration. Then we
-introduce a separate package @code{Declst} to contain the actual
-task object. This separates the elaboration issues for
-the @code{task type}
-declaration, which causes no trouble, from the elaboration issues
-of the task object, which is also unproblematic, since it is now independent
-of the elaboration of @code{Utils}.
-This separation of concerns also corresponds to
-a generally sound engineering principle of separating declarations
-from instances. This version of the program also compiles, binds, links,
-and executes, generating the expected output.
-
-@item
-Use No_Entry_Calls_In_Elaboration_Code restriction.
-@cindex No_Entry_Calls_In_Elaboration_Code
-
-The previous two approaches described how a program can be restructured
-to avoid the special problems caused by library task bodies. in practice,
-however, such restructuring may be difficult to apply to existing legacy code,
-so we must consider solutions that do not require massive rewriting.
-
-Let us consider more carefully why our original sample program works
-under the dynamic model of elaboration. The reason is that the code
-in the task body blocks immediately on the @code{accept}
-statement. Now of course there is nothing to prohibit elaboration
-code from making entry calls (for example from another library level task),
-so we cannot tell in isolation that
-the task will not execute the accept statement during elaboration.
-
-However, in practice it is very unusual to see elaboration code
-make any entry calls, and the pattern of tasks starting
-at elaboration time and then immediately blocking on @code{accept} or
-@code{select} statements is very common. What this means is that
-the compiler is being too pessimistic when it analyzes the
-whole package body as though it might be executed at elaboration
-time.
-
-If we know that the elaboration code contains no entry calls, (a very safe
-assumption most of the time, that could almost be made the default
-behavior), then we can compile all units of the program under control
-of the following configuration pragma:
-
-@smallexample
-pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);
-@end smallexample
-
-@noindent
-This pragma can be placed in the @file{gnat.adc} file in the usual
-manner. If we take our original unmodified program and compile it
-in the presence of a @file{gnat.adc} containing the above pragma,
-then once again, we can compile, bind, link, and execute, obtaining
-the expected result. In the presence of this pragma, the compiler does
-not trace calls in a task body, that appear after the first @code{accept}
-or @code{select} statement, and therefore does not report a potential
-circularity in the original program.
-
-The compiler will check to the extent it can that the above
-restriction is not violated, but it is not always possible to do a
-complete check at compile time, so it is important to use this
-pragma only if the stated restriction is in fact met, that is to say
-no task receives an entry call before elaboration of all units is completed.
-
-@end itemize
-
-@node Mixing Elaboration Models
-@section Mixing Elaboration Models
-@noindent
-So far, we have assumed that the entire program is either compiled
-using the dynamic model or static model, ensuring consistency. It
-is possible to mix the two models, but rules have to be followed
-if this mixing is done to ensure that elaboration checks are not
-omitted.
-
-The basic rule is that @emph{a unit compiled with the static model cannot
-be @code{with'ed} by a unit compiled with the dynamic model}. The
-reason for this is that in the static model, a unit assumes that
-its clients guarantee to use (the equivalent of) pragma
-@code{Elaborate_All} so that no elaboration checks are required
-in inner subprograms, and this assumption is violated if the
-client is compiled with dynamic checks.
-
-The precise rule is as follows. A unit that is compiled with dynamic
-checks can only @code{with} a unit that meets at least one of the
-following criteria:
-
-@itemize @bullet
-
-@item
-The @code{with'ed} unit is itself compiled with dynamic elaboration
-checks (that is with the @option{-gnatE} switch.
-
-@item
-The @code{with'ed} unit is an internal GNAT implementation unit from
-the System, Interfaces, Ada, or GNAT hierarchies.
-
-@item
-The @code{with'ed} unit has pragma Preelaborate or pragma Pure.
-
-@item
-The @code{with'ing} unit (that is the client) has an explicit pragma
-@code{Elaborate_All} for the @code{with'ed} unit.
-
-@end itemize
-
-@noindent
-If this rule is violated, that is if a unit with dynamic elaboration
-checks @code{with's} a unit that does not meet one of the above four
-criteria, then the binder (@code{gnatbind}) will issue a warning
-similar to that in the following example:
-
-@smallexample
-warning: "x.ads" has dynamic elaboration checks and with's
-warning: "y.ads" which has static elaboration checks
-@end smallexample
-
-@noindent
-These warnings indicate that the rule has been violated, and that as a result
-elaboration checks may be missed in the resulting executable file.
-This warning may be suppressed using the @code{-ws} binder switch
-in the usual manner.
-
-One useful application of this mixing rule is in the case of a subsystem
-which does not itself @code{with} units from the remainder of the
-application. In this case, the entire subsystem can be compiled with
-dynamic checks to resolve a circularity in the subsystem, while
-allowing the main application that uses this subsystem to be compiled
-using the more reliable default static model.
-
-@node What to Do If the Default Elaboration Behavior Fails
-@section What to Do If the Default Elaboration Behavior Fails
-
-@noindent
-If the binder cannot find an acceptable order, it outputs detailed
-diagnostics. For example:
-@smallexample
-@group
-@iftex
-@leftskip=0cm
-@end iftex
-error: elaboration circularity detected
-info: "proc (body)" must be elaborated before "pack (body)"
-info: reason: Elaborate_All probably needed in unit "pack (body)"
-info: recompile "pack (body)" with -gnatwl
-info: for full details
-info: "proc (body)"
-info: is needed by its spec:
-info: "proc (spec)"
-info: which is withed by:
-info: "pack (body)"
-info: "pack (body)" must be elaborated before "proc (body)"
-info: reason: pragma Elaborate in unit "proc (body)"
-@end group
-
-@end smallexample
-
-@noindent
-In this case we have a cycle that the binder cannot break. On the one
-hand, there is an explicit pragma Elaborate in @code{proc} for
-@code{pack}. This means that the body of @code{pack} must be elaborated
-before the body of @code{proc}. On the other hand, there is elaboration
-code in @code{pack} that calls a subprogram in @code{proc}. This means
-that for maximum safety, there should really be a pragma
-Elaborate_All in @code{pack} for @code{proc} which would require that
-the body of @code{proc} be elaborated before the body of
-@code{pack}. Clearly both requirements cannot be satisfied.
-Faced with a circularity of this kind, you have three different options.
-
-@table @asis
-@item Fix the program
-The most desirable option from the point of view of long-term maintenance
-is to rearrange the program so that the elaboration problems are avoided.
-One useful technique is to place the elaboration code into separate
-child packages. Another is to move some of the initialization code to
-explicitly called subprograms, where the program controls the order
-of initialization explicitly. Although this is the most desirable option,
-it may be impractical and involve too much modification, especially in
-the case of complex legacy code.
-
-@item Perform dynamic checks
-If the compilations are done using the
-@option{-gnatE}
-(dynamic elaboration check) switch, then GNAT behaves in
-a quite different manner. Dynamic checks are generated for all calls
-that could possibly result in raising an exception. With this switch,
-the compiler does not generate implicit @code{Elaborate_All} pragmas.
-The behavior then is exactly as specified in the Ada 95 Reference Manual.
-The binder will generate an executable program that may or may not
-raise @code{Program_Error}, and then it is the programmer's job to ensure
-that it does not raise an exception. Note that it is important to
-compile all units with the switch, it cannot be used selectively.
-
-@item Suppress checks
-The drawback of dynamic checks is that they generate a
-significant overhead at run time, both in space and time. If you
-are absolutely sure that your program cannot raise any elaboration
-exceptions, and you still want to use the dynamic elaboration model,
-then you can use the configuration pragma
-@code{Suppress (Elaboration_Checks)} to suppress all such checks. For
-example this pragma could be placed in the @file{gnat.adc} file.
-
-@item Suppress checks selectively
-When you know that certain calls in elaboration code cannot possibly
-lead to an elaboration error, and the binder nevertheless generates warnings
-on those calls and inserts Elaborate_All pragmas that lead to elaboration
-circularities, it is possible to remove those warnings locally and obtain
-a program that will bind. Clearly this can be unsafe, and it is the
-responsibility of the programmer to make sure that the resulting program has
-no elaboration anomalies. The pragma @code{Suppress (Elaboration_Check)} can
-be used with different granularity to suppress warnings and break
-elaboration circularities:
-
-@itemize @bullet
-@item
-Place the pragma that names the called subprogram in the declarative part
-that contains the call.
-
-@item
-Place the pragma in the declarative part, without naming an entity. This
-disables warnings on all calls in the corresponding declarative region.
-
-@item
-Place the pragma in the package spec that declares the called subprogram,
-and name the subprogram. This disables warnings on all elaboration calls to
-that subprogram.
-
-@item
-Place the pragma in the package spec that declares the called subprogram,
-without naming any entity. This disables warnings on all elaboration calls to
-all subprograms declared in this spec.
-@end itemize
-
-@noindent
-These four cases are listed in order of decreasing safety, and therefore
-require increasing programmer care in their application. Consider the
-following program:
-@smallexample
-
-package Pack1 is
- function F1 return Integer;
- X1 : Integer;
-end Pack1;
-
-package Pack2 is
- function F2 return Integer;
- function Pure (x : integer) return integer;
- -- pragma Suppress (Elaboration_Check, On => Pure); -- (3)
- -- pragma Suppress (Elaboration_Check); -- (4)
-end Pack2;
-
-with Pack2;
-package body Pack1 is
- function F1 return Integer is
- begin
- return 100;
- end F1;
- Val : integer := Pack2.Pure (11); -- Elab. call (1)
-begin
- declare
- -- pragma Suppress(Elaboration_Check, Pack2.F2); -- (1)
- -- pragma Suppress(Elaboration_Check); -- (2)
- begin
- X1 := Pack2.F2 + 1; -- Elab. call (2)
- end;
-end Pack1;
-
-with Pack1;
-package body Pack2 is
- function F2 return Integer is
- begin
- return Pack1.F1;
- end F2;
- function Pure (x : integer) return integer is
- begin
- return x ** 3 - 3 * x;
- end;
-end Pack2;
-
-with Pack1, Ada.Text_IO;
-procedure Proc3 is
-begin
- Ada.Text_IO.Put_Line(Pack1.X1'Img); -- 101
-end Proc3;
-@end smallexample
-In the absence of any pragmas, an attempt to bind this program produces
-the following diagnostics:
-@smallexample
-@group
-@iftex
-@leftskip=.5cm
-@end iftex
-error: elaboration circularity detected
-info: "pack1 (body)" must be elaborated before "pack1 (body)"
-info: reason: Elaborate_All probably needed in unit "pack1 (body)"
-info: recompile "pack1 (body)" with -gnatwl for full details
-info: "pack1 (body)"
-info: must be elaborated along with its spec:
-info: "pack1 (spec)"
-info: which is withed by:
-info: "pack2 (body)"
-info: which must be elaborated along with its spec:
-info: "pack2 (spec)"
-info: which is withed by:
-info: "pack1 (body)"
-@end group
-@end smallexample
-The sources of the circularity are the two calls to @code{Pack2.Pure} and
-@code{Pack2.F2} in the body of @code{Pack1}. We can see that the call to
-F2 is safe, even though F2 calls F1, because the call appears after the
-elaboration of the body of F1. Therefore the pragma (1) is safe, and will
-remove the warning on the call. It is also possible to use pragma (2)
-because there are no other potentially unsafe calls in the block.
-
-@noindent
-The call to @code{Pure} is safe because this function does not depend on the
-state of @code{Pack2}. Therefore any call to this function is safe, and it
-is correct to place pragma (3) in the corresponding package spec.
-
-@noindent
-Finally, we could place pragma (4) in the spec of @code{Pack2} to disable
-warnings on all calls to functions declared therein. Note that this is not
-necessarily safe, and requires more detailed examination of the subprogram
-bodies involved. In particular, a call to @code{F2} requires that @code{F1}
-be already elaborated.
-@end table
-
-@noindent
-It is hard to generalize on which of these four approaches should be
-taken. Obviously if it is possible to fix the program so that the default
-treatment works, this is preferable, but this may not always be practical.
-It is certainly simple enough to use
-@option{-gnatE}
-but the danger in this case is that, even if the GNAT binder
-finds a correct elaboration order, it may not always do so,
-and certainly a binder from another Ada compiler might not. A
-combination of testing and analysis (for which the warnings generated
-with the
-@option{-gnatwl}
-switch can be useful) must be used to ensure that the program is free
-of errors. One switch that is useful in this testing is the
-@code{^-p (pessimistic elaboration order)^/PESSIMISTIC_ELABORATION_ORDER^}
-switch for
-@code{gnatbind}.
-Normally the binder tries to find an order that has the best chance of
-of avoiding elaboration problems. With this switch, the binder
-plays a devil's advocate role, and tries to choose the order that
-has the best chance of failing. If your program works even with this
-switch, then it has a better chance of being error free, but this is still
-not a guarantee.
-
-For an example of this approach in action, consider the C-tests (executable
-tests) from the ACVC suite. If these are compiled and run with the default
-treatment, then all but one of them succeed without generating any error
-diagnostics from the binder. However, there is one test that fails, and
-this is not surprising, because the whole point of this test is to ensure
-that the compiler can handle cases where it is impossible to determine
-a correct order statically, and it checks that an exception is indeed
-raised at run time.
-
-This one test must be compiled and run using the
-@option{-gnatE}
-switch, and then it passes. Alternatively, the entire suite can
-be run using this switch. It is never wrong to run with the dynamic
-elaboration switch if your code is correct, and we assume that the
-C-tests are indeed correct (it is less efficient, but efficiency is
-not a factor in running the ACVC tests.)
-
-@node Elaboration for Access-to-Subprogram Values
-@section Elaboration for Access-to-Subprogram Values
-@cindex Access-to-subprogram
-
-@noindent
-The introduction of access-to-subprogram types in Ada 95 complicates
-the handling of elaboration. The trouble is that it becomes
-impossible to tell at compile time which procedure
-is being called. This means that it is not possible for the binder
-to analyze the elaboration requirements in this case.
-
-If at the point at which the access value is created
-(i.e., the evaluation of @code{P'Access} for a subprogram @code{P}),
-the body of the subprogram is
-known to have been elaborated, then the access value is safe, and its use
-does not require a check. This may be achieved by appropriate arrangement
-of the order of declarations if the subprogram is in the current unit,
-or, if the subprogram is in another unit, by using pragma
-@code{Pure}, @code{Preelaborate}, or @code{Elaborate_Body}
-on the referenced unit.
-
-If the referenced body is not known to have been elaborated at the point
-the access value is created, then any use of the access value must do a
-dynamic check, and this dynamic check will fail and raise a
-@code{Program_Error} exception if the body has not been elaborated yet.
-GNAT will generate the necessary checks, and in addition, if the
-@option{-gnatwl}
-switch is set, will generate warnings that such checks are required.
-
-The use of dynamic dispatching for tagged types similarly generates
-a requirement for dynamic checks, and premature calls to any primitive
-operation of a tagged type before the body of the operation has been elaborated,
-will result in the raising of @code{Program_Error}.
-
-@node Summary of Procedures for Elaboration Control
-@section Summary of Procedures for Elaboration Control
-@cindex Elaboration control
-
-@noindent
-First, compile your program with the default options, using none of
-the special elaboration control switches. If the binder successfully
-binds your program, then you can be confident that, apart from issues
-raised by the use of access-to-subprogram types and dynamic dispatching,
-the program is free of elaboration errors. If it is important that the
-program be portable, then use the
-@option{-gnatwl}
-switch to generate warnings about missing @code{Elaborate_All}
-pragmas, and supply the missing pragmas.
-
-If the program fails to bind using the default static elaboration
-handling, then you can fix the program to eliminate the binder
-message, or recompile the entire program with the
-@option{-gnatE} switch to generate dynamic elaboration checks,
-and, if you are sure there really are no elaboration problems,
-use a global pragma @code{Suppress (Elaboration_Checks)}.
-
-@node Other Elaboration Order Considerations
-@section Other Elaboration Order Considerations
-@noindent
-This section has been entirely concerned with the issue of finding a valid
-elaboration order, as defined by the Ada Reference Manual. In a case
-where several elaboration orders are valid, the task is to find one
-of the possible valid elaboration orders (and the static model in GNAT
-will ensure that this is achieved).
-
-The purpose of the elaboration rules in the Ada Reference Manual is to
-make sure that no entity is accessed before it has been elaborated. For
-a subprogram, this means that the spec and body must have been elaborated
-before the subprogram is called. For an object, this means that the object
-must have been elaborated before its value is read or written. A violation
-of either of these two requirements is an access before elaboration order,
-and this section has been all about avoiding such errors.
-
-In the case where more than one order of elaboration is possible, in the
-sense that access before elaboration errors are avoided, then any one of
-the orders is "correct" in the sense that it meets the requirements of
-the Ada Reference Manual, and no such error occurs.
-
-However, it may be the case for a given program, that there are
-constraints on the order of elaboration that come not from consideration
-of avoiding elaboration errors, but rather from extra-lingual logic
-requirements. Consider this example:
-
-@smallexample
-with Init_Constants;
-package Constants is
- X : Integer := 0;
- Y : Integer := 0;
-end Constants;
-
-package Init_Constants is
- procedure Calc;
-end Init_Constants;
-
-with Constants;
-package body Init_Constants is
- procedure Calc is begin null; end;
-begin
- Constants.X := 3;
- Constants.Y := 4;
-end Init_Constants;
-
-with Constants;
-package Calc is
- Z : Integer := Constants.X + Constants.Y;
-end Calc;
-
-with Calc;
-with Text_IO; use Text_IO;
-procedure Main is
-begin
- Put_Line (Calc.Z'Img);
-end Main;
-@end smallexample
-
-@noindent
-In this example, there is more than one valid order of elaboration. For
-example both the following are correct orders:
-
-@smallexample
-Init_Constants spec
-Constants spec
-Calc spec
-Main body
-Init_Constants body
-
- and
-
-Init_Constants spec
-Init_Constants body
-Constants spec
-Calc spec
-Main body
-@end smallexample
-
-@noindent
-There is no language rule to prefer one or the other, both are correct
-from an order of elaboration point of view. But the programmatic effects
-of the two orders are very different. In the first, the elaboration routine
-of @code{Calc} initializes @code{Z} to zero, and then the main program
-runs with this value of zero. But in the second order, the elaboration
-routine of @code{Calc} runs after the body of Init_Constants has set
-@code{X} and @code{Y} and thus @code{Z} is set to 7 before @code{Main}
-runs.
-
-One could perhaps by applying pretty clever non-artificial intelligence
-to the situation guess that it is more likely that the second order of
-elaboration is the one desired, but there is no formal linguistic reason
-to prefer one over the other. In fact in this particular case, GNAT will
-prefer the second order, because of the rule that bodies are elaborated
-as soon as possible, but it's just luck that this is what was wanted
-(if indeed the second order was preferred).
-
-If the program cares about the order of elaboration routines in a case like
-this, it is important to specify the order required. In this particular
-case, that could have been achieved by adding to the spec of Calc:
-
-@smallexample
-pragma Elaborate_All (Constants);
-@end smallexample
-
-@noindent
-which requires that the body (if any) and spec of @code{Constants},
-as well as the body and spec of any unit @code{with}'ed by
-@code{Constants} be elaborated before @code{Calc} is elaborated.
-
-Clearly no automatic method can always guess which alternative you require,
-and if you are working with legacy code that had constraints of this kind
-which were not properly specified by adding @code{Elaborate} or
-@code{Elaborate_All} pragmas, then indeed it is possible that two different
-compilers can choose different orders.
-
-The @code{gnatbind}
-@code{^-p^/PESSIMISTIC_ELABORATION^} switch may be useful in smoking
-out problems. This switch causes bodies to be elaborated as late as possible
-instead of as early as possible. In the example above, it would have forced
-the choice of the first elaboration order. If you get different results
-when using this switch, and particularly if one set of results is right,
-and one is wrong as far as you are concerned, it shows that you have some
-missing @code{Elaborate} pragmas. For the example above, we have the
-following output:
-
-@smallexample
-gnatmake -f -q main
-main
- 7
-gnatmake -f -q main -bargs -p
-main
- 0
-@end smallexample
-
-@noindent
-It is of course quite unlikely that both these results are correct, so
-it is up to you in a case like this to investigate the source of the
-difference, by looking at the two elaboration orders that are chosen,
-and figuring out which is correct, and then adding the necessary
-@code{Elaborate_All} pragmas to ensure the desired order.
-
-@node The Cross-Referencing Tools gnatxref and gnatfind
-@chapter The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
-@findex gnatxref
-@findex gnatfind
-
-@noindent
-The compiler generates cross-referencing information (unless
-you set the @samp{-gnatx} switch), which are saved in the @file{.ali} files.
-This information indicates where in the source each entity is declared and
-referenced. Note that entities in package Standard are not included, but
-entities in all other predefined units are included in the output.
-
-Before using any of these two tools, you need to compile successfully your
-application, so that GNAT gets a chance to generate the cross-referencing
-information.
-
-The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
-information to provide the user with the capability to easily locate the
-declaration and references to an entity. These tools are quite similar,
-the difference being that @code{gnatfind} is intended for locating
-definitions and/or references to a specified entity or entities, whereas
-@code{gnatxref} is oriented to generating a full report of all
-cross-references.
-
-To use these tools, you must not compile your application using the
-@option{-gnatx} switch on the @file{gnatmake} command line (@inforef{The
-GNAT Make Program gnatmake,,gnat_ug}). Otherwise, cross-referencing
-information will not be generated.
-
-@menu
-* gnatxref Switches::
-* gnatfind Switches::
-* Project Files for gnatxref and gnatfind::
-* Regular Expressions in gnatfind and gnatxref::
-* Examples of gnatxref Usage::
-* Examples of gnatfind Usage::
-@end menu
-
-@node gnatxref Switches
-@section @code{gnatxref} Switches
-
-@noindent
-The command lines for @code{gnatxref} is:
-@smallexample
-$ gnatxref [switches] sourcefile1 [sourcefile2 ...]
-@end smallexample
-
-@noindent
-where
-
-@table @code
-@item sourcefile1, sourcefile2
-identifies the source files for which a report is to be generated. The
-'with'ed units will be processed too. You must provide at least one file.
-
-These file names are considered to be regular expressions, so for instance
-specifying 'source*.adb' is the same as giving every file in the current
-directory whose name starts with 'source' and whose extension is 'adb'.
-
-@end table
-
-@noindent
-The switches can be :
-@table @code
-@item ^-a^/ALL_FILES^
-If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
-the read-only files found in the library search path. Otherwise, these files
-will be ignored. This option can be used to protect Gnat sources or your own
-libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
-much faster, and their output much smaller.
-
-@item -aIDIR
-When looking for source files also look in directory DIR. The order in which
-source file search is undertaken is the same as for @file{gnatmake}.
-
-@item -aODIR
-When searching for library and object files, look in directory
-DIR. The order in which library files are searched is the same as for
-@file{gnatmake}.
-
-@item -nostdinc
-Do not look for sources in the system default directory.
-
-@item -nostdlib
-Do not look for library files in the system default directory.
-
-@item --RTS=@var{rts-path}
-@cindex @code{--RTS} (@code{gnatxref})
-Specifies the default location of the runtime library. Same meaning as the
-equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
-
-@item -d
-If this switch is set @code{gnatxref} will output the parent type
-reference for each matching derived types.
-
-@item ^-f^/FULL_PATHNAME^
-If this switch is set, the output file names will be preceded by their
-directory (if the file was found in the search path). If this switch is
-not set, the directory will not be printed.
-
-@item ^-g^/IGNORE_LOCALS^
-If this switch is set, information is output only for library-level
-entities, ignoring local entities. The use of this switch may accelerate
-@code{gnatfind} and @code{gnatxref}.
-
-@item -IDIR
-Equivalent to @samp{-aODIR -aIDIR}.
-
-@item -pFILE
-Specify a project file to use @xref{Project Files}.
-By default, @code{gnatxref} and @code{gnatfind} will try to locate a
-project file in the current directory.
-
-If a project file is either specified or found by the tools, then the content
-of the source directory and object directory lines are added as if they
-had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^}
-and @samp{^-aO^OBJECT_SEARCH^}.
-@item ^-u^/UNUSED^
-Output only unused symbols. This may be really useful if you give your
-main compilation unit on the command line, as @code{gnatxref} will then
-display every unused entity and 'with'ed package.
-
-@ifclear vms
-@item -v
-Instead of producing the default output, @code{gnatxref} will generate a
-@file{tags} file that can be used by vi. For examples how to use this
-feature, see @xref{Examples of gnatxref Usage}. The tags file is output
-to the standard output, thus you will have to redirect it to a file.
-@end ifclear
-
-@end table
-
-All these switches may be in any order on the command line, and may even
-appear after the file names. They need not be separated by spaces, thus
-you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
-@samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
-
-@node gnatfind Switches
-@section @code{gnatfind} Switches
-
-@noindent
-The command line for @code{gnatfind} is:
-
-@smallexample
-$ gnatfind [switches] pattern[:sourcefile[:line[:column]]]
- [file1 file2 ...]
-@end smallexample
-
-@noindent
-where
-
-@table @code
-@item pattern
-An entity will be output only if it matches the regular expression found
-in @samp{pattern}, see @xref{Regular Expressions in gnatfind and gnatxref}.
-
-Omitting the pattern is equivalent to specifying @samp{*}, which
-will match any entity. Note that if you do not provide a pattern, you
-have to provide both a sourcefile and a line.
-
-Entity names are given in Latin-1, with uppercase/lowercase equivalence
-for matching purposes. At the current time there is no support for
-8-bit codes other than Latin-1, or for wide characters in identifiers.
-
-@item sourcefile
-@code{gnatfind} will look for references, bodies or declarations
-of symbols referenced in @file{sourcefile}, at line @samp{line}
-and column @samp{column}. See @pxref{Examples of gnatfind Usage}
-for syntax examples.
-
-@item line
-is a decimal integer identifying the line number containing
-the reference to the entity (or entities) to be located.
-
-@item column
-is a decimal integer identifying the exact location on the
-line of the first character of the identifier for the
-entity reference. Columns are numbered from 1.
-
-@item file1 file2 ...
-The search will be restricted to these files. If none are given, then
-the search will be done for every library file in the search path.
-These file must appear only after the pattern or sourcefile.
-
-These file names are considered to be regular expressions, so for instance
-specifying 'source*.adb' is the same as giving every file in the current
-directory whose name starts with 'source' and whose extension is 'adb'.
-
-Not that if you specify at least one file in this part, @code{gnatfind} may
-sometimes not be able to find the body of the subprograms...
-
-@end table
-
-At least one of 'sourcefile' or 'pattern' has to be present on
-the command line.
-
-The following switches are available:
-@table @code
-
-@item ^-a^/ALL_FILES^
-If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
-the read-only files found in the library search path. Otherwise, these files
-will be ignored. This option can be used to protect Gnat sources or your own
-libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
-much faster, and their output much smaller.
-
-@item -aIDIR
-When looking for source files also look in directory DIR. The order in which
-source file search is undertaken is the same as for @file{gnatmake}.
-
-@item -aODIR
-When searching for library and object files, look in directory
-DIR. The order in which library files are searched is the same as for
-@file{gnatmake}.
-
-@item -nostdinc
-Do not look for sources in the system default directory.
-
-@item -nostdlib
-Do not look for library files in the system default directory.
-
-@item --RTS=@var{rts-path}
-@cindex @code{--RTS} (@code{gnatfind})
-Specifies the default location of the runtime library. Same meaning as the
-equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
-
-@item -d
-If this switch is set, then @code{gnatfind} will output the parent type
-reference for each matching derived types.
-
-@item ^-e^/EXPRESSIONS^
-By default, @code{gnatfind} accept the simple regular expression set for
-@samp{pattern}. If this switch is set, then the pattern will be
-considered as full Unix-style regular expression.
-
-@item ^-f^/FULL_PATHNAME^
-If this switch is set, the output file names will be preceded by their
-directory (if the file was found in the search path). If this switch is
-not set, the directory will not be printed.
-
-@item ^-g^/IGNORE_LOCALS^
-If this switch is set, information is output only for library-level
-entities, ignoring local entities. The use of this switch may accelerate
-@code{gnatfind} and @code{gnatxref}.
-
-@item -IDIR
-Equivalent to @samp{-aODIR -aIDIR}.
-
-@item -pFILE
-Specify a project file (@pxref{Project Files}) to use.
-By default, @code{gnatxref} and @code{gnatfind} will try to locate a
-project file in the current directory.
-
-If a project file is either specified or found by the tools, then the content
-of the source directory and object directory lines are added as if they
-had been specified respectively by @samp{^-aI^/SOURCE_SEARCH^} and
-@samp{^-aO^/OBJECT_SEARCH^}.
-
-@item ^-r^/REFERENCES^
-By default, @code{gnatfind} will output only the information about the
-declaration, body or type completion of the entities. If this switch is
-set, the @code{gnatfind} will locate every reference to the entities in
-the files specified on the command line (or in every file in the search
-path if no file is given on the command line).
-
-@item ^-s^/PRINT_LINES^
-If this switch is set, then @code{gnatfind} will output the content
-of the Ada source file lines were the entity was found.
-
-@item -t
-If this switch is set, then @code{gnatfind} will output the type hierarchy for
-the specified type. It act like -d option but recursively from parent
-type to parent type. When this switch is set it is not possible to
-specify more than one file.
-
-@end table
-
-All these switches may be in any order on the command line, and may even
-appear after the file names. They need not be separated by spaces, thus
-you can say @samp{gnatxref ^-ag^/ALL_FILES/IGNORE_LOCALS^} instead of
-@samp{gnatxref ^-a -g^/ALL_FILES /IGNORE_LOCALS^}.
-
-As stated previously, gnatfind will search in every directory in the
-search path. You can force it to look only in the current directory if
-you specify @code{*} at the end of the command line.
-
-
-@node Project Files for gnatxref and gnatfind
-@section Project Files for @command{gnatxref} and @command{gnatfind}
-
-@noindent
-Project files allow a programmer to specify how to compile its
-application, where to find sources,... These files are used primarily by
-the Glide Ada mode, but they can also be used by the two tools
-@code{gnatxref} and @code{gnatfind}.
-
-A project file name must end with @file{.adp}. If a single one is
-present in the current directory, then @code{gnatxref} and @code{gnatfind} will
-extract the information from it. If multiple project files are found, none of
-them is read, and you have to use the @samp{-p} switch to specify the one
-you want to use.
-
-The following lines can be included, even though most of them have default
-values which can be used in most cases.
-The lines can be entered in any order in the file.
-Except for @samp{src_dir} and @samp{obj_dir}, you can only have one instance of
-each line. If you have multiple instances, only the last one is taken into
-account.
-
-@table @code
-@item src_dir=DIR [default: "^./^[]^"]
-specifies a directory where to look for source files. Multiple src_dir lines
-can be specified and they will be searched in the order they
-are specified.
-
-@item obj_dir=DIR [default: "^./^[]^"]
-specifies a directory where to look for object and library files. Multiple
-obj_dir lines can be specified and they will be searched in the order they
-are specified
-
-@item comp_opt=SWITCHES [default: ""]
-creates a variable which can be referred to subsequently by using
-the @samp{$@{comp_opt@}} notation. This is intended to store the default
-switches given to @file{gnatmake} and @file{gcc}.
-
-@item bind_opt=SWITCHES [default: ""]
-creates a variable which can be referred to subsequently by using
-the @samp{$@{bind_opt@}} notation. This is intended to store the default
-switches given to @file{gnatbind}.
-
-@item link_opt=SWITCHES [default: ""]
-creates a variable which can be referred to subsequently by using
-the @samp{$@{link_opt@}} notation. This is intended to store the default
-switches given to @file{gnatlink}.
-
-@item main=EXECUTABLE [default: ""]
-specifies the name of the executable for the application. This variable can
-be referred to in the following lines by using the @samp{$@{main@}} notation.
-
-@ifset vms
-@item comp_cmd=COMMAND [default: "GNAT COMPILE /SEARCH=$@{src_dir@} /DEBUG /TRY_SEMANTICS"]
-@end ifset
-@ifclear vms
-@item comp_cmd=COMMAND [default: "gcc -c -I$@{src_dir@} -g -gnatq"]
-@end ifclear
-specifies the command used to compile a single file in the application.
-
-@ifset vms
-@item make_cmd=COMMAND [default: "GNAT MAKE $@{main@} /SOURCE_SEARCH=$@{src_dir@} /OBJECT_SEARCH=$@{obj_dir@} /DEBUG /TRY_SEMANTICS /COMPILER_QUALIFIERS $@{comp_opt@} /BINDER_QUALIFIERS $@{bind_opt@} /LINKER_QUALIFIERS $@{link_opt@}"]
-@end ifset
-@ifclear vms
-@item make_cmd=COMMAND [default: "gnatmake $@{main@} -aI$@{src_dir@} -aO$@{obj_dir@} -g -gnatq -cargs $@{comp_opt@} -bargs $@{bind_opt@} -largs $@{link_opt@}"]
-@end ifclear
-specifies the command used to recompile the whole application.
-
-@item run_cmd=COMMAND [default: "$@{main@}"]
-specifies the command used to run the application.
-
-@item debug_cmd=COMMAND [default: "gdb $@{main@}"]
-specifies the command used to debug the application
-
-@end table
-
-@code{gnatxref} and @code{gnatfind} only take into account the @samp{src_dir}
-and @samp{obj_dir} lines, and ignore the others.
-
-@node Regular Expressions in gnatfind and gnatxref
-@section Regular Expressions in @code{gnatfind} and @code{gnatxref}
-
-@noindent
-As specified in the section about @code{gnatfind}, the pattern can be a
-regular expression. Actually, there are to set of regular expressions
-which are recognized by the program :
-
-@table @code
-@item globbing patterns
-These are the most usual regular expression. They are the same that you
-generally used in a Unix shell command line, or in a DOS session.
-
-Here is a more formal grammar :
-@smallexample
-@group
-@iftex
-@leftskip=.5cm
-@end iftex
-regexp ::= term
-term ::= elmt -- matches elmt
-term ::= elmt elmt -- concatenation (elmt then elmt)
-term ::= * -- any string of 0 or more characters
-term ::= ? -- matches any character
-term ::= [char @{char@}] -- matches any character listed
-term ::= [char - char] -- matches any character in range
-@end group
-@end smallexample
-
-@item full regular expression
-The second set of regular expressions is much more powerful. This is the
-type of regular expressions recognized by utilities such a @file{grep}.
-
-The following is the form of a regular expression, expressed in Ada
-reference manual style BNF is as follows
-
-@smallexample
-@iftex
-@leftskip=.5cm
-@end iftex
-@group
-regexp ::= term @{| term@} -- alternation (term or term ...)
-
-term ::= item @{item@} -- concatenation (item then item)
-
-item ::= elmt -- match elmt
-item ::= elmt * -- zero or more elmt's
-item ::= elmt + -- one or more elmt's
-item ::= elmt ? -- matches elmt or nothing
-@end group
-@group
-elmt ::= nschar -- matches given character
-elmt ::= [nschar @{nschar@}] -- matches any character listed
-elmt ::= [^^^ nschar @{nschar@}] -- matches any character not listed
-elmt ::= [char - char] -- matches chars in given range
-elmt ::= \ char -- matches given character
-elmt ::= . -- matches any single character
-elmt ::= ( regexp ) -- parens used for grouping
-
-char ::= any character, including special characters
-nschar ::= any character except ()[].*+?^^^
-@end group
-@end smallexample
-
-Following are a few examples :
-
-@table @samp
-@item abcde|fghi
-will match any of the two strings 'abcde' and 'fghi'.
-
-@item abc*d
-will match any string like 'abd', 'abcd', 'abccd', 'abcccd', and so on
-
-@item [a-z]+
-will match any string which has only lowercase characters in it (and at
-least one character
-
-@end table
-@end table
-
-@node Examples of gnatxref Usage
-@section Examples of @code{gnatxref} Usage
-
-@subsection General Usage
-
-@noindent
-For the following examples, we will consider the following units :
-
-@smallexample
-@group
-@cartouche
-main.ads:
-1: @b{with} Bar;
-2: @b{package} Main @b{is}
-3: @b{procedure} Foo (B : @b{in} Integer);
-4: C : Integer;
-5: @b{private}
-6: D : Integer;
-7: @b{end} Main;
-
-main.adb:
-1: @b{package body} Main @b{is}
-2: @b{procedure} Foo (B : @b{in} Integer) @b{is}
-3: @b{begin}
-4: C := B;
-5: D := B;
-6: Bar.Print (B);
-7: Bar.Print (C);
-8: @b{end} Foo;
-9: @b{end} Main;
-
-bar.ads:
-1: @b{package} Bar @b{is}
-2: @b{procedure} Print (B : Integer);
-3: @b{end} bar;
-@end cartouche
-@end group
-@end smallexample
-
-@table @code
-
-@noindent
-The first thing to do is to recompile your application (for instance, in
-that case just by doing a @samp{gnatmake main}, so that GNAT generates
-the cross-referencing information.
-You can then issue any of the following commands:
-
-@item gnatxref main.adb
-@code{gnatxref} generates cross-reference information for main.adb
-and every unit 'with'ed by main.adb.
-
-The output would be:
-@smallexample
-@iftex
-@leftskip=0cm
-@end iftex
-B Type: Integer
- Decl: bar.ads 2:22
-B Type: Integer
- Decl: main.ads 3:20
- Body: main.adb 2:20
- Ref: main.adb 4:13 5:13 6:19
-Bar Type: Unit
- Decl: bar.ads 1:9
- Ref: main.adb 6:8 7:8
- main.ads 1:6
-C Type: Integer
- Decl: main.ads 4:5
- Modi: main.adb 4:8
- Ref: main.adb 7:19
-D Type: Integer
- Decl: main.ads 6:5
- Modi: main.adb 5:8
-Foo Type: Unit
- Decl: main.ads 3:15
- Body: main.adb 2:15
-Main Type: Unit
- Decl: main.ads 2:9
- Body: main.adb 1:14
-Print Type: Unit
- Decl: bar.ads 2:15
- Ref: main.adb 6:12 7:12
-@end smallexample
-
-@noindent
-that is the entity @code{Main} is declared in main.ads, line 2, column 9,
-its body is in main.adb, line 1, column 14 and is not referenced any where.
-
-The entity @code{Print} is declared in bar.ads, line 2, column 15 and it
-it referenced in main.adb, line 6 column 12 and line 7 column 12.
-
-@item gnatxref package1.adb package2.ads
-@code{gnatxref} will generates cross-reference information for
-package1.adb, package2.ads and any other package 'with'ed by any
-of these.
-
-@end table
-
-@ifclear vms
-@subsection Using gnatxref with vi
-
-@code{gnatxref} can generate a tags file output, which can be used
-directly from @file{vi}. Note that the standard version of @file{vi}
-will not work properly with overloaded symbols. Consider using another
-free implementation of @file{vi}, such as @file{vim}.
-
-@smallexample
-$ gnatxref -v gnatfind.adb > tags
-@end smallexample
-
-@noindent
-will generate the tags file for @code{gnatfind} itself (if the sources
-are in the search path!).
-
-From @file{vi}, you can then use the command @samp{:tag @i{entity}}
-(replacing @i{entity} by whatever you are looking for), and vi will
-display a new file with the corresponding declaration of entity.
-@end ifclear
-
-@node Examples of gnatfind Usage
-@section Examples of @code{gnatfind} Usage
-
-@table @code
-
-@item gnatfind ^-f^/FULL_PATHNAME^ xyz:main.adb
-Find declarations for all entities xyz referenced at least once in
-main.adb. The references are search in every library file in the search
-path.
-
-The directories will be printed as well (as the @samp{^-f^/FULL_PATHNAME^}
-switch is set)
-
-The output will look like:
-@smallexample
-^directory/^[directory]^main.ads:106:14: xyz <= declaration
-^directory/^[directory]^main.adb:24:10: xyz <= body
-^directory/^[directory]^foo.ads:45:23: xyz <= declaration
-@end smallexample
-
-@noindent
-that is to say, one of the entities xyz found in main.adb is declared at
-line 12 of main.ads (and its body is in main.adb), and another one is
-declared at line 45 of foo.ads
-
-@item gnatfind ^-fs^/FULL_PATHNAME/SOURCE_LINE^ xyz:main.adb
-This is the same command as the previous one, instead @code{gnatfind} will
-display the content of the Ada source file lines.
-
-The output will look like:
-
-@smallexample
-^directory/^[directory]^main.ads:106:14: xyz <= declaration
- procedure xyz;
-^directory/^[directory]^main.adb:24:10: xyz <= body
- procedure xyz is
-^directory/^[directory]^foo.ads:45:23: xyz <= declaration
- xyz : Integer;
-@end smallexample
-
-@noindent
-This can make it easier to find exactly the location your are looking
-for.
-
-@item gnatfind ^-r^/REFERENCES^ "*x*":main.ads:123 foo.adb
-Find references to all entities containing an x that are
-referenced on line 123 of main.ads.
-The references will be searched only in main.adb and foo.adb.
-
-@item gnatfind main.ads:123
-Find declarations and bodies for all entities that are referenced on
-line 123 of main.ads.
-
-This is the same as @code{gnatfind "*":main.adb:123}.
-
-@item gnatfind ^mydir/^[mydir]^main.adb:123:45
-Find the declaration for the entity referenced at column 45 in
-line 123 of file main.adb in directory mydir. Note that it
-is usual to omit the identifier name when the column is given,
-since the column position identifies a unique reference.
-
-The column has to be the beginning of the identifier, and should not
-point to any character in the middle of the identifier.
-
-@end table
-
-@node File Name Krunching Using gnatkr
-@chapter File Name Krunching Using @code{gnatkr}
-@findex gnatkr
-
-@noindent
-This chapter discusses the method used by the compiler to shorten
-the default file names chosen for Ada units so that they do not
-exceed the maximum length permitted. It also describes the
-@code{gnatkr} utility that can be used to determine the result of
-applying this shortening.
-@menu
-* About gnatkr::
-* Using gnatkr::
-* Krunching Method::
-* Examples of gnatkr Usage::
-@end menu
-
-@node About gnatkr
-@section About @code{gnatkr}
-
-@noindent
-The default file naming rule in GNAT
-is that the file name must be derived from
-the unit name. The exact default rule is as follows:
-@itemize @bullet
-@item
-Take the unit name and replace all dots by hyphens.
-@item
-If such a replacement occurs in the
-second character position of a name, and the first character is
-^a, g, s, or i^A, G, S, or I^ then replace the dot by the character
-^~ (tilde)^$ (dollar sign)^
-instead of a minus.
-@end itemize
-The reason for this exception is to avoid clashes
-with the standard names for children of System, Ada, Interfaces,
-and GNAT, which use the prefixes ^s- a- i- and g-^S- A- I- and G-^
-respectively.
-
-The @code{^-gnatk^/FILE_NAME_MAX_LENGTH=^@var{nn}}
-switch of the compiler activates a "krunching"
-circuit that limits file names to nn characters (where nn is a decimal
-integer). For example, using OpenVMS,
-where the maximum file name length is
-39, the value of nn is usually set to 39, but if you want to generate
-a set of files that would be usable if ported to a system with some
-different maximum file length, then a different value can be specified.
-The default value of 39 for OpenVMS need not be specified.
-
-The @code{gnatkr} utility can be used to determine the krunched name for
-a given file, when krunched to a specified maximum length.
-
-@node Using gnatkr
-@section Using @code{gnatkr}
-
-@noindent
-The @code{gnatkr} command has the form
-
-@ifclear vms
-@smallexample
-$ gnatkr @var{name} [@var{length}]
-@end smallexample
-@end ifclear
-
-@ifset vms
-@smallexample
-$ gnatkr @var{name} /COUNT=nn
-@end smallexample
-@end ifset
-
-@noindent
-@var{name} can be an Ada name with dots or the GNAT name of the unit,
-where the dots representing child units or subunit are replaced by
-hyphens. The only confusion arises if a name ends in @code{.ads} or
-@code{.adb}. @code{gnatkr} takes this to be an extension if there are
-no other dots in the name^ and the whole name is in lowercase^^.
-
-@var{length} represents the length of the krunched name. The default
-when no argument is given is ^8^39^ characters. A length of zero stands for
-unlimited, in other words do not chop except for system files which are
-always ^8^39^.
-
-@noindent
-The output is the krunched name. The output has an extension only if the
-original argument was a file name with an extension.
-
-@node Krunching Method
-@section Krunching Method
-
-@noindent
-The initial file name is determined by the name of the unit that the file
-contains. The name is formed by taking the full expanded name of the
-unit and replacing the separating dots with hyphens and
-using ^lowercase^uppercase^
-for all letters, except that a hyphen in the second character position is
-replaced by a ^tilde^dollar sign^ if the first character is
-^a, i, g, or s^A, I, G, or S^.
-The extension is @code{.ads} for a
-specification and @code{.adb} for a body.
-Krunching does not affect the extension, but the file name is shortened to
-the specified length by following these rules:
-
-@itemize @bullet
-@item
-The name is divided into segments separated by hyphens, tildes or
-underscores and all hyphens, tildes, and underscores are
-eliminated. If this leaves the name short enough, we are done.
-
-@item
-If the name is too long, the longest segment is located (left-most if there are two
-of equal length), and shortened by dropping its last character. This is
-repeated until the name is short enough.
-
-As an example, consider the krunching of @*@file{our-strings-wide_fixed.adb}
-to fit the name into 8 characters as required by some operating systems.
-
-@smallexample
-our-strings-wide_fixed 22
-our strings wide fixed 19
-our string wide fixed 18
-our strin wide fixed 17
-our stri wide fixed 16
-our stri wide fixe 15
-our str wide fixe 14
-our str wid fixe 13
-our str wid fix 12
-ou str wid fix 11
-ou st wid fix 10
-ou st wi fix 9
-ou st wi fi 8
-Final file name: oustwifi.adb
-@end smallexample
-
-@item
-The file names for all predefined units are always krunched to eight
-characters. The krunching of these predefined units uses the following
-special prefix replacements:
-
-@table @file
-@item ada-
-replaced by @file{^a^A^-}
-
-@item gnat-
-replaced by @file{^g^G^-}
-
-@item interfaces-
-replaced by @file{^i^I^-}
-
-@item system-
-replaced by @file{^s^S^-}
-@end table
-
-These system files have a hyphen in the second character position. That
-is why normal user files replace such a character with a
-^tilde^dollar sign^, to
-avoid confusion with system file names.
-
-As an example of this special rule, consider
-@*@file{ada-strings-wide_fixed.adb}, which gets krunched as follows:
-
-@smallexample
-ada-strings-wide_fixed 22
-a- strings wide fixed 18
-a- string wide fixed 17
-a- strin wide fixed 16
-a- stri wide fixed 15
-a- stri wide fixe 14
-a- str wide fixe 13
-a- str wid fixe 12
-a- str wid fix 11
-a- st wid fix 10
-a- st wi fix 9
-a- st wi fi 8
-Final file name: a-stwifi.adb
-@end smallexample
-@end itemize
-
-Of course no file shortening algorithm can guarantee uniqueness over all
-possible unit names, and if file name krunching is used then it is your
-responsibility to ensure that no name clashes occur. The utility
-program @code{gnatkr} is supplied for conveniently determining the
-krunched name of a file.
-
-@node Examples of gnatkr Usage
-@section Examples of @code{gnatkr} Usage
-
-@smallexample
-@iftex
-@leftskip=0cm
-@end iftex
-@ifclear vms
-$ gnatkr very_long_unit_name.ads --> velounna.ads
-$ gnatkr grandparent-parent-child.ads --> grparchi.ads
-$ gnatkr Grandparent.Parent.Child --> grparchi
-@end ifclear
-$ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
-$ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
-@end smallexample
-
-@node Preprocessing Using gnatprep
-@chapter Preprocessing Using @code{gnatprep}
-@findex gnatprep
-
-@noindent
-The @code{gnatprep} utility provides
-a simple preprocessing capability for Ada programs.
-It is designed for use with GNAT, but is not dependent on any special
-features of GNAT.
-
-@menu
-* Using gnatprep::
-* Switches for gnatprep::
-* Form of Definitions File::
-* Form of Input Text for gnatprep::
-@end menu
-
-@node Using gnatprep
-@section Using @code{gnatprep}
-
-@noindent
-To call @code{gnatprep} use
-
-@smallexample
-$ gnatprep [-bcrsu] [-Dsymbol=value] infile outfile [deffile]
-@end smallexample
-
-@noindent
-where
-@table @code
-@item infile
-is the full name of the input file, which is an Ada source
-file containing preprocessor directives.
-
-@item outfile
-is the full name of the output file, which is an Ada source
-in standard Ada form. When used with GNAT, this file name will
-normally have an ads or adb suffix.
-
-@item deffile
-is the full name of a text file containing definitions of
-symbols to be referenced by the preprocessor. This argument is
-optional, and can be replaced by the use of the @code{-D} switch.
-
-@item switches
-is an optional sequence of switches as described in the next section.
-@end table
-
-@node Switches for gnatprep
-@section Switches for @code{gnatprep}
-
-@table @code
-
-@item ^-b^/BLANK_LINES^
-Causes both preprocessor lines and the lines deleted by
-preprocessing to be replaced by blank lines in the output source file,
-preserving line numbers in the output file.
-
-@item ^-c^/COMMENTS^
-Causes both preprocessor lines and the lines deleted
-by preprocessing to be retained in the output source as comments marked
-with the special string "--! ". This option will result in line numbers
-being preserved in the output file.
-
-@item -Dsymbol=value
-Defines a new symbol, associated with value. If no value is given on the
-command line, then symbol is considered to be @code{True}. This switch
-can be used in place of a definition file.
-
-@ifset vms
-@item /REMOVE (default)
-This is the default setting which causes lines deleted by preprocessing
-to be entirely removed from the output file.
-@end ifset
-
-@item ^-r^/REFERENCE^
-Causes a @code{Source_Reference} pragma to be generated that
-references the original input file, so that error messages will use
-the file name of this original file. The use of this switch implies
-that preprocessor lines are not to be removed from the file, so its
-use will force @code{^-b^/BLANK_LINES^} mode if
-@code{^-c^/COMMENTS^}
-has not been specified explicitly.
-
-Note that if the file to be preprocessed contains multiple units, then
-it will be necessary to @code{gnatchop} the output file from
-@code{gnatprep}. If a @code{Source_Reference} pragma is present
-in the preprocessed file, it will be respected by
-@code{gnatchop ^-r^/REFERENCE^}
-so that the final chopped files will correctly refer to the original
-input source file for @code{gnatprep}.
-
-@item ^-s^/SYMBOLS^
-Causes a sorted list of symbol names and values to be
-listed on the standard output file.
-
-@item ^-u^/UNDEFINED^
-Causes undefined symbols to be treated as having the value FALSE in the context
-of a preprocessor test. In the absence of this option, an undefined symbol in
-a @code{#if} or @code{#elsif} test will be treated as an error.
-
-@end table
-
-@ifclear vms
-@noindent
-Note: if neither @code{-b} nor @code{-c} is present,
-then preprocessor lines and
-deleted lines are completely removed from the output, unless -r is
-specified, in which case -b is assumed.
-@end ifclear
-
-@node Form of Definitions File
-@section Form of Definitions File
-
-@noindent
-The definitions file contains lines of the form
-
-@smallexample
-symbol := value
-@end smallexample
-
-@noindent
-where symbol is an identifier, following normal Ada (case-insensitive)
-rules for its syntax, and value is one of the following:
-
-@itemize @bullet
-@item
-Empty, corresponding to a null substitution
-@item
-A string literal using normal Ada syntax
-@item
-Any sequence of characters from the set
-(letters, digits, period, underline).
-@end itemize
-
-@noindent
-Comment lines may also appear in the definitions file, starting with
-the usual @code{--},
-and comments may be added to the definitions lines.
-
-@node Form of Input Text for gnatprep
-@section Form of Input Text for @code{gnatprep}
-
-@noindent
-The input text may contain preprocessor conditional inclusion lines,
-as well as general symbol substitution sequences.
-
-The preprocessor conditional inclusion commands have the form
-
-@smallexample
-@group
-@cartouche
-#if @i{expression} [then]
- lines
-#elsif @i{expression} [then]
- lines
-#elsif @i{expression} [then]
- lines
-...
-#else
- lines
-#end if;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-In this example, @i{expression} is defined by the following grammar:
-@smallexample
-@i{expression} ::= <symbol>
-@i{expression} ::= <symbol> = "<value>"
-@i{expression} ::= <symbol> = <symbol>
-@i{expression} ::= <symbol> 'Defined
-@i{expression} ::= not @i{expression}
-@i{expression} ::= @i{expression} and @i{expression}
-@i{expression} ::= @i{expression} or @i{expression}
-@i{expression} ::= @i{expression} and then @i{expression}
-@i{expression} ::= @i{expression} or else @i{expression}
-@i{expression} ::= ( @i{expression} )
-@end smallexample
-
-@noindent
-For the first test (@i{expression} ::= <symbol>) the symbol must have
-either the value true or false, that is to say the right-hand of the
-symbol definition must be one of the (case-insensitive) literals
-@code{True} or @code{False}. If the value is true, then the
-corresponding lines are included, and if the value is false, they are
-excluded.
-
-The test (@i{expression} ::= <symbol> @code{'Defined}) is true only if
-the symbol has been defined in the definition file or by a @code{-D}
-switch on the command line. Otherwise, the test is false.
-
-The equality tests are case insensitive, as are all the preprocessor lines.
-
-If the symbol referenced is not defined in the symbol definitions file,
-then the effect depends on whether or not switch @code{-u}
-is specified. If so, then the symbol is treated as if it had the value
-false and the test fails. If this switch is not specified, then
-it is an error to reference an undefined symbol. It is also an error to
-reference a symbol that is defined with a value other than @code{True}
-or @code{False}.
-
-The use of the @code{not} operator inverts the sense of this logical test, so
-that the lines are included only if the symbol is not defined.
-The @code{then} keyword is optional as shown
-
-The @code{#} must be the first non-blank character on a line, but
-otherwise the format is free form. Spaces or tabs may appear between
-the @code{#} and the keyword. The keywords and the symbols are case
-insensitive as in normal Ada code. Comments may be used on a
-preprocessor line, but other than that, no other tokens may appear on a
-preprocessor line. Any number of @code{elsif} clauses can be present,
-including none at all. The @code{else} is optional, as in Ada.
-
-The @code{#} marking the start of a preprocessor line must be the first
-non-blank character on the line, i.e. it must be preceded only by
-spaces or horizontal tabs.
-
-Symbol substitution outside of preprocessor lines is obtained by using
-the sequence
-
-@smallexample
-$symbol
-@end smallexample
-
-@noindent
-anywhere within a source line, except in a comment or within a
-string literal. The identifier
-following the @code{$} must match one of the symbols defined in the symbol
-definition file, and the result is to substitute the value of the
-symbol in place of @code{$symbol} in the output file.
-
-Note that although the substitution of strings within a string literal
-is not possible, it is possible to have a symbol whose defined value is
-a string literal. So instead of setting XYZ to @code{hello} and writing:
-
-@smallexample
-Header : String := "$XYZ";
-@end smallexample
-
-@noindent
-you should set XYZ to @code{"hello"} and write:
-
-@smallexample
-Header : String := $XYZ;
-@end smallexample
-
-@noindent
-and then the substitution will occur as desired.
-
-@ifset vms
-@node The GNAT Run-Time Library Builder gnatlbr
-@chapter The GNAT Run-Time Library Builder @code{gnatlbr}
-@findex gnatlbr
-@cindex Library builder
-
-@noindent
-@code{gnatlbr} is a tool for rebuilding the GNAT run time with user
-supplied configuration pragmas.
-
-@menu
-* Running gnatlbr::
-* Switches for gnatlbr::
-* Examples of gnatlbr Usage::
-@end menu
-
-@node Running gnatlbr
-@section Running @code{gnatlbr}
-
-@noindent
-The @code{gnatlbr} command has the form
-
-@smallexample
-@ifclear vms
-$ gnatlbr --[create | set | delete]=directory --config=file
-@end ifclear
-@ifset vms
-$ GNAT LIBRARY /[CREATE | SET | DELETE]=directory [/CONFIG=file]
-@end ifset
-@end smallexample
-
-@node Switches for gnatlbr
-@section Switches for @code{gnatlbr}
-
-@noindent
-@code{gnatlbr} recognizes the following switches:
-
-@table @code
-@item ^--create^/CREATE^=directory
-@cindex @code{^--create^/CREATE^=directory} (@code{gnatlbr})
- Create the new run-time library in the specified directory.
-
-@item ^--set^/SET^=directory
-@cindex @code{^--set^/SET^=directory} (@code{gnatlbr})
- Make the library in the specified directory the current run-time
- library.
-
-@item ^--delete^/DELETE^=directory
-@cindex @code{^--delete^/DELETE^=directory} (@code{gnatlbr})
- Delete the run-time library in the specified directory.
-
-@item ^--config^/CONFIG^=file
-@cindex @code{^--config^/CONFIG^=file} (@code{gnatlbr})
- With ^--create^/CREATE^:
- Use the configuration pragmas in the specified file when building
- the library.
-
- With ^--set^/SET^:
- Use the configuration pragmas in the specified file when compiling.
-
-@end table
-
-@node Examples of gnatlbr Usage
-@section Example of @code{gnatlbr} Usage
-
-@smallexample
-Contents of VAXFLOAT.ADC:
-pragma Float_Representation (VAX_Float);
-
-$ GNAT LIBRARY /CREATE=[.VAXFLOAT] /CONFIG=VAXFLOAT.ADC
-
-GNAT LIBRARY rebuilds the run-time library in directory [.VAXFLOAT]
-
-@end smallexample
-@end ifset
-
-@node The GNAT Library Browser gnatls
-@chapter The GNAT Library Browser @code{gnatls}
-@findex gnatls
-@cindex Library browser
-
-@noindent
-@code{gnatls} is a tool that outputs information about compiled
-units. It gives the relationship between objects, unit names and source
-files. It can also be used to check the source dependencies of a unit
-as well as various characteristics.
-
-@menu
-* Running gnatls::
-* Switches for gnatls::
-* Examples of gnatls Usage::
-@end menu
-
-@node Running gnatls
-@section Running @code{gnatls}
-
-@noindent
-The @code{gnatls} command has the form
-
-@smallexample
-$ gnatls switches @var{object_or_ali_file}
-@end smallexample
-
-@noindent
-The main argument is the list of object or @file{ali} files
-(@pxref{The Ada Library Information Files})
-for which information is requested.
-
-In normal mode, without additional option, @code{gnatls} produces a
-four-column listing. Each line represents information for a specific
-object. The first column gives the full path of the object, the second
-column gives the name of the principal unit in this object, the third
-column gives the status of the source and the fourth column gives the
-full path of the source representing this unit.
-Here is a simple example of use:
-
-@smallexample
-$ gnatls *.o
-^./^[]^demo1.o demo1 DIF demo1.adb
-^./^[]^demo2.o demo2 OK demo2.adb
-^./^[]^hello.o h1 OK hello.adb
-^./^[]^instr-child.o instr.child MOK instr-child.adb
-^./^[]^instr.o instr OK instr.adb
-^./^[]^tef.o tef DIF tef.adb
-^./^[]^text_io_example.o text_io_example OK text_io_example.adb
-^./^[]^tgef.o tgef DIF tgef.adb
-@end smallexample
-
-@noindent
-The first line can be interpreted as follows: the main unit which is
-contained in
-object file @file{demo1.o} is demo1, whose main source is in
-@file{demo1.adb}. Furthermore, the version of the source used for the
-compilation of demo1 has been modified (DIF). Each source file has a status
-qualifier which can be:
-
-@table @code
-@item OK (unchanged)
-The version of the source file used for the compilation of the
-specified unit corresponds exactly to the actual source file.
-
-@item MOK (slightly modified)
-The version of the source file used for the compilation of the
-specified unit differs from the actual source file but not enough to
-require recompilation. If you use gnatmake with the qualifier
-@code{^-m (minimal recompilation)^/MINIMAL_RECOMPILATION^}, a file marked
-MOK will not be recompiled.
-
-@item DIF (modified)
-No version of the source found on the path corresponds to the source
-used to build this object.
-
-@item ??? (file not found)
-No source file was found for this unit.
-
-@item HID (hidden, unchanged version not first on PATH)
-The version of the source that corresponds exactly to the source used
-for compilation has been found on the path but it is hidden by another
-version of the same source that has been modified.
-
-@end table
-
-@node Switches for gnatls
-@section Switches for @code{gnatls}
-
-@noindent
-@code{gnatls} recognizes the following switches:
-
-@table @code
-@item ^-a^/ALL_UNITS^
-@cindex @code{^-a^/ALL_UNITS^} (@code{gnatls})
-Consider all units, including those of the predefined Ada library.
-Especially useful with @code{^-d^/DEPENDENCIES^}.
-
-@item ^-d^/DEPENDENCIES^
-@cindex @code{^-d^/DEPENDENCIES^} (@code{gnatls})
-List sources from which specified units depend on.
-
-@item ^-h^/OUTPUT=OPTIONS^
-@cindex @code{^-h^/OUTPUT=OPTIONS^} (@code{gnatls})
-Output the list of options.
-
-@item ^-o^/OUTPUT=OBJECTS^
-@cindex @code{^-o^/OUTPUT=OBJECTS^} (@code{gnatls})
-Only output information about object files.
-
-@item ^-s^/OUTPUT=SOURCES^
-@cindex @code{^-s^/OUTPUT=SOURCES^} (@code{gnatls})
-Only output information about source files.
-
-@item ^-u^/OUTPUT=UNITS^
-@cindex @code{^-u^/OUTPUT=UNITS^} (@code{gnatls})
-Only output information about compilation units.
-
-@item ^-aO^/OBJECT_SEARCH=^@var{dir}
-@itemx ^-aI^/SOURCE_SEARCH=^@var{dir}
-@itemx ^-I^/SEARCH=^@var{dir}
-@itemx ^-I-^/NOCURRENT_DIRECTORY^
-@itemx -nostdinc
-Source path manipulation. Same meaning as the equivalent @code{gnatmake} flags
-(see @ref{Switches for gnatmake}).
-
-@item --RTS=@var{rts-path}
-@cindex @code{--RTS} (@code{gnatls})
-Specifies the default location of the runtime library. Same meaning as the
-equivalent @code{gnatmake} flag (see @ref{Switches for gnatmake}).
-
-@item ^-v^/OUTPUT=VERBOSE^
-@cindex @code{^-s^/OUTPUT=VERBOSE^} (@code{gnatls})
-Verbose mode. Output the complete source and object paths. Do not use
-the default column layout but instead use long format giving as much as
-information possible on each requested units, including special
-characteristics such as:
-
-@table @code
-@item Preelaborable
-The unit is preelaborable in the Ada 95 sense.
-
-@item No_Elab_Code
-No elaboration code has been produced by the compiler for this unit.
-
-@item Pure
-The unit is pure in the Ada 95 sense.
-
-@item Elaborate_Body
-The unit contains a pragma Elaborate_Body.
-
-@item Remote_Types
-The unit contains a pragma Remote_Types.
-
-@item Shared_Passive
-The unit contains a pragma Shared_Passive.
-
-@item Predefined
-This unit is part of the predefined environment and cannot be modified
-by the user.
-
-@item Remote_Call_Interface
-The unit contains a pragma Remote_Call_Interface.
-
-@end table
-
-@end table
-
-@node Examples of gnatls Usage
-@section Example of @code{gnatls} Usage
-@ifclear vms
-
-@noindent
-Example of using the verbose switch. Note how the source and
-object paths are affected by the ^-I^/SEARCH^ switch.
-
-@smallexample
-$ gnatls -v -I.. demo1.o
-
-GNATLS 3.10w (970212) Copyright 1999 Free Software Foundation, Inc.
-
-Source Search Path:
- <Current_Directory>
- ../
- /home/comar/local/adainclude/
-
-Object Search Path:
- <Current_Directory>
- ../
- /home/comar/local/lib/gcc-lib/mips-sni-sysv4/2.7.2/adalib/
-
-./demo1.o
- Unit =>
- Name => demo1
- Kind => subprogram body
- Flags => No_Elab_Code
- Source => demo1.adb modified
-@end smallexample
-
-@noindent
-The following is an example of use of the dependency list.
-Note the use of the -s switch
-which gives a straight list of source files. This can be useful for
-building specialized scripts.
-
-@smallexample
-$ gnatls -d demo2.o
-./demo2.o demo2 OK demo2.adb
- OK gen_list.ads
- OK gen_list.adb
- OK instr.ads
- OK instr-child.ads
-
-$ gnatls -d -s -a demo1.o
-demo1.adb
-/home/comar/local/adainclude/ada.ads
-/home/comar/local/adainclude/a-finali.ads
-/home/comar/local/adainclude/a-filico.ads
-/home/comar/local/adainclude/a-stream.ads
-/home/comar/local/adainclude/a-tags.ads
-gen_list.ads
-gen_list.adb
-/home/comar/local/adainclude/gnat.ads
-/home/comar/local/adainclude/g-io.ads
-instr.ads
-/home/comar/local/adainclude/system.ads
-/home/comar/local/adainclude/s-exctab.ads
-/home/comar/local/adainclude/s-finimp.ads
-/home/comar/local/adainclude/s-finroo.ads
-/home/comar/local/adainclude/s-secsta.ads
-/home/comar/local/adainclude/s-stalib.ads
-/home/comar/local/adainclude/s-stoele.ads
-/home/comar/local/adainclude/s-stratt.ads
-/home/comar/local/adainclude/s-tasoli.ads
-/home/comar/local/adainclude/s-unstyp.ads
-/home/comar/local/adainclude/unchconv.ads
-@end smallexample
-@end ifclear
-
-@ifset vms
-@smallexample
-GNAT LIST /DEPENDENCIES /OUTPUT=SOURCES /ALL_UNITS DEMO1.ADB
-
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]ada.ads
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-finali.ads
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-filico.ads
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-stream.ads
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]a-tags.ads
-demo1.adb
-gen_list.ads
-gen_list.adb
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]gnat.ads
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]g-io.ads
-instr.ads
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]system.ads
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-exctab.ads
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finimp.ads
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-finroo.ads
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-secsta.ads
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stalib.ads
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stoele.ads
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-stratt.ads
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-tasoli.ads
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]s-unstyp.ads
-GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB]unchconv.ads
-@end smallexample
-@end ifset
-
-@ifclear vms
-@node GNAT and Libraries
-@chapter GNAT and Libraries
-@cindex Library, building, installing
-
-@noindent
-This chapter addresses some of the issues related to building and using
-a library with GNAT. It also shows how the GNAT run-time library can be
-recompiled.
-
-@menu
-* Creating an Ada Library::
-* Installing an Ada Library::
-* Using an Ada Library::
-* Creating an Ada Library to be Used in a Non-Ada Context::
-* Rebuilding the GNAT Run-Time Library::
-@end menu
-
-@node Creating an Ada Library
-@section Creating an Ada Library
-
-@noindent
-In the GNAT environment, a library has two components:
-@itemize @bullet
-@item
-Source files.
-@item
-Compiled code and Ali files. See @ref{The Ada Library Information Files}.
-@end itemize
-
-@noindent
-In order to use other packages @ref{The GNAT Compilation Model}
-requires a certain number of sources to be available to the compiler.
-The minimal set of
-sources required includes the specs of all the packages that make up the
-visible part of the library as well as all the sources upon which they
-depend. The bodies of all visible generic units must also be provided.
-@noindent
-Although it is not strictly mandatory, it is recommended that all sources
-needed to recompile the library be provided, so that the user can make
-full use of inter-unit inlining and source-level debugging. This can also
-make the situation easier for users that need to upgrade their compilation
-toolchain and thus need to recompile the library from sources.
-
-@noindent
-The compiled code can be provided in different ways. The simplest way is
-to provide directly the set of objects produced by the compiler during
-the compilation of the library. It is also possible to group the objects
-into an archive using whatever commands are provided by the operating
-system. Finally, it is also possible to create a shared library (see
-option -shared in the GCC manual).
-
-@noindent
-There are various possibilities for compiling the units that make up the
-library: for example with a Makefile @ref{Using the GNU make Utility},
-or with a conventional script.
-For simple libraries, it is also possible to create a
-dummy main program which depends upon all the packages that comprise the
-interface of the library. This dummy main program can then be given to
-gnatmake, in order to build all the necessary objects. Here is an example
-of such a dummy program and the generic commands used to build an
-archive or a shared library.
-
-@smallexample
-@iftex
-@leftskip=.7cm
-@end iftex
-@b{with} My_Lib.Service1;
-@b{with} My_Lib.Service2;
-@b{with} My_Lib.Service3;
-@b{procedure} My_Lib_Dummy @b{is}
-@b{begin}
- @b{null};
-@b{end};
-
-# compiling the library
-$ gnatmake -c my_lib_dummy.adb
-
-# we don't need the dummy object itself
-$ rm my_lib_dummy.o my_lib_dummy.ali
-
-# create an archive with the remaining objects
-$ ar rc libmy_lib.a *.o
-# some systems may require "ranlib" to be run as well
-
-# or create a shared library
-$ gcc -shared -o libmy_lib.so *.o
-# some systems may require the code to have been compiled with -fPIC
-@end smallexample
-
-@noindent
-When the objects are grouped in an archive or a shared library, the user
-needs to specify the desired library at link time, unless a pragma
-linker_options has been used in one of the sources:
-@smallexample
-@b{pragma} Linker_Options ("-lmy_lib");
-@end smallexample
-
-@node Installing an Ada Library
-@section Installing an Ada Library
-
-@noindent
-In the GNAT model, installing a library consists in copying into a specific
-location the files that make up this library. It is possible to install
-the sources in a different directory from the other files (ALI, objects,
-archives) since the source path and the object path can easily be
-specified separately.
-
-@noindent
-For general purpose libraries, it is possible for the system
-administrator to put those libraries in the default compiler paths. To
-achieve this, he must specify their location in the configuration files
-"ada_source_path" and "ada_object_path" that must be located in the GNAT
-installation tree at the same place as the gcc spec file. The location of
-the gcc spec file can be determined as follows:
-@smallexample
-$ gcc -v
-@end smallexample
-
-@noindent
-The configuration files mentioned above have simple format: each line in them
-must contain one unique
-directory name. Those names are added to the corresponding path
-in their order of appearance in the file. The names can be either absolute
-or relative, in the latter case, they are relative to where theses files
-are located.
-
-@noindent
-"ada_source_path" and "ada_object_path" might actually not be present in a
-GNAT installation, in which case, GNAT will look for its run-time library in
-the directories "adainclude" for the sources and "adalib" for the
-objects and ALI files. When the files exist, the compiler does not
-look in "adainclude" and "adalib" at all, and thus the "ada_source_path" file
-must contain the location for the GNAT run-time sources (which can simply
-be "adainclude"). In the same way, the "ada_object_path" file must contain
-the location for the GNAT run-time objects (which can simply
-be "adalib").
-
-@noindent
-You can also specify a new default path to the runtime library at compilation
-time with the switch "--RTS=@var{rts-path}". You can easily choose and change
-the runtime you want your program to be compiled with. This switch is
-recognized by gcc, gnatmake, gnatbind, gnatls, gnatfind and gnatxref.
-
-@noindent
-It is possible to install a library before or after the standard GNAT
-library, by reordering the lines in the configuration files. In general, a
-library must be installed before the GNAT library if it redefines any part of it.
-
-@node Using an Ada Library
-@section Using an Ada Library
-
-@noindent
-In order to use a Ada library, you need to make sure that this
-library is on both your source and object path
-@ref{Search Paths and the Run-Time Library (RTL)}
-and @ref{Search Paths for gnatbind}. For
-instance, you can use the library "mylib" installed in "/dir/my_lib_src"
-and "/dir/my_lib_obj" with the following commands:
-
-@smallexample
-$ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \
- -largs -lmy_lib
-@end smallexample
-
-@noindent
-This can be simplified down to the following:
-@smallexample
-$ gnatmake my_appl
-@end smallexample
-when the following conditions are met:
-@itemize @bullet
-@item
-"/dir/my_lib_src" has been added by the user to the environment
-variable "ADA_INCLUDE_PATH", or by the administrator to the file
-"ada_source_path"
-@item
-"/dir/my_lib_obj" has been added by the user to the environment
-variable "ADA_OBJECTS_PATH", or by the administrator to the file
-"ada_object_path"
-@item
-a pragma linker_options, as mentioned in @ref{Creating an Ada Library}
-as been added to the sources.
-@end itemize
-@noindent
-
-@node Creating an Ada Library to be Used in a Non-Ada Context
-@section Creating an Ada Library to be Used in a Non-Ada Context
-
-@noindent
-The previous sections detailed how to create and install a library that
-was usable from an Ada main program. Using this library in a non-Ada
-context is not possible, because the elaboration of the library is
-automatically done as part of the main program elaboration.
-
-GNAT also provides the ability to build libraries that can be used both
-in an Ada and non-Ada context. This section describes how to build such
-a library, and then how to use it from a C program. The method for
-interfacing with the library from other languages such as Fortran for
-instance remains the same.
-
-@subsection Creating the Library
-
-@itemize @bullet
-@item Identify the units representing the interface of the library.
-
-Here is an example of simple library interface:
-
-@smallexample
-package Interface is
-
- procedure Do_Something;
-
- procedure Do_Something_Else;
-
-end Interface;
-@end smallexample
-
-@item Use @code{pragma Export} or @code{pragma Convention} for the
-exported entities.
-
-Our package @code{Interface} is then updated as follow:
-@smallexample
-package Interface is
-
- procedure Do_Something;
- pragma Export (C, Do_Something, "do_something");
-
- procedure Do_Something_Else;
- pragma Export (C, Do_Something_Else, "do_something_else");
-
-end Interface;
-@end smallexample
-
-@item Compile all the units composing the library.
-
-@item Bind the library objects.
-
-This step is performed by invoking gnatbind with the @code{-L<prefix>}
-switch. @code{gnatbind} will then generate the library elaboration
-procedure (named @code{<prefix>init}) and the run-time finalization
-procedure (named @code{<prefix>final}).
-
-@smallexample
-# generate the binder file in Ada
-$ gnatbind -Lmylib interface
-
-# generate the binder file in C
-$ gnatbind -C -Lmylib interface
-@end smallexample
-
-@item Compile the files generated by the binder
-
-@smallexample
-$ gcc -c b~interface.adb
-@end smallexample
-
-@item Create the library;
-
-The procedure is identical to the procedure explained in
-@ref{Creating an Ada Library},
-except that @file{b~interface.o} needs to be added to
-the list of objects.
-
-@smallexample
-# create an archive file
-$ ar cr libmylib.a b~interface.o <other object files>
-
-# create a shared library
-$ gcc -shared -o libmylib.so b~interface.o <other object files>
-@end smallexample
-
-@item Provide a "foreign" view of the library interface;
-
-The example below shows the content of @code{mylib_interface.h} (note
-that there is no rule for the naming of this file, any name can be used)
-@smallexample
-/* the library elaboration procedure */
-extern void mylibinit (void);
-
-/* the library finalization procedure */
-extern void mylibfinal (void);
-
-/* the interface exported by the library */
-extern void do_something (void);
-extern void do_something_else (void);
-@end smallexample
-@end itemize
-
-@subsection Using the Library
-
-@noindent
-Libraries built as explained above can be used from any program, provided
-that the elaboration procedures (named @code{mylibinit} in the previous
-example) are called before the library services are used. Any number of
-libraries can be used simultaneously, as long as the elaboration
-procedure of each library is called.
-
-Below is an example of C program that uses our @code{mylib} library.
-
-@smallexample
-#include "mylib_interface.h"
-
-int
-main (void)
-@{
- /* First, elaborate the library before using it */
- mylibinit ();
-
- /* Main program, using the library exported entities */
- do_something ();
- do_something_else ();
-
- /* Library finalization at the end of the program */
- mylibfinal ();
- return 0;
-@}
-@end smallexample
-
-@noindent
-Note that this same library can be used from an equivalent Ada main
-program. In addition, if the libraries are installed as detailed in
-@ref{Installing an Ada Library}, it is not necessary to invoke the
-library elaboration and finalization routines. The binder will ensure
-that this is done as part of the main program elaboration and
-finalization phases.
-
-@subsection The Finalization Phase
-
-@noindent
-Invoking any library finalization procedure generated by @code{gnatbind}
-shuts down the Ada run time permanently. Consequently, the finalization
-of all Ada libraries must be performed at the end of the program. No
-call to these libraries nor the Ada run time should be made past the
-finalization phase.
-
-@subsection Restrictions in Libraries
-
-@noindent
-The pragmas listed below should be used with caution inside libraries,
-as they can create incompatibilities with other Ada libraries:
-@itemize @bullet
-@item pragma @code{Locking_Policy}
-@item pragma @code{Queuing_Policy}
-@item pragma @code{Task_Dispatching_Policy}
-@item pragma @code{Unreserve_All_Interrupts}
-@end itemize
-When using a library that contains such pragmas, the user must make sure
-that all libraries use the same pragmas with the same values. Otherwise,
-a @code{Program_Error} will
-be raised during the elaboration of the conflicting
-libraries. The usage of these pragmas and its consequences for the user
-should therefore be well documented.
-
-Similarly, the traceback in exception occurrences mechanism should be
-enabled or disabled in a consistent manner across all libraries.
-Otherwise, a Program_Error will be raised during the elaboration of the
-conflicting libraries.
-
-If the @code{'Version} and @code{'Body_Version}
-attributes are used inside a library, then it is necessary to
-perform a @code{gnatbind} step that mentions all ali files in all
-libraries, so that version identifiers can be properly computed.
-In practice these attributes are rarely used, so this is unlikely
-to be a consideration.
-
-@node Rebuilding the GNAT Run-Time Library
-@section Rebuilding the GNAT Run-Time Library
-
-@noindent
-It may be useful to recompile the GNAT library in various contexts, the
-most important one being the use of partition-wide configuration pragmas
-such as Normalize_Scalar. A special Makefile called
-@code{Makefile.adalib} is provided to that effect and can be found in
-the directory containing the GNAT library. The location of this
-directory depends on the way the GNAT environment has been installed and can
-be determined by means of the command:
-
-@smallexample
-$ gnatls -v
-@end smallexample
-
-@noindent
-The last entry in the object search path usually contains the
-gnat library. This Makefile contains its own documentation and in
-particular the set of instructions needed to rebuild a new library and
-to use it.
-
-@node Using the GNU make Utility
-@chapter Using the GNU @code{make} Utility
-@findex make
-
-@noindent
-This chapter offers some examples of makefiles that solve specific
-problems. It does not explain how to write a makefile (see the GNU make
-documentation), nor does it try to replace the @code{gnatmake} utility
-(@pxref{The GNAT Make Program gnatmake}).
-
-All the examples in this section are specific to the GNU version of
-make. Although @code{make} is a standard utility, and the basic language
-is the same, these examples use some advanced features found only in
-@code{GNU make}.
-
-@menu
-* Using gnatmake in a Makefile::
-* Automatically Creating a List of Directories::
-* Generating the Command Line Switches::
-* Overcoming Command Line Length Limits::
-@end menu
-
-@node Using gnatmake in a Makefile
-@section Using gnatmake in a Makefile
-@findex makefile
-@cindex GNU make
-
-@noindent
-Complex project organizations can be handled in a very powerful way by
-using GNU make combined with gnatmake. For instance, here is a Makefile
-which allows you to build each subsystem of a big project into a separate
-shared library. Such a makefile allows you to significantly reduce the link
-time of very big applications while maintaining full coherence at
-each step of the build process.
-
-The list of dependencies are handled automatically by
-@code{gnatmake}. The Makefile is simply used to call gnatmake in each of
-the appropriate directories.
-
-Note that you should also read the example on how to automatically
-create the list of directories (@pxref{Automatically Creating a List of Directories})
-which might help you in case your project has a lot of
-subdirectories.
-
-@smallexample
-@iftex
-@leftskip=0cm
-@font@heightrm=cmr8
-@heightrm
-@end iftex
-## This Makefile is intended to be used with the following directory
-## configuration:
-## - The sources are split into a series of csc (computer software components)
-## Each of these csc is put in its own directory.
-## Their name are referenced by the directory names.
-## They will be compiled into shared library (although this would also work
-## with static libraries
-## - The main program (and possibly other packages that do not belong to any
-## csc is put in the top level directory (where the Makefile is).
-## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
-## \_ second_csc (sources) __ lib (will contain the library)
-## \_ ...
-## Although this Makefile is build for shared library, it is easy to modify
-## to build partial link objects instead (modify the lines with -shared and
-## gnatlink below)
-##
-## With this makefile, you can change any file in the system or add any new
-## file, and everything will be recompiled correctly (only the relevant shared
-## objects will be recompiled, and the main program will be re-linked).
-
-# The list of computer software component for your project. This might be
-# generated automatically.
-CSC_LIST=aa bb cc
-
-# Name of the main program (no extension)
-MAIN=main
-
-# If we need to build objects with -fPIC, uncomment the following line
-#NEED_FPIC=-fPIC
-
-# The following variable should give the directory containing libgnat.so
-# You can get this directory through 'gnatls -v'. This is usually the last
-# directory in the Object_Path.
-GLIB=...
-
-# The directories for the libraries
-# (This macro expands the list of CSC to the list of shared libraries, you
-# could simply use the expanded form :
-# LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
-LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
-
-$@{MAIN@}: objects $@{LIB_DIR@}
- gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
- gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
-
-objects::
- # recompile the sources
- gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
-
-# Note: In a future version of GNAT, the following commands will be simplified
-# by a new tool, gnatmlib
-$@{LIB_DIR@}:
- mkdir -p $@{dir $@@ @}
- cd $@{dir $@@ @}; gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
- cd $@{dir $@@ @}; cp -f ../*.ali .
-
-# The dependencies for the modules
-# Note that we have to force the expansion of *.o, since in some cases make won't
-# be able to do it itself.
-aa/lib/libaa.so: $@{wildcard aa/*.o@}
-bb/lib/libbb.so: $@{wildcard bb/*.o@}
-cc/lib/libcc.so: $@{wildcard cc/*.o@}
-
-# Make sure all of the shared libraries are in the path before starting the
-# program
-run::
- LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
-
-clean::
- $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
- $@{RM@} $@{CSC_LIST:%=%/*.ali@}
- $@{RM@} $@{CSC_LIST:%=%/*.o@}
- $@{RM@} *.o *.ali $@{MAIN@}
-@end smallexample
-
-@node Automatically Creating a List of Directories
-@section Automatically Creating a List of Directories
-
-@noindent
-In most makefiles, you will have to specify a list of directories, and
-store it in a variable. For small projects, it is often easier to
-specify each of them by hand, since you then have full control over what
-is the proper order for these directories, which ones should be
-included...
-
-However, in larger projects, which might involve hundreds of
-subdirectories, it might be more convenient to generate this list
-automatically.
-
-The example below presents two methods. The first one, although less
-general, gives you more control over the list. It involves wildcard
-characters, that are automatically expanded by @code{make}. Its
-shortcoming is that you need to explicitly specify some of the
-organization of your project, such as for instance the directory tree
-depth, whether some directories are found in a separate tree,...
-
-The second method is the most general one. It requires an external
-program, called @code{find}, which is standard on all Unix systems. All
-the directories found under a given root directory will be added to the
-list.
-
-@smallexample
-@iftex
-@leftskip=0cm
-@font@heightrm=cmr8
-@heightrm
-@end iftex
-# The examples below are based on the following directory hierarchy:
-# All the directories can contain any number of files
-# ROOT_DIRECTORY -> a -> aa -> aaa
-# -> ab
-# -> ac
-# -> b -> ba -> baa
-# -> bb
-# -> bc
-# This Makefile creates a variable called DIRS, that can be reused any time
-# you need this list (see the other examples in this section)
-
-# The root of your project's directory hierarchy
-ROOT_DIRECTORY=.
-
-####
-# First method: specify explicitly the list of directories
-# This allows you to specify any subset of all the directories you need.
-####
-
-DIRS := a/aa/ a/ab/ b/ba/
-
-####
-# Second method: use wildcards
-# Note that the argument(s) to wildcard below should end with a '/'.
-# Since wildcards also return file names, we have to filter them out
-# to avoid duplicate directory names.
-# We thus use make's @code{dir} and @code{sort} functions.
-# It sets DIRs to the following value (note that the directories aaa and baa
-# are not given, unless you change the arguments to wildcard).
-# DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
-####
-
-DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/ $@{ROOT_DIRECTORY@}/*/*/@}@}@}
-
-####
-# Third method: use an external program
-# This command is much faster if run on local disks, avoiding NFS slowdowns.
-# This is the most complete command: it sets DIRs to the following value:
-# DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
-####
-
-DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
-
-@end smallexample
-
-@node Generating the Command Line Switches
-@section Generating the Command Line Switches
-
-@noindent
-Once you have created the list of directories as explained in the
-previous section (@pxref{Automatically Creating a List of Directories}),
-you can easily generate the command line arguments to pass to gnatmake.
-
-For the sake of completeness, this example assumes that the source path
-is not the same as the object path, and that you have two separate lists
-of directories.
-
-@smallexample
-# see "Automatically creating a list of directories" to create
-# these variables
-SOURCE_DIRS=
-OBJECT_DIRS=
-
-GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
-GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
-
-all:
- gnatmake $@{GNATMAKE_SWITCHES@} main_unit
-@end smallexample
-
-@node Overcoming Command Line Length Limits
-@section Overcoming Command Line Length Limits
-
-@noindent
-One problem that might be encountered on big projects is that many
-operating systems limit the length of the command line. It is thus hard to give
-gnatmake the list of source and object directories.
-
-This example shows how you can set up environment variables, which will
-make @code{gnatmake} behave exactly as if the directories had been
-specified on the command line, but have a much higher length limit (or
-even none on most systems).
-
-It assumes that you have created a list of directories in your Makefile,
-using one of the methods presented in
-@ref{Automatically Creating a List of Directories}.
-For the sake of completeness, we assume that the object
-path (where the ALI files are found) is different from the sources patch.
-
-Note a small trick in the Makefile below: for efficiency reasons, we
-create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
-expanded immediately by @code{make}. This way we overcome the standard
-make behavior which is to expand the variables only when they are
-actually used.
-
-@smallexample
-@iftex
-@leftskip=0cm
-@font@heightrm=cmr8
-@heightrm
-@end iftex
-# In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECT_PATH.
-# This is the same thing as putting the -I arguments on the command line.
-# (the equivalent of using -aI on the command line would be to define
-# only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECT_PATH).
-# You can of course have different values for these variables.
-#
-# Note also that we need to keep the previous values of these variables, since
-# they might have been set before running 'make' to specify where the GNAT
-# library is installed.
-
-# see "Automatically creating a list of directories" to create these
-# variables
-SOURCE_DIRS=
-OBJECT_DIRS=
-
-empty:=
-space:=$@{empty@} $@{empty@}
-SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
-OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
-ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
-ADA_OBJECT_PATH += $@{OBJECT_LIST@}
-export ADA_INCLUDE_PATH
-export ADA_OBJECT_PATH
-
-all:
- gnatmake main_unit
-@end smallexample
-
-@ifclear vxworks
-@node Finding Memory Problems with gnatmem
-@chapter Finding Memory Problems with @code{gnatmem}
-@findex gnatmem
-
-@noindent
-@code{gnatmem}, is a tool that monitors dynamic allocation and
-deallocation activity in a program, and displays information about
-incorrect deallocations and possible sources of memory leaks. Gnatmem
-provides three type of information:
-@itemize @bullet
-@item
-General information concerning memory management, such as the total
-number of allocations and deallocations, the amount of allocated
-memory and the high water mark, i.e. the largest amount of allocated
-memory in the course of program execution.
-
-@item
-Backtraces for all incorrect deallocations, that is to say deallocations
-which do not correspond to a valid allocation.
-
-@item
-Information on each allocation that is potentially the origin of a memory
-leak.
-@end itemize
-
-The @code{gnatmem} command has two modes. It can be used with @code{gdb}
-or with instrumented allocation and deallocation routines. The later
-mode is called the @code{GMEM} mode. Both modes produce the very same
-output.
-
-@menu
-* Running gnatmem (GDB Mode)::
-* Running gnatmem (GMEM Mode)::
-* Switches for gnatmem::
-* Examples of gnatmem Usage::
-* GDB and GMEM Modes::
-* Implementation Note::
-@end menu
-
-@node Running gnatmem (GDB Mode)
-@section Running @code{gnatmem} (GDB Mode)
-
-@noindent
-The @code{gnatmem} command has the form
-
-@smallexample
- $ gnatmem [-q] [n] [-o file] user_program [program_arg]*
-or
- $ gnatmem [-q] [n] -i file
-@end smallexample
-
-@noindent
-Gnatmem must be supplied with the executable to examine, followed by its
-run-time inputs. For example, if a program is executed with the command:
-@smallexample
-$ my_program arg1 arg2
-@end smallexample
-then it can be run under @code{gnatmem} control using the command:
-@smallexample
-$ gnatmem my_program arg1 arg2
-@end smallexample
-
-The program is transparently executed under the control of the debugger
-@ref{The GNAT Debugger GDB}. This does not affect the behavior
-of the program, except for sensitive real-time programs. When the program
-has completed execution, @code{gnatmem} outputs a report containing general
-allocation/deallocation information and potential memory leak.
-For better results, the user program should be compiled with
-debugging options @ref{Switches for gcc}.
-
-Here is a simple example of use:
-
-*************** debut cc
-@smallexample
-$ gnatmem test_gm
-
-Global information
-------------------
- Total number of allocations : 45
- Total number of deallocations : 6
- Final Water Mark (non freed mem) : 11.29 Kilobytes
- High Water Mark : 11.40 Kilobytes
-
-.
-.
-.
-Allocation Root # 2
--------------------
- Number of non freed allocations : 11
- Final Water Mark (non freed mem) : 1.16 Kilobytes
- High Water Mark : 1.27 Kilobytes
- Backtrace :
- test_gm.adb:23 test_gm.alloc
-.
-.
-.
-@end smallexample
-
-The first block of output give general information. In this case, the
-Ada construct "@b{new}" was executed 45 times, and only 6 calls to an
-unchecked deallocation routine occurred.
-
-Subsequent paragraphs display information on all allocation roots.
-An allocation root is a specific point in the execution of the program
-that generates some dynamic allocation, such as a "@b{new}" construct. This
-root is represented by an execution backtrace (or subprogram call
-stack). By default the backtrace depth for allocations roots is 1, so
-that a root corresponds exactly to a source location. The backtrace can
-be made deeper, to make the root more specific.
-
-@node Running gnatmem (GMEM Mode)
-@section Running @code{gnatmem} (GMEM Mode)
-@cindex @code{GMEM} (@code{gnatmem})
-
-@noindent
-The @code{gnatmem} command has the form
-
-@smallexample
- $ gnatmem [-q] [n] -i gmem.out user_program [program_arg]*
-@end smallexample
-
-The program must have been linked with the instrumented version of the
-allocation and deallocation routines. This is done with linking with the
-@file{libgmem.a} library. For better results, the user program should be
-compiled with debugging options @ref{Switches for gcc}. For example to
-build @file{my_program}:
-
-@smallexample
-$ gnatmake -g my_program -largs -lgmem
-@end smallexample
-
-@noindent
-When running @file{my_program} the file @file{gmem.out} is produced. This file
-contains information about all allocations and deallocations done by the
-program. It is produced by the instrumented allocations and
-deallocations routines and will be used by @code{gnatmem}.
-
-@noindent
-Gnatmem must be supplied with the @file{gmem.out} file and the executable to
-examine followed by its run-time inputs. For example, if a program is
-executed with the command:
-@smallexample
-$ my_program arg1 arg2
-@end smallexample
-then @file{gmem.out} can be analysed by @code{gnatmem} using the command:
-@smallexample
-$ gnatmem -i gmem.out my_program arg1 arg2
-@end smallexample
-
-@node Switches for gnatmem
-@section Switches for @code{gnatmem}
-
-@noindent
-@code{gnatmem} recognizes the following switches:
-
-@table @code
-
-@item @code{-q}
-@cindex @code{-q} (@code{gnatmem})
-Quiet. Gives the minimum output needed to identify the origin of the
-memory leaks. Omit statistical information.
-
-@item @code{n}
-@cindex @code{n} (@code{gnatmem})
-N is an integer literal (usually between 1 and 10) which controls the
-depth of the backtraces defining allocation root. The default value for
-N is 1. The deeper the backtrace, the more precise the localization of
-the root. Note that the total number of roots can depend on this
-parameter.
-
-@item @code{-o file}
-@cindex @code{-o} (@code{gnatmem})
-Direct the gdb output to the specified file. The @code{gdb} script used
-to generate this output is also saved in the file @file{gnatmem.tmp}.
-
-@item @code{-i file}
-@cindex @code{-i} (@code{gnatmem})
-Do the @code{gnatmem} processing starting from @file{file} which has
-been generated by a previous call to @code{gnatmem} with the -o
-switch or @file{gmem.out} produced by @code{GMEM} mode. This is useful
-for post mortem processing.
-
-@end table
-
-@node Examples of gnatmem Usage
-@section Example of @code{gnatmem} Usage
-
-@noindent
-This section is based on the @code{GDB} mode of @code{gnatmem}. The same
-results can be achieved using @code{GMEM} mode. See section
-@ref{Running gnatmem (GMEM Mode)}.
-
-@noindent
-The first example shows the use of @code{gnatmem}
-on a simple leaking program.
-Suppose that we have the following Ada program:
-
-@smallexample
-@group
-@cartouche
-@b{with} Unchecked_Deallocation;
-@b{procedure} Test_Gm @b{is}
-
- @b{type} T @b{is array} (1..1000) @b{of} Integer;
- @b{type} Ptr @b{is access} T;
- @b{procedure} Free @b{is new} Unchecked_Deallocation (T, Ptr);
- A : Ptr;
-
- @b{procedure} My_Alloc @b{is}
- @b{begin}
- A := @b{new} T;
- @b{end} My_Alloc;
-
- @b{procedure} My_DeAlloc @b{is}
- B : Ptr := A;
- @b{begin}
- Free (B);
- @b{end} My_DeAlloc;
-
-@b{begin}
- My_Alloc;
- @b{for} I @b{in} 1 .. 5 @b{loop}
- @b{for} J @b{in} I .. 5 @b{loop}
- My_Alloc;
- @b{end loop};
- My_Dealloc;
- @b{end loop};
-@b{end};
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-The program needs to be compiled with debugging option:
-
-@smallexample
-$ gnatmake -g test_gm
-@end smallexample
-
-@code{gnatmem} is invoked simply with
-@smallexample
-$ gnatmem test_gm
-@end smallexample
-
-@noindent
-which produces the following output:
-
-@smallexample
-Global information
-------------------
- Total number of allocations : 18
- Total number of deallocations : 5
- Final Water Mark (non freed mem) : 53.00 Kilobytes
- High Water Mark : 56.90 Kilobytes
-
-Allocation Root # 1
--------------------
- Number of non freed allocations : 11
- Final Water Mark (non freed mem) : 42.97 Kilobytes
- High Water Mark : 46.88 Kilobytes
- Backtrace :
- test_gm.adb:11 test_gm.my_alloc
-
-Allocation Root # 2
--------------------
- Number of non freed allocations : 1
- Final Water Mark (non freed mem) : 10.02 Kilobytes
- High Water Mark : 10.02 Kilobytes
- Backtrace :
- s-secsta.adb:81 system.secondary_stack.ss_init
-
-Allocation Root # 3
--------------------
- Number of non freed allocations : 1
- Final Water Mark (non freed mem) : 12 Bytes
- High Water Mark : 12 Bytes
- Backtrace :
- s-secsta.adb:181 system.secondary_stack.ss_init
-@end smallexample
-
-@noindent
-Note that the GNAT run time contains itself a certain number of
-allocations that have no corresponding deallocation,
-as shown here for root #2 and root
-#1. This is a normal behavior when the number of non freed allocations
-is one, it locates dynamic data structures that the run time needs for
-the complete lifetime of the program. Note also that there is only one
-allocation root in the user program with a single line back trace:
-test_gm.adb:11 test_gm.my_alloc, whereas a careful analysis of the
-program shows that 'My_Alloc' is called at 2 different points in the
-source (line 21 and line 24). If those two allocation roots need to be
-distinguished, the backtrace depth parameter can be used:
-
-@smallexample
-$ gnatmem 3 test_gm
-@end smallexample
-
-@noindent
-which will give the following output:
-
-@smallexample
-Global information
-------------------
- Total number of allocations : 18
- Total number of deallocations : 5
- Final Water Mark (non freed mem) : 53.00 Kilobytes
- High Water Mark : 56.90 Kilobytes
-
-Allocation Root # 1
--------------------
- Number of non freed allocations : 10
- Final Water Mark (non freed mem) : 39.06 Kilobytes
- High Water Mark : 42.97 Kilobytes
- Backtrace :
- test_gm.adb:11 test_gm.my_alloc
- test_gm.adb:24 test_gm
- b_test_gm.c:52 main
-
-Allocation Root # 2
--------------------
- Number of non freed allocations : 1
- Final Water Mark (non freed mem) : 10.02 Kilobytes
- High Water Mark : 10.02 Kilobytes
- Backtrace :
- s-secsta.adb:81 system.secondary_stack.ss_init
- s-secsta.adb:283 <system__secondary_stack___elabb>
- b_test_gm.c:33 adainit
-
-Allocation Root # 3
--------------------
- Number of non freed allocations : 1
- Final Water Mark (non freed mem) : 3.91 Kilobytes
- High Water Mark : 3.91 Kilobytes
- Backtrace :
- test_gm.adb:11 test_gm.my_alloc
- test_gm.adb:21 test_gm
- b_test_gm.c:52 main
-
-Allocation Root # 4
--------------------
- Number of non freed allocations : 1
- Final Water Mark (non freed mem) : 12 Bytes
- High Water Mark : 12 Bytes
- Backtrace :
- s-secsta.adb:181 system.secondary_stack.ss_init
- s-secsta.adb:283 <system__secondary_stack___elabb>
- b_test_gm.c:33 adainit
-@end smallexample
-
-@noindent
-The allocation root #1 of the first example has been split in 2 roots #1
-and #3 thanks to the more precise associated backtrace.
-
-@node GDB and GMEM Modes
-@section GDB and GMEM Modes
-
-@noindent
-The main advantage of the @code{GMEM} mode is that it is a lot faster than the
-@code{GDB} mode where the application must be monitored by a @code{GDB} script.
-But the @code{GMEM} mode is available only for DEC Unix, Linux x86,
-Solaris (sparc and x86) and Windows 95/98/NT/2000 (x86).
-
-@noindent
-The main advantage of the @code{GDB} mode is that it is available on all
-supported platforms. But it can be very slow if the application does a
-lot of allocations and deallocations.
-
-@node Implementation Note
-@section Implementation Note
-
-@menu
-* gnatmem Using GDB Mode::
-* gnatmem Using GMEM Mode::
-@end menu
-
-@node gnatmem Using GDB Mode
-@subsection @code{gnatmem} Using @code{GDB} Mode
-
-@noindent
-@code{gnatmem} executes the user program under the control of @code{GDB} using
-a script that sets breakpoints and gathers information on each dynamic
-allocation and deallocation. The output of the script is then analyzed
-by @code{gnatmem}
-in order to locate memory leaks and their origin in the
-program. Gnatmem works by recording each address returned by the
-allocation procedure (@code{__gnat_malloc})
-along with the backtrace at the
-allocation point. On each deallocation, the deallocated address is
-matched with the corresponding allocation. At the end of the processing,
-the unmatched allocations are considered potential leaks. All the
-allocations associated with the same backtrace are grouped together and
-form an allocation root. The allocation roots are then sorted so that
-those with the biggest number of unmatched allocation are printed
-first. A delicate aspect of this technique is to distinguish between the
-data produced by the user program and the data produced by the gdb
-script. Currently, on systems that allow probing the terminal, the gdb
-command "tty" is used to force the program output to be redirected to the
-current terminal while the @code{gdb} output is directed to a file or to a
-pipe in order to be processed subsequently by @code{gnatmem}.
-
-@node gnatmem Using GMEM Mode
-@subsection @code{gnatmem} Using @code{GMEM} Mode
-
-@noindent
-This mode use the same algorithm to detect memory leak as the @code{GDB}
-mode of @code{gnatmem}, the only difference is in the way data are
-gathered. In @code{GMEM} mode the program is linked with instrumented
-version of @code{__gnat_malloc} and @code{__gnat_free}
-routines. Information needed to find memory leak are recorded by these
-routines in file @file{gmem.out}. This mode also require that the stack
-traceback be available, this is only implemented on some platforms
-@ref{GDB and GMEM Modes}.
-
-@end ifclear
-@end ifclear
-
-@node Finding Memory Problems with GNAT Debug Pool
-@chapter Finding Memory Problems with GNAT Debug Pool
-@findex Debug Pool
-@cindex storage, pool, memory corruption
-
-@noindent
-The use of unchecked deallocation and unchecked conversion can easily
-lead to incorrect memory references. The problems generated by such
-references are usually difficult to tackle because the symptoms can be
-very remote from the origin of the problem. In such cases, it is
-very helpful to detect the problem as early as possible. This is the
-purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
-
-@noindent
-In order to use the GNAT specific debugging pool, the user must
-associate a debug pool object with each of the access types that may be
-related to suspected memory problems. See Ada Reference Manual
-13.11.
-@smallexample
-@b{type} Ptr @b{is} @b{access} Some_Type;
-Pool : GNAT.Debug_Pools.Debug_Pool;
-@b{for} Ptr'Storage_Pool @b{use} Pool;
-@end smallexample
-
-@code{GNAT.Debug_Pools} is derived from of a GNAT-specific kind of
-pool: the Checked_Pool. Such pools, like standard Ada storage pools,
-allow the user to redefine allocation and deallocation strategies. They
-also provide a checkpoint for each dereference, through the use of
-the primitive operation @code{Dereference} which is implicitly called at
-each dereference of an access value.
-
-Once an access type has been associated with a debug pool, operations on
-values of the type may raise four distinct exceptions,
-which correspond to four potential kinds of memory corruption:
-@itemize @bullet
-@item
-@code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
-@item
-@code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
-@item
-@code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
-@item
-@code{GNAT.Debug_Pools.Freeing_Deallocated_Storage }
-@end itemize
-
-@noindent
-For types associated with a Debug_Pool, dynamic allocation is performed using
-the standard
-GNAT allocation routine. References to all allocated chunks of memory
-are kept in an internal dictionary. The deallocation strategy consists
-in not releasing the memory to the underlying system but rather to fill
-it with a memory pattern easily recognizable during debugging sessions:
-The memory pattern is the old IBM hexadecimal convention: 16#DEADBEEF#.
-Upon each dereference, a check is made that the access value denotes a properly
-allocated memory location. Here is a complete example of use of
-@code{Debug_Pools}, that includes typical instances of memory corruption:
-@smallexample
-@iftex
-@leftskip=0cm
-@end iftex
-@b{with} Gnat.Io; @b{use} Gnat.Io;
-@b{with} Unchecked_Deallocation;
-@b{with} Unchecked_Conversion;
-@b{with} GNAT.Debug_Pools;
-@b{with} System.Storage_Elements;
-@b{with} Ada.Exceptions; @b{use} Ada.Exceptions;
-@b{procedure} Debug_Pool_Test @b{is}
-
- @b{type} T @b{is} @b{access} Integer;
- @b{type} U @b{is} @b{access} @b{all} T;
-
- P : GNAT.Debug_Pools.Debug_Pool;
- @b{for} T'Storage_Pool @b{use} P;
-
- @b{procedure} Free @b{is} @b{new} Unchecked_Deallocation (Integer, T);
- @b{function} UC @b{is} @b{new} Unchecked_Conversion (U, T);
- A, B : @b{aliased} T;
-
- @b{procedure} Info @b{is} @b{new} GNAT.Debug_Pools.Print_Info(Put_Line);
-
-@b{begin}
- Info (P);
- A := @b{new} Integer;
- B := @b{new} Integer;
- B := A;
- Info (P);
- Free (A);
- @b{begin}
- Put_Line (Integer'Image(B.@b{all}));
- @b{exception}
- @b{when} E : @b{others} => Put_Line ("raised: " & Exception_Name (E));
- @b{end};
- @b{begin}
- Free (B);
- @b{exception}
- @b{when} E : @b{others} => Put_Line ("raised: " & Exception_Name (E));
- @b{end};
- B := UC(A'Access);
- @b{begin}
- Put_Line (Integer'Image(B.@b{all}));
- @b{exception}
- @b{when} E : @b{others} => Put_Line ("raised: " & Exception_Name (E));
- @b{end};
- @b{begin}
- Free (B);
- @b{exception}
- @b{when} E : @b{others} => Put_Line ("raised: " & Exception_Name (E));
- @b{end};
- Info (P);
-@b{end} Debug_Pool_Test;
-@end smallexample
-@noindent
-The debug pool mechanism provides the following precise diagnostics on the
-execution of this erroneous program:
-@smallexample
-Debug Pool info:
- Total allocated bytes : 0
- Total deallocated bytes : 0
- Current Water Mark: 0
- High Water Mark: 0
-
-Debug Pool info:
- Total allocated bytes : 8
- Total deallocated bytes : 0
- Current Water Mark: 8
- High Water Mark: 8
-
-raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
-raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
-raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
-raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
-Debug Pool info:
- Total allocated bytes : 8
- Total deallocated bytes : 4
- Current Water Mark: 4
- High Water Mark: 8
-
-@end smallexample
-
-@node Creating Sample Bodies Using gnatstub
-@chapter Creating Sample Bodies Using @code{gnatstub}
-@findex gnatstub
-
-@noindent
-@code{gnatstub} creates body stubs, that is, empty but compilable bodies
-for library unit declarations.
-
-To create a body stub, @code{gnatstub} has to compile the library
-unit declaration. Therefore, bodies can be created only for legal
-library units. Moreover, if a library unit depends semantically upon
-units located outside the current directory, you have to provide
-the source search path when calling @code{gnatstub}, see the description
-of @code{gnatstub} switches below.
-
-@menu
-* Running gnatstub::
-* Switches for gnatstub::
-@end menu
-
-@node Running gnatstub
-@section Running @code{gnatstub}
-
-@noindent
-@code{gnatstub} has the command-line interface of the form
-
-@smallexample
-$ gnatstub [switches] filename [directory]
-@end smallexample
-
-@noindent
-where
-@table @code
-@item filename
-is the name of the source file that contains a library unit declaration
-for which a body must be created. This name should follow the GNAT file name
-conventions. No crunching is allowed for this file name. The file
-name may contain the path information.
-
-@item directory
-indicates the directory to place a body stub (default is the
-current directory)
-
-@item switches
-is an optional sequence of switches as described in the next section
-@end table
-
-@node Switches for gnatstub
-@section Switches for @code{gnatstub}
-
-@table @code
-
-@item ^-f^/FULL^
-If the destination directory already contains a file with a name of the body file
-for the argument spec file, replace it with the generated body stub.
-
-@item ^-hs^/HEADER=SPEC^
-Put the comment header (i.e. all the comments preceding the
-compilation unit) from the source of the library unit declaration
-into the body stub.
-
-@item ^-hg^/HEADER=GENERAL^
-Put a sample comment header into the body stub.
-
-@item -IDIR
-@itemx ^-I-^/NOCURRENT_DIRECTORY^
-These switches have the same meaning as in calls to gcc.
-They define the source search path in the call to gcc issued
-by @code{gnatstub} to compile an argument source file.
-
-@item ^-i^/INDENTATION=^@var{n}
-(@var{n} is a decimal natural number). Set the indentation level in the
-generated body sample to n, '^-i0^/INDENTATION=0^' means "no indentation",
-the default indentation is 3.
-
-@item ^-k^/TREE_FILE=SAVE^
-Do not remove the tree file (i.e. the snapshot of the compiler internal
-structures used by @code{gnatstub}) after creating the body stub.
-
-@item ^-l^/LINE_LENGTH=^@var{n}
-(@var{n} is a decimal positive number) Set the maximum line length in the
-body stub to n, the default is 78.
-
-@item ^-q^/QUIET^
-Quiet mode: do not generate a confirmation when a body is
-successfully created or a message when a body is not required for an
-argument unit.
-
-@item ^-r^/TREE_FILE=REUSE^
-Reuse the tree file (if it exists) instead of creating it: instead of
-creating the tree file for the library unit declaration, gnatstub
-tries to find it in the current directory and use it for creating
-a body. If the tree file is not found, no body is created. @code{^-r^/REUSE^}
-also implies @code{^-k^/SAVE^}, whether or not
-@code{^-k^/SAVE^} is set explicitly.
-
-@item ^-t^/TREE_FILE=OVERWRITE^
-Overwrite the existing tree file: if the current directory already
-contains the file which, according to the GNAT file name rules should
-be considered as a tree file for the argument source file, gnatstub
-will refuse to create the tree file needed to create a body sampler,
-unless @code{-t} option is set
-
-@item ^-v^/VERBOSE^
-Verbose mode: generate version information.
-
-@end table
-
-@node Reducing the Size of Ada Executables with gnatelim
-@chapter Reducing the Size of Ada Executables with @code{gnatelim}
-@findex gnatelim
-
-@menu
-* About gnatelim::
-* Eliminate Pragma::
-* Tree Files::
-* Preparing Tree and Bind Files for gnatelim::
-* Running gnatelim::
-* Correcting the List of Eliminate Pragmas::
-* Making Your Executables Smaller::
-* Summary of the gnatelim Usage Cycle::
-@end menu
-
-@node About gnatelim
-@section About @code{gnatelim}
-
-@noindent
-When a program shares a set of Ada
-packages with other programs, it may happen that this program uses
-only a fraction of the subprograms defined in these packages. The code
-created for these unused subprograms increases the size of the executable.
-
-@code{gnatelim} tracks unused subprograms in an Ada program and
-outputs a list of GNAT-specific @code{Eliminate} pragmas (see next
-section) marking all the subprograms that are declared but never called.
-By placing the list of @code{Eliminate} pragmas in the GNAT configuration
-file @file{gnat.adc} and recompiling your program, you may decrease the
-size of its executable, because the compiler will not generate the code
-for 'eliminated' subprograms.
-
-@code{gnatelim} needs as its input data a set of tree files
-(see @ref{Tree Files}) representing all the components of a program to
-process and a bind file for a main subprogram (see
-@ref{Preparing Tree and Bind Files for gnatelim}).
-
-@node Eliminate Pragma
-@section @code{Eliminate} Pragma
-@findex Eliminate
-
-@noindent
-The simplified syntax of the Eliminate pragma used by @code{gnatelim} is:
-
-@smallexample
-@cartouche
-@b{pragma} Eliminate (Library_Unit_Name, Subprogram_Name);
-@end cartouche
-@end smallexample
-
-@noindent
-where
-@table @code
-@item Library_Unit_Name
-full expanded Ada name of a library unit
-
-@item Subprogram_Name
-a simple or expanded name of a subprogram declared within this
-compilation unit
-
-@end table
-
-@noindent
-The effect of an @code{Eliminate} pragma placed in the GNAT configuration
-file @file{gnat.adc} is:
-
-@itemize @bullet
-
-@item
-If the subprogram @code{Subprogram_Name} is declared within
-the library unit @code{Library_Unit_Name}, the compiler will not generate
-code for this subprogram. This applies to all overloaded subprograms denoted
-by @code{Subprogram_Name}.
-
-@item
-If a subprogram marked by the pragma @code{Eliminate} is used (called)
-in a program, the compiler will produce an error message in the place where
-it is called.
-@end itemize
-
-@node Tree Files
-@section Tree Files
-@cindex Tree file
-
-@noindent
-A tree file stores a snapshot of the compiler internal data
-structures at the very end of a successful compilation. It contains all the
-syntactic and semantic information for the compiled unit and all the
-units upon which it depends semantically.
-To use tools that make use of tree files, you
-need to first produce the right set of tree files.
-
-GNAT produces correct tree files when -gnatt -gnatc options are set
-in a gcc call. The tree files have an .adt extension.
-Therefore, to produce a tree file for the compilation unit contained in a file
-named @file{foo.adb}, you must use the command
-
-@smallexample
-$ gcc -c -gnatc -gnatt foo.adb
-@end smallexample
-
-@noindent
-and you will get the tree file @file{foo.adt}.
-compilation.
-
-@node Preparing Tree and Bind Files for gnatelim
-@section Preparing Tree and Bind Files for @code{gnatelim}
-
-@noindent
-A set of tree files covering the program to be analyzed with
-@code{gnatelim} and
-the bind file for the main subprogram does not have to
-be in the current directory.
-'-T' gnatelim option may be used to provide
-the search path for tree files, and '-b'
-option may be used to point to the bind
-file to process (see @ref{Running gnatelim})
-
-If you do not have the appropriate set of tree
-files and the right bind file, you
-may create them in the current directory using the following procedure.
-
-Let @code{Main_Prog} be the name of a main subprogram, and suppose
-this subprogram is in a file named @file{main_prog.adb}.
-
-To create a bind file for @code{gnatelim}, run @code{gnatbind} for
-the main subprogram. @code{gnatelim} can work with both Ada and C
-bind files; when both are present, it uses the Ada bind file.
-The following commands will build the program and create the bind file:
-
-@smallexample
-$ gnatmake ^-c Main_Prog^/ACTIONS=COMPILE MAIN_PROG^
-$ gnatbind main_prog
-@end smallexample
-
-@noindent
-To create a minimal set of tree files covering the whole program, call
-@code{gnatmake} for this program as follows:
-
-@smallexample
-@ifset vms
-$ GNAT MAKE /FORCE_COMPILE /ACTIONS=COMPILE /NOLOAD /TREE_OUTPUT MAIN_PROG
-@end ifset
-@ifclear vms
-$ gnatmake -f -c -gnatc -gnatt Main_Prog
-@end ifclear
-@end smallexample
-
-@noindent
-The @code{^-c^/ACTIONS=COMPILE^} gnatmake option turns off the bind and link
-steps, that are useless anyway because the sources are compiled with
-@option{-gnatc} option which turns off code generation.
-
-The @code{^-f^/FORCE_COMPILE^} gnatmake option forces
-recompilation of all the needed sources.
-
-This sequence of actions will create all the data needed by @code{gnatelim}
-from scratch and therefore guarantee its consistency. If you would like to
-use some existing set of files as @code{gnatelim} output, you must make
-sure that the set of files is complete and consistent. You can use the
-@code{-m} switch to check if there are missed tree files
-
-Note, that @code{gnatelim} needs neither object nor ALI files.
-
-@node Running gnatelim
-@section Running @code{gnatelim}
-
-@noindent
-@code{gnatelim} has the following command-line interface:
-
-@smallexample
-$ gnatelim [options] name
-@end smallexample
-
-@noindent
-@code{name} should be a full expanded Ada name of a main subprogram
-of a program (partition).
-
-@code{gnatelim} options:
-
-@table @code
-@item ^-q^/QUIET^
-Quiet mode: by default @code{gnatelim} generates to the standard error
-stream a trace of the source file names of the compilation units being
-processed. This option turns this trace off.
-
-@item ^-v^/VERBOSE^
-Verbose mode: @code{gnatelim} version information is printed as Ada
-comments to the standard output stream.
-
-@item ^-a^/ALL^
-Also look for subprograms from the GNAT run time that can be eliminated.
-
-@item ^-m^/MISSED^
-Check if any tree files are missing for an accurate result.
-
-@item ^-T^/TREE_DIRS=^@var{dir}
-When looking for tree files also look in directory @var{dir}
-
-@item ^-b^/BIND_FILE=^@var{bind_file}
-Specifies @var{bind_file} as the bind file to process. If not set, the name
-of the bind file is computed from the full expanded Ada name of a main subprogram.
-
-@item -d@var{x}
-Activate internal debugging switches. @var{x} is a letter or digit, or
-string of letters or digits, which specifies the type of debugging
-mode desired. Normally these are used only for internal development
-or system debugging purposes. You can find full documentation for these
-switches in the body of the @code{Gnatelim.Options} unit in the compiler
-source file @file{gnatelim-options.adb}.
-@end table
-
-@noindent
-@code{gnatelim} sends its output to the standard output stream, and all the
-tracing and debug information is sent to the standard error stream.
-In order to produce a proper GNAT configuration file
-@file{gnat.adc}, redirection must be used:
-
-@smallexample
-@ifset vms
-$ PIPE GNAT ELIM MAIN_PROG > GNAT.ADC
-@end ifset
-@ifclear vms
-$ gnatelim Main_Prog > gnat.adc
-@end ifclear
-@end smallexample
-
-@ifclear vms
-@noindent
-or
-
-@smallexample
-$ gnatelim Main_Prog >> gnat.adc
-@end smallexample
-@end ifclear
-
-@noindent
-In order to append the @code{gnatelim} output to the existing contents of
-@file{gnat.adc}.
-
-@node Correcting the List of Eliminate Pragmas
-@section Correcting the List of Eliminate Pragmas
-
-@noindent
-In some rare cases it may happen that @code{gnatelim} will try to eliminate
-subprograms which are actually called in the program. In this case, the
-compiler will generate an error message of the form:
-
-@smallexample
-file.adb:106:07: cannot call eliminated subprogram "My_Prog"
-@end smallexample
-
-@noindent
-You will need to manually remove the wrong @code{Eliminate} pragmas from
-the @file{gnat.adc} file. It is advised that you recompile your program
-from scratch after that because you need a consistent @file{gnat.adc} file
-during the entire compilation.
-
-@node Making Your Executables Smaller
-@section Making Your Executables Smaller
-
-@noindent
-In order to get a smaller executable for your program you now have to
-recompile the program completely with the new @file{gnat.adc} file
-created by @code{gnatelim} in your current directory:
-
-@smallexample
-$ gnatmake ^-f Main_Prog^/FORCE_COMPILE MAIN_PROG^
-@end smallexample
-
-@noindent
-(you will need @code{^-f^/FORCE_COMPILE^} option for gnatmake to
-recompile everything
-with the set of pragmas @code{Eliminate} you have obtained with
-@code{gnatelim}).
-
-Be aware that the set of @code{Eliminate} pragmas is specific to each
-program. It is not recommended to merge sets of @code{Eliminate}
-pragmas created for different programs in one @file{gnat.adc} file.
-
-@node Summary of the gnatelim Usage Cycle
-@section Summary of the gnatelim Usage Cycle
-
-@noindent
-Here is a quick summary of the steps to be taken in order to reduce
-the size of your executables with @code{gnatelim}. You may use
-other GNAT options to control the optimization level,
-to produce the debugging information, to set search path, etc.
-
-@enumerate
-@item
-Produce a bind file and a set of tree files
-
-@smallexample
-$ gnatmake ^-c Main_Prog^/ACTIONS=COMPILE MAIN_PROG^
-$ gnatbind main_prog
-@ifset vms
-$ GNAT MAKE /FORCE_COMPILE /NO_LINK /NOLOAD /TREE_OUTPUT MAIN_PROG
-@end ifset
-@ifclear vms
-$ gnatmake -f -c -gnatc -gnatt Main_Prog
-@end ifclear
-@end smallexample
-
-@item
-Generate a list of @code{Eliminate} pragmas
-@smallexample
-@ifset vms
-$ PIPE GNAT ELIM MAIN_PROG > GNAT.ADC
-@end ifset
-@ifclear vms
-$ gnatelim Main_Prog >[>] gnat.adc
-@end ifclear
-@end smallexample
-
-@item
-Recompile the application
-
-@smallexample
-$ gnatmake ^-f Main_Prog^/FORCE_COMPILE MAIN_PROG^
-@end smallexample
-
-@end enumerate
-
-@node Other Utility Programs
-@chapter Other Utility Programs
-
-@noindent
-This chapter discusses some other utility programs available in the Ada
-environment.
-
-@menu
-* Using Other Utility Programs with GNAT::
-* The gnatpsta Utility Program::
-* The External Symbol Naming Scheme of GNAT::
-* Ada Mode for Glide::
-* Converting Ada Files to html with gnathtml::
-* Installing gnathtml::
-@ifset vms
-* LSE::
-* Profiling::
-@end ifset
-@end menu
-
-@node Using Other Utility Programs with GNAT
-@section Using Other Utility Programs with GNAT
-
-@noindent
-The object files generated by GNAT are in standard system format and in
-particular the debugging information uses this format. This means
-programs generated by GNAT can be used with existing utilities that
-depend on these formats.
-
-@ifclear vms
-In general, any utility program that works with C will also often work with
-Ada programs generated by GNAT. This includes software utilities such as
-gprof (a profiling program), @code{gdb} (the FSF debugger), and utilities such
-as Purify.
-@end ifclear
-
-@node The gnatpsta Utility Program
-@section The @code{gnatpsta} Utility Program
-
-@noindent
-Many of the definitions in package Standard are implementation-dependent.
-However, the source of this package does not exist as an Ada source
-file, so these values cannot be determined by inspecting the source.
-They can be determined by examining in detail the coding of
-@file{cstand.adb} which creates the image of Standard in the compiler,
-but this is awkward and requires a great deal of internal knowledge
-about the system.
-
-The @code{gnatpsta} utility is designed to deal with this situation.
-It is an Ada program that dynamically determines the
-values of all the relevant parameters in Standard, and prints them
-out in the form of an Ada source listing for Standard, displaying all
-the values of interest. This output is generated to
-@file{stdout}.
-
-To determine the value of any parameter in package Standard, simply
-run @code{gnatpsta} with no qualifiers or arguments, and examine
-the output. This is preferable to consulting documentation, because
-you know that the values you are getting are the actual ones provided
-by the executing system.
-
-@node The External Symbol Naming Scheme of GNAT
-@section The External Symbol Naming Scheme of GNAT
-
-@noindent
-In order to interpret the output from GNAT, when using tools that are
-originally intended for use with other languages, it is useful to
-understand the conventions used to generate link names from the Ada
-entity names.
-
-All link names are in all lowercase letters. With the exception of library
-procedure names, the mechanism used is simply to use the full expanded
-Ada name with dots replaced by double underscores. For example, suppose
-we have the following package spec:
-
-@smallexample
-@group
-@cartouche
-@b{package} QRS @b{is}
- MN : Integer;
-@b{end} QRS;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
-the corresponding link name is @code{qrs__mn}.
-@findex Export
-Of course if a @code{pragma Export} is used this may be overridden:
-
-@smallexample
-@group
-@cartouche
-@b{package} Exports @b{is}
- Var1 : Integer;
- @b{pragma} Export (Var1, C, External_Name => "var1_name");
- Var2 : Integer;
- @b{pragma} Export (Var2, C, Link_Name => "var2_link_name");
-@b{end} Exports;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-In this case, the link name for @var{Var1} is whatever link name the
-C compiler would assign for the C function @var{var1_name}. This typically
-would be either @var{var1_name} or @var{_var1_name}, depending on operating
-system conventions, but other possibilities exist. The link name for
-@var{Var2} is @var{var2_link_name}, and this is not operating system
-dependent.
-
-@findex _main
-One exception occurs for library level procedures. A potential ambiguity
-arises between the required name @code{_main} for the C main program,
-and the name we would otherwise assign to an Ada library level procedure
-called @code{Main} (which might well not be the main program).
-
-To avoid this ambiguity, we attach the prefix @code{_ada_} to such
-names. So if we have a library level procedure such as
-
-@smallexample
-@group
-@cartouche
-@b{procedure} Hello (S : String);
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-the external name of this procedure will be @var{_ada_hello}.
-
-@node Ada Mode for Glide
-@section Ada Mode for @code{Glide}
-
-@noindent
-The Glide mode for programming in Ada (both, Ada83 and Ada95) helps the
-user in understanding existing code and facilitates writing new code. It
-furthermore provides some utility functions for easier integration of
-standard Emacs features when programming in Ada.
-
-@subsection General Features:
-
-@itemize @bullet
-@item
-Full Integrated Development Environment :
-
-@itemize @bullet
-@item
-support of 'project files' for the configuration (directories,
-compilation options,...)
-
-@item
-compiling and stepping through error messages.
-
-@item
-running and debugging your applications within Glide.
-@end itemize
-
-@item
-easy to use for beginners by pull-down menus,
-
-@item
-user configurable by many user-option variables.
-@end itemize
-
-@subsection Ada Mode Features That Help Understanding Code:
-
-@itemize @bullet
-@item
-functions for easy and quick stepping through Ada code,
-
-@item
-getting cross reference information for identifiers (e.g. find the
-defining place by a keystroke),
-
-@item
-displaying an index menu of types and subprograms and move point to
-the chosen one,
-
-@item
-automatic color highlighting of the various entities in Ada code.
-@end itemize
-
-@subsection Glide Support for Writing Ada Code:
-
-@itemize @bullet
-@item
-switching between spec and body files with possible
-autogeneration of body files,
-
-@item
-automatic formating of subprograms parameter lists.
-
-@item
-automatic smart indentation according to Ada syntax,
-
-@item
-automatic completion of identifiers,
-
-@item
-automatic casing of identifiers, keywords, and attributes,
-
-@item
-insertion of statement templates,
-
-@item
-filling comment paragraphs like filling normal text,
-@end itemize
-
-For more information, please refer to the online Glide documentation
-available in the Glide --> Help Menu.
-
-@node Converting Ada Files to html with gnathtml
-@section Converting Ada Files to html with @code{gnathtml}
-
-@noindent
-This @code{Perl} script allows Ada source files to be browsed using
-standard Web browsers. For installation procedure, see the section
-@xref{Installing gnathtml}.
-
-Ada reserved keywords are highlighted in a bold font and Ada comments in
-a blue font. Unless your program was compiled with the gcc @option{-gnatx}
-switch to suppress the generation of cross-referencing information, user
-defined variables and types will appear in a different color; you will
-be able to click on any identifier and go to its declaration.
-
-The command line is as follow:
-@smallexample
-$ perl gnathtml.pl [switches] ada-files
-@end smallexample
-
-You can pass it as many Ada files as you want. @code{gnathtml} will generate
-an html file for every ada file, and a global file called @file{index.htm}.
-This file is an index of every identifier defined in the files.
-
-The available switches are the following ones :
-
-@table @code
-@item -83
-@cindex @code{-83} (@code{gnathtml})
-Only the subset on the Ada 83 keywords will be highlighted, not the full
-Ada 95 keywords set.
-
-@item -cc @var{color}
-This option allows you to change the color used for comments. The default
-value is green. The color argument can be any name accepted by html.
-
-@item -d
-@cindex @code{-d} (@code{gnathtml})
-If the ada files depend on some other files (using for instance the
-@code{with} command, the latter will also be converted to html.
-Only the files in the user project will be converted to html, not the files
-in the run-time library itself.
-
-@item -D
-This command is the same as -d above, but @code{gnathtml} will also look
-for files in the run-time library, and generate html files for them.
-
-@item -f
-@cindex @code{-f} (@code{gnathtml})
-By default, gnathtml will generate html links only for global entities
-('with'ed units, global variables and types,...). If you specify the
-@code{-f} on the command line, then links will be generated for local
-entities too.
-
-@item -l @var{number}
-@cindex @code{-l} (@code{gnathtml})
-If this switch is provided and @var{number} is not 0, then @code{gnathtml}
-will number the html files every @var{number} line.
-
-@item -I @var{dir}
-@cindex @code{-I} (@code{gnathtml})
-Specify a directory to search for library files (@file{.ali} files) and
-source files. You can provide several -I switches on the command line,
-and the directories will be parsed in the order of the command line.
-
-@item -o @var{dir}
-@cindex @code{-o} (@code{gnathtml})
-Specify the output directory for html files. By default, gnathtml will
-saved the generated html files in a subdirectory named @file{html/}.
-
-@item -p @var{file}
-@cindex @code{-p} (@code{gnathtml})
-If you are using Emacs and the most recent Emacs Ada mode, which provides
-a full Integrated Development Environment for compiling, checking,
-running and debugging applications, you may be using @file{.adp} files
-to give the directories where Emacs can find sources and object files.
-
-Using this switch, you can tell gnathtml to use these files. This allows
-you to get an html version of your application, even if it is spread
-over multiple directories.
-
-@item -sc @var{color}
-@cindex @code{-sc} (@code{gnathtml})
-This option allows you to change the color used for symbol definitions.
-The default value is red. The color argument can be any name accepted by html.
-
-@item -t @var{file}
-@cindex @code{-t} (@code{gnathtml})
-This switch provides the name of a file. This file contains a list of
-file names to be converted, and the effect is exactly as though they had
-appeared explicitly on the command line. This
-is the recommended way to work around the command line length limit on some
-systems.
-
-@end table
-
-@node Installing gnathtml
-@section Installing @code{gnathtml}
-
-@noindent
-@code{Perl} needs to be installed on your machine to run this script.
-@code{Perl} is freely available for almost every architecture and
-Operating System via the Internet.
-
-On Unix systems, you may want to modify the first line of the script
-@code{gnathtml}, to explicitly tell the Operating system where Perl
-is. The syntax of this line is :
-@smallexample
-#!full_path_name_to_perl
-@end smallexample
-
-@noindent
-Alternatively, you may run the script using the following command line:
-
-@smallexample
-$ perl gnathtml.pl [switches] files
-@end smallexample
-
-@ifset vms
-@node LSE
-@section LSE
-@findex LSE
-
-@noindent
-The GNAT distribution provides an Ada 95 template for the Digital Language
-Sensitive Editor (LSE), a component of DECset. In order to
-access it, invoke LSE with the qualifier /ENVIRONMENT=GNU:[LIB]ADA95.ENV.
-
-@node Profiling
-@section Profiling
-@findex PCA
-
-@noindent
-GNAT supports The Digital Performance Coverage Analyzer (PCA), a component
-of DECset. To use it proceed as outlined under "HELP PCA", except for running
-the collection phase with the /DEBUG qualifier.
-
-@smallexample
-$ GNAT MAKE /DEBUG <PROGRAM_NAME>
-$ DEFINE LIB$DEBUG PCA$COLLECTOR
-$ RUN/DEBUG <PROGRAM_NAME>
-@end smallexample
-@noindent
-@end ifset
-
-@node Running and Debugging Ada Programs
-@chapter Running and Debugging Ada Programs
-@cindex Debugging
-
-@noindent
-This chapter discusses how to debug Ada programs. An incorrect Ada program
-may be handled in three ways by the GNAT compiler:
-
-@enumerate
-@item
-The illegality may be a violation of the static semantics of Ada. In
-that case GNAT diagnoses the constructs in the program that are illegal.
-It is then a straightforward matter for the user to modify those parts of
-the program.
-
-@item
-The illegality may be a violation of the dynamic semantics of Ada. In
-that case the program compiles and executes, but may generate incorrect
-results, or may terminate abnormally with some exception.
-
-@item
-When presented with a program that contains convoluted errors, GNAT
-itself may terminate abnormally without providing full diagnostics on
-the incorrect user program.
-@end enumerate
-
-@menu
-* The GNAT Debugger GDB::
-* Running GDB::
-* Introduction to GDB Commands::
-* Using Ada Expressions::
-* Calling User-Defined Subprograms::
-* Using the Next Command in a Function::
-* Ada Exceptions::
-* Ada Tasks::
-* Debugging Generic Units::
-* GNAT Abnormal Termination or Failure to Terminate::
-* Naming Conventions for GNAT Source Files::
-* Getting Internal Debugging Information::
-* Stack Traceback::
-@end menu
-
-@cindex Debugger
-@findex gdb
-
-@node The GNAT Debugger GDB
-@section The GNAT Debugger GDB
-
-@noindent
-@code{GDB} is a general purpose, platform-independent debugger that
-can be used to debug mixed-language programs compiled with @code{GCC},
-and in particular is capable of debugging Ada programs compiled with
-GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
-complex Ada data structures.
-
-The manual @cite{Debugging with GDB}
-@ifset vms
-, located in the GNU:[DOCS] directory,
-@end ifset
-contains full details on the usage of @code{GDB}, including a section on
-its usage on programs. This manual should be consulted for full
-details. The section that follows is a brief introduction to the
-philosophy and use of @code{GDB}.
-
-When GNAT programs are compiled, the compiler optionally writes debugging
-information into the generated object file, including information on
-line numbers, and on declared types and variables. This information is
-separate from the generated code. It makes the object files considerably
-larger, but it does not add to the size of the actual executable that
-will be loaded into memory, and has no impact on run-time performance. The
-generation of debug information is triggered by the use of the
-^-g^/DEBUG^ switch in the gcc or gnatmake command used to carry out
-the compilations. It is important to emphasize that the use of these
-options does not change the generated code.
-
-The debugging information is written in standard system formats that
-are used by many tools, including debuggers and profilers. The format
-of the information is typically designed to describe C types and
-semantics, but GNAT implements a translation scheme which allows full
-details about Ada types and variables to be encoded into these
-standard C formats. Details of this encoding scheme may be found in
-the file exp_dbug.ads in the GNAT source distribution. However, the
-details of this encoding are, in general, of no interest to a user,
-since @code{GDB} automatically performs the necessary decoding.
-
-When a program is bound and linked, the debugging information is
-collected from the object files, and stored in the executable image of
-the program. Again, this process significantly increases the size of
-the generated executable file, but it does not increase the size of
-the executable program itself. Furthermore, if this program is run in
-the normal manner, it runs exactly as if the debug information were
-not present, and takes no more actual memory.
-
-However, if the program is run under control of @code{GDB}, the
-debugger is activated. The image of the program is loaded, at which
-point it is ready to run. If a run command is given, then the program
-will run exactly as it would have if @code{GDB} were not present. This
-is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
-entirely non-intrusive until a breakpoint is encountered. If no
-breakpoint is ever hit, the program will run exactly as it would if no
-debugger were present. When a breakpoint is hit, @code{GDB} accesses
-the debugging information and can respond to user commands to inspect
-variables, and more generally to report on the state of execution.
-
-@node Running GDB
-@section Running GDB
-
-@ifclear vxworks
-@noindent
-The debugger can be launched directly and simply from @code{glide} or
-through its graphical interface: @code{gvd}. It can also be used
-directly in text mode. Here is described the basic use of @code{GDB}
-in text mode. All the commands described below can be used in the
-@code{gvd} console window eventhough there is usually other more
-graphical ways to achieve the same goals.
-
-@ifclear vms
-@noindent
-The command to run de graphical interface of the debugger is
-@smallexample
-$ gvd program
-@end smallexample
-@end ifclear
-
-@noindent
-The command to run @code{GDB} in text mode is
-
-@smallexample
-$ ^gdb program^$ GDB PROGRAM^
-@end smallexample
-
-@noindent
-where @code{^program^PROGRAM^} is the name of the executable file. This
-activates the debugger and results in a prompt for debugger commands.
-The simplest command is simply @code{run}, which causes the program to run
-exactly as if the debugger were not present. The following section
-describes some of the additional commands that can be given to @code{GDB}.
-@end ifclear
-
-@ifset vxworks
-Please refer to the debugging section of the chapter specific to your
-cross environment at the end of this manual.
-@end ifset
-
-@node Introduction to GDB Commands
-@section Introduction to GDB Commands
-
-@noindent
-@code{GDB} contains a large repertoire of commands. The manual
-@cite{Debugging with GDB}
-@ifset vms
-, located in the GNU:[DOCS] directory,
-@end ifset
-includes extensive documentation on the use
-of these commands, together with examples of their use. Furthermore,
-the command @var{help} invoked from within @code{GDB} activates a simple help
-facility which summarizes the available commands and their options.
-In this section we summarize a few of the most commonly
-used commands to give an idea of what @code{GDB} is about. You should create
-a simple program with debugging information and experiment with the use of
-these @code{GDB} commands on the program as you read through the
-following section.
-
-@table @code
-@item set args @var{arguments}
-The @var{arguments} list above is a list of arguments to be passed to
-the program on a subsequent run command, just as though the arguments
-had been entered on a normal invocation of the program. The @code{set args}
-command is not needed if the program does not require arguments.
-
-@item run
-The @code{run} command causes execution of the program to start from
-the beginning. If the program is already running, that is to say if
-you are currently positioned at a breakpoint, then a prompt will ask
-for confirmation that you want to abandon the current execution and
-restart.
-
-@item breakpoint @var{location}
-The breakpoint command sets a breakpoint, that is to say a point at which
-execution will halt and @code{GDB} will await further
-commands. @var{location} is
-either a line number within a file, given in the format @code{file:linenumber},
-or it is the name of a subprogram. If you request that a breakpoint be set on
-a subprogram that is overloaded, a prompt will ask you to specify on which of
-those subprograms you want to breakpoint. You can also
-specify that all of them should be breakpointed. If the program is run
-and execution encounters the breakpoint, then the program
-stops and @code{GDB} signals that the breakpoint was encountered by
-printing the line of code before which the program is halted.
-
-@item breakpoint exception @var{name}
-A special form of the breakpoint command which breakpoints whenever
-exception @var{name} is raised.
-If @var{name} is omitted,
-then a breakpoint will occur when any exception is raised.
-
-@item print @var{expression}
-This will print the value of the given expression. Most simple
-Ada expression formats are properly handled by @code{GDB}, so the expression
-can contain function calls, variables, operators, and attribute references.
-
-@item continue
-Continues execution following a breakpoint, until the next breakpoint or the
-termination of the program.
-
-@item step
-Executes a single line after a breakpoint. If the next statement is a subprogram
-call, execution continues into (the first statement of) the
-called subprogram.
-
-@item next
-Executes a single line. If this line is a subprogram call, executes and
-returns from the call.
-
-@item list
-Lists a few lines around the current source location. In practice, it
-is usually more convenient to have a separate edit window open with the
-relevant source file displayed. Successive applications of this command
-print subsequent lines. The command can be given an argument which is a
-line number, in which case it displays a few lines around the specified one.
-
-@item backtrace
-Displays a backtrace of the call chain. This command is typically
-used after a breakpoint has occurred, to examine the sequence of calls that
-leads to the current breakpoint. The display includes one line for each
-activation record (frame) corresponding to an active subprogram.
-
-@item up
-At a breakpoint, @code{GDB} can display the values of variables local
-to the current frame. The command @code{up} can be used to
-examine the contents of other active frames, by moving the focus up
-the stack, that is to say from callee to caller, one frame at a time.
-
-@item down
-Moves the focus of @code{GDB} down from the frame currently being
-examined to the frame of its callee (the reverse of the previous command),
-
-@item frame @var{n}
-Inspect the frame with the given number. The value 0 denotes the frame
-of the current breakpoint, that is to say the top of the call stack.
-
-@end table
-
-The above list is a very short introduction to the commands that
-@code{GDB} provides. Important additional capabilities, including conditional
-breakpoints, the ability to execute command sequences on a breakpoint,
-the ability to debug at the machine instruction level and many other
-features are described in detail in @cite{Debugging with GDB}.
-Note that most commands can be abbreviated
-(for example, c for continue, bt for backtrace).
-
-@node Using Ada Expressions
-@section Using Ada Expressions
-@cindex Ada expressions
-
-@noindent
-@code{GDB} supports a fairly large subset of Ada expression syntax, with some
-extensions. The philosophy behind the design of this subset is
-
-@itemize @bullet
-@item
-That @code{GDB} should provide basic literals and access to operations for
-arithmetic, dereferencing, field selection, indexing, and subprogram calls,
-leaving more sophisticated computations to subprograms written into the
-program (which therefore may be called from @code{GDB}).
-
-@item
-That type safety and strict adherence to Ada language restrictions
-are not particularly important to the @code{GDB} user.
-
-@item
-That brevity is important to the @code{GDB} user.
-@end itemize
-
-Thus, for brevity, the debugger acts as if there were
-implicit @code{with} and @code{use} clauses in effect for all user-written
-packages, thus making it unnecessary to fully qualify most names with
-their packages, regardless of context. Where this causes ambiguity,
-@code{GDB} asks the user's intent.
-
-For details on the supported Ada syntax, see @cite{Debugging with GDB}.
-
-@node Calling User-Defined Subprograms
-@section Calling User-Defined Subprograms
-
-@noindent
-An important capability of @code{GDB} is the ability to call user-defined
-subprograms while debugging. This is achieved simply by entering
-a subprogram call statement in the form:
-
-@smallexample
-call subprogram-name (parameters)
-@end smallexample
-
-@noindent
-The keyword @code{call} can be omitted in the normal case where the
-@code{subprogram-name} does not coincide with any of the predefined
-@code{GDB} commands.
-
-The effect is to invoke the given subprogram, passing it the
-list of parameters that is supplied. The parameters can be expressions and
-can include variables from the program being debugged. The
-subprogram must be defined
-at the library level within your program, and @code{GDB} will call the
-subprogram within the environment of your program execution (which
-means that the subprogram is free to access or even modify variables
-within your program).
-
-The most important use of this facility is in allowing the inclusion of
-debugging routines that are tailored to particular data structures
-in your program. Such debugging routines can be written to provide a suitably
-high-level description of an abstract type, rather than a low-level dump
-of its physical layout. After all, the standard
-@code{GDB print} command only knows the physical layout of your
-types, not their abstract meaning. Debugging routines can provide information
-at the desired semantic level and are thus enormously useful.
-
-For example, when debugging GNAT itself, it is crucial to have access to
-the contents of the tree nodes used to represent the program internally.
-But tree nodes are represented simply by an integer value (which in turn
-is an index into a table of nodes).
-Using the @code{print} command on a tree node would simply print this integer
-value, which is not very useful. But the PN routine (defined in file
-treepr.adb in the GNAT sources) takes a tree node as input, and displays
-a useful high level representation of the tree node, which includes the
-syntactic category of the node, its position in the source, the integers
-that denote descendant nodes and parent node, as well as varied
-semantic information. To study this example in more detail, you might want to
-look at the body of the PN procedure in the stated file.
-
-@node Using the Next Command in a Function
-@section Using the Next Command in a Function
-
-@noindent
-When you use the @code{next} command in a function, the current source
-location will advance to the next statement as usual. A special case
-arises in the case of a @code{return} statement.
-
-Part of the code for a return statement is the "epilog" of the function.
-This is the code that returns to the caller. There is only one copy of
-this epilog code, and it is typically associated with the last return
-statement in the function if there is more than one return. In some
-implementations, this epilog is associated with the first statement
-of the function.
-
-The result is that if you use the @code{next} command from a return
-statement that is not the last return statement of the function you
-may see a strange apparent jump to the last return statement or to
-the start of the function. You should simply ignore this odd jump.
-The value returned is always that from the first return statement
-that was stepped through.
-
-@node Ada Exceptions
-@section Breaking on Ada Exceptions
-@cindex Exceptions
-
-@noindent
-You can set breakpoints that trip when your program raises
-selected exceptions.
-
-@table @code
-@item break exception
-Set a breakpoint that trips whenever (any task in the) program raises
-any exception.
-
-@item break exception @var{name}
-Set a breakpoint that trips whenever (any task in the) program raises
-the exception @var{name}.
-
-@item break exception unhandled
-Set a breakpoint that trips whenever (any task in the) program raises an
-exception for which there is no handler.
-
-@item info exceptions
-@itemx info exceptions @var{regexp}
-The @code{info exceptions} command permits the user to examine all defined
-exceptions within Ada programs. With a regular expression, @var{regexp}, as
-argument, prints out only those exceptions whose name matches @var{regexp}.
-@end table
-
-@node Ada Tasks
-@section Ada Tasks
-@cindex Tasks
-
-@noindent
-@code{GDB} allows the following task-related commands:
-
-@table @code
-@item info tasks
-This command shows a list of current Ada tasks, as in the following example:
-
-@smallexample
-@iftex
-@leftskip=0cm
-@end iftex
-(gdb) info tasks
- ID TID P-ID Thread Pri State Name
- 1 8088000 0 807e000 15 Child Activation Wait main_task
- 2 80a4000 1 80ae000 15 Accept/Select Wait b
- 3 809a800 1 80a4800 15 Child Activation Wait a
-* 4 80ae800 3 80b8000 15 Running c
-@end smallexample
-
-@noindent
-In this listing, the asterisk before the first task indicates it to be the
-currently running task. The first column lists the task ID that is used
-to refer to tasks in the following commands.
-
-@item break @var{linespec} task @var{taskid}
-@itemx break @var{linespec} task @var{taskid} if @dots{}
-@cindex Breakpoints and tasks
-These commands are like the @code{break @dots{} thread @dots{}}.
-@var{linespec} specifies source lines.
-
-Use the qualifier @samp{task @var{taskid}} with a breakpoint command
-to specify that you only want @code{GDB} to stop the program when a
-particular Ada task reaches this breakpoint. @var{taskid} is one of the
-numeric task identifiers assigned by @code{GDB}, shown in the first
-column of the @samp{info tasks} display.
-
-If you do not specify @samp{task @var{taskid}} when you set a
-breakpoint, the breakpoint applies to @emph{all} tasks of your
-program.
-
-You can use the @code{task} qualifier on conditional breakpoints as
-well; in this case, place @samp{task @var{taskid}} before the
-breakpoint condition (before the @code{if}).
-
-@item task @var{taskno}
-@cindex Task switching
-
-This command allows to switch to the task referred by @var{taskno}. In
-particular, This allows to browse the backtrace of the specified
-task. It is advised to switch back to the original task before
-continuing execution otherwise the scheduling of the program may be
-perturbated.
-@end table
-
-@noindent
-For more detailed information on the tasking support, see @cite{Debugging with GDB}.
-
-@node Debugging Generic Units
-@section Debugging Generic Units
-@cindex Debugging Generic Units
-@cindex Generics
-
-@noindent
-GNAT always uses code expansion for generic instantiation. This means that
-each time an instantiation occurs, a complete copy of the original code is
-made, with appropriate substitutions of formals by actuals.
-
-It is not possible to refer to the original generic entities in
-@code{GDB}, but it is always possible to debug a particular instance of
-a generic, by using the appropriate expanded names. For example, if we have
-
-@smallexample
-@group
-@cartouche
-@b{procedure} g @b{is}
-
- @b{generic package} k @b{is}
- @b{procedure} kp (v1 : @b{in out} integer);
- @b{end} k;
-
- @b{package body} k @b{is}
- @b{procedure} kp (v1 : @b{in out} integer) @b{is}
- @b{begin}
- v1 := v1 + 1;
- @b{end} kp;
- @b{end} k;
-
- @b{package} k1 @b{is new} k;
- @b{package} k2 @b{is new} k;
-
- var : integer := 1;
-
-@b{begin}
- k1.kp (var);
- k2.kp (var);
- k1.kp (var);
- k2.kp (var);
-@b{end};
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-Then to break on a call to procedure kp in the k2 instance, simply
-use the command:
-
-@smallexample
-(gdb) break g.k2.kp
-@end smallexample
-
-@noindent
-When the breakpoint occurs, you can step through the code of the
-instance in the normal manner and examine the values of local variables, as for
-other units.
-
-@node GNAT Abnormal Termination or Failure to Terminate
-@section GNAT Abnormal Termination or Failure to Terminate
-@cindex GNAT Abnormal Termination or Failure to Terminate
-
-@noindent
-When presented with programs that contain serious errors in syntax
-or semantics,
-GNAT may on rare occasions experience problems in operation, such
-as aborting with a
-segmentation fault or illegal memory access, raising an internal
-exception, terminating abnormally, or failing to terminate at all.
-In such cases, you can activate
-various features of GNAT that can help you pinpoint the construct in your
-program that is the likely source of the problem.
-
-The following strategies are presented in increasing order of
-difficulty, corresponding to your experience in using GNAT and your
-familiarity with compiler internals.
-
-@enumerate
-@item
-Run @code{gcc} with the @option{-gnatf}. This first
-switch causes all errors on a given line to be reported. In its absence,
-only the first error on a line is displayed.
-
-The @option{-gnatdO} switch causes errors to be displayed as soon as they
-are encountered, rather than after compilation is terminated. If GNAT
-terminates prematurely or goes into an infinite loop, the last error
-message displayed may help to pinpoint the culprit.
-
-@item
-Run @code{gcc} with the @code{^-v (verbose)^/VERBOSE^} switch. In this mode,
-@code{gcc} produces ongoing information about the progress of the
-compilation and provides the name of each procedure as code is
-generated. This switch allows you to find which Ada procedure was being
-compiled when it encountered a code generation problem.
-
-@item
-@cindex @option{-gnatdc} switch
-Run @code{gcc} with the @option{-gnatdc} switch. This is a GNAT specific
-switch that does for the front-end what @code{^-v^VERBOSE^} does for the back end.
-The system prints the name of each unit, either a compilation unit or
-nested unit, as it is being analyzed.
-@item
-Finally, you can start
-@code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
-front-end of GNAT, and can be run independently (normally it is just
-called from @code{gcc}). You can use @code{gdb} on @code{gnat1} as you
-would on a C program (but @pxref{The GNAT Debugger GDB} for caveats). The
-@code{where} command is the first line of attack; the variable
-@code{lineno} (seen by @code{print lineno}), used by the second phase of
-@code{gnat1} and by the @code{gcc} backend, indicates the source line at
-which the execution stopped, and @code{input_file name} indicates the name of
-the source file.
-@end enumerate
-
-@node Naming Conventions for GNAT Source Files
-@section Naming Conventions for GNAT Source Files
-
-@noindent
-In order to examine the workings of the GNAT system, the following
-brief description of its organization may be helpful:
-
-@itemize @bullet
-@item
-Files with prefix @file{^sc^SC^} contain the lexical scanner.
-
-@item
-All files prefixed with @file{^par^PAR^} are components of the parser. The
-numbers correspond to chapters of the Ada 95 Reference Manual. For example,
-parsing of select statements can be found in @file{par-ch9.adb}.
-
-@item
-All files prefixed with @file{^sem^SEM^} perform semantic analysis. The
-numbers correspond to chapters of the Ada standard. For example, all
-issues involving context clauses can be found in @file{sem_ch10.adb}. In
-addition, some features of the language require sufficient special processing
-to justify their own semantic files: sem_aggr for aggregates, sem_disp for
-dynamic dispatching, etc.
-
-@item
-All files prefixed with @file{^exp^EXP^} perform normalization and
-expansion of the intermediate representation (abstract syntax tree, or AST).
-these files use the same numbering scheme as the parser and semantics files.
-For example, the construction of record initialization procedures is done in
-@file{exp_ch3.adb}.
-
-@item
-The files prefixed with @file{^bind^BIND^} implement the binder, which
-verifies the consistency of the compilation, determines an order of
-elaboration, and generates the bind file.
-
-@item
-The files @file{atree.ads} and @file{atree.adb} detail the low-level
-data structures used by the front-end.
-
-@item
-The files @file{sinfo.ads} and @file{sinfo.adb} detail the structure of
-the abstract syntax tree as produced by the parser.
-
-@item
-The files @file{einfo.ads} and @file{einfo.adb} detail the attributes of
-all entities, computed during semantic analysis.
-
-@item
-Library management issues are dealt with in files with prefix
-@file{^lib^LIB^}.
-
-@item
-@findex Ada
-@cindex Annex A
-Ada files with the prefix @file{^a-^A-^} are children of @code{Ada}, as
-defined in Annex A.
-
-@item
-@findex Interfaces
-@cindex Annex B
-Files with prefix @file{^i-^I-^} are children of @code{Interfaces}, as
-defined in Annex B.
-
-@item
-@findex System
-Files with prefix @file{^s-^S-^} are children of @code{System}. This includes
-both language-defined children and GNAT run-time routines.
-
-@item
-@findex GNAT
-Files with prefix @file{^g-^G-^} are children of @code{GNAT}. These are useful
-general-purpose packages, fully documented in their specifications. All
-the other @file{.c} files are modifications of common @code{gcc} files.
-@end itemize
-
-@node Getting Internal Debugging Information
-@section Getting Internal Debugging Information
-
-@noindent
-Most compilers have internal debugging switches and modes. GNAT
-does also, except GNAT internal debugging switches and modes are not
-secret. A summary and full description of all the compiler and binder
-debug flags are in the file @file{debug.adb}. You must obtain the
-sources of the compiler to see the full detailed effects of these flags.
-
-The switches that print the source of the program (reconstructed from
-the internal tree) are of general interest for user programs, as are the
-options to print
-the full internal tree, and the entity table (the symbol table
-information). The reconstructed source provides a readable version of the
-program after the front-end has completed analysis and expansion, and is useful
-when studying the performance of specific constructs. For example, constraint
-checks are indicated, complex aggregates are replaced with loops and
-assignments, and tasking primitives are replaced with run-time calls.
-
-@node Stack Traceback
-@section Stack Traceback
-@cindex traceback
-@cindex stack traceback
-@cindex stack unwinding
-
-@noindent
-Traceback is a mechanism to display the sequence of subprogram calls that
-leads to a specified execution point in a program. Often (but not always)
-the execution point is an instruction at which an exception has been raised.
-This mechanism is also known as @i{stack unwinding} because it obtains
-its information by scanning the run-time stack and recovering the activation
-records of all active subprograms. Stack unwinding is one of the most
-important tools for program debugging.
-
-@noindent
-The first entry stored in traceback corresponds to the deepest calling level,
-that is to say the subprogram currently executing the instruction
-from which we want to obtain the traceback.
-
-@noindent
-Note that there is no runtime performance penalty when stack traceback
-is enabled and no exception are raised during program execution.
-
-@menu
-* Non-Symbolic Traceback::
-* Symbolic Traceback::
-@end menu
-
-@node Non-Symbolic Traceback
-@subsection Non-Symbolic Traceback
-@cindex traceback, non-symbolic
-
-@noindent
-Note: this feature is not supported on all platforms. See
-@file{GNAT.Traceback spec in g-traceb.ads} for a complete list of supported
-platforms.
-
-@menu
-* Tracebacks From an Unhandled Exception::
-* Tracebacks From Exception Occurrences (non-symbolic)::
-* Tracebacks From Anywhere in a Program (non-symbolic)::
-@end menu
-
-@node Tracebacks From an Unhandled Exception
-@subsubsection Tracebacks From an Unhandled Exception
-
-@noindent
-A runtime non-symbolic traceback is a list of addresses of call instructions.
-To enable this feature you must use the @code{-E}
-@code{gnatbind}'s option. With this option a stack traceback is stored as part
-of exception information. It is possible to retrieve this information using the
-standard @code{Ada.Exception.Exception_Information} routine.
-
-@noindent
-Let's have a look at a simple example:
-
-@smallexample
-@cartouche
-@group
-procedure STB is
-
- procedure P1 is
- begin
- raise Constraint_Error;
- end P1;
-
- procedure P2 is
- begin
- P1;
- end P2;
-
-begin
- P2;
-end STB;
-@end group
-@end cartouche
-@end smallexample
-
-@smallexample
-$ gnatmake stb -bargs -E
-$ stb
-
-Execution terminated by unhandled exception
-Exception name: CONSTRAINT_ERROR
-Message: stb.adb:5
-Call stack traceback locations:
-0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
-@end smallexample
-
-@noindent
-As we see the traceback lists a sequence of addresses for the unhandled
-exception @code{CONSTAINT_ERROR} raised in procedure P1. It is easy to
-guess that this exception come from procedure P1. To translate these
-addresses into the source lines where the calls appear, the
-@code{addr2line} tool, described below, is invaluable. The use of this tool
-requires the program to be compiled with debug information.
-
-@smallexample
-$ gnatmake -g stb -bargs -E
-$ stb
-
-Execution terminated by unhandled exception
-Exception name: CONSTRAINT_ERROR
-Message: stb.adb:5
-Call stack traceback locations:
-0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
-
-$ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
- 0x4011f1 0x77e892a4
-
-00401373 at d:/stb/stb.adb:5
-0040138B at d:/stb/stb.adb:10
-0040139C at d:/stb/stb.adb:14
-00401335 at d:/stb/b~stb.adb:104
-004011C4 at /build/.../crt1.c:200
-004011F1 at /build/.../crt1.c:222
-77E892A4 in ?? at ??:0
-@end smallexample
-
-@noindent
-@code{addr2line} has a number of other useful options:
-
-@table @code
-@item --functions
-to get the function name corresponding to any location
-
-@item --demangle=gnat
-to use the @b{gnat} decoding mode for the function names. Note that
-for binutils version 2.9.x the option is simply @code{--demangle}.
-@end table
-
-@smallexample
-$ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
- 0x40139c 0x401335 0x4011c4 0x4011f1
-
-00401373 in stb.p1 at d:/stb/stb.adb:5
-0040138B in stb.p2 at d:/stb/stb.adb:10
-0040139C in stb at d:/stb/stb.adb:14
-00401335 in main at d:/stb/b~stb.adb:104
-004011C4 in <__mingw_CRTStartup> at /build/.../crt1.c:200
-004011F1 in <mainCRTStartup> at /build/.../crt1.c:222
-@end smallexample
-
-@noindent
-From this traceback we can see that the exception was raised in
-@file{stb.adb} at line 5, which was reached from a procedure call in
-@file{stb.adb} at line 10, and so on. The @file{b~std.adb} is the binder file,
-which contains the call to the main program.
-@pxref{Running gnatbind}. The remaining entries are assorted runtime routines,
-and the output will vary from platform to platform.
-
-@noindent
-It is also possible to use @code{GDB} with these traceback addresses to debug
-the program. For example, we can break at a given code location, as reported
-in the stack traceback:
-
-@smallexample
-$ gdb -nw stb
-@ifset wnt
-@noindent
-Furthermore, this feature is not implemented inside Windows DLL. Only
-the non-symbolic traceback is reported in this case.
-@end ifset
-
-(gdb) break *0x401373
-Breakpoint 1 at 0x401373: file stb.adb, line 5.
-@end smallexample
-
-@noindent
-It is important to note that the stack traceback addresses
-do not change when debug information is included. This is particularly useful
-because it makes it possible to release software without debug information (to
-minimize object size), get a field report that includes a stack traceback
-whenever an internal bug occurs, and then be able to retrieve the sequence
-of calls with the same program compiled with debug information.
-
-@node Tracebacks From Exception Occurrences (non-symbolic)
-@subsubsection Tracebacks From Exception Occurrences
-
-@noindent
-Non-symbolic tracebacks are obtained by using the @code{-E} binder argument.
-The stack traceback is attached to the exception information string, and can
-be retrieved in an exception handler within the Ada program, by means of the
-Ada95 facilities defined in @code{Ada.Exceptions}. Here is a simple example:
-
-@smallexample
-@cartouche
-@group
-with Ada.Text_IO;
-with Ada.Exceptions;
-
-procedure STB is
-
- use Ada;
- use Ada.Exceptions;
-
- procedure P1 is
- K : Positive := 1;
- begin
- K := K - 1;
- exception
- when E : others =>
- Text_IO.Put_Line (Exception_Information (E));
- end P1;
-
- procedure P2 is
- begin
- P1;
- end P2;
-
-begin
- P2;
-end STB;
-@end group
-@end cartouche
-@end smallexample
-
-@noindent
-This program will output:
-
-@smallexample
-$ stb
-
-Exception name: CONSTRAINT_ERROR
-Message: stb.adb:12
-Call stack traceback locations:
-0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
-@end smallexample
-
-@node Tracebacks From Anywhere in a Program (non-symbolic)
-@subsubsection Tracebacks From Anywhere in a Program
-
-@noindent
-It is also possible to retrieve a stack traceback from anywhere in a
-program. For this you need to
-use the @code{GNAT.Traceback} API. This package includes a procedure called
-@code{Call_Chain} that computes a complete stack traceback, as well as useful
-display procedures described below. It is not necessary to use the
-@code{-E gnatbind} option in this case, because the stack traceback mechanism
-is invoked explicitly.
-
-@noindent
-In the following example we compute a traceback at a specific location in
-the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
-convert addresses to strings:
-
-@smallexample
-@cartouche
-@group
-with Ada.Text_IO;
-with GNAT.Traceback;
-with GNAT.Debug_Utilities;
-
-procedure STB is
-
- use Ada;
- use GNAT;
- use GNAT.Traceback;
-
- procedure P1 is
- TB : Tracebacks_Array (1 .. 10);
- -- We are asking for a maximum of 10 stack frames.
- Len : Natural;
- -- Len will receive the actual number of stack frames returned.
- begin
- Call_Chain (TB, Len);
-
- Text_IO.Put ("In STB.P1 : ");
-
- for K in 1 .. Len loop
- Text_IO.Put (Debug_Utilities.Image (TB (K)));
- Text_IO.Put (' ');
- end loop;
-
- Text_IO.New_Line;
- end P1;
-
- procedure P2 is
- begin
- P1;
- end P2;
-
-begin
- P2;
-end STB;
-@end group
-@end cartouche
-@end smallexample
-
-@smallexample
-$ gnatmake stb
-$ stb
-
-In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
-16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
-@end smallexample
-
-@node Symbolic Traceback
-@subsection Symbolic Traceback
-@cindex traceback, symbolic
-
-@noindent
-A symbolic traceback is a stack traceback in which procedure names are
-associated with each code location.
-
-@noindent
-Note that this feature is not supported on all platforms. See
-@file{GNAT.Traceback.Symbolic spec in g-trasym.ads} for a complete
-list of currently supported platforms.
-
-@noindent
-Note that the symbolic traceback requires that the program be compiled
-with debug information. If it is not compiled with debug information
-only the non-symbolic information will be valid.
-
-@menu
-* Tracebacks From Exception Occurrences (symbolic)::
-* Tracebacks From Anywhere in a Program (symbolic)::
-@end menu
-
-@node Tracebacks From Exception Occurrences (symbolic)
-@subsubsection Tracebacks From Exception Occurrences
-
-@smallexample
-@cartouche
-@group
-with Ada.Text_IO;
-with GNAT.Traceback.Symbolic;
-
-procedure STB is
-
- procedure P1 is
- begin
- raise Constraint_Error;
- end P1;
-
- procedure P2 is
- begin
- P1;
- end P2;
-
- procedure P3 is
- begin
- P2;
- end P3;
-
-begin
- P3;
-exception
- when E : others =>
- Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
-end STB;
-@end group
-@end cartouche
-@end smallexample
-
-@smallexample
-$ gnatmake -g stb -bargs -E -largs -lgnat -laddr2line -lintl
-$ stb
-
-0040149F in stb.p1 at stb.adb:8
-004014B7 in stb.p2 at stb.adb:13
-004014CF in stb.p3 at stb.adb:18
-004015DD in ada.stb at stb.adb:22
-00401461 in main at b~stb.adb:168
-004011C4 in __mingw_CRTStartup at crt1.c:200
-004011F1 in mainCRTStartup at crt1.c:222
-77E892A4 in ?? at ??:0
-@end smallexample
-
-@noindent
-The exact sequence of linker options may vary from platform to platform.
-The above @code{-largs} section is for Windows platforms. By contrast,
-under Unix there is no need for the @code{-largs} section.
-Differences across platforms are due to details of linker implementation.
-
-@node Tracebacks From Anywhere in a Program (symbolic)
-@subsubsection Tracebacks From Anywhere in a Program
-
-@noindent
-It is possible to get a symbolic stack traceback
-from anywhere in a program, just as for non-symbolic tracebacks.
-The first step is to obtain a non-symbolic
-traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
-information. Here is an example:
-
-@smallexample
-@cartouche
-@group
-with Ada.Text_IO;
-with GNAT.Traceback;
-with GNAT.Traceback.Symbolic;
-
-procedure STB is
-
- use Ada;
- use GNAT.Traceback;
- use GNAT.Traceback.Symbolic;
-
- procedure P1 is
- TB : Tracebacks_Array (1 .. 10);
- -- We are asking for a maximum of 10 stack frames.
- Len : Natural;
- -- Len will receive the actual number of stack frames returned.
- begin
- Call_Chain (TB, Len);
- Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
- end P1;
-
- procedure P2 is
- begin
- P1;
- end P2;
-
-begin
- P2;
-end STB;
-@end group
-@end cartouche
-@end smallexample
-
-@ifset vms
-@node Compatibility with DEC Ada
-@chapter Compatibility with DEC Ada
-@cindex Compatibility
-
-@noindent
-This section of the manual compares DEC Ada for OpenVMS Alpha and GNAT
-OpenVMS Alpha. GNAT achieves a high level of compatibility
-with DEC Ada, and it should generally be straightforward to port code
-from the DEC Ada environment to GNAT. However, there are a few language
-and implementation differences of which the user must be aware. These
-differences are discussed in this section. In
-addition, the operating environment and command structure for the
-compiler are different, and these differences are also discussed.
-
-Note that this discussion addresses specifically the implementation
-of Ada 83 for DIGITAL OpenVMS Alpha Systems. In cases where the implementation
-of DEC Ada differs between OpenVMS Alpha Systems and OpenVMS VAX Systems, GNAT
-always follows the Alpha implementation.
-
-@menu
-* Ada 95 Compatibility::
-* Differences in the Definition of Package System::
-* Language-Related Features::
-* The Package STANDARD::
-* The Package SYSTEM::
-* Tasking and Task-Related Features::
-* Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems::
-* Pragmas and Pragma-Related Features::
-* Library of Predefined Units::
-* Bindings::
-* Main Program Definition::
-* Implementation-Defined Attributes::
-* Compiler and Run-Time Interfacing::
-* Program Compilation and Library Management::
-* Input-Output::
-* Implementation Limits::
-* Tools::
-@end menu
-
-@node Ada 95 Compatibility
-@section Ada 95 Compatibility
-
-@noindent
-GNAT is an Ada 95 compiler, and DEC Ada is an Ada 83
-compiler. Ada 95 is almost completely upwards compatible
-with Ada 83, and therefore Ada 83 programs will compile
-and run under GNAT with
-no changes or only minor changes. The Ada 95 Reference
-Manual (ANSI/ISO/IEC-8652:1995) provides details on specific
-incompatibilities.
-
-GNAT provides the switch /83 on the GNAT COMPILE command,
-as well as the pragma ADA_83, to force the compiler to
-operate in Ada 83 mode. This mode does not guarantee complete
-conformance to Ada 83, but in practice is sufficient to
-eliminate most sources of incompatibilities.
-In particular, it eliminates the recognition of the
-additional Ada 95 keywords, so that their use as identifiers
-in Ada83 program is legal, and handles the cases of packages
-with optional bodies, and generics that instantiate unconstrained
-types without the use of @code{(<>)}.
-
-@node Differences in the Definition of Package System
-@section Differences in the Definition of Package System
-
-@noindent
-Both the Ada 95 and Ada 83 reference manuals permit a compiler to add
-implementation-dependent declarations to package System. In normal mode,
-GNAT does not take advantage of this permission, and the version of System
-provided by GNAT exactly matches that in the Ada 95 Reference Manual.
-
-However, DEC Ada adds an extensive set of declarations to package System,
-as fully documented in the DEC Ada manuals. To minimize changes required
-for programs that make use of these extensions, GNAT provides the pragma
-Extend_System for extending the definition of package System. By using:
-
-@smallexample
-@group
-@cartouche
-@b{pragma} Extend_System (Aux_DEC);
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-The set of definitions in System is extended to include those in package
-@code{System.Aux_DEC}.
-These definitions are incorporated directly into package
-System, as though they had been declared there in the first place. For a
-list of the declarations added, see the specification of this package,
-which can be found in the file @code{s-auxdec.ads} in the GNAT library.
-The pragma Extend_System is a configuration pragma, which means that
-it can be placed in the file @file{gnat.adc}, so that it will automatically
-apply to all subsequent compilations. See the section on Configuration
-Pragmas for further details.
-
-An alternative approach that avoids the use of the non-standard
-Extend_System pragma is to add a context clause to the unit that
-references these facilities:
-
-@smallexample
-@group
-@cartouche
-@b{with} System.Aux_DEC;
-@b{use} System.Aux_DEC;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-The effect is not quite semantically identical to incorporating the declarations
-directly into package @code{System},
-but most programs will not notice a difference
-unless they use prefix notation (e.g. @code{System.Integer_8})
-to reference the
-entities directly in package @code{System}.
-For units containing such references,
-the prefixes must either be removed, or the pragma @code{Extend_System}
-must be used.
-
-@node Language-Related Features
-@section Language-Related Features
-
-@noindent
-The following sections highlight differences in types,
-representations of types, operations, alignment, and
-related topics.
-
-@menu
-* Integer Types and Representations::
-* Floating-Point Types and Representations::
-* Pragmas Float_Representation and Long_Float::
-* Fixed-Point Types and Representations::
-* Record and Array Component Alignment::
-* Address Clauses::
-* Other Representation Clauses::
-@end menu
-
-@node Integer Types and Representations
-@subsection Integer Types and Representations
-
-@noindent
-The set of predefined integer types is identical in DEC Ada and GNAT.
-Furthermore the representation of these integer types is also identical,
-including the capability of size clauses forcing biased representation.
-
-In addition,
-DEC Ada for OpenVMS Alpha systems has defined the
-following additional integer types in package System:
-
-@itemize @bullet
-
-@item
-INTEGER_8
-
-@item
-INTEGER_16
-
-@item
-INTEGER_32
-
-@item
-INTEGER_64
-
-@item
-LARGEST_INTEGER
-@end itemize
-
-@noindent
-When using GNAT, the first four of these types may be obtained from the
-standard Ada 95 package @code{Interfaces}.
-Alternatively, by use of the pragma
-@code{Extend_System}, identical
-declarations can be referenced directly in package @code{System}.
-On both GNAT and DEC Ada, the maximum integer size is 64 bits.
-
-@node Floating-Point Types and Representations
-@subsection Floating-Point Types and Representations
-@cindex Floating-Point types
-
-@noindent
-The set of predefined floating-point types is identical in DEC Ada and GNAT.
-Furthermore the representation of these floating-point
-types is also identical. One important difference is that the default
-representation for DEC Ada is VAX_Float, but the default representation
-for GNAT is IEEE.
-
-Specific types may be declared to be VAX_Float or IEEE, using the pragma
-@code{Float_Representation} as described in the DEC Ada documentation.
-For example, the declarations:
-
-@smallexample
-@group
-@cartouche
-@b{type} F_Float @b{is digits} 6;
-@b{pragma} Float_Representation (VAX_Float, F_Float);
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-declare a type F_Float that will be represented in VAX_Float format.
-This set of declarations actually appears in System.Aux_DEC, which provides
-the full set of additional floating-point declarations provided in
-the DEC Ada version of package
-System. This and similar declarations may be accessed in a user program by using
-pragma @code{Extend_System}. The use of this
-pragma, and the related pragma @code{Long_Float} is described in further
-detail in the following section.
-
-@node Pragmas Float_Representation and Long_Float
-@subsection Pragmas Float_Representation and Long_Float
-
-@noindent
-DEC Ada provides the pragma @code{Float_Representation}, which
-acts as a program library switch to allow control over
-the internal representation chosen for the predefined
-floating-point types declared in the package @code{Standard}.
-The format of this pragma is as follows:
-
-@smallexample
-@group
-@cartouche
-@b{pragma} @code{Float_Representation}(VAX_Float | IEEE_Float);
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-This pragma controls the representation of floating-point
-types as follows:
-
-@itemize @bullet
-@item
-@code{VAX_Float} specifies that floating-point
-types are represented by default with the VAX hardware types
-F-floating, D-floating, G-floating. Note that the H-floating
-type is available only on DIGITAL Vax systems, and is not available
-in either DEC Ada or GNAT for Alpha systems.
-
-@item
-@code{IEEE_Float} specifies that floating-point
-types are represented by default with the IEEE single and
-double floating-point types.
-@end itemize
-
-@noindent
-GNAT provides an identical implementation of the pragma
-@code{Float_Representation}, except that it functions as a
-configuration pragma, as defined by Ada 95. Note that the
-notion of configuration pragma corresponds closely to the
-DEC Ada notion of a program library switch.
-
-When no pragma is used in GNAT, the default is IEEE_Float, which is different
-from DEC Ada 83, where the default is VAX_Float. In addition, the
-predefined libraries in GNAT are built using IEEE_Float, so it is not
-advisable to change the format of numbers passed to standard library
-routines, and if necessary explicit type conversions may be needed.
-
-The use of IEEE_Float is recommended in GNAT since it is more efficient,
-and (given that it conforms to an international standard) potentially more
-portable. The situation in which VAX_Float may be useful is in interfacing
-to existing code and data that expects the use of VAX_Float. There are
-two possibilities here. If the requirement for the use of VAX_Float is
-localized, then the best approach is to use the predefined VAX_Float
-types in package @code{System}, as extended by
-@code{Extend_System}. For example, use @code{System.F_Float}
-to specify the 32-bit @code{F-Float} format.
-
-Alternatively, if an entire program depends heavily on the use of
-the @code{VAX_Float} and in particular assumes that the types in
-package @code{Standard} are in @code{Vax_Float} format, then it
-may be desirable to reconfigure GNAT to assume Vax_Float by default.
-This is done by using the GNAT LIBRARY command to rebuild the library, and
-then using the general form of the @code{Float_Representation}
-pragma to ensure that this default format is used throughout.
-The form of the GNAT LIBRARY command is:
-
-@smallexample
-GNAT LIBRARY /CONFIG=@i{file} /CREATE=@i{directory}
-@end smallexample
-
-@noindent
-where @i{file} contains the new configuration pragmas
-and @i{directory} is the directory to be created to contain
-the new library.
-
-@noindent
-On OpenVMS systems, DEC Ada provides the pragma @code{Long_Float}
-to allow control over the internal representation chosen
-for the predefined type @code{Long_Float} and for floating-point
-type declarations with digits specified in the range 7 .. 15.
-The format of this pragma is as follows:
-
-@smallexample
-@cartouche
-@b{pragma} Long_Float (D_FLOAT | G_FLOAT);
-@end cartouche
-@end smallexample
-
-@node Fixed-Point Types and Representations
-@subsection Fixed-Point Types and Representations
-
-@noindent
-On DEC Ada for OpenVMS Alpha systems, rounding is
-away from zero for both positive and negative numbers.
-Therefore, +0.5 rounds to 1 and -0.5 rounds to -1.
-
-On GNAT for OpenVMS Alpha, the results of operations
-on fixed-point types are in accordance with the Ada 95
-rules. In particular, results of operations on decimal
-fixed-point types are truncated.
-
-@node Record and Array Component Alignment
-@subsection Record and Array Component Alignment
-
-@noindent
-On DEC Ada for OpenVMS Alpha, all non composite components
-are aligned on natural boundaries. For example, 1-byte
-components are aligned on byte boundaries, 2-byte
-components on 2-byte boundaries, 4-byte components on 4-byte
-byte boundaries, and so on. The OpenVMS Alpha hardware
-runs more efficiently with naturally aligned data.
-
-ON GNAT for OpenVMS Alpha, alignment rules are compatible
-with DEC Ada for OpenVMS Alpha.
-
-@node Address Clauses
-@subsection Address Clauses
-
-@noindent
-In DEC Ada and GNAT, address clauses are supported for
-objects and imported subprograms.
-The predefined type @code{System.Address} is a private type
-in both compilers, with the same representation (it is simply
-a machine pointer). Addition, subtraction, and comparison
-operations are available in the standard Ada 95 package
-@code{System.Storage_Elements}, or in package @code{System}
-if it is extended to include @code{System.Aux_DEC} using a
-pragma @code{Extend_System} as previously described.
-
-Note that code that with's both this extended package @code{System}
-and the package @code{System.Storage_Elements} should not @code{use}
-both packages, or ambiguities will result. In general it is better
-not to mix these two sets of facilities. The Ada 95 package was
-designed specifically to provide the kind of features that DEC Ada
-adds directly to package @code{System}.
-
-GNAT is compatible with DEC Ada in its handling of address
-clauses, except for some limitations in
-the form of address clauses for composite objects with
-initialization. Such address clauses are easily replaced
-by the use of an explicitly-defined constant as described
-in the Ada 95 Reference Manual (13.1(22)). For example, the sequence
-of declarations:
-
-@smallexample
-@group
-@cartouche
-X, Y : Integer := Init_Func;
-Q : String (X .. Y) := "abc";
-...
-@b{for} Q'Address @b{use} Compute_Address;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-will be rejected by GNAT, since the address cannot be computed at the time
-that Q is declared. To achieve the intended effect, write instead:
-
-@smallexample
-@group
-@cartouche
-X, Y : Integer := Init_Func;
-Q_Address : @b{constant} Address := Compute_Address;
-Q : String (X .. Y) := "abc";
-...
-@b{for} Q'Address @b{use} Q_Address;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-which will be accepted by GNAT (and other Ada 95 compilers), and is also
-backwards compatible with Ada 83. A fuller description of the restrictions
-on address specifications is found in the GNAT Reference Manual.
-
-@node Other Representation Clauses
-@subsection Other Representation Clauses
-
-@noindent
-GNAT supports in a compatible manner all the representation
-clauses supported by DEC Ada. In addition, it
-supports representation clause forms that are new in Ada 95
-including COMPONENT_SIZE and SIZE clauses for objects.
-
-@node The Package STANDARD
-@section The Package STANDARD
-
-@noindent
-The package STANDARD, as implemented by DEC Ada, is fully
-described in the Reference Manual for the Ada Programming
-Language (ANSI/MIL-STD-1815A-1983) and in the DEC Ada
-Language Reference Manual. As implemented by GNAT, the
-package STANDARD is described in the Ada 95 Reference
-Manual.
-
-In addition, DEC Ada supports the Latin-1 character set in
-the type CHARACTER. GNAT supports the Latin-1 character set
-in the type CHARACTER and also Unicode (ISO 10646 BMP) in
-the type WIDE_CHARACTER.
-
-The floating-point types supported by GNAT are those
-supported by DEC Ada, but defaults are different, and are controlled by
-pragmas. See @pxref{Floating-Point Types and Representations} for details.
-
-@node The Package SYSTEM
-@section The Package SYSTEM
-
-@noindent
-DEC Ada provides a system-specific version of the package
-SYSTEM for each platform on which the language ships.
-For the complete specification of the package SYSTEM, see
-Appendix F of the DEC Ada Language Reference Manual.
-
-On DEC Ada, the package SYSTEM includes the following conversion functions:
-@itemize @bullet
-@item TO_ADDRESS(INTEGER)
-
-@item TO_ADDRESS(UNSIGNED_LONGWORD)
-
-@item TO_ADDRESS(universal_integer)
-
-@item TO_INTEGER(ADDRESS)
-
-@item TO_UNSIGNED_LONGWORD(ADDRESS)
-
-@item Function IMPORT_VALUE return UNSIGNED_LONGWORD and the
- functions IMPORT_ADDRESS and IMPORT_LARGEST_VALUE
-@end itemize
-
-@noindent
-By default, GNAT supplies a version of SYSTEM that matches
-the definition given in the Ada 95 Reference Manual.
-This
-is a subset of the DIGITAL system definitions, which is as
-close as possible to the original definitions. The only difference
-is that the definition of SYSTEM_NAME is different:
-
-@smallexample
-@group
-@cartouche
-@b{type} Name @b{is} (SYSTEM_NAME_GNAT);
-System_Name : @b{constant} Name := SYSTEM_NAME_GNAT;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-Also, GNAT adds the new Ada 95 declarations for
-BIT_ORDER and DEFAULT_BIT_ORDER.
-
-However, the use of the following pragma causes GNAT
-to extend the definition of package SYSTEM so that it
-encompasses the full set of DIGITAL-specific extensions,
-including the functions listed above:
-
-@smallexample
-@cartouche
-@b{pragma} Extend_System (Aux_DEC);
-@end cartouche
-@end smallexample
-
-@noindent
-The pragma Extend_System is a configuration pragma that
-is most conveniently placed in the @file{gnat.adc} file. See the
-GNAT Reference Manual for further details.
-
-DEC Ada does not allow the recompilation of the package
-SYSTEM. Instead DEC Ada provides several pragmas (SYSTEM_
-NAME, STORAGE_UNIT, and MEMORY_SIZE) to modify values in
-the package SYSTEM. On OpenVMS Alpha systems, the pragma
-SYSTEM_NAME takes the enumeration literal OPENVMS_AXP as
-its single argument.
-
-GNAT does permit the recompilation of package SYSTEM using
-a special switch (-gnatg) and this switch can be used if
-it is necessary to change constants in SYSTEM. GNAT does
-not permit the specification of SYSTEM_NAME, STORAGE_UNIT
-or MEMORY_SIZE by any other means.
-
-On GNAT systems, the pragma SYSTEM_NAME takes the
-enumeration literal SYSTEM_NAME_GNAT.
-
-The definitions provided by the use of
-
-@smallexample
-pragma Extend_System (AUX_Dec);
-@end smallexample
-
-@noindent
-are virtually identical to those provided by the DEC Ada 83 package
-System. One important difference is that the name of the TO_ADDRESS
-function for type UNSIGNED_LONGWORD is changed to TO_ADDRESS_LONG.
-See the GNAT Reference manual for a discussion of why this change was
-necessary.
-
-@noindent
-The version of TO_ADDRESS taking a universal integer argument is in fact
-an extension to Ada 83 not strictly compatible with the reference manual.
-In GNAT, we are constrained to be exactly compatible with the standard,
-and this means we cannot provide this capability. In DEC Ada 83, the
-point of this definition is to deal with a call like:
-
-@smallexample
-TO_ADDRESS (16#12777#);
-@end smallexample
-
-@noindent
-Normally, according to the Ada 83 standard, one would expect this to be
-ambiguous, since it matches both the INTEGER and UNSIGNED_LONGWORD forms
-of TO_ADDRESS. However, in DEC Ada 83, there is no ambiguity, since the
-definition using universal_integer takes precedence.
-
-In GNAT, since the version with universal_integer cannot be supplied, it is
-not possible to be 100% compatible. Since there are many programs using
-numeric constants for the argument to TO_ADDRESS, the decision in GNAT was
-to change the name of the function in the UNSIGNED_LONGWORD case, so the
-declarations provided in the GNAT version of AUX_Dec are:
-
-@smallexample
-function To_Address (X : Integer) return Address;
-pragma Pure_Function (To_Address);
-
-function To_Address_Long (X : Unsigned_Longword) return Address;
-pragma Pure_Function (To_Address_Long);
-@end smallexample
-
-@noindent
-This means that programs using TO_ADDRESS for UNSIGNED_LONGWORD must
-change the name to TO_ADDRESS_LONG.
-
-@node Tasking and Task-Related Features
-@section Tasking and Task-Related Features
-
-@noindent
-The concepts relevant to a comparison of tasking on GNAT
-and on DEC Ada for OpenVMS Alpha systems are discussed in
-the following sections.
-
-For detailed information on concepts related to tasking in
-DEC Ada, see the DEC Ada Language Reference Manual and the
-relevant run-time reference manual.
-
-@node Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems
-@section Implementation of Tasks in DEC Ada for OpenVMS Alpha Systems
-
-@noindent
-On OpenVMS Alpha systems, each Ada task (except a passive
-task) is implemented as a single stream of execution
-that is created and managed by the kernel. On these
-systems, DEC Ada tasking support is based on DECthreads,
-an implementation of the POSIX standard for threads.
-
-Although tasks are implemented as threads, all tasks in
-an Ada program are part of the same process. As a result,
-resources such as open files and virtual memory can be
-shared easily among tasks. Having all tasks in one process
-allows better integration with the programming environment
-(the shell and the debugger, for example).
-
-Also, on OpenVMS Alpha systems, DEC Ada tasks and foreign
-code that calls DECthreads routines can be used together.
-The interaction between Ada tasks and DECthreads routines
-can have some benefits. For example when on OpenVMS Alpha,
-DEC Ada can call C code that is already threaded.
-GNAT on OpenVMS Alpha uses the facilities of DECthreads,
-and Ada tasks are mapped to threads.
-
-@menu
-* Assigning Task IDs::
-* Task IDs and Delays::
-* Task-Related Pragmas::
-* Scheduling and Task Priority::
-* The Task Stack::
-* External Interrupts::
-@end menu
-
-@node Assigning Task IDs
-@subsection Assigning Task IDs
-
-@noindent
-The DEC Ada Run-Time Library always assigns %TASK 1 to
-the environment task that executes the main program. On
-OpenVMS Alpha systems, %TASK 0 is often used for tasks
-that have been created but are not yet activated.
-
-On OpenVMS Alpha systems, task IDs are assigned at
-activation. On GNAT systems, task IDs are also assigned at
-task creation but do not have the same form or values as
-task ID values in DEC Ada. There is no null task, and the
-environment task does not have a specific task ID value.
-
-@node Task IDs and Delays
-@subsection Task IDs and Delays
-
-@noindent
-On OpenVMS Alpha systems, tasking delays are implemented
-using Timer System Services. The Task ID is used for the
-identification of the timer request (the REQIDT parameter).
-If Timers are used in the application take care not to use
-0 for the identification, because cancelling such a timer
-will cancel all timers and may lead to unpredictable results.
-
-@node Task-Related Pragmas
-@subsection Task-Related Pragmas
-
-@noindent
-Ada supplies the pragma TASK_STORAGE, which allows
-specification of the size of the guard area for a task
-stack. (The guard area forms an area of memory that has no
-read or write access and thus helps in the detection of
-stack overflow.) On OpenVMS Alpha systems, if the pragma
-TASK_STORAGE specifies a value of zero, a minimal guard
-area is created. In the absence of a pragma TASK_STORAGE, a default guard
-area is created.
-
-GNAT supplies the following task-related pragmas:
-
-@itemize @bullet
-@item TASK_INFO
-
- This pragma appears within a task definition and
- applies to the task in which it appears. The argument
- must be of type SYSTEM.TASK_INFO.TASK_INFO_TYPE.
-
-@item TASK_STORAGE
-
- GNAT implements pragma TASK_STORAGE in the same way as
- DEC Ada.
- Both DEC Ada and GNAT supply the pragmas PASSIVE,
- SUPPRESS, and VOLATILE.
-@end itemize
-@node Scheduling and Task Priority
-@subsection Scheduling and Task Priority
-
-@noindent
-DEC Ada implements the Ada language requirement that
-when two tasks are eligible for execution and they have
-different priorities, the lower priority task does not
-execute while the higher priority task is waiting. The DEC
-Ada Run-Time Library keeps a task running until either the
-task is suspended or a higher priority task becomes ready.
-
-On OpenVMS Alpha systems, the default strategy is round-
-robin with preemption. Tasks of equal priority take turns
-at the processor. A task is run for a certain period of
-time and then placed at the rear of the ready queue for
-its priority level.
-
-DEC Ada provides the implementation-defined pragma TIME_SLICE,
-which can be used to enable or disable round-robin
-scheduling of tasks with the same priority.
-See the relevant DEC Ada run-time reference manual for
-information on using the pragmas to control DEC Ada task
-scheduling.
-
-GNAT follows the scheduling rules of Annex D (real-time
-Annex) of the Ada 95 Reference Manual. In general, this
-scheduling strategy is fully compatible with DEC Ada
-although it provides some additional constraints (as
-fully documented in Annex D).
-GNAT implements time slicing control in a manner compatible with
-DEC Ada 83, by means of the pragma Time_Slice, whose semantics are identical
-to the DEC Ada 83 pragma of the same name.
-Note that it is not possible to mix GNAT tasking and
-DEC Ada 83 tasking in the same program, since the two run times are
-not compatible.
-
-@node The Task Stack
-@subsection The Task Stack
-
-@noindent
-In DEC Ada, a task stack is allocated each time a
-non passive task is activated. As soon as the task is
-terminated, the storage for the task stack is deallocated.
-If you specify a size of zero (bytes) with T'STORAGE_SIZE,
-a default stack size is used. Also, regardless of the size
-specified, some additional space is allocated for task
-management purposes. On OpenVMS Alpha systems, at least
-one page is allocated.
-
-GNAT handles task stacks in a similar manner. According to
-the Ada 95 rules, it provides the pragma STORAGE_SIZE as
-an alternative method for controlling the task stack size.
-The specification of the attribute T'STORAGE_SIZE is also
-supported in a manner compatible with DEC Ada.
-
-@node External Interrupts
-@subsection External Interrupts
-
-@noindent
-On DEC Ada, external interrupts can be associated with task entries.
-GNAT is compatible with DEC Ada in its handling of external interrupts.
-
-@node Pragmas and Pragma-Related Features
-@section Pragmas and Pragma-Related Features
-
-@noindent
-Both DEC Ada and GNAT supply all language-defined pragmas
-as specified by the Ada 83 standard. GNAT also supplies all
-language-defined pragmas specified in the Ada 95 Reference Manual.
-In addition, GNAT implements the implementation-defined pragmas
-from DEC Ada 83.
-
-@itemize @bullet
-@item AST_ENTRY
-
-@item COMMON_OBJECT
-
-@item COMPONENT_ALIGNMENT
-
-@item EXPORT_EXCEPTION
-
-@item EXPORT_FUNCTION
-
-@item EXPORT_OBJECT
-
-@item EXPORT_PROCEDURE
-
-@item EXPORT_VALUED_PROCEDURE
-
-@item FLOAT_REPRESENTATION
-
-@item IDENT
-
-@item IMPORT_EXCEPTION
-
-@item IMPORT_FUNCTION
-
-@item IMPORT_OBJECT
-
-@item IMPORT_PROCEDURE
-
-@item IMPORT_VALUED_PROCEDURE
-
-@item INLINE_GENERIC
-
-@item INTERFACE_NAME
-
-@item LONG_FLOAT
-
-@item MAIN_STORAGE
-
-@item PASSIVE
-
-@item PSET_OBJECT
-
-@item SHARE_GENERIC
-
-@item SUPPRESS_ALL
-
-@item TASK_STORAGE
-
-@item TIME_SLICE
-
-@item TITLE
-@end itemize
-
-@noindent
-These pragmas are all fully implemented, with the exception of @code{Title},
-@code{Passive}, and @code{Share_Generic}, which are
-recognized, but which have no
-effect in GNAT. The effect of @code{Passive} may be obtained by the
-use of protected objects in Ada 95. In GNAT, all generics are inlined.
-
-Unlike DEC Ada, the GNAT 'EXPORT_@i{subprogram}' pragmas require
-a separate subprogram specification which must appear before the
-subprogram body.
-
-GNAT also supplies a number of implementation-defined pragmas as follows:
-@itemize @bullet
-@item C_PASS_BY_COPY
-
-@item EXTEND_SYSTEM
-
-@item SOURCE_FILE_NAME
-
-@item UNSUPPRESS
-
-@item WARNINGS
-
-@item ABORT_DEFER
-
-@item ADA_83
-
-@item ADA_95
-
-@item ANNOTATE
-
-@item ASSERT
-
-@item CPP_CLASS
-
-@item CPP_CONSTRUCTOR
-
-@item CPP_DESTRUCTOR
-
-@item CPP_VIRTUAL
-
-@item CP_VTABLE
-
-@item DEBUG
-
-@item LINKER_ALIAS
-
-@item LINKER_SECTION
-
-@item MACHINE_ATTRIBUTE
-
-@item NO_RETURN
-
-@item PURE_FUNCTION
-
-@item SOURCE_REFERENCE
-
-@item TASK_INFO
-
-@item UNCHECKED_UNION
-
-@item UNIMPLEMENTED_UNIT
-
-@item WEAK_EXTERNAL
-@end itemize
-
-@noindent
-For full details on these GNAT implementation-defined pragmas, see
-the GNAT Reference Manual.
-
-@menu
-* Restrictions on the Pragma INLINE::
-* Restrictions on the Pragma INTERFACE::
-* Restrictions on the Pragma SYSTEM_NAME::
-@end menu
-
-@node Restrictions on the Pragma INLINE
-@subsection Restrictions on the Pragma INLINE
-
-@noindent
-DEC Ada applies the following restrictions to the pragma INLINE:
-@itemize @bullet
-@item Parameters cannot be a task type.
-
-@item Function results cannot be task types, unconstrained
-array types, or unconstrained types with discriminants.
-
-@item Bodies cannot declare the following:
-@itemize @bullet
-@item Subprogram body or stub (imported subprogram is allowed)
-
-@item Tasks
-
-@item Generic declarations
-
-@item Instantiations
-
-@item Exceptions
-
-@item Access types (types derived from access types allowed)
-
-@item Array or record types
-
-@item Dependent tasks
-
-@item Direct recursive calls of subprogram or containing
-subprogram, directly or via a renaming
-
-@end itemize
-@end itemize
-
-@noindent
-In GNAT, the only restriction on pragma INLINE is that the
-body must occur before the call if both are in the same
-unit, and the size must be appropriately small. There are
-no other specific restrictions which cause subprograms to
-be incapable of being inlined.
-
-@node Restrictions on the Pragma INTERFACE
-@subsection Restrictions on the Pragma INTERFACE
-
-@noindent
-The following lists and describes the restrictions on the
-pragma INTERFACE on DEC Ada and GNAT:
-@itemize @bullet
-@item Languages accepted: Ada, Bliss, C, Fortran, Default.
-Default is the default on OpenVMS Alpha systems.
-
-@item Parameter passing: Language specifies default
-mechanisms but can be overridden with an EXPORT pragma.
-
-@itemize @bullet
-@item Ada: Use internal Ada rules.
-
-@item Bliss, C: Parameters must be mode @code{in}; cannot be
-record or task type. Result cannot be a string, an
-array, or a record.
-
-@item Fortran: Parameters cannot be a task. Result cannot
-be a string, an array, or a record.
-@end itemize
-@end itemize
-
-@noindent
-GNAT is entirely upwards compatible with DEC Ada, and in addition allows
-record parameters for all languages.
-
-@node Restrictions on the Pragma SYSTEM_NAME
-@subsection Restrictions on the Pragma SYSTEM_NAME
-
-@noindent
-For DEC Ada for OpenVMS Alpha, the enumeration literal
-for the type NAME is OPENVMS_AXP. In GNAT, the enumeration
-literal for the type NAME is SYSTEM_NAME_GNAT.
-
-@node Library of Predefined Units
-@section Library of Predefined Units
-
-@noindent
-A library of predefined units is provided as part of the
-DEC Ada and GNAT implementations. DEC Ada does not provide
-the package MACHINE_CODE but instead recommends importing
-assembler code.
-
-The GNAT versions of the DEC Ada Run-Time Library (ADA$PREDEFINED:)
-units are taken from the OpenVMS Alpha version, not the OpenVMS VAX
-version. During GNAT installation, the DEC Ada Predefined
-Library units are copied into the GNU:[LIB.OPENVMS7_x.2_8_x.DECLIB]
-(aka DECLIB) directory and patched to remove Ada 95 incompatibilities
-and to make them interoperable with GNAT, @pxref{Changes to DECLIB}
-for details.
-
-The GNAT RTL is contained in
-the GNU:[LIB.OPENVMS7_x.2_8_x.ADALIB] (aka ADALIB) directory and
-the default search path is set up to find DECLIB units in preference
-to ADALIB units with the same name (TEXT_IO, SEQUENTIAL_IO, and DIRECT_IO,
-for example).
-
-However, it is possible to change the default so that the
-reverse is true, or even to mix them using child package
-notation. The DEC Ada 83 units are available as DEC.xxx where xxx
-is the package name, and the Ada units are available in the
-standard manner defined for Ada 95, that is to say as Ada.xxx. To
-change the default, set ADA_INCLUDE_PATH and ADA_OBJECTS_PATH
-appropriately. For example, to change the default to use the Ada95
-versions do:
-
-@smallexample
-$ DEFINE ADA_INCLUDE_PATH GNU:[LIB.OPENVMS7_1.2_8_1.ADAINCLUDE],-
- GNU:[LIB.OPENVMS7_1.2_8_1.DECLIB]
-$ DEFINE ADA_OBJECTS_PATH GNU:[LIB.OPENVMS7_1.2_8_1.ADALIB],-
- GNU:[LIB.OPENVMS7_1.2_8_1.DECLIB]
-@end smallexample
-
-@menu
-* Changes to DECLIB::
-@end menu
-
-@node Changes to DECLIB
-@subsection Changes to DECLIB
-
-@noindent
-The changes made to the DEC Ada predefined library for GNAT and Ada 95
-compatibility are minor and include the following:
-
-@itemize @bullet
-@item Adjusting the location of pragmas and record representation
-clauses to obey Ada 95 rules
-
-@item Adding the proper notation to generic formal parameters
-that take unconstrained types in instantiation
-
-@item Adding pragma ELABORATE_BODY to package specifications
-that have package bodies not otherwise allowed
-
-@item Occurrences of the identifier "PROTECTED" are renamed to "PROTECTD".
-Currently these are found only in the STARLET package spec.
-@end itemize
-
-@noindent
-None of the above changes is visible to users.
-
-@node Bindings
-@section Bindings
-
-@noindent
-On OpenVMS Alpha, DEC Ada provides the following strongly-typed bindings:
-@itemize @bullet
-
-@item Command Language Interpreter (CLI interface)
-
-@item DECtalk Run-Time Library (DTK interface)
-
-@item Librarian utility routines (LBR interface)
-
-@item General Purpose Run-Time Library (LIB interface)
-
-@item Math Run-Time Library (MTH interface)
-
-@item National Character Set Run-Time Library (NCS interface)
-
-@item Compiled Code Support Run-Time Library (OTS interface)
-
-@item Parallel Processing Run-Time Library (PPL interface)
-
-@item Screen Management Run-Time Library (SMG interface)
-
-@item Sort Run-Time Library (SOR interface)
-
-@item String Run-Time Library (STR interface)
-
-@item STARLET System Library
-@findex Starlet
-
-@item X Window System Version 11R4 and 11R5 (X, XLIB interface)
-
-@item X Windows Toolkit (XT interface)
-
-@item X/Motif Version 1.1.3 and 1.2 (XM interface)
-@end itemize
-
-@noindent
-GNAT provides implementations of these DEC bindings in the DECLIB directory.
-
-The X/Motif bindings used to build DECLIB are whatever versions are in the
-DEC Ada ADA$PREDEFINED directory with extension .ADC. The build script will
-automatically add a pragma Linker_Options to packages Xm, Xt, and X_Lib
-causing the default X/Motif shareable image libraries to be linked in. This
-is done via options files named xm.opt, xt.opt, and x_lib.opt (also located
-in the DECLIB directory).
-
-It may be necessary to edit these options files to update or correct the
-library names if, for example, the newer X/Motif bindings from ADA$EXAMPLES
-had been (previous to installing GNAT) copied and renamed to superseded the
-default ADA$PREDEFINED versions.
-
-@menu
-* Shared Libraries and Options Files::
-* Interfaces to C::
-@end menu
-
-@node Shared Libraries and Options Files
-@subsection Shared Libraries and Options Files
-
-@noindent
-When using the DEC Ada
-predefined X and Motif bindings, the linking with their shareable images is
-done automatically by GNAT LINK. When using other X and Motif bindings, it
-is necessary to add the corresponding shareable images to the command line for
-GNAT LINK. When linking with shared libraries, or with .OPT files, it is
-also necessary to add them to the command line for GNAT LINK.
-
-A shared library to be used with GNAT is built in the same way as other
-libraries under VMS. The VMS Link command can be used in standard fashion.
-
-@node Interfaces to C
-@subsection Interfaces to C
-
-@noindent
-DEC Ada
-provides the following Ada types and operations:
-
-@itemize @bullet
-@item C types package (C_TYPES)
-
-@item C strings (C_TYPES.NULL_TERMINATED)
-
-@item Other_types (SHORT_INT)
-@end itemize
-
-@noindent
-Interfacing to C with GNAT, one can use the above approach
-described for DEC Ada or the facilities of Annex B of
-the Ada 95 Reference Manual (packages INTERFACES.C,
-INTERFACES.C.STRINGS and INTERFACES.C.POINTERS). For more
-information, see the section "Interfacing to C" in the
-GNAT Reference Manual.
-
-The @option{-gnatF} qualifier forces default and explicit
-@code{External_Name} parameters in pragmas Import and Export
-to be uppercased for compatibility with the default behavior
-of DEC C. The qualifier has no effect on @code{Link_Name} parameters.
-
-@node Main Program Definition
-@section Main Program Definition
-
-@noindent
-The following section discusses differences in the
-definition of main programs on DEC Ada and GNAT.
-On DEC Ada, main programs are defined to meet the
-following conditions:
-@itemize @bullet
-@item Procedure with no formal parameters (returns 0 upon
- normal completion)
-
-@item Procedure with no formal parameters (returns 42 when
- unhandled exceptions are raised)
-
-@item Function with no formal parameters whose returned value
- is of a discrete type
-
-@item Procedure with one OUT formal of a discrete type for
- which a specification of pragma EXPORT_VALUED_PROCEDURE is given.
-
-@end itemize
-
-@noindent
-When declared with the pragma EXPORT_VALUED_PROCEDURE,
-a main function or main procedure returns a discrete
-value whose size is less than 64 bits (32 on VAX systems),
-the value is zero- or sign-extended as appropriate.
-On GNAT, main programs are defined as follows:
-@itemize @bullet
-@item Must be a non-generic, parameter-less subprogram that
-is either a procedure or function returning an Ada
-STANDARD.INTEGER (the predefined type)
-
-@item Cannot be a generic subprogram or an instantiation of a
-generic subprogram
-@end itemize
-
-@node Implementation-Defined Attributes
-@section Implementation-Defined Attributes
-
-@noindent
-GNAT provides all DEC Ada implementation-defined
-attributes.
-
-@node Compiler and Run-Time Interfacing
-@section Compiler and Run-Time Interfacing
-
-@noindent
-DEC Ada provides the following ways to pass options to the linker (ACS LINK):
-@itemize @bullet
-@item /WAIT and /SUBMIT qualifiers
-
-@item /COMMAND qualifier
-
-@item /[NO]MAP qualifier
-
-@item /OUTPUT=file-spec
-
-@item /[NO]DEBUG and /[NO]TRACEBACK qualifiers
-@end itemize
-
-@noindent
-To pass options to the linker, GNAT provides the following
-switches:
-
-@itemize @bullet
-@item /EXECUTABLE=exec-name
-
-@item /VERBOSE qualifier
-
-@item /[NO]DEBUG and /[NO]TRACEBACK qualifiers
-@end itemize
-
-@noindent
-For more information on these switches, see the section
-"Switches for gnatlink" in the corresponding section of this Guide.
-In DEC Ada, the command-line switch /OPTIMIZE is available
-to control optimization. DEC Ada also supplies the
-following pragmas:
-@itemize @bullet
-@item OPTIMIZE
-
-@item INLINE
-
-@item INLINE_GENERIC
-
-@item SUPPRESS_ALL
-
-@item PASSIVE
-@end itemize
-
-@noindent
-In GNAT, optimization is controlled strictly by command
-line parameters, as described in the corresponding section of this guide.
-The DIGITAL pragmas for control of optimization are
-recognized but ignored.
-
-Note that in GNAT, the default is optimization off, whereas in DEC Ada 83,
-the default is that optimization is turned on.
-
-@node Program Compilation and Library Management
-@section Program Compilation and Library Management
-
-@noindent
-DEC Ada and GNAT provide a comparable set of commands to
-build programs. DEC Ada also provides a program library,
-which is a concept that does not exist on GNAT. Instead,
-GNAT provides directories of sources that are compiled as
-needed.
-
-The following table summarizes
-the DEC Ada commands and provides
-equivalent GNAT commands. In this table, some GNAT
-equivalents reflect the fact that GNAT does not use the
-concept of a program library. Instead, it uses a model
-in which collections of source and object files are used
-in a manner consistent with other languages like C and
-Fortran. Therefore, standard system file commands are used
-to manipulate these elements. Those GNAT commands are marked with
-an asterisk in the table that follows.
-Note that, unlike DEC Ada, none of the GNAT commands accepts wild cards.
-
-@need 1500
-@multitable @columnfractions .31 .30 .39
-
-@item @strong{DEC_Ada_Command}
-@tab @strong{GNAT_Equivalent}
-@tab @strong{Description}
-
-@item ADA
-@tab GNAT COMPILE
-@tab Invokes the compiler to compile one or more Ada source files.
-
-@item ACS ATTACH
-@tab No equivalent
-@tab Switches control of terminal from current process running the program
- library manager.
-
-@item ACS CHECK
-@tab GNAT MAKE /DEPENDENCY_LIST
-@tab Forms the execution closure of one
- or more compiled units and checks completeness and currency.
-
-@item ACS COMPILE
-@tab GNAT MAKE /ACTIONS=COMPILE
-@tab Forms the execution closure of one or
- more specified units, checks completeness and currency,
- identifies units that have revised source files, compiles same,
- and recompiles units that are or will become obsolete.
- Also completes incomplete generic instantiations.
-
-@item ACS COPY FOREIGN
-@tab Copy (*)
-@tab Copies a foreign object file into the program library as a
- library unit body.
-
-@item ACS COPY UNIT
-@tab Copy (*)
-@tab Copies a compiled unit from one program library to another.
-
-@item ACS CREATE LIBRARY
-@tab Create /directory (*)
-@tab Creates a program library.
-
-@item ACS CREATE SUBLIBRARY
-@tab Create /directory (*)
-@tab Creates a program sublibrary.
-
-@item ACS DELETE LIBRARY
-@tab
-@tab Deletes a program library and its contents.
-
-@item ACS DELETE SUBLIBRARY
-@tab
-@tab Deletes a program sublibrary and its contents.
-
-@item ACS DELETE UNIT
-@tab Delete @i{file} (*)
-@tab On OpenVMS systems, deletes one or more compiled units from
- the current program library.
-
-@item ACS DIRECTORY
-@tab Directory (*)
-@tab On OpenVMS systems, lists units contained in the current
- program library.
-
-@item ACS ENTER FOREIGN
-@tab Copy (*)
-@tab Allows the import of a foreign body as an Ada library
- specification and enters a reference to a pointer.
-
-@item ACS ENTER UNIT
-@tab Copy (*)
-@tab Enters a reference (pointer) from the current program library to
- a unit compiled into another program library.
-
-@item ACS EXIT
-@tab No equivalent
-@tab Exits from the program library manager.
-
-@item ACS EXPORT
-@tab Copy (*)
-@tab Creates an object file that contains system-specific object code
- for one or more units. With GNAT, object files can simply be copied
- into the desired directory.
-
-@item ACS EXTRACT SOURCE
-@tab Copy (*)
-@tab Allows access to the copied source file for each Ada compilation unit
-
-@item ACS HELP
-@tab HELP GNAT
-@tab Provides online help.
-
-@item ACS LINK
-@tab GNAT LINK
-@tab Links an object file containing Ada units into an executable
- file.
-
-@item ACS LOAD
-@tab Copy (*)
-@tab Loads (partially compiles) Ada units into the program library.
- Allows loading a program from a collection of files into a library
- without knowing the relationship among units.
-
-@item ACS MERGE
-@tab Copy (*)
-@tab Merges into the current program library, one or more units from
- another library where they were modified.
-
-@item ACS RECOMPILE
-@tab GNAT MAKE /ACTIONS=COMPILE
-@tab Recompiles from external or copied source files any obsolete
- unit in the closure. Also, completes any incomplete generic
- instantiations.
-
-@item ACS REENTER
-@tab GNAT MAKE
-@tab Reenters current references to units compiled after last entered
- with the ACS ENTER UNIT command.
-
-@item ACS SET LIBRARY
-@tab Set default (*)
-@tab Defines a program library to be the compilation context as well
- as the target library for compiler output and commands in general.
-
-@item ACS SET PRAGMA
-@tab Edit gnat.adc (*)
-@tab Redefines specified values of the library characteristics
- LONG_ FLOAT, MEMORY_SIZE, SYSTEM_NAME, and @code{Float_Representation}.
-
-@item ACS SET SOURCE
-@tab define @* ADA_INCLUDE_PATH @i{path} (*)
-@tab Defines the source file search list for the ACS COMPILE command.
-
-@item ACS SHOW LIBRARY
-@tab Directory (*)
-@tab Lists information about one or more program libraries.
-
-@item ACS SHOW PROGRAM
-@tab No equivalent
-@tab Lists information about the execution closure of one or
- more units in the program library.
-
-@item ACS SHOW SOURCE
-@tab Show logical @* ADA_INCLUDE_PATH
-@tab Shows the source file search used when compiling units.
-
-@item ACS SHOW VERSION
-@tab Compile with VERBOSE option
-@tab Displays the version number of the compiler and program library
- manager used.
-
-@item ACS SPAWN
-@tab No equivalent
-@tab Creates a subprocess of the current process (same as DCL SPAWN
- command).
-
-@item ACS VERIFY
-@tab No equivalent
-@tab Performs a series of consistency checks on a program library to
- determine whether the library structure and library files are in
- valid_form.
-
-@end multitable
-
-@noindent
-
-@node Input-Output
-@section Input-Output
-
-@noindent
-On OpenVMS Alpha systems, DEC Ada uses OpenVMS Record
-Management Services (RMS) to perform operations on
-external files.
-
-@noindent
-DEC Ada and GNAT predefine an identical set of input-
-output packages. To make the use of the
-generic TEXT_IO operations more convenient, DEC Ada
-provides predefined library packages that instantiate the
-integer and floating-point operations for the predefined
-integer and floating-point types as shown in the following table.
-
-@table @code
-
-@item Package_Name
- Instantiation
-
-@item INTEGER_TEXT_IO
- INTEGER_IO(INTEGER)
-
-@item SHORT_INTEGER_TEXT_IO
- INTEGER_IO(SHORT_INTEGER)
-
-@item SHORT_SHORT_INTEGER_TEXT_IO
- INTEGER_IO(SHORT_SHORT_ INTEGER)
-
-@item FLOAT_TEXT_IO
- FLOAT_IO(FLOAT)
-
-@item LONG_FLOAT_TEXT_IO
- FLOAT_IO(LONG_FLOAT)
-@end table
-
-@noindent
-The DEC Ada predefined packages and their operations
-are implemented using OpenVMS Alpha files and input-
-output facilities. DEC Ada supports asynchronous input-
-output on OpenVMS Alpha. Familiarity with the following is
-recommended:
-@itemize @bullet
-@item RMS file organizations and access methods
-
-@item OpenVMS file specifications and directories
-
-@item OpenVMS File Definition Language (FDL)
-@end itemize
-
-@noindent
-GNAT provides I/O facilities that are completely
-compatible with DEC Ada. The distribution includes the
-standard DEC Ada versions of all I/O packages, operating
-in a manner compatible with DEC Ada. In particular, the
-following packages are by default the DEC Ada (Ada 83)
-versions of these packages rather than the renamings
-suggested in annex J of the Ada 95 Reference Manual:
-@itemize @bullet
-@item TEXT_IO
-
-@item SEQUENTIAL_IO
-
-@item DIRECT_IO
-@end itemize
-
-@noindent
-The use of the standard Ada 95 syntax for child packages (for
-example, ADA.TEXT_IO) retrieves the Ada 95 versions of these
-packages, as defined in the Ada 95 Reference Manual.
-GNAT provides DIGITAL-compatible predefined instantiations
-of the TEXT_IO packages, and also
-provides the standard predefined instantiations required
-by the Ada 95 Reference Manual.
-
-For further information on how GNAT interfaces to the file
-system or how I/O is implemented in programs written in
-mixed languages, see the chapter "Implementation of the
-Standard I/O" in the GNAT Reference Manual.
-This chapter covers the following:
-@itemize @bullet
-@item Standard I/O packages
-
-@item FORM strings
-
-@item DIRECT_IO
-
-@item SEQUENTIAL_IO
-
-@item TEXT_IO
-
-@item Stream pointer positioning
-
-@item Reading and writing non-regular files
-
-@item GET_IMMEDIATE
-
-@item Treating TEXT_IO files as streams
-
-@item Shared files
-
-@item Open modes
-@end itemize
-
-@node Implementation Limits
-@section Implementation Limits
-
-@noindent
-The following table lists implementation limits for DEC Ada and GNAT systems.
-@multitable @columnfractions .60 .20 .20
-@item Compilation Parameter
-@tab DEC Ada
-@tab GNAT
-
-@item In a subprogram or entry declaration, maximum number of
- formal parameters that are of an unconstrained record type
-@tab 32
-@tab No set limit
-
-@item Maximum identifier length (number of characters)
-@tab 255
-@tab 255
-
-@item Maximum number of characters in a source line
-@tab 255
-@tab 255
-
-@item Maximum collection size (number of bytes)
-@tab 2**31-1
-@tab 2**31-1
-
-@item Maximum number of discriminants for a record type
-@tab 245
-@tab No set limit
-
-@item Maximum number of formal parameters in an entry or
- subprogram declaration
-@tab 246
-@tab No set limit
-
-@item Maximum number of dimensions in an array type
-@tab 255
-@tab No set limit
-
-@item Maximum number of library units and subunits in a compilation.
-@tab 4095
-@tab No set limit
-
-@item Maximum number of library units and subunits in an execution.
-@tab 16383
-@tab No set limit
-
-@item Maximum number of objects declared with the pragma COMMON_OBJECT
- or PSECT_OBJECT
-@tab 32757
-@tab No set limit
-
-@item Maximum number of enumeration literals in an enumeration type
- definition
-@tab 65535
-@tab No set limit
-
-@item Maximum number of lines in a source file
-@tab 65534
-@tab No set limit
-
-@item Maximum number of bits in any object
-@tab 2**31-1
-@tab 2**31-1
-
-@item Maximum size of the static portion of a stack frame (approximate)
-@tab 2**31-1
-@tab 2**31-1
-@end multitable
-
-@node Tools
-@section Tools
-
-@end ifset
-
-@node Inline Assembler
-@chapter Inline Assembler
-
-@noindent
-If you need to write low-level software that interacts directly with the hardware, Ada provides two ways to incorporate assembly language code into your program. First, you can import and invoke external routines written in assembly language, an Ada feature fully supported by GNAT. However, for small sections of code it may be simpler or more efficient to include assembly language statements directly in your Ada source program, using the facilities of the implementation-defined package @code{System.Machine_Code}, which incorporates the gcc Inline Assembler. The Inline Assembler approach offers a number of advantages, including the following:
-
-@itemize @bullet
-@item No need to use non-Ada tools
-@item Consistent interface over different targets
-@item Automatic usage of the proper calling conventions
-@item Access to Ada constants and variables
-@item Definition of intrinsic routines
-@item Possibility of inlining a subprogram comprising assembler code
-@item Code optimizer can take Inline Assembler code into account
-@end itemize
-
-This chapter presents a series of examples to show you how to use the Inline Assembler. Although it focuses on the Intel x86, the general approach applies also to other processors. It is assumed that you are familiar with Ada and with assembly language programming.
-
-@menu
-* Basic Assembler Syntax::
-* A Simple Example of Inline Assembler::
-* Output Variables in Inline Assembler::
-* Input Variables in Inline Assembler::
-* Inlining Inline Assembler Code::
-* Other Asm Functionality::
-* A Complete Example::
-@end menu
-
-@c ---------------------------------------------------------------------------
-@node Basic Assembler Syntax
-@section Basic Assembler Syntax
-
-@noindent
-The assembler used by GNAT and gcc is based not on the Intel assembly language, but rather on a
-language that descends from the AT&T Unix assembler @emph{as} (and which is often
-referred to as ``AT&T syntax'').
-The following table summarizes the main features of @emph{as} syntax and points out the differences from the Intel conventions.
-See the gcc @emph{as} and @emph{gas} (an @emph{as} macro
-pre-processor) documentation for further information.
-
-@table @asis
-@item Register names
-gcc / @emph{as}: Prefix with ``%''; for example @code{%eax}
-@*
-Intel: No extra punctuation; for example @code{eax}
-
-@item Immediate operand
-gcc / @emph{as}: Prefix with ``$''; for example @code{$4}
-@*
-Intel: No extra punctuation; for example @code{4}
-
-@item Address
-gcc / @emph{as}: Prefix with ``$''; for example @code{$loc}
-@*
-Intel: No extra punctuation; for example @code{loc}
-
-@item Memory contents
-gcc / @emph{as}: No extra punctuation; for example @code{loc}
-@*
-Intel: Square brackets; for example @code{[loc]}
-
-@item Register contents
-gcc / @emph{as}: Parentheses; for example @code{(%eax)}
-@*
-Intel: Square brackets; for example @code{[eax]}
-
-@item Hexadecimal numbers
-gcc / @emph{as}: Leading ``0x'' (C language syntax); for example @code{0xA0}
-@*
-Intel: Trailing ``h''; for example @code{A0h}
-
-@item Operand size
-gcc / @emph{as}: Explicit in op code; for example @code{movw} to move a 16-bit word
-@*
-Intel: Implicit, deduced by assembler; for example @code{mov}
-
-@item Instruction repetition
-gcc / @emph{as}: Split into two lines; for example
-@*
-@code{rep}
-@*
-@code{stosl}
-@*
-Intel: Keep on one line; for example @code{rep stosl}
-
-@item Order of operands
-gcc / @emph{as}: Source first; for example @code{movw $4, %eax}
-@*
-Intel: Destination first; for example @code{mov eax, 4}
-@end table
-
-@c ---------------------------------------------------------------------------
-@node A Simple Example of Inline Assembler
-@section A Simple Example of Inline Assembler
-
-@noindent
-The following example will generate a single assembly language statement, @code{nop}, which does nothing. Despite its lack of run-time effect, the example will be useful in illustrating the basics of the Inline Assembler facility.
-
-@smallexample
-@group
-with System.Machine_Code; use System.Machine_Code;
-procedure Nothing is
-begin
- Asm ("nop");
-end Nothing;
-@end group
-@end smallexample
-
-@code{Asm} is a procedure declared in package @code{System.Machine_Code}; here it takes one parameter, a @emph{template string} that must be a static expression and that will form the generated instruction.
-@code{Asm} may be regarded as a compile-time procedure that parses the template string and additional parameters (none here), from which it generates a sequence of assembly language instructions.
-
-The examples in this chapter will illustrate several of the forms for invoking @code{Asm}; a complete specification of the syntax is found in the @cite{GNAT Reference Manual}.
-
-Under the standard GNAT conventions, the @code{Nothing} procedure should be in a file named @file{nothing.adb}. You can build the executable in the usual way:
-@smallexample
-gnatmake nothing
-@end smallexample
-However, the interesting aspect of this example is not its run-time behavior but rather the
-generated assembly code. To see this output, invoke the compiler as follows:
-@smallexample
- gcc -c -S -fomit-frame-pointer -gnatp @file{nothing.adb}
-@end smallexample
-where the options are:
-
-@table @code
-@item -c
-compile only (no bind or link)
-@item -S
-generate assembler listing
-@item -fomit-frame-pointer
-do not set up separate stack frames
-@item -gnatp
-do not add runtime checks
-@end table
-
-This gives a human-readable assembler version of the code. The resulting
-file will have the same name as the Ada source file, but with a @code{.s} extension.
-In our example, the file @file{nothing.s} has the following contents:
-
-@smallexample
-@group
-.file "nothing.adb"
-gcc2_compiled.:
-___gnu_compiled_ada:
-.text
- .align 4
-.globl __ada_nothing
-__ada_nothing:
-#APP
- nop
-#NO_APP
- jmp L1
- .align 2,0x90
-L1:
- ret
-@end group
-@end smallexample
-
-The assembly code you included is clearly indicated by
-the compiler, between the @code{#APP} and @code{#NO_APP}
-delimiters. The character before the 'APP' and 'NOAPP'
-can differ on different targets. For example, Linux uses '#APP' while
-on NT you will see '/APP'.
-
-If you make a mistake in your assembler code (such as using the
-wrong size modifier, or using a wrong operand for the instruction) GNAT
-will report this error in a temporary file, which will be deleted when
-the compilation is finished. Generating an assembler file will help
-in such cases, since you can assemble this file separately using the
-@emph{as} assembler that comes with gcc.
-
-Assembling the file using the command
-
-@smallexample
-as @file{nothing.s}
-@end smallexample
-@noindent
-will give you error messages whose lines correspond to the assembler
-input file, so you can easily find and correct any mistakes you made.
-If there are no errors, @emph{as} will generate an object file @file{nothing.out}.
-
-@c ---------------------------------------------------------------------------
-@node Output Variables in Inline Assembler
-@section Output Variables in Inline Assembler
-
-@noindent
-The examples in this section, showing how to access the processor flags, illustrate how to specify the destination operands for assembly language statements.
-
-@smallexample
-@group
-with Interfaces; use Interfaces;
-with Ada.Text_IO; use Ada.Text_IO;
-with System.Machine_Code; use System.Machine_Code;
-procedure Get_Flags is
- Flags : Unsigned_32;
- use ASCII;
-begin
- Asm ("pushfl" & LF & HT & -- push flags on stack
- "popl %%eax" & LF & HT & -- load eax with flags
- "movl %%eax, %0", -- store flags in variable
- Outputs => Unsigned_32'Asm_Output ("=g", Flags));
- Put_Line ("Flags register:" & Flags'Img);
-end Get_Flags;
-@end group
-@end smallexample
-
-In order to have a nicely aligned assembly listing, we have separated
-multiple assembler statements in the Asm template string with linefeed (ASCII.LF)
-and horizontal tab (ASCII.HT) characters. The resulting section of the
-assembly output file is:
-
-@smallexample
-@group
-#APP
- pushfl
- popl %eax
- movl %eax, -40(%ebp)
-#NO_APP
-@end group
-@end smallexample
-
-It would have been legal to write the Asm invocation as:
-
-@smallexample
-Asm ("pushfl popl %%eax movl %%eax, %0")
-@end smallexample
-
-but in the generated assembler file, this would come out as:
-
-@smallexample
-#APP
- pushfl popl %eax movl %eax, -40(%ebp)
-#NO_APP
-@end smallexample
-
-which is not so convenient for the human reader.
-
-We use Ada comments
-at the end of each line to explain what the assembler instructions
-actually do. This is a useful convention.
-
-When writing Inline Assembler instructions, you need to precede each register and variable name with a percent sign. Since the assembler already requires a percent sign at the beginning of a register name, you need two consecutive percent signs for such names in the Asm template string, thus @code{%%eax}. In the generated assembly code, one of the percent signs will be stripped off.
-
-Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output variables: operands you later define using @code{Input} or @code{Output} parameters to @code{Asm}.
-An output variable is illustrated in
-the third statement in the Asm template string:
-@smallexample
-movl %%eax, %0
-@end smallexample
-The intent is to store the contents of the eax register in a variable that can be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not necessarily work, since the compiler might optimize by using a register to hold Flags, and the expansion of the @code{movl} instruction would not be aware of this optimization. The solution is not to store the result directly but rather to advise the compiler to choose the correct operand form; that is the purpose of the @code{%0} output variable.
-
-Information about the output variable is supplied in the @code{Outputs} parameter to @code{Asm}:
-@smallexample
-Outputs => Unsigned_32'Asm_Output ("=g", Flags));
-@end smallexample
-
-The output is defined by the @code{Asm_Output} attribute of the target type; the general format is
-@smallexample
-Type'Asm_Output (constraint_string, variable_name)
-@end smallexample
-
-The constraint string directs the compiler how
-to store/access the associated variable. In the example
-@smallexample
-Unsigned_32'Asm_Output ("=m", Flags);
-@end smallexample
-the @code{"m"} (memory) constraint tells the compiler that the variable
-@code{Flags} should be stored in a memory variable, thus preventing
-the optimizer from keeping it in a register. In contrast,
-@smallexample
-Unsigned_32'Asm_Output ("=r", Flags);
-@end smallexample
-uses the @code{"r"} (register) constraint, telling the compiler to
-store the variable in a register.
-
-If the constraint is preceded by the equal character (@strong{=}), it tells the
-compiler that the variable will be used to store data into it.
-
-In the @code{Get_Flags} example, we used the "g" (global) constraint, allowing the optimizer
-to choose whatever it deems best.
-
-There are a fairly large number of constraints, but the ones that are most useful (for the Intel x86 processor) are the following:
-
-@table @code
-@item =
-output constraint
-@item g
-global (i.e. can be stored anywhere)
-@item m
-in memory
-@item I
-a constant
-@item a
-use eax
-@item b
-use ebx
-@item c
-use ecx
-@item d
-use edx
-@item S
-use esi
-@item D
-use edi
-@item r
-use one of eax, ebx, ecx or edx
-@item q
-use one of eax, ebx, ecx, edx, esi or edi
-@end table
-
-The full set of constraints is described in the gcc and @emph{as} documentation; note that it is possible to combine certain constraints in one constraint string.
-
-You specify the association of an output variable with an assembler operand through the @code{%}@emph{n} notation, where @emph{n} is a non-negative integer. Thus in
-@smallexample
-@group
-Asm ("pushfl" & LF & HT & -- push flags on stack
- "popl %%eax" & LF & HT & -- load eax with flags
- "movl %%eax, %0", -- store flags in variable
- Outputs => Unsigned_32'Asm_Output ("=g", Flags));
-@end group
-@end smallexample
-@noindent
-@code{%0} will be replaced in the expanded code by the appropriate operand,
-whatever
-the compiler decided for the @code{Flags} variable.
-
-In general, you may have any number of output variables:
-@itemize @bullet
-@item
-Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
-@item
-Specify the @code{Outputs} parameter as a parenthesized comma-separated list of @code{Asm_Output} attributes
-@end itemize
-
-For example:
-@smallexample
-@group
-Asm ("movl %%eax, %0" & LF & HT &
- "movl %%ebx, %1" & LF & HT &
- "movl %%ecx, %2",
- Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
- Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
- Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
-@end group
-@end smallexample
-@noindent
-where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables in the Ada program.
-
-As a variation on the @code{Get_Flags} example, we can use the constraints string to direct the compiler to store the eax register into the @code{Flags} variable, instead of including the store instruction explicitly in the @code{Asm} template string:
-
-@smallexample
-@group
-with Interfaces; use Interfaces;
-with Ada.Text_IO; use Ada.Text_IO;
-with System.Machine_Code; use System.Machine_Code;
-procedure Get_Flags_2 is
- Flags : Unsigned_32;
- use ASCII;
-begin
- Asm ("pushfl" & LF & HT & -- push flags on stack
- "popl %%eax", -- save flags in eax
- Outputs => Unsigned_32'Asm_Output ("=a", Flags));
- Put_Line ("Flags register:" & Flags'Img);
-end Get_Flags_2;
-@end group
-@end smallexample
-
-@noindent
-The @code{"a"} constraint tells the compiler that the @code{Flags}
-variable will come from the eax register. Here is the resulting code:
-
-@smallexample
-@group
-#APP
- pushfl
- popl %eax
-#NO_APP
- movl %eax,-40(%ebp)
-@end group
-@end smallexample
-
-@noindent
-The compiler generated the store of eax into Flags after
-expanding the assembler code.
-
-Actually, there was no need to pop the flags into the eax register; more simply, we could just pop the flags directly into the program variable:
-
-@smallexample
-@group
-with Interfaces; use Interfaces;
-with Ada.Text_IO; use Ada.Text_IO;
-with System.Machine_Code; use System.Machine_Code;
-procedure Get_Flags_3 is
- Flags : Unsigned_32;
- use ASCII;
-begin
- Asm ("pushfl" & LF & HT & -- push flags on stack
- "pop %0", -- save flags in Flags
- Outputs => Unsigned_32'Asm_Output ("=g", Flags));
- Put_Line ("Flags register:" & Flags'Img);
-end Get_Flags_3;
-@end group
-@end smallexample
-
-@c ---------------------------------------------------------------------------
-@node Input Variables in Inline Assembler
-@section Input Variables in Inline Assembler
-
-@noindent
-The example in this section illustrates how to specify the source operands for assembly language statements. The program simply increments its input value by 1:
-
-@smallexample
-@group
-with Interfaces; use Interfaces;
-with Ada.Text_IO; use Ada.Text_IO;
-with System.Machine_Code; use System.Machine_Code;
-procedure Increment is
-
- function Incr (Value : Unsigned_32) return Unsigned_32 is
- Result : Unsigned_32;
- begin
- Asm ("incl %0",
- Inputs => Unsigned_32'Asm_Input ("a", Value),
- Outputs => Unsigned_32'Asm_Output ("=a", Result));
- return Result;
- end Incr;
-
- Value : Unsigned_32;
-
-begin
- Value := 5;
- Put_Line ("Value before is" & Value'Img);
- Value := Incr (Value);
- Put_Line ("Value after is" & Value'Img);
-end Increment;
-@end group
-@end smallexample
-
-The @code{Outputs} parameter to @code{Asm} specifies
-that the result will be in the eax register and that it is to be stored in the @code{Result}
-variable.
-
-The @code{Inputs} parameter looks much like the @code{Outputs} parameter, but with an
-@code{Asm_Input} attribute. The
-@code{"="} constraint, indicating an output value, is not present.
-
-You can have multiple input variables, in the same way that you can have more
-than one output variable.
-
-The parameter count (%0, %1) etc, now starts at the first input
-statement, and continues with the output statements.
-When both parameters use the same variable, the
-compiler will treat them as the same %n operand, which is the case here.
-
-Just as the @code{Outputs} parameter causes the register to be stored into the
-target variable after execution of the assembler statements, so does the
-@code{Inputs} parameter cause its variable to be loaded into the register before execution
-of the
-assembler statements.
-
-Thus the effect of the @code{Asm} invocation is:
-@enumerate
-@item load the 32-bit value of @code{Value} into eax
-@item execute the @code{incl %eax} instruction
-@item store the contents of eax into the @code{Result} variable
-@end enumerate
-
-The resulting assembler file (with @code{-O2} optimization) contains:
-@smallexample
-@group
-_increment__incr.1:
- subl $4,%esp
- movl 8(%esp),%eax
-#APP
- incl %eax
-#NO_APP
- movl %eax,%edx
- movl %ecx,(%esp)
- addl $4,%esp
- ret
-@end group
-@end smallexample
-
-@c ---------------------------------------------------------------------------
-@node Inlining Inline Assembler Code
-@section Inlining Inline Assembler Code
-
-@noindent
-For a short subprogram such as the @code{Incr} function in the previous section, the overhead of the call and return (creating / deleting the stack frame)
-can be significant, compared to the amount of code in the subprogram body.
-A solution is to apply Ada's @code{Inline} pragma to the subprogram,
-which directs the compiler to expand invocations of the subprogram at the point(s)
-of call, instead of setting up a stack frame for out-of-line calls.
-Here is the resulting program:
-
-@smallexample
-@group
-with Interfaces; use Interfaces;
-with Ada.Text_IO; use Ada.Text_IO;
-with System.Machine_Code; use System.Machine_Code;
-procedure Increment_2 is
-
- function Incr (Value : Unsigned_32) return Unsigned_32 is
- Result : Unsigned_32;
- begin
- Asm ("incl %0",
- Inputs => Unsigned_32'Asm_Input ("a", Value),
- Outputs => Unsigned_32'Asm_Output ("=a", Result));
- return Result;
- end Incr;
- pragma Inline (Increment);
-
- Value : Unsigned_32;
-
-begin
- Value := 5;
- Put_Line ("Value before is" & Value'Img);
- Value := Increment (Value);
- Put_Line ("Value after is" & Value'Img);
-end Increment_2;
-@end group
-@end smallexample
-
-Compile the program with both optimization (@code{-O2}) and inlining
-enabled (@option{-gnatpn} instead of @option{-gnatp}).
-
-The @code{Incr} function is still compiled as usual, but at the
-point in @code{Increment} where our function used to be called:
-
-@smallexample
-@group
-pushl %edi
-call _increment__incr.1
-@end group
-@end smallexample
-
-@noindent
-the code for the function body directly appears:
-
-@smallexample
-@group
-movl %esi,%eax
-#APP
- incl %eax
-#NO_APP
- movl %eax,%edx
-@end group
-@end smallexample
-
-@noindent
-thus saving the overhead of stack frame setup and an out-of-line call.
-
-@c ---------------------------------------------------------------------------
-@node Other Asm Functionality
-@section Other @code{Asm} Functionality
-
-@noindent
-This section describes two important parameters to the @code{Asm} procedure: @code{Clobber}, which identifies register usage; and @code{Volatile}, which inhibits unwanted optimizations.
-
-@menu
-* The Clobber Parameter::
-* The Volatile Parameter::
-@end menu
-
-@c ---------------------------------------------------------------------------
-@node The Clobber Parameter
-@subsection The @code{Clobber} Parameter
-
-@noindent
-One of the dangers of intermixing assembly language and a compiled language such as Ada is
-that the compiler needs to be aware of which registers are being used by the assembly code.
-In some cases, such as the earlier examples, the constraint string is sufficient to
-indicate register usage (e.g. "a" for the eax register). But more generally, the
-compiler needs an explicit identification of the registers that are used by the Inline
-Assembly statements.
-
-Using a register that the compiler doesn't know about
-could be a side effect of an instruction (like @code{mull}
-storing its result in both eax and edx).
-It can also arise from explicit register usage in your
-assembly code; for example:
-@smallexample
-@group
-Asm ("movl %0, %%ebx" & LF & HT &
- "movl %%ebx, %1",
- Inputs => Unsigned_32'Asm_Input ("g", Var_In),
- Outputs => Unsigned_32'Asm_Output ("=g", Var_Out));
-@end group
-@end smallexample
-@noindent
-where the compiler (since it does not analyze the @code{Asm} template string)
-does not know you are using the ebx register.
-
-In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
-to identify the registers that will be used by your assembly code:
-
-@smallexample
-@group
-Asm ("movl %0, %%ebx" & LF & HT &
- "movl %%ebx, %1",
- Inputs => Unsigned_32'Asm_Input ("g", Var_In),
- Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
- Clobber => "ebx");
-@end group
-@end smallexample
-
-The Clobber parameter is a static string expression specifying the
-register(s) you are using. Note that register names are @emph{not} prefixed by a percent sign.
-Also, if more than one register is used then their names are separated by commas; e.g., @code{"eax, ebx"}
-
-The @code{Clobber} parameter has several additional uses:
-@enumerate
-@item Use the "register" name @code{cc} to indicate that flags might have changed
-@item Use the "register" name @code{memory} if you changed a memory location
-@end enumerate
-
-@c ---------------------------------------------------------------------------
-@node The Volatile Parameter
-@subsection The @code{Volatile} Parameter
-@cindex Volatile parameter
-
-@noindent
-Compiler optimizations in the presence of Inline Assembler may sometimes have unwanted effects.
-For example, when
-an @code{Asm} invocation with an input variable is inside a loop, the compiler might move
-the loading of the input variable outside the loop, regarding it as a
-one-time initialization.
-
-If this effect is not desired, you can disable such optimizations by setting the
-@code{Volatile} parameter to @code{True}; for example:
-
-@smallexample
-@group
-Asm ("movl %0, %%ebx" & LF & HT &
- "movl %%ebx, %1",
- Inputs => Unsigned_32'Asm_Input ("g", Var_In),
- Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
- Clobber => "ebx",
- Volatile => True);
-@end group
-@end smallexample
-
-By default, @code{Volatile} is set to @code{False} unless there is no @code{Outputs}
-parameter.
-
-Although setting @code{Volatile} to @code{True} prevents unwanted optimizations,
-it will also disable other optimizations that might be important for efficiency.
-In general, you should set @code{Volatile} to @code{True} only if the compiler's
-optimizations have created problems.
-
-@c ---------------------------------------------------------------------------
-@node A Complete Example
-@section A Complete Example
-
-@noindent
-This section contains a complete program illustrating a realistic usage of GNAT's Inline Assembler
-capabilities. It comprises a main procedure @code{Check_CPU} and a package @code{Intel_CPU}.
-The package declares a collection of functions that detect the properties of the 32-bit
-x86 processor that is running the program. The main procedure invokes these functions
-and displays the information.
-
-The Intel_CPU package could be enhanced by adding functions to
-detect the type of x386 co-processor, the processor caching options and
-special operations such as the SIMD extensions.
-
-Although the Intel_CPU package has been written for 32-bit Intel
-compatible CPUs, it is OS neutral. It has been tested on DOS,
-Windows/NT and Linux.
-
-@menu
-* Check_CPU Procedure::
-* Intel_CPU Package Specification::
-* Intel_CPU Package Body::
-@end menu
-
-@c ---------------------------------------------------------------------------
-@node Check_CPU Procedure
-@subsection @code{Check_CPU} Procedure
-@cindex Check_CPU procedure
-
-@smallexample
----------------------------------------------------------------------
--- --
--- Uses the Intel_CPU package to identify the CPU the program is --
--- running on, and some of the features it supports. --
--- --
----------------------------------------------------------------------
-
-with Intel_CPU; -- Intel CPU detection functions
-with Ada.Text_IO; -- Standard text I/O
-with Ada.Command_Line; -- To set the exit status
-
-procedure Check_CPU is
-
- Type_Found : Boolean := False;
- -- Flag to indicate that processor was identified
-
- Features : Intel_CPU.Processor_Features;
- -- The processor features
-
- Signature : Intel_CPU.Processor_Signature;
- -- The processor type signature
-
-begin
-
- -----------------------------------
- -- Display the program banner. --
- -----------------------------------
-
- Ada.Text_IO.Put_Line (Ada.Command_Line.Command_Name &
- ": check Intel CPU version and features, v1.0");
- Ada.Text_IO.Put_Line ("distribute freely, but no warranty whatsoever");
- Ada.Text_IO.New_Line;
-
- -----------------------------------------------------------------------
- -- We can safely start with the assumption that we are on at least --
- -- a x386 processor. If the CPUID instruction is present, then we --
- -- have a later processor type. --
- -----------------------------------------------------------------------
-
- if Intel_CPU.Has_CPUID = False then
-
- -- No CPUID instruction, so we assume this is indeed a x386
- -- processor. We can still check if it has a FP co-processor.
- if Intel_CPU.Has_FPU then
- Ada.Text_IO.Put_Line
- ("x386-type processor with a FP co-processor");
- else
- Ada.Text_IO.Put_Line
- ("x386-type processor without a FP co-processor");
- end if; -- check for FPU
-
- -- Program done
- Ada.Command_Line.Set_Exit_Status (Ada.Command_Line.Success);
- return;
-
- end if; -- check for CPUID
-
- -----------------------------------------------------------------------
- -- If CPUID is supported, check if this is a true Intel processor, --
- -- if it is not, display a warning. --
- -----------------------------------------------------------------------
-
- if Intel_CPU.Vendor_ID /= Intel_CPU.Intel_Processor then
- Ada.Text_IO.Put_Line ("*** This is a Intel compatible processor");
- Ada.Text_IO.Put_Line ("*** Some information may be incorrect");
- end if; -- check if Intel
-
- ----------------------------------------------------------------------
- -- With the CPUID instruction present, we can assume at least a --
- -- x486 processor. If the CPUID support level is < 1 then we have --
- -- to leave it at that. --
- ----------------------------------------------------------------------
-
- if Intel_CPU.CPUID_Level < 1 then
-
- -- Ok, this is a x486 processor. we still can get the Vendor ID
- Ada.Text_IO.Put_Line ("x486-type processor");
- Ada.Text_IO.Put_Line ("Vendor ID is " & Intel_CPU.Vendor_ID);
-
- -- We can also check if there is a FPU present
- if Intel_CPU.Has_FPU then
- Ada.Text_IO.Put_Line ("Floating-Point support");
- else
- Ada.Text_IO.Put_Line ("No Floating-Point support");
- end if; -- check for FPU
-
- -- Program done
- Ada.Command_Line.Set_Exit_Status (Ada.Command_Line.Success);
- return;
-
- end if; -- check CPUID level
-
- ---------------------------------------------------------------------
- -- With a CPUID level of 1 we can use the processor signature to --
- -- determine it's exact type. --
- ---------------------------------------------------------------------
-
- Signature := Intel_CPU.Signature;
-
- ----------------------------------------------------------------------
- -- Ok, now we go into a lot of messy comparisons to get the --
- -- processor type. For clarity, no attememt to try to optimize the --
- -- comparisons has been made. Note that since Intel_CPU does not --
- -- support getting cache info, we cannot distinguish between P5 --
- -- and Celeron types yet. --
- ----------------------------------------------------------------------
-
- -- x486SL
- if Signature.Processor_Type = 2#00# and
- Signature.Family = 2#0100# and
- Signature.Model = 2#0100# then
- Type_Found := True;
- Ada.Text_IO.Put_Line ("x486SL processor");
- end if;
-
- -- x486DX2 Write-Back
- if Signature.Processor_Type = 2#00# and
- Signature.Family = 2#0100# and
- Signature.Model = 2#0111# then
- Type_Found := True;
- Ada.Text_IO.Put_Line ("Write-Back Enhanced x486DX2 processor");
- end if;
-
- -- x486DX4
- if Signature.Processor_Type = 2#00# and
- Signature.Family = 2#0100# and
- Signature.Model = 2#1000# then
- Type_Found := True;
- Ada.Text_IO.Put_Line ("x486DX4 processor");
- end if;
-
- -- x486DX4 Overdrive
- if Signature.Processor_Type = 2#01# and
- Signature.Family = 2#0100# and
- Signature.Model = 2#1000# then
- Type_Found := True;
- Ada.Text_IO.Put_Line ("x486DX4 OverDrive processor");
- end if;
-
- -- Pentium (60, 66)
- if Signature.Processor_Type = 2#00# and
- Signature.Family = 2#0101# and
- Signature.Model = 2#0001# then
- Type_Found := True;
- Ada.Text_IO.Put_Line ("Pentium processor (60, 66)");
- end if;
-
- -- Pentium (75, 90, 100, 120, 133, 150, 166, 200)
- if Signature.Processor_Type = 2#00# and
- Signature.Family = 2#0101# and
- Signature.Model = 2#0010# then
- Type_Found := True;
- Ada.Text_IO.Put_Line
- ("Pentium processor (75, 90, 100, 120, 133, 150, 166, 200)");
- end if;
-
- -- Pentium OverDrive (60, 66)
- if Signature.Processor_Type = 2#01# and
- Signature.Family = 2#0101# and
- Signature.Model = 2#0001# then
- Type_Found := True;
- Ada.Text_IO.Put_Line ("Pentium OverDrive processor (60, 66)");
- end if;
-
- -- Pentium OverDrive (75, 90, 100, 120, 133, 150, 166, 200)
- if Signature.Processor_Type = 2#01# and
- Signature.Family = 2#0101# and
- Signature.Model = 2#0010# then
- Type_Found := True;
- Ada.Text_IO.Put_Line
- ("Pentium OverDrive cpu (75, 90, 100, 120, 133, 150, 166, 200)");
- end if;
-
- -- Pentium OverDrive processor for x486 processor-based systems
- if Signature.Processor_Type = 2#01# and
- Signature.Family = 2#0101# and
- Signature.Model = 2#0011# then
- Type_Found := True;
- Ada.Text_IO.Put_Line
- ("Pentium OverDrive processor for x486 processor-based systems");
- end if;
-
- -- Pentium processor with MMX technology (166, 200)
- if Signature.Processor_Type = 2#00# and
- Signature.Family = 2#0101# and
- Signature.Model = 2#0100# then
- Type_Found := True;
- Ada.Text_IO.Put_Line
- ("Pentium processor with MMX technology (166, 200)");
- end if;
-
- -- Pentium OverDrive with MMX for Pentium (75, 90, 100, 120, 133)
- if Signature.Processor_Type = 2#01# and
- Signature.Family = 2#0101# and
- Signature.Model = 2#0100# then
- Type_Found := True;
- Ada.Text_IO.Put_Line
- ("Pentium OverDrive processor with MMX " &
- "technology for Pentium processor (75, 90, 100, 120, 133)");
- end if;
-
- -- Pentium Pro processor
- if Signature.Processor_Type = 2#00# and
- Signature.Family = 2#0110# and
- Signature.Model = 2#0001# then
- Type_Found := True;
- Ada.Text_IO.Put_Line ("Pentium Pro processor");
- end if;
-
- -- Pentium II processor, model 3
- if Signature.Processor_Type = 2#00# and
- Signature.Family = 2#0110# and
- Signature.Model = 2#0011# then
- Type_Found := True;
- Ada.Text_IO.Put_Line ("Pentium II processor, model 3");
- end if;
-
- -- Pentium II processor, model 5 or Celeron processor
- if Signature.Processor_Type = 2#00# and
- Signature.Family = 2#0110# and
- Signature.Model = 2#0101# then
- Type_Found := True;
- Ada.Text_IO.Put_Line
- ("Pentium II processor, model 5 or Celeron processor");
- end if;
-
- -- Pentium Pro OverDrive processor
- if Signature.Processor_Type = 2#01# and
- Signature.Family = 2#0110# and
- Signature.Model = 2#0011# then
- Type_Found := True;
- Ada.Text_IO.Put_Line ("Pentium Pro OverDrive processor");
- end if;
-
- -- If no type recognized, we have an unknown. Display what
- -- we _do_ know
- if Type_Found = False then
- Ada.Text_IO.Put_Line ("Unknown processor");
- end if;
-
- -----------------------------------------
- -- Display processor stepping level. --
- -----------------------------------------
-
- Ada.Text_IO.Put_Line ("Stepping level:" & Signature.Stepping'Img);
-
- ---------------------------------
- -- Display vendor ID string. --
- ---------------------------------
-
- Ada.Text_IO.Put_Line ("Vendor ID: " & Intel_CPU.Vendor_ID);
-
- ------------------------------------
- -- Get the processors features. --
- ------------------------------------
-
- Features := Intel_CPU.Features;
-
- -----------------------------
- -- Check for a FPU unit. --
- -----------------------------
-
- if Features.FPU = True then
- Ada.Text_IO.Put_Line ("Floating-Point unit available");
- else
- Ada.Text_IO.Put_Line ("no Floating-Point unit");
- end if; -- check for FPU
-
- --------------------------------
- -- List processor features. --
- --------------------------------
-
- Ada.Text_IO.Put_Line ("Supported features: ");
-
- -- Virtual Mode Extension
- if Features.VME = True then
- Ada.Text_IO.Put_Line (" VME - Virtual Mode Extension");
- end if;
-
- -- Debugging Extension
- if Features.DE = True then
- Ada.Text_IO.Put_Line (" DE - Debugging Extension");
- end if;
-
- -- Page Size Extension
- if Features.PSE = True then
- Ada.Text_IO.Put_Line (" PSE - Page Size Extension");
- end if;
-
- -- Time Stamp Counter
- if Features.TSC = True then
- Ada.Text_IO.Put_Line (" TSC - Time Stamp Counter");
- end if;
-
- -- Model Specific Registers
- if Features.MSR = True then
- Ada.Text_IO.Put_Line (" MSR - Model Specific Registers");
- end if;
-
- -- Physical Address Extension
- if Features.PAE = True then
- Ada.Text_IO.Put_Line (" PAE - Physical Address Extension");
- end if;
-
- -- Machine Check Extension
- if Features.MCE = True then
- Ada.Text_IO.Put_Line (" MCE - Machine Check Extension");
- end if;
-
- -- CMPXCHG8 instruction supported
- if Features.CX8 = True then
- Ada.Text_IO.Put_Line (" CX8 - CMPXCHG8 instruction");
- end if;
-
- -- on-chip APIC hardware support
- if Features.APIC = True then
- Ada.Text_IO.Put_Line (" APIC - on-chip APIC hardware support");
- end if;
-
- -- Fast System Call
- if Features.SEP = True then
- Ada.Text_IO.Put_Line (" SEP - Fast System Call");
- end if;
-
- -- Memory Type Range Registers
- if Features.MTRR = True then
- Ada.Text_IO.Put_Line (" MTTR - Memory Type Range Registers");
- end if;
-
- -- Page Global Enable
- if Features.PGE = True then
- Ada.Text_IO.Put_Line (" PGE - Page Global Enable");
- end if;
-
- -- Machine Check Architecture
- if Features.MCA = True then
- Ada.Text_IO.Put_Line (" MCA - Machine Check Architecture");
- end if;
-
- -- Conditional Move Instruction Supported
- if Features.CMOV = True then
- Ada.Text_IO.Put_Line
- (" CMOV - Conditional Move Instruction Supported");
- end if;
-
- -- Page Attribute Table
- if Features.PAT = True then
- Ada.Text_IO.Put_Line (" PAT - Page Attribute Table");
- end if;
-
- -- 36-bit Page Size Extension
- if Features.PSE_36 = True then
- Ada.Text_IO.Put_Line (" PSE_36 - 36-bit Page Size Extension");
- end if;
-
- -- MMX technology supported
- if Features.MMX = True then
- Ada.Text_IO.Put_Line (" MMX - MMX technology supported");
- end if;
-
- -- Fast FP Save and Restore
- if Features.FXSR = True then
- Ada.Text_IO.Put_Line (" FXSR - Fast FP Save and Restore");
- end if;
-
- ---------------------
- -- Program done. --
- ---------------------
-
- Ada.Command_Line.Set_Exit_Status (Ada.Command_Line.Success);
-
-exception
-
- when others =>
- Ada.Command_Line.Set_Exit_Status (Ada.Command_Line.Failure);
- raise;
-
-end Check_CPU;
-@end smallexample
-
-@c ---------------------------------------------------------------------------
-@node Intel_CPU Package Specification
-@subsection @code{Intel_CPU} Package Specification
-@cindex Intel_CPU package specification
-
-@smallexample
--------------------------------------------------------------------------
--- --
--- file: intel_cpu.ads --
--- --
--- ********************************************* --
--- * WARNING: for 32-bit Intel processors only * --
--- ********************************************* --
--- --
--- This package contains a number of subprograms that are useful in --
--- determining the Intel x86 CPU (and the features it supports) on --
--- which the program is running. --
--- --
--- The package is based upon the information given in the Intel --
--- Application Note AP-485: "Intel Processor Identification and the --
--- CPUID Instruction" as of April 1998. This application note can be --
--- found on www.intel.com. --
--- --
--- It currently deals with 32-bit processors only, will not detect --
--- features added after april 1998, and does not guarantee proper --
--- results on Intel-compatible processors. --
--- --
--- Cache info and x386 fpu type detection are not supported. --
--- --
--- This package does not use any privileged instructions, so should --
--- work on any OS running on a 32-bit Intel processor. --
--- --
--------------------------------------------------------------------------
-
-with Interfaces; use Interfaces;
--- for using unsigned types
-
-with System.Machine_Code; use System.Machine_Code;
--- for using inline assembler code
-
-with Ada.Characters.Latin_1; use Ada.Characters.Latin_1;
--- for inserting control characters
-
-package Intel_CPU is
-
- ----------------------
- -- Processor bits --
- ----------------------
-
- subtype Num_Bits is Natural range 0 .. 31;
- -- the number of processor bits (32)
-
- --------------------------
- -- Processor register --
- --------------------------
-
- -- define a processor register type for easy access to
- -- the individual bits
-
- type Processor_Register is array (Num_Bits) of Boolean;
- pragma Pack (Processor_Register);
- for Processor_Register'Size use 32;
-
- -------------------------
- -- Unsigned register --
- -------------------------
-
- -- define a processor register type for easy access to
- -- the individual bytes
-
- type Unsigned_Register is
- record
- L1 : Unsigned_8;
- H1 : Unsigned_8;
- L2 : Unsigned_8;
- H2 : Unsigned_8;
- end record;
-
- for Unsigned_Register use
- record
- L1 at 0 range 0 .. 7;
- H1 at 0 range 8 .. 15;
- L2 at 0 range 16 .. 23;
- H2 at 0 range 24 .. 31;
- end record;
-
- for Unsigned_Register'Size use 32;
-
- ---------------------------------
- -- Intel processor vendor ID --
- ---------------------------------
-
- Intel_Processor : constant String (1 .. 12) := "GenuineIntel";
- -- indicates an Intel manufactured processor
-
- ------------------------------------
- -- Processor signature register --
- ------------------------------------
-
- -- a register type to hold the processor signature
-
- type Processor_Signature is
- record
- Stepping : Natural range 0 .. 15;
- Model : Natural range 0 .. 15;
- Family : Natural range 0 .. 15;
- Processor_Type : Natural range 0 .. 3;
- Reserved : Natural range 0 .. 262143;
- end record;
-
- for Processor_Signature use
- record
- Stepping at 0 range 0 .. 3;
- Model at 0 range 4 .. 7;
- Family at 0 range 8 .. 11;
- Processor_Type at 0 range 12 .. 13;
- Reserved at 0 range 14 .. 31;
- end record;
-
- for Processor_Signature'Size use 32;
-
- -----------------------------------
- -- Processor features register --
- -----------------------------------
-
- -- a processor register to hold the processor feature flags
-
- type Processor_Features is
- record
- FPU : Boolean; -- floating point unit on chip
- VME : Boolean; -- virtual mode extension
- DE : Boolean; -- debugging extension
- PSE : Boolean; -- page size extension
- TSC : Boolean; -- time stamp counter
- MSR : Boolean; -- model specific registers
- PAE : Boolean; -- physical address extension
- MCE : Boolean; -- machine check extension
- CX8 : Boolean; -- cmpxchg8 instruction
- APIC : Boolean; -- on-chip apic hardware
- Res_1 : Boolean; -- reserved for extensions
- SEP : Boolean; -- fast system call
- MTRR : Boolean; -- memory type range registers
- PGE : Boolean; -- page global enable
- MCA : Boolean; -- machine check architecture
- CMOV : Boolean; -- conditional move supported
- PAT : Boolean; -- page attribute table
- PSE_36 : Boolean; -- 36-bit page size extension
- Res_2 : Natural range 0 .. 31; -- reserved for extensions
- MMX : Boolean; -- MMX technology supported
- FXSR : Boolean; -- fast FP save and restore
- Res_3 : Natural range 0 .. 127; -- reserved for extensions
- end record;
-
- for Processor_Features use
- record
- FPU at 0 range 0 .. 0;
- VME at 0 range 1 .. 1;
- DE at 0 range 2 .. 2;
- PSE at 0 range 3 .. 3;
- TSC at 0 range 4 .. 4;
- MSR at 0 range 5 .. 5;
- PAE at 0 range 6 .. 6;
- MCE at 0 range 7 .. 7;
- CX8 at 0 range 8 .. 8;
- APIC at 0 range 9 .. 9;
- Res_1 at 0 range 10 .. 10;
- SEP at 0 range 11 .. 11;
- MTRR at 0 range 12 .. 12;
- PGE at 0 range 13 .. 13;
- MCA at 0 range 14 .. 14;
- CMOV at 0 range 15 .. 15;
- PAT at 0 range 16 .. 16;
- PSE_36 at 0 range 17 .. 17;
- Res_2 at 0 range 18 .. 22;
- MMX at 0 range 23 .. 23;
- FXSR at 0 range 24 .. 24;
- Res_3 at 0 range 25 .. 31;
- end record;
-
- for Processor_Features'Size use 32;
-
- -------------------
- -- Subprograms --
- -------------------
-
- function Has_FPU return Boolean;
- -- return True if a FPU is found
- -- use only if CPUID is not supported
-
- function Has_CPUID return Boolean;
- -- return True if the processor supports the CPUID instruction
-
- function CPUID_Level return Natural;
- -- return the CPUID support level (0, 1 or 2)
- -- can only be called if the CPUID instruction is supported
-
- function Vendor_ID return String;
- -- return the processor vendor identification string
- -- can only be called if the CPUID instruction is supported
-
- function Signature return Processor_Signature;
- -- return the processor signature
- -- can only be called if the CPUID instruction is supported
-
- function Features return Processor_Features;
- -- return the processors features
- -- can only be called if the CPUID instruction is supported
-
-private
-
- ------------------------
- -- EFLAGS bit names --
- ------------------------
-
- ID_Flag : constant Num_Bits := 21;
- -- ID flag bit
-
-end Intel_CPU;
-@end smallexample
-
-@c ---------------------------------------------------------------------------
-@node Intel_CPU Package Body
-@subsection @code{Intel_CPU} Package Body
-@cindex Intel_CPU package body
-
-@smallexample
-package body Intel_CPU is
-
- ---------------------------
- -- Detect FPU presence --
- ---------------------------
-
- -- There is a FPU present if we can set values to the FPU Status
- -- and Control Words.
-
- function Has_FPU return Boolean is
-
- Register : Unsigned_16;
- -- processor register to store a word
-
- begin
-
- -- check if we can change the status word
- Asm (
-
- -- the assembler code
- "finit" & LF & HT & -- reset status word
- "movw $0x5A5A, %%ax" & LF & HT & -- set value status word
- "fnstsw %0" & LF & HT & -- save status word
- "movw %%ax, %0", -- store status word
-
- -- output stored in Register
- -- register must be a memory location
- Outputs => Unsigned_16'Asm_output ("=m", Register),
-
- -- tell compiler that we used eax
- Clobber => "eax");
-
- -- if the status word is zero, there is no FPU
- if Register = 0 then
- return False; -- no status word
- end if; -- check status word value
-
- -- check if we can get the control word
- Asm (
-
- -- the assembler code
- "fnstcw %0", -- save the control word
-
- -- output into Register
- -- register must be a memory location
- Outputs => Unsigned_16'Asm_output ("=m", Register));
-
- -- check the relevant bits
- if (Register and 16#103F#) /= 16#003F# then
- return False; -- no control word
- end if; -- check control word value
-
- -- FPU found
- return True;
-
- end Has_FPU;
-
- --------------------------------
- -- Detect CPUID instruction --
- --------------------------------
-
- -- The processor supports the CPUID instruction if it is possible
- -- to change the value of ID flag bit in the EFLAGS register.
-
- function Has_CPUID return Boolean is
-
- Original_Flags, Modified_Flags : Processor_Register;
- -- EFLAG contents before and after changing the ID flag
-
- begin
-
- -- try flipping the ID flag in the EFLAGS register
- Asm (
-
- -- the assembler code
- "pushfl" & LF & HT & -- push EFLAGS on stack
- "pop %%eax" & LF & HT & -- pop EFLAGS into eax
- "movl %%eax, %0" & LF & HT & -- save EFLAGS content
- "xor $0x200000, %%eax" & LF & HT & -- flip ID flag
- "push %%eax" & LF & HT & -- push EFLAGS on stack
- "popfl" & LF & HT & -- load EFLAGS register
- "pushfl" & LF & HT & -- push EFLAGS on stack
- "pop %1", -- save EFLAGS content
-
- -- output values, may be anything
- -- Original_Flags is %0
- -- Modified_Flags is %1
- Outputs =>
- (Processor_Register'Asm_output ("=g", Original_Flags),
- Processor_Register'Asm_output ("=g", Modified_Flags)),
-
- -- tell compiler eax is destroyed
- Clobber => "eax");
-
- -- check if CPUID is supported
- if Original_Flags(ID_Flag) /= Modified_Flags(ID_Flag) then
- return True; -- ID flag was modified
- else
- return False; -- ID flag unchanged
- end if; -- check for CPUID
-
- end Has_CPUID;
-
- -------------------------------
- -- Get CPUID support level --
- -------------------------------
-
- function CPUID_Level return Natural is
-
- Level : Unsigned_32;
- -- returned support level
-
- begin
-
- -- execute CPUID, storing the results in the Level register
- Asm (
-
- -- the assembler code
- "cpuid", -- execute CPUID
-
- -- zero is stored in eax
- -- returning the support level in eax
- Inputs => Unsigned_32'Asm_input ("a", 0),
-
- -- eax is stored in Level
- Outputs => Unsigned_32'Asm_output ("=a", Level),
-
- -- tell compiler ebx, ecx and edx registers are destroyed
- Clobber => "ebx, ecx, edx");
-
- -- return the support level
- return Natural (Level);
-
- end CPUID_Level;
-
- --------------------------------
- -- Get CPU Vendor ID String --
- --------------------------------
-
- -- The vendor ID string is returned in the ebx, ecx and edx register
- -- after executing the CPUID instruction with eax set to zero.
- -- In case of a true Intel processor the string returned is
- -- "GenuineIntel"
-
- function Vendor_ID return String is
-
- Ebx, Ecx, Edx : Unsigned_Register;
- -- registers containing the vendor ID string
-
- Vendor_ID : String (1 .. 12);
- -- the vendor ID string
-
- begin
-
- -- execute CPUID, storing the results in the processor registers
- Asm (
-
- -- the assembler code
- "cpuid", -- execute CPUID
-
- -- zero stored in eax
- -- vendor ID string returned in ebx, ecx and edx
- Inputs => Unsigned_32'Asm_input ("a", 0),
-
- -- ebx is stored in Ebx
- -- ecx is stored in Ecx
- -- edx is stored in Edx
- Outputs => (Unsigned_Register'Asm_output ("=b", Ebx),
- Unsigned_Register'Asm_output ("=c", Ecx),
- Unsigned_Register'Asm_output ("=d", Edx)));
-
- -- now build the vendor ID string
- Vendor_ID( 1) := Character'Val (Ebx.L1);
- Vendor_ID( 2) := Character'Val (Ebx.H1);
- Vendor_ID( 3) := Character'Val (Ebx.L2);
- Vendor_ID( 4) := Character'Val (Ebx.H2);
- Vendor_ID( 5) := Character'Val (Edx.L1);
- Vendor_ID( 6) := Character'Val (Edx.H1);
- Vendor_ID( 7) := Character'Val (Edx.L2);
- Vendor_ID( 8) := Character'Val (Edx.H2);
- Vendor_ID( 9) := Character'Val (Ecx.L1);
- Vendor_ID(10) := Character'Val (Ecx.H1);
- Vendor_ID(11) := Character'Val (Ecx.L2);
- Vendor_ID(12) := Character'Val (Ecx.H2);
-
- -- return string
- return Vendor_ID;
-
- end Vendor_ID;
-
- -------------------------------
- -- Get processor signature --
- -------------------------------
-
- function Signature return Processor_Signature is
-
- Result : Processor_Signature;
- -- processor signature returned
-
- begin
-
- -- execute CPUID, storing the results in the Result variable
- Asm (
-
- -- the assembler code
- "cpuid", -- execute CPUID
-
- -- one is stored in eax
- -- processor signature returned in eax
- Inputs => Unsigned_32'Asm_input ("a", 1),
-
- -- eax is stored in Result
- Outputs => Processor_Signature'Asm_output ("=a", Result),
-
- -- tell compiler that ebx, ecx and edx are also destroyed
- Clobber => "ebx, ecx, edx");
-
- -- return processor signature
- return Result;
-
- end Signature;
-
- ------------------------------
- -- Get processor features --
- ------------------------------
-
- function Features return Processor_Features is
-
- Result : Processor_Features;
- -- processor features returned
-
- begin
-
- -- execute CPUID, storing the results in the Result variable
- Asm (
-
- -- the assembler code
- "cpuid", -- execute CPUID
-
- -- one stored in eax
- -- processor features returned in edx
- Inputs => Unsigned_32'Asm_input ("a", 1),
-
- -- edx is stored in Result
- Outputs => Processor_Features'Asm_output ("=d", Result),
-
- -- tell compiler that ebx and ecx are also destroyed
- Clobber => "ebx, ecx");
-
- -- return processor signature
- return Result;
-
- end Features;
-
-end Intel_CPU;
-@end smallexample
-@c END OF INLINE ASSEMBLER CHAPTER
-@c ===============================
-
-@ifset wnt
-@node Microsoft Windows Topics
-@chapter Microsoft Windows Topics
-@cindex Windows NT
-@cindex Windows 95
-@cindex Windows 98
-
-@noindent
-This chapter describes topics that are specific to the Microsoft Windows
-platforms (NT, 95 and 98).
-
-@menu
-* Using GNAT on Windows::
-* GNAT Setup Tool::
-* CONSOLE and WINDOWS subsystems::
-* Temporary Files::
-* Mixed-Language Programming on Windows::
-* Windows Calling Conventions::
-* Introduction to Dynamic Link Libraries (DLLs)::
-* Using DLLs with GNAT::
-* Building DLLs with GNAT::
-* GNAT and Windows Resources::
-* Debugging a DLL::
-* GNAT and COM/DCOM Objects::
-@end menu
-
-@node Using GNAT on Windows
-@section Using GNAT on Windows
-
-@noindent
-One of the strengths of the GNAT technology is that its tool set
-(@code{gcc}, @code{gnatbind}, @code{gnatlink}, @code{gnatmake}, the
-@code{gdb} debugger, etc.) is used in the same way regardless of the
-platform.
-
-On Windows this tool set is complemented by a number of Microsoft-specific
-tools that have been provided to facilitate interoperability with Windows
-when this is required. With these tools:
-
-@itemize @bullet
-
-@item
-You can build applications using the @code{CONSOLE} or @code{WINDOWS}
-subsystems.
-
-@item
-You can use any Dynamically Linked Library (DLL) in your Ada code (both
-relocatable and non-relocatable DLLs are supported).
-
-@item
-You can build Ada DLLs for use in other applications. These applications
-can be written in a language other than Ada (e.g., C, C++, etc). Again both
-relocatable and non-relocatable Ada DLLs are supported.
-
-@item
-You can include Windows resources in your Ada application.
-
-@item
-You can use or create COM/DCOM objects.
-@end itemize
-
-@noindent
-Immediately below are listed all known general GNAT-for-Windows restrictions.
-Other restrictions about specific features like Windows Resources and DLLs
-are listed in separate sections below.
-
-@itemize @bullet
-
-@item
-It is not possible to use @code{GetLastError} and @code{SetLastError}
-when tasking, protected records, or exceptions are used. In these
-cases, in order to implement Ada semantics, the GNAT run-time system
-calls certain Win32 routines that set the last error variable to 0 upon
-success. It should be possible to use @code{GetLastError} and
-@code{SetLastError} when tasking, protected record, and exception
-features are not used, but it is not guaranteed to work.
-@end itemize
-
-@node GNAT Setup Tool
-@section GNAT Setup Tool
-@cindex GNAT Setup Tool
-@cindex Setup Tool
-@cindex gnatreg
-
-@menu
-* Command-line arguments::
-* Creating a network installation of GNAT::
-* Registering and unregistering additional libraries::
-@end menu
-
-@noindent
-GNAT installation on Windows is using the Windows registry in order to
-locate proper executables and standard libraries. GNAT setup tool, called
-@code{gnatreg.exe}, is provided in order to display and modify GNAT-specific
-registry entries, allowing to create network GNAT installations, modify the
-locations of GNAT components, as well as register and unregister additional
-libraries for use with GNAT.
-
-@node Command-line arguments
-@subsection Command-line arguments
-
-@noindent
-@code{gnatreg [switches] [parameter]}
-
-@noindent
-Specifying no arguments causes gnatreg to display current configuration.
-
-@noindent
-The switches understood by gnatreg are:
-@table @asis
-@item -h
- print the help message
-@item -a
- add a standard library
-@item -r
- remove a standard library
-@item -f
- force creation of keys if they don't exist
-@item -q
- be quiet/terse
-@end table
-
-@node Creating a network installation of GNAT
-@subsection Creating a network installation of GNAT
-
-@noindent
-Make sure the system on which GNAT is installed is accessible from the
-current machine.
-
-Use the command
-
-@code{@ @ @ gnatreg -f \\server\sharename\path}
-
-in order to setup the registry entries on a current machine.
-
-For example, if GNAT is installed in @file{\GNAT} directory of a share location
-called @file{c-drive} on a machine @file{LOKI}, the command that can be used on
-other machines to allow the remote use of GNAT is,
-
-@code{@ @ @ gnatreg -f \\loki\c-drive\gnat}
-
-Remember to also add @file{\\loki\c-drive\gnat\bin} in front of your PATH variable.
-
-Be aware that every compilation using the network installation results in the
-transfer of large amounts of data across the network and may cause serious
-performance penalty.
-
-@node Registering and unregistering additional libraries
-@subsection Registering and unregistering additional libraries
-
-@noindent
-To register a standard library use a command:
-
-@code{@ @ @ gnatreg -a <library_name>=<path>}
-
-For example:
-
-@code{@ @ @ gnatreg -a WIN32ADA=c:\Win32Ada}
-
-The libraries registered in this manner will be treated like standard libraries
-by the compiler (i.e. they don't have to be specified in -I and -l switches to
-various GNAT tools).
-
-To unregister a library, enter
-@code{ gnatreg -r <library_name>}
-
-e.g.,
-@code{ gnatreg -r WIN32ADA}
-
-@node CONSOLE and WINDOWS subsystems
-@section CONSOLE and WINDOWS subsystems
-@cindex CONSOLE Subsystem
-@cindex WINDOWS Subsystem
-@cindex -mwindows
-
-@noindent
-Under Windows there is two main subsystems. The @code{CONSOLE} subsystem
-(which is the default subsystem) will always create a console when
-launching the application. This is not something desirable when the
-application has a Windows GUI. To get rid of this console the
-application must be using the @code{WINDOWS} subsystem. To do so
-the @code{-mwindows} linker option must be specified.
-
-@smallexample
-$ gnatmake winprog -largs -mwindows
-@end smallexample
-
-@node Temporary Files
-@section Temporary Files
-@cindex Temporary files
-
-@noindent
-It is possible to control where temporary files gets created by setting
-the TMP environment variable. The file will be created:
-
-@itemize
-@item Under the directory pointed to by the TMP environment variable if
-this directory exists.
-
-@item Under c:\temp, if the TMP environment variable is not set (or not
-pointing to a directory) and if this directory exists.
-
-@item Under the current working directory otherwise.
-@end itemize
-
-@noindent
-This allows you to determine exactly where the temporary
-file will be created. This is particularly useful in networked
-environments where you may not have write access to some
-directories.
-
-@node Mixed-Language Programming on Windows
-@section Mixed-Language Programming on Windows
-
-@noindent
-Developing pure Ada applications on Windows is no different than on
-other GNAT-supported platforms. However, when developing or porting an
-application that contains a mix of Ada and C/C++, the choice of your
-Windows C/C++ development environment conditions your overall
-interoperability strategy.
-
-If you use @code{gcc} to compile the non-Ada part of your application,
-there are no Windows-specific restrictions that affect the overall
-interoperability with your Ada code. If you plan to use
-Microsoft tools (e.g. Microsoft Visual C/C++), you should be aware of
-the following limitations:
-
-@itemize @bullet
-@item
-You cannot link your Ada code with an object or library generated with
-Microsoft tools if these use the @code{.tls} section (Thread Local
-Storage section) since the GNAT linker does not yet support this section.
-
-@item
-You cannot link your Ada code with an object or library generated with
-Microsoft tools if these use I/O routines other than those provided in
-the Microsoft DLL: @code{msvcrt.dll}. This is because the GNAT run time
-uses the services of @code{msvcrt.dll} for its I/Os. Use of other I/O
-libraries can cause a conflict with @code{msvcrt.dll} services. For
-instance Visual C++ I/O stream routines conflict with those in
-@code{msvcrt.dll}.
-@end itemize
-
-@noindent
-If you do want to use the Microsoft tools for your non-Ada code and hit one
-of the above limitations, you have two choices:
-
-@enumerate
-@item
-Encapsulate your non Ada code in a DLL to be linked with your Ada
-application. In this case, use the Microsoft or whatever environment to
-build the DLL and use GNAT to build your executable
-(@pxref{Using DLLs with GNAT}).
-
-@item
-Or you can encapsulate your Ada code in a DLL to be linked with the
-other part of your application. In this case, use GNAT to build the DLL
-(@pxref{Building DLLs with GNAT}) and use the Microsoft or whatever
-environment to build your executable.
-@end enumerate
-
-@node Windows Calling Conventions
-@section Windows Calling Conventions
-@findex Stdcall
-@findex APIENTRY
-
-@menu
-* C Calling Convention::
-* Stdcall Calling Convention::
-* DLL Calling Convention::
-@end menu
-
-@noindent
-When a subprogram @code{F} (caller) calls a subprogram @code{G}
-(callee), there are several ways to push @code{G}'s parameters on the
-stack and there are several possible scenarios to clean up the stack
-upon @code{G}'s return. A calling convention is an agreed upon software
-protocol whereby the responsibilities between the caller (@code{F}) and
-the callee (@code{G}) are clearly defined. Several calling conventions
-are available for Windows:
-
-@itemize @bullet
-@item
-@code{C} (Microsoft defined)
-
-@item
-@code{Stdcall} (Microsoft defined)
-
-@item
-@code{DLL} (GNAT specific)
-@end itemize
-
-@node C Calling Convention
-@subsection @code{C} Calling Convention
-
-@noindent
-This is the default calling convention used when interfacing to C/C++
-routines compiled with either @code{gcc} or Microsoft Visual C++.
-
-In the @code{C} calling convention subprogram parameters are pushed on the
-stack by the caller from right to left. The caller itself is in charge of
-cleaning up the stack after the call. In addition, the name of a routine
-with @code{C} calling convention is mangled by adding a leading underscore.
-
-The name to use on the Ada side when importing (or exporting) a routine
-with @code{C} calling convention is the name of the routine. For
-instance the C function:
-
-@smallexample
-int get_val (long);
-@end smallexample
-
-@noindent
-should be imported from Ada as follows:
-
-@smallexample
-@group
-@b{function} Get_Val (V : Interfaces.C.long) @b{return} Interfaces.C.int;
-@b{pragma} Import (C, Get_Val, External_Name => "get_val");
-@end group
-@end smallexample
-
-@noindent
-Note that in this particular case the @code{External_Name} parameter could
-have been omitted since, when missing, this parameter is taken to be the
-name of the Ada entity in lower case. When the @code{Link_Name} parameter
-is missing, as in the above example, this parameter is set to be the
-@code{External_Name} with a leading underscore.
-
-When importing a variable defined in C, you should always use the @code{C}
-calling convention unless the object containing the variable is part of a
-DLL (in which case you should use the @code{DLL} calling convention,
-@pxref{DLL Calling Convention}).
-
-@node Stdcall Calling Convention
-@subsection @code{Stdcall} Calling Convention
-
-@noindent
-This convention, which was the calling convention used for Pascal
-programs, is used by Microsoft for all the routines in the Win32 API for
-efficiency reasons. It must be used to import any routine for which this
-convention was specified.
-
-In the @code{Stdcall} calling convention subprogram parameters are pushed
-on the stack by the caller from right to left. The callee (and not the
-caller) is in charge of cleaning the stack on routine exit. In addition,
-the name of a routine with @code{Stdcall} calling convention is mangled by
-adding a leading underscore (as for the @code{C} calling convention) and a
-trailing @code{@@}@code{@i{nn}}, where @i{nn} is the overall size (in
-bytes) of the parameters passed to the routine.
-
-The name to use on the Ada side when importing a C routine with a
-@code{Stdcall} calling convention is the name of the C routine. The leading
-underscore and trailing @code{@@}@code{@i{nn}} are added automatically by
-the compiler. For instance the Win32 function:
-
-@smallexample
-@b{APIENTRY} int get_val (long);
-@end smallexample
-
-@noindent
-should be imported from Ada as follows:
-
-@smallexample
-@group
-@b{function} Get_Val (V : Interfaces.C.long) @b{return} Interfaces.C.int;
-@b{pragma} Import (Stdcall, Get_Val);
--- @i{On the x86 a long is 4 bytes, so the Link_Name is }"_get_val@@4"
-@end group
-@end smallexample
-
-@noindent
-As for the @code{C} calling convention, when the @code{External_Name}
-parameter is missing, it is taken to be the name of the Ada entity in lower
-case. If instead of writing the above import pragma you write:
-
-@smallexample
-@group
-@b{function} Get_Val (V : Interfaces.C.long) @b{return} Interfaces.C.int;
-@b{pragma} Import (Stdcall, Get_Val, External_Name => "retrieve_val");
-@end group
-@end smallexample
-
-@noindent
-then the imported routine is @code{_retrieve_val@@4}. However, if instead
-of specifying the @code{External_Name} parameter you specify the
-@code{Link_Name} as in the following example:
-
-@smallexample
-@group
-@b{function} Get_Val (V : Interfaces.C.long) @b{return} Interfaces.C.int;
-@b{pragma} Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
-@end group
-@end smallexample
-
-@noindent
-then the imported routine is @code{retrieve_val@@4}, that is, there is no
-trailing underscore but the appropriate @code{@@}@code{@i{nn}} is always
-added at the end of the @code{Link_Name} by the compiler.
-
-@noindent
-Note, that in some special cases a DLL's entry point name lacks a trailing
-@code{@@}@code{@i{nn}} while the exported name generated for a call has it.
-The @code{gnatdll} tool, which creates the import library for the DLL, is able
-to handle those cases (see the description of the switches in
-@pxref{Using gnatdll} section).
-
-@node DLL Calling Convention
-@subsection @code{DLL} Calling Convention
-
-@noindent
-This convention, which is GNAT-specific, must be used when you want to
-import in Ada a variables defined in a DLL. For functions and procedures
-this convention is equivalent to the @code{Stdcall} convention. As an
-example, if a DLL contains a variable defined as:
-
-@smallexample
-int my_var;
-@end smallexample
-
-@noindent
-then, to access this variable from Ada you should write:
-
-@smallexample
-@group
-My_Var : Interfaces.C.int;
-@b{pragma} Import (DLL, My_Var);
-@end group
-@end smallexample
-
-The remarks concerning the @code{External_Name} and @code{Link_Name}
-parameters given in the previous sections equally apply to the @code{DLL}
-calling convention.
-
-@node Introduction to Dynamic Link Libraries (DLLs)
-@section Introduction to Dynamic Link Libraries (DLLs)
-@findex DLL
-
-@noindent
-A Dynamically Linked Library (DLL) is a library that can be shared by
-several applications running under Windows. A DLL can contain any number of
-routines and variables.
-
-One advantage of DLLs is that you can change and enhance them without
-forcing all the applications that depend on them to be relinked or
-recompiled. However, you should be aware than all calls to DLL routines are
-slower since, as you will understand below, such calls are indirect.
-
-To illustrate the remainder of this section, suppose that an application
-wants to use the services of a DLL @file{API.dll}. To use the services
-provided by @file{API.dll} you must statically link against an import
-library which contains a jump table with an entry for each routine and
-variable exported by the DLL. In the Microsoft world this import library is
-called @file{API.lib}. When using GNAT this import library is called either
-@file{libAPI.a} or @file{libapi.a} (names are case insensitive).
-
-After you have statically linked your application with the import library
-and you run your application, here is what happens:
-
-@enumerate
-@item
-Your application is loaded into memory.
-
-@item
-The DLL @file{API.dll} is mapped into the address space of your
-application. This means that:
-
-@itemize @bullet
-@item
-The DLL will use the stack of the calling thread.
-
-@item
-The DLL will use the virtual address space of the calling process.
-
-@item
-The DLL will allocate memory from the virtual address space of the calling
-process.
-
-@item
-Handles (pointers) can be safely exchanged between routines in the DLL
-routines and routines in the application using the DLL.
-@end itemize
-
-@item
-The entries in the @file{libAPI.a} or @file{API.lib} jump table which is
-part of your application are initialized with the addresses of the routines
-and variables in @file{API.dll}.
-
-@item
-If present in @file{API.dll}, routines @code{DllMain} or
-@code{DllMainCRTStartup} are invoked. These routines typically contain
-the initialization code needed for the well-being of the routines and
-variables exported by the DLL.
-@end enumerate
-
-@noindent
-There is an additional point which is worth mentioning. In the Windows
-world there are two kind of DLLs: relocatable and non-relocatable
-DLLs. Non-relocatable DLLs can only be loaded at a very specific address
-in the target application address space. If the addresses of two
-non-relocatable DLLs overlap and these happen to be used by the same
-application, a conflict will occur and the application will run
-incorrectly. Hence, when possible, it is always preferable to use and
-build relocatable DLLs. Both relocatable and non-relocatable DLLs are
-supported by GNAT.
-
-As a side note, an interesting difference between Microsoft DLLs and
-Unix shared libraries, is the fact that on most Unix systems all public
-routines are exported by default in a Unix shared library, while under
-Windows the exported routines must be listed explicitly in a definition
-file (@pxref{The Definition File}).
-
-@node Using DLLs with GNAT
-@section Using DLLs with GNAT
-
-@menu
-* Creating an Ada Spec for the DLL Services::
-* Creating an Import Library::
-@end menu
-
-@noindent
-To use the services of a DLL, say @file{API.dll}, in your Ada application
-you must have:
-
-@enumerate
-@item
-The Ada spec for the routines and/or variables you want to access in
-@file{API.dll}. If not available this Ada spec must be built from the C/C++
-header files provided with the DLL.
-
-@item
-The import library (@file{libAPI.a} or @file{API.lib}). As previously
-mentioned an import library is a statically linked library containing the
-import table which will be filled at load time to point to the actual
-@file{API.dll} routines. Sometimes you don't have an import library for the
-DLL you want to use. The following sections will explain how to build one.
-
-@item
-The actual DLL, @file{API.dll}.
-@end enumerate
-
-@noindent
-Once you have all the above, to compile an Ada application that uses the
-services of @file{API.dll} and whose main subprogram is @code{My_Ada_App},
-you simply issue the command
-
-@smallexample
-$ gnatmake my_ada_app -largs -lAPI
-@end smallexample
-
-@noindent
-The argument @code{-largs -lAPI} at the end of the @code{gnatmake} command
-tells the GNAT linker to look first for a library named @file{API.lib}
-(Microsoft-style name) and if not found for a library named @file{libAPI.a}
-(GNAT-style name). Note that if the Ada package spec for @file{API.dll}
-contains the following pragma
-
-@smallexample
-@b{pragma} Linker_Options ("-lAPI");
-@end smallexample
-
-@noindent
-you do not have to add @code{-largs -lAPI} at the end of the @code{gnatmake}
-command.
-
-If any one of the items above is missing you will have to create it
-yourself. The following sections explain how to do so using as an
-example a fictitious DLL called @file{API.dll}.
-
-@node Creating an Ada Spec for the DLL Services
-@subsection Creating an Ada Spec for the DLL Services
-
-@noindent
-A DLL typically comes with a C/C++ header file which provides the
-definitions of the routines and variables exported by the DLL. The Ada
-equivalent of this header file is a package spec that contains definitions
-for the imported entities. If the DLL you intend to use does not come with
-an Ada spec you have to generate one such spec yourself. For example if
-the header file of @file{API.dll} is a file @file{api.h} containing the
-following two definitions:
-
-@smallexample
-@group
-@cartouche
-int some_var;
-int get (char *);
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-then the equivalent Ada spec could be:
-
-@smallexample
-@group
-@cartouche
-@b{with} Interfaces.C.Strings;
-@b{package} API @b{is}
- @b{use} Interfaces;
-
- Some_Var : C.int;
- @b{function} Get (Str : C.Strings.Chars_Ptr) @b{return} C.int;
-
-@b{private}
- @b{pragma} Import (C, Get);
- @b{pragma} Import (DLL, Some_Var);
-@b{end} API;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-Note that a variable is @strong{always imported with a DLL convention}. A
-function can have @code{C}, @code{Stdcall} or @code{DLL} convention. For
-subprograms, the @code{DLL} convention is a synonym of @code{Stdcall}
-(@pxref{Windows Calling Conventions}).
-
-@node Creating an Import Library
-@subsection Creating an Import Library
-@cindex Import library
-
-@menu
-* The Definition File::
-* GNAT-Style Import Library::
-* Microsoft-Style Import Library::
-@end menu
-
-@noindent
-If a Microsoft-style import library @file{API.lib} or a GNAT-style
-import library @file{libAPI.a} is available with @file{API.dll} you
-can skip this section. Otherwise read on.
-
-@node The Definition File
-@subsubsection The Definition File
-@cindex Definition file
-@findex .def
-
-@noindent
-As previously mentioned, and unlike Unix systems, the list of symbols
-that are exported from a DLL must be provided explicitly in Windows.
-The main goal of a definition file is precisely that: list the symbols
-exported by a DLL. A definition file (usually a file with a @code{.def}
-suffix) has the following structure:
-
-@smallexample
-@group
-@cartouche
-[LIBRARY @i{name}]
-[DESCRIPTION @i{string}]
-EXPORTS
- @i{symbol1}
- @i{symbol2}
- ...
-@end cartouche
-@end group
-@end smallexample
-
-@table @code
-@item LIBRARY @i{name}
-This section, which is optional, gives the name of the DLL.
-
-@item DESCRIPTION @i{string}
-This section, which is optional, gives a description string that will be
-embedded in the import library.
-
-@item EXPORTS
-This section gives the list of exported symbols (procedures, functions or
-variables). For instance in the case of @file{API.dll} the @code{EXPORTS}
-section of @file{API.def} looks like:
-
-@smallexample
-@group
-@cartouche
-EXPORTS
- some_var
- get
-@end cartouche
-@end group
-@end smallexample
-@end table
-
-@noindent
-Note that you must specify the correct suffix (@code{@@}@code{@i{nn}})
-(@pxref{Windows Calling Conventions}) for a Stdcall
-calling convention function in the exported symbols list.
-
-@noindent
-There can actually be other sections in a definition file, but these
-sections are not relevant to the discussion at hand.
-
-@node GNAT-Style Import Library
-@subsubsection GNAT-Style Import Library
-
-@noindent
-To create a static import library from @file{API.dll} with the GNAT tools
-you should proceed as follows:
-
-@enumerate
-@item
-Create the definition file @file{API.def} (@pxref{The Definition File}).
-For that use the @code{dll2def} tool as follows:
-
-@smallexample
-$ dll2def API.dll > API.def
-@end smallexample
-
-@noindent
-@code{dll2def} is a very simple tool: it takes as input a DLL and prints
-to standard output the list of entry points in the DLL. Note that if
-some routines in the DLL have the @code{Stdcall} convention
-(@pxref{Windows Calling Conventions}) with stripped @code{@@}@i{nn}
-suffix then you'll have to edit @file{api.def} to add it.
-
-@noindent
-Here are some hints to find the right @code{@@}@i{nn} suffix.
-
-@enumerate
-@item
-If you have the Microsoft import library (.lib), it is possible to get
-the right symbols by using Microsoft @code{dumpbin} tool (see the
-corresponding Microsoft documentation for further details).
-
-@smallexample
-$ dumpbin /exports api.lib
-@end smallexample
-
-@item
-If you have a message about a missing symbol at link time the compiler
-tells you what symbol is expected. You just have to go back to the
-definition file and add the right suffix.
-@end enumerate
-
-@item
-Build the import library @code{libAPI.a}, using @code{gnatdll}
-(@pxref{Using gnatdll}) as follows:
-
-@smallexample
-$ gnatdll -e API.def -d API.dll
-@end smallexample
-
-@noindent
-@code{gnatdll} takes as input a definition file @file{API.def} and the
-name of the DLL containing the services listed in the definition file
-@file{API.dll}. The name of the static import library generated is
-computed from the name of the definition file as follows: if the
-definition file name is @i{xyz}@code{.def}, the import library name will
-be @code{lib}@i{xyz}@code{.a}. Note that in the previous example option
-@code{-e} could have been removed because the name of the definition
-file (before the "@code{.def}" suffix) is the same as the name of the
-DLL (@pxref{Using gnatdll} for more information about @code{gnatdll}).
-@end enumerate
-
-@node Microsoft-Style Import Library
-@subsubsection Microsoft-Style Import Library
-
-@noindent
-With GNAT you can either use a GNAT-style or Microsoft-style import
-library. A Microsoft import library is needed only if you plan to make an
-Ada DLL available to applications developed with Microsoft
-tools (@pxref{Mixed-Language Programming on Windows}).
-
-To create a Microsoft-style import library for @file{API.dll} you
-should proceed as follows:
-
-@enumerate
-@item
-Create the definition file @file{API.def} from the DLL. For this use either
-the @code{dll2def} tool as described above or the Microsoft @code{dumpbin}
-tool (see the corresponding Microsoft documentation for further details).
-
-@item
-Build the actual import library using Microsoft's @code{lib} utility:
-
-@smallexample
-$ lib -machine:IX86 -def:API.def -out:API.lib
-@end smallexample
-
-@noindent
-If you use the above command the definition file @file{API.def} must
-contain a line giving the name of the DLL:
-
-@smallexample
-LIBRARY "API"
-@end smallexample
-
-@noindent
-See the Microsoft documentation for further details about the usage of
-@code{lib}.
-@end enumerate
-
-@node Building DLLs with GNAT
-@section Building DLLs with GNAT
-@cindex DLLs, building
-
-@menu
-* Limitations When Using Ada DLLs from Ada::
-* Exporting Ada Entities::
-* Ada DLLs and Elaboration::
-* Ada DLLs and Finalization::
-* Creating a Spec for Ada DLLs::
-* Creating the Definition File::
-* Using gnatdll::
-@end menu
-
-@noindent
-This section explains how to build DLLs containing Ada code. These DLLs
-will be referred to as Ada DLLs in the remainder of this section.
-
-The steps required to build an Ada DLL that is to be used by Ada as well as
-non-Ada applications are as follows:
-
-@enumerate
-@item
-You need to mark each Ada @i{entity} exported by the DLL with a @code{C} or
-@code{Stdcall} calling convention to avoid any Ada name mangling for the
-entities exported by the DLL (@pxref{Exporting Ada Entities}). You can
-skip this step if you plan to use the Ada DLL only from Ada applications.
-
-@item
-Your Ada code must export an initialization routine which calls the routine
-@code{adainit} generated by @code{gnatbind} to perform the elaboration of
-the Ada code in the DLL (@pxref{Ada DLLs and Elaboration}). The initialization
-routine exported by the Ada DLL must be invoked by the clients of the DLL
-to initialize the DLL.
-
-@item
-When useful, the DLL should also export a finalization routine which calls
-routine @code{adafinal} generated by @code{gnatbind} to perform the
-finalization of the Ada code in the DLL (@pxref{Ada DLLs and Finalization}).
-The finalization routine exported by the Ada DLL must be invoked by the
-clients of the DLL when the DLL services are no further needed.
-
-@item
-You must provide a spec for the services exported by the Ada DLL in each
-of the programming languages to which you plan to make the DLL available.
-
-@item
-You must provide a definition file listing the exported entities
-(@pxref{The Definition File}).
-
-@item
-Finally you must use @code{gnatdll} to produce the DLL and the import
-library (@pxref{Using gnatdll}).
-@end enumerate
-
-@node Limitations When Using Ada DLLs from Ada
-@subsection Limitations When Using Ada DLLs from Ada
-
-@noindent
-When using Ada DLLs from Ada applications there is a limitation users
-should be aware of. Because on Windows the GNAT run time is not in a DLL of
-its own, each Ada DLL includes a part of the GNAT run time. Specifically,
-each Ada DLL includes the services of the GNAT run time that are necessary
-to the Ada code inside the DLL. As a result, when an Ada program uses an
-Ada DLL there are two independent GNAT run times: one in the Ada DLL and
-one in the main program.
-
-It is therefore not possible to exchange GNAT run-time objects between the
-Ada DLL and the main Ada program. Example of GNAT run-time objects are file
-handles (e.g. @code{Text_IO.File_Type}), tasks types, protected objects
-types, etc.
-
-It is completely safe to exchange plain elementary, array or record types,
-Windows object handles, etc.
-
-@node Exporting Ada Entities
-@subsection Exporting Ada Entities
-@cindex Export table
-
-@noindent
-Building a DLL is a way to encapsulate a set of services usable from any
-application. As a result, the Ada entities exported by a DLL should be
-exported with the @code{C} or @code{Stdcall} calling conventions to avoid
-any Ada name mangling. Please note that the @code{Stdcall} convention
-should only be used for subprograms, not for variables. As an example here
-is an Ada package @code{API}, spec and body, exporting two procedures, a
-function, and a variable:
-
-@smallexample
-@group
-@cartouche
-@b{with} Interfaces.C; @b{use} Interfaces;
-@b{package} API @b{is}
- Count : C.int := 0;
- @b{function} Factorial (Val : C.int) @b{return} C.int;
-
- @b{procedure} Initialize_API;
- @b{procedure} Finalize_API;
- -- @i{Initialization & Finalization routines. More in the next section.}
-@b{private}
- @b{pragma} Export (C, Initialize_API);
- @b{pragma} Export (C, Finalize_API);
- @b{pragma} Export (C, Count);
- @b{pragma} Export (C, Factorial);
-@b{end} API;
-@end cartouche
-@end group
-@end smallexample
-
-@smallexample
-@group
-@cartouche
-@b{package body} API @b{is}
- @b{function} Factorial (Val : C.int) @b{return} C.int @b{is}
- Fact : C.int := 1;
- @b{begin}
- Count := Count + 1;
- @b{for} K @b{in} 1 .. Val @b{loop}
- Fact := Fact * K;
- @b{end loop};
- @b{return} Fact;
- @b{end} Factorial;
-
- @b{procedure} Initialize_API @b{is}
- @b{procedure} Adainit;
- @b{pragma} Import (C, Adainit);
- @b{begin}
- Adainit;
- @b{end} Initialize_API;
-
- @b{procedure} Finalize_API @b{is}
- @b{procedure} Adafinal;
- @b{pragma} Import (C, Adafinal);
- @b{begin}
- Adafinal;
- @b{end} Finalize_API;
-@b{end} API;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-If the Ada DLL you are building will only be used by Ada applications
-you do not have to export Ada entities with a @code{C} or @code{Stdcall}
-convention. As an example, the previous package could be written as
-follows:
-
-@smallexample
-@group
-@cartouche
-@b{package} API @b{is}
- Count : Integer := 0;
- @b{function} Factorial (Val : Integer) @b{return} Integer;
-
- @b{procedure} Initialize_API;
- @b{procedure} Finalize_API;
- -- @i{Initialization and Finalization routines.}
-@b{end} API;
-@end cartouche
-@end group
-@end smallexample
-
-@smallexample
-@group
-@cartouche
-@b{package body} API @b{is}
- @b{function} Factorial (Val : Integer) @b{return} Integer @b{is}
- Fact : Integer := 1;
- @b{begin}
- Count := Count + 1;
- @b{for} K @b{in} 1 .. Val @b{loop}
- Fact := Fact * K;
- @b{end loop};
- @b{return} Fact;
- @b{end} Factorial;
-
- ...
- -- @i{The remainder of this package body is unchanged.}
-@b{end} API;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-Note that if you do not export the Ada entities with a @code{C} or
-@code{Stdcall} convention you will have to provide the mangled Ada names
-in the definition file of the Ada DLL
-(@pxref{Creating the Definition File}).
-
-@node Ada DLLs and Elaboration
-@subsection Ada DLLs and Elaboration
-@cindex DLLs and elaboration
-
-@noindent
-The DLL that you are building contains your Ada code as well as all the
-routines in the Ada library that are needed by it. The first thing a
-user of your DLL must do is elaborate the Ada code
-(@pxref{Elaboration Order Handling in GNAT}).
-
-To achieve this you must export an initialization routine
-(@code{Initialize_API} in the previous example), which must be invoked
-before using any of the DLL services. This elaboration routine must call
-the Ada elaboration routine @code{adainit} generated by the GNAT binder
-(@pxref{Binding with Non-Ada Main Programs}). See the body of
-@code{Initialize_Api} for an example. Note that the GNAT binder is
-automatically invoked during the DLL build process by the @code{gnatdll}
-tool (@pxref{Using gnatdll}).
-
-When a DLL is loaded, Windows systematically invokes a routine called
-@code{DllMain}. It would therefore be possible to call @code{adainit}
-directly from @code{DllMain} without having to provide an explicit
-initialization routine. Unfortunately, it is not possible to call
-@code{adainit} from the @code{DllMain} if your program has library level
-tasks because access to the @code{DllMain} entry point is serialized by
-the system (that is, only a single thread can execute "through" it at a
-time), which means that the GNAT run time will deadlock waiting for the
-newly created task to complete its initialization.
-
-@node Ada DLLs and Finalization
-@subsection Ada DLLs and Finalization
-@cindex DLLs and finalization
-
-@noindent
-When the services of an Ada DLL are no longer needed, the client code should
-invoke the DLL finalization routine, if available. The DLL finalization
-routine is in charge of releasing all resources acquired by the DLL. In the
-case of the Ada code contained in the DLL, this is achieved by calling
-routine @code{adafinal} generated by the GNAT binder
-(@pxref{Binding with Non-Ada Main Programs}).
-See the body of @code{Finalize_Api} for an
-example. As already pointed out the GNAT binder is automatically invoked
-during the DLL build process by the @code{gnatdll} tool
-(@pxref{Using gnatdll}).
-
-@code{-g}
-@cindex @code{-g} (@code{gnatdll})
-@*
-Generate debugging information. This information is stored in the object
-file and copied from there to the final DLL file by the linker,
-where it can be read by the debugger. You must use the
-@code{-g} switch if you plan on using the debugger or the symbolic
-stack traceback.
-
-@node Creating a Spec for Ada DLLs
-@subsection Creating a Spec for Ada DLLs
-
-@noindent
-To use the services exported by the Ada DLL from another programming
-language (e.g. C), you have to translate the specs of the exported Ada
-entities in that language. For instance in the case of @code{API.dll},
-the corresponding C header file could look like:
-
-@smallexample
-@group
-@cartouche
-extern int *__imp__count;
-#define count (*__imp__count)
-int factorial (int);
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-It is important to understand that when building an Ada DLL to be used by
-other Ada applications, you need two different specs for the packages
-contained in the DLL: one for building the DLL and the other for using
-the DLL. This is because the @code{DLL} calling convention is needed to
-use a variable defined in a DLL, but when building the DLL, the variable
-must have either the @code{Ada} or @code{C} calling convention. As an
-example consider a DLL comprising the following package @code{API}:
-
-@smallexample
-@group
-@cartouche
-@b{package} API @b{is}
- Count : Integer := 0;
- ...
- -- @i{Remainder of the package omitted.}
-@b{end} API;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-After producing a DLL containing package @code{API}, the spec that
-must be used to import @code{API.Count} from Ada code outside of the
-DLL is:
-
-@smallexample
-@group
-@cartouche
-@b{package} API @b{is}
- Count : Integer;
- @b{pragma} Import (DLL, Count);
-@b{end} API;
-@end cartouche
-@end group
-@end smallexample
-
-@node Creating the Definition File
-@subsection Creating the Definition File
-
-@noindent
-The definition file is the last file needed to build the DLL. It lists
-the exported symbols. As an example, the definition file for a DLL
-containing only package @code{API} (where all the entities are exported
-with a @code{C} calling convention) is:
-
-@smallexample
-@group
-@cartouche
-EXPORTS
- count
- factorial
- finalize_api
- initialize_api
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-If the @code{C} calling convention is missing from package @code{API},
-then the definition file contains the mangled Ada names of the above
-entities, which in this case are:
-
-@smallexample
-@group
-@cartouche
-EXPORTS
- api__count
- api__factorial
- api__finalize_api
- api__initialize_api
-@end cartouche
-@end group
-@end smallexample
-
-@node Using gnatdll
-@subsection Using @code{gnatdll}
-@findex gnatdll
-
-@menu
-* gnatdll Example::
-* gnatdll behind the Scenes::
-* Using dlltool::
-@end menu
-
-@noindent
-@code{gnatdll} is a tool to automate the DLL build process once all the Ada
-and non-Ada sources that make up your DLL have been compiled.
-@code{gnatdll} is actually in charge of two distinct tasks: build the
-static import library for the DLL and the actual DLL. The form of the
-@code{gnatdll} command is
-
-@smallexample
-@cartouche
-$ gnatdll [@var{switches}] @var{list-of-files} [-largs @var{opts}]
-@end cartouche
-@end smallexample
-
-@noindent
-where @i{list-of-files} is a list of ALI and object files. The object
-file list must be the exact list of objects corresponding to the non-Ada
-sources whose services are to be included in the DLL. The ALI file list
-must be the exact list of ALI files for the corresponding Ada sources
-whose services are to be included in the DLL. If @i{list-of-files} is
-missing, only the static import library is generated.
-
-@noindent
-You may specify any of the following switches to @code{gnatdll}:
-
-@table @code
-@item -a[@var{address}]
-@cindex @code{-a} (@code{gnatdll})
-Build a non-relocatable DLL at @var{address}. If @var{address} is not
-specified the default address @var{0x11000000} will be used. By default,
-when this switch is missing, @code{gnatdll} builds relocatable DLL. We
-advise the reader to build relocatable DLL.
-
-@item -b @var{address}
-@cindex @code{-b} (@code{gnatdll})
-Set the relocatable DLL base address. By default the address is
-@var{0x11000000}.
-
-@item -d @var{dllfile}
-@cindex @code{-d} (@code{gnatdll})
-@var{dllfile} is the name of the DLL. This switch must be present for
-@code{gnatdll} to do anything. The name of the generated import library is
-obtained algorithmically from @var{dllfile} as shown in the following
-example: if @var{dllfile} is @code{xyz.dll}, the import library name is
-@code{libxyz.a}. The name of the definition file to use (if not specified
-by option @code{-e}) is obtained algorithmically from @var{dllfile} as shown in
-the following example: if @var{dllfile} is @code{xyz.dll}, the definition
-file used is @code{xyz.def}.
-
-@item -e @var{deffile}
-@cindex @code{-e} (@code{gnatdll})
-@var{deffile} is the name of the definition file.
-
-@item -h
-@cindex @code{-h} (@code{gnatdll})
-Help mode. Displays @code{gnatdll} switch usage information.
-
-@item -Idir
-Direct @code{gnatdll} to search the @var{dir} directory for source and
-object files needed to build the DLL.
-(@pxref{Search Paths and the Run-Time Library (RTL)}).
-
-@item -k
-Removes the @code{@@}@i{nn} suffix from the import library's exported
-names. You must specified this option if you want to use a
-@code{Stdcall} function in a DLL for which the @code{@@}@i{nn} suffix
-has been removed. This is the case for most of the Windows NT DLL for
-example. This option has no effect when @code{-n} option is specified.
-
-@item -l @var{file}
-@cindex @code{-l} (@code{gnatdll})
-The list of ALI and object files used to build the DLL are listed in
-@var{file}, instead of being given in the command line. Each line in
-@var{file} contains the name of an ALI or object file.
-
-@item -n
-@cindex @code{-n} (@code{gnatdll})
-No Import. Do not create the import library.
-
-@item -q
-@cindex @code{-q} (@code{gnatdll})
-Quiet mode. Do not display unnecessary messages.
-
-@item -v
-@cindex @code{-v} (@code{gnatdll})
-Verbose mode. Display extra information.
-
-@item -largs @var{opts}
-@cindex @code{-largs} (@code{gnatdll})
-Linker options. Pass @var{opts} to the linker.
-@end table
-
-@node gnatdll Example
-@subsubsection @code{gnatdll} Example
-
-@noindent
-As an example the command to build a relocatable DLL from @file{api.adb}
-once @file{api.adb} has been compiled and @file{api.def} created is
-
-@smallexample
-$ gnatdll -d api.dll api.ali
-@end smallexample
-
-@noindent
-The above command creates two files: @file{libapi.a} (the import
-library) and @file{api.dll} (the actual DLL). If you want to create
-only the DLL, just type:
-
-@smallexample
-$ gnatdll -d api.dll -n api.ali
-@end smallexample
-
-@noindent
-Alternatively if you want to create just the import library, type:
-
-@smallexample
-$ gnatdll -d api.dll
-@end smallexample
-
-@node gnatdll behind the Scenes
-@subsubsection @code{gnatdll} behind the Scenes
-
-@noindent
-This section details the steps involved in creating a DLL. @code{gnatdll}
-does these steps for you. Unless you are interested in understanding what
-goes on behind the scenes, you should skip this section.
-
-We use the previous example of a DLL containing the Ada package @code{API},
-to illustrate the steps necessary to build a DLL. The starting point is a
-set of objects that will make up the DLL and the corresponding ALI
-files. In the case of this example this means that @file{api.o} and
-@file{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
-the following:
-
-@enumerate
-@item
-@code{gnatdll} builds the base file (@file{api.base}). A base file gives
-the information necessary to generate relocation information for the
-DLL.
-
-@smallexample
-@group
-$ gnatbind -n api
-$ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
-@end group
-@end smallexample
-
-@noindent
-In addition to the base file, the @code{gnatlink} command generates an
-output file @file{api.jnk} which can be discarded. The @code{-mdll} switch
-asks @code{gnatlink} to generate the routines @code{DllMain} and
-@code{DllMainCRTStartup} that are called by the Windows loader when the DLL
-is loaded into memory.
-
-@item
-@code{gnatdll} uses @code{dlltool} (@pxref{Using dlltool}) to build the
-export table (@file{api.exp}). The export table contains the relocation
-information in a form which can be used during the final link to ensure
-that the Windows loader is able to place the DLL anywhere in memory.
-
-@smallexample
-@group
-$ dlltool --dllname api.dll --def api.def --base-file api.base \
- --output-exp api.exp
-@end group
-@end smallexample
-
-@item
-@code{gnatdll} builds the base file using the new export table. Note that
-@code{gnatbind} must be called once again since the binder generated file
-has been deleted during the previous call to @code{gnatlink}.
-
-@smallexample
-@group
-$ gnatbind -n api
-$ gnatlink api -o api.jnk api.exp -mdll
- -Wl,--base-file,api.base
-@end group
-@end smallexample
-
-@item
-@code{gnatdll} builds the new export table using the new base file and
-generates the DLL import library @file{libAPI.a}.
-
-@smallexample
-@group
-$ dlltool --dllname api.dll --def api.def --base-file api.base \
- --output-exp api.exp --output-lib libAPI.a
-@end group
-@end smallexample
-
-@item
-Finally @code{gnatdll} builds the relocatable DLL using the final export
-table.
-
-@smallexample
-@group
-$ gnatbind -n api
-$ gnatlink api api.exp -o api.dll -mdll
-@end group
-@end smallexample
-@end enumerate
-
-@node Using dlltool
-@subsubsection Using @code{dlltool}
-
-@noindent
-@code{dlltool} is the low-level tool used by @code{gnatdll} to build
-DLLs and static import libraries. This section summarizes the most
-common @code{dlltool} switches. The form of the @code{dlltool} command
-is
-
-@smallexample
-$ dlltool [@var{switches}]
-@end smallexample
-
-@noindent
-@code{dlltool} switches include:
-
-@table @code
-@item --base-file @var{basefile}
-Read the base file @var{basefile} generated by the linker. This switch
-is used to create a relocatable DLL.
-
-@item --def @var{deffile}
-Read the definition file.
-
-@item --dllname @var{name}
-Gives the name of the DLL. This switch is used to embed the name of the
-DLL in the static import library generated by @code{dlltool} with switch
-@code{--output-lib}.
-
-@item -k
-Kill @code{@@}@i{nn} from exported names
-(@pxref{Windows Calling Conventions}
-for a discussion about @code{Stdcall}-style symbols.
-
-@item --help
-Prints the @code{dlltool} switches with a concise description.
-
-@item --output-exp @var{exportfile}
-Generate an export file @var{exportfile}. The export file contains the
-export table (list of symbols in the DLL) and is used to create the DLL.
-
-@item --output-lib @i{libfile}
-Generate a static import library @var{libfile}.
-
-@item -v
-Verbose mode.
-
-@item --as @i{assembler-name}
-Use @i{assembler-name} as the assembler. The default is @code{as}.
-@end table
-
-@node GNAT and Windows Resources
-@section GNAT and Windows Resources
-@cindex Resources, windows
-
-@menu
-* Building Resources::
-* Compiling Resources::
-* Using Resources::
-* Limitations::
-@end menu
-
-@noindent
-Resources are an easy way to add Windows specific objects to your
-application. The objects that can be added as resources include:
-
-@itemize @bullet
-@item
-menus
-
-@item
-accelerators
-
-@item
-dialog boxes
-
-@item
-string tables
-
-@item
-bitmaps
-
-@item
-cursors
-
-@item
-icons
-
-@item
-fonts
-@end itemize
-
-@noindent
-This section explains how to build, compile and use resources.
-
-@node Building Resources
-@subsection Building Resources
-@cindex Resources, building
-
-@noindent
-A resource file is an ASCII file. By convention resource files have an
-@file{.rc} extension.
-The easiest way to build a resource file is to use Microsoft tools
-such as @code{imagedit.exe} to build bitmaps, icons and cursors and
-@code{dlgedit.exe} to build dialogs.
-It is always possible to build an @file{.rc} file yourself by writing a
-resource script.
-
-It is not our objective to explain how to write a resource file. A
-complete description of the resource script language can be found in the
-Microsoft documentation.
-
-@node Compiling Resources
-@subsection Compiling Resources
-@findex rc
-@findex rcl
-@findex res2coff
-@cindex Resources, compiling
-
-@noindent
-This section describes how to build a GNAT-compatible (COFF) object file
-containing the resources. This is done using the Resource Compiler
-@code{rcl} as follows:
-
-@smallexample
-$ rcl -i myres.rc -o myres.o
-@end smallexample
-
-@noindent
-By default @code{rcl} will run @code{gcc} to preprocess the @file{.rc}
-file. You can specify an alternate preprocessor (usually named
-@file{cpp.exe}) using the @code{rcl} @code{-cpp} parameter. A list of
-all possible options may be obtained by entering the command @code{rcl}
-with no parameters.
-
-It is also possible to use the Microsoft resource compiler @code{rc.exe}
-to produce a @file{.res} file (binary resource file). See the
-corresponding Microsoft documentation for further details. In this case
-you need to use @code{res2coff} to translate the @file{.res} file to a
-GNAT-compatible object file as follows:
-
-@smallexample
-$ res2coff -i myres.res -o myres.o
-@end smallexample
-
-@node Using Resources
-@subsection Using Resources
-@cindex Resources, using
-
-@noindent
-To include the resource file in your program just add the
-GNAT-compatible object file for the resource(s) to the linker
-arguments. With @code{gnatmake} this is done by using the @code{-largs}
-option:
-
-@smallexample
-$ gnatmake myprog -largs myres.o
-@end smallexample
-
-@node Limitations
-@subsection Limitations
-@cindex Resources, limitations
-
-@noindent
-In this section we describe the current limitations together with
-suggestions for workarounds.
-
-@itemize @bullet
-@item
-@code{rcl} does not handle the @code{RCINCLUDE} directive.
-@*
-Workaround: replace @code{RCINCLUDE} by an @code{#include} directive.
-
-@item
-@code{rcl} does not handle the brackets as block delimiters.
-@*
-Workaround: replace character '@{' by @code{BEGIN} and '@}' by
-@code{END}. Note that Microsoft's @code{rc} handles both forms of block
-delimiters.
-
-@item
-@code{rcl} does not handle @code{TypeLib} resources. This type of
-resource is used to build COM, DCOM or ActiveX objects.
-@*
-Workaround: use @code{rc}, the Microsoft resource compiler.
-
-@item
-It is not possible to use @code{strip} to remove the debugging symbols
-from a program with resources.
-@*
-Workaround: use linker option @code{-s} to strip debugging symbols from
-the final executable.
-@end itemize
-
-@node Debugging a DLL
-@section Debugging a DLL
-@cindex DLL debugging
-
-@menu
-* The Program and the DLL Are Built with GCC/GNAT::
-* The Program Is Built with Some Foreign Tools and the DLL Is Built with GCC/GNAT::
-@end menu
-
-@noindent
-Debugging a DLL is similar to debugging a standard program. But
-we have to deal with two different executable parts: the DLL and the
-program that uses it. We have the following four possibilities:
-
-@enumerate 1
-@item
-The program and the DLL are built with @code{GCC/GNAT}.
-@item
-The program is built with foreign tools and the DLL is built with
-@code{GCC/GNAT}.
-@item
-The program is built with @code{GCC/GNAT} and the DLL is built with
-foreign tools.
-@item
-@end enumerate
-
-@noindent
-In this section we address only cases one and two above.
-There is no point in trying to debug
-a DLL with @code{GNU/GDB}, if there is no GDB-compatible debugging
-information in it. To do so you must use a debugger compatible with the
-tools suite used to build the DLL.
-
-@node The Program and the DLL Are Built with GCC/GNAT
-@subsection The Program and the DLL Are Built with GCC/GNAT
-
-@noindent
-This is the simplest case. Both the DLL and the program have @code{GDB}
-compatible debugging information. It is then possible to break anywhere in
-the process. Let's suppose here that the main procedure is named
-@code{ada_main} and that in the DLL there is an entry point named
-@code{ada_dll}.
-
-@noindent
-The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) and
-program must have been built with the debugging information (see GNAT -g
-switch). Here are the step-by-step instructions for debugging it:
-
-@enumerate 1
-@item Launch @code{GDB} on the main program.
-
-@smallexample
-$ gdb -nw ada_main
-@end smallexample
-
-@item Break on the main procedure and run the program.
-
-@smallexample
-(gdb) break ada_main
-(gdb) run
-@end smallexample
-
-@noindent
-This step is required to be able to set a breakpoint inside the DLL. As long
-as the program is not run, the DLL is not loaded. This has the
-consequence that the DLL debugging information is also not loaded, so it is not
-possible to set a breakpoint in the DLL.
-
-@item Set a breakpoint inside the DLL
-
-@smallexample
-(gdb) break ada_dll
-(gdb) run
-@end smallexample
-
-@end enumerate
-
-@noindent
-At this stage a breakpoint is set inside the DLL. From there on
-you can use the standard approach to debug the whole program
-(@pxref{Running and Debugging Ada Programs}).
-
-@node The Program Is Built with Some Foreign Tools and the DLL Is Built with GCC/GNAT
-@subsection The Program Is Built with Some Foreign Tools and the DLL Is Built with GCC/GNAT
-
-@menu
-* Debugging the DLL Directly::
-* Attaching to a Running Process::
-@end menu
-
-@noindent
-In this case things are slightly more complex because it is not possible to
-start the main program and then break at the beginning to load the DLL and the
-associated DLL debugging information. It is not possible to break at the
-beginning of the program because there is no @code{GDB} debugging information,
-and therefore there is no direct way of getting initial control. This
-section addresses this issue by describing some methods that can be used
-to break somewhere in the DLL to debug it.
-
-@noindent
-First suppose that the main procedure is named @code{main} (this is for
-example some C code built with Microsoft Visual C) and that there is a
-DLL named @code{test.dll} containing an Ada entry point named
-@code{ada_dll}.
-
-@noindent
-The DLL (@pxref{Introduction to Dynamic Link Libraries (DLLs)}) must have
-been built with debugging information (see GNAT -g option).
-
-@node Debugging the DLL Directly
-@subsubsection Debugging the DLL Directly
-
-@enumerate 1
-@item
-Launch the debugger on the DLL.
-
-@smallexample
-$ gdb -nw test.dll
-@end smallexample
-
-@item Set a breakpoint on a DLL subroutine.
-
-@smallexample
-(gdb) break ada_dll
-@end smallexample
-
-@item
-Specify the executable file to @code{GDB}.
-
-@smallexample
-(gdb) exec-file main.exe
-@end smallexample
-
-@item
-Run the program.
-
-@smallexample
-(gdb) run
-@end smallexample
-
-@noindent
-This will run the program until it reaches the breakpoint that has been
-set. From that point you can use the standard way to debug a program
-as described in (@pxref{Running and Debugging Ada Programs}).
-
-@end enumerate
-
-@noindent
-It is also possible to debug the DLL by attaching to a running process.
-
-@node Attaching to a Running Process
-@subsubsection Attaching to a Running Process
-@cindex DLL debugging, attach to process
-
-@noindent
-With @code{GDB} it is always possible to debug a running process by
-attaching to it. It is possible to debug a DLL this way. The limitation
-of this approach is that the DLL must run long enough to perform the
-attach operation. It may be useful for instance to insert a time wasting
-loop in the code of the DLL to meet this criterion.
-
-@enumerate 1
-
-@item Launch the main program @file{main.exe}.
-
-@smallexample
-$ main
-@end smallexample
-
-@item Use the Windows @i{Task Manager} to find the process ID. Let's say
-that the process PID for @file{main.exe} is 208.
-
-@item Launch gdb.
-
-@smallexample
-$ gdb -nw
-@end smallexample
-
-@item Attach to the running process to be debugged.
-
-@smallexample
-(gdb) attach 208
-@end smallexample
-
-@item Load the process debugging information.
-
-@smallexample
-(gdb) symbol-file main.exe
-@end smallexample
-
-@item Break somewhere in the DLL.
-
-@smallexample
-(gdb) break ada_dll
-@end smallexample
-
-@item Continue process execution.
-
-@smallexample
-(gdb) continue
-@end smallexample
-
-@end enumerate
-
-@noindent
-This last step will resume the process execution, and stop at
-the breakpoint we have set. From there you can use the standard
-approach to debug a program as described in
-(@pxref{Running and Debugging Ada Programs}).
-
-@node GNAT and COM/DCOM Objects
-@section GNAT and COM/DCOM Objects
-@findex COM
-@findex DCOM
-
-@noindent
-This section is temporarily left blank.
-
-@ignore
-@reread
-???????????? WE NEED TO DECIDE WHETHER TO DISTRIBUTE IT ??????????????????????
-
-@node gnatreg : Registry Tool for NT
-@section @code{gnatreg} : Registry Tool for NT
-@findex gnatreg
-@cindex Registry
-
-@menu
-* Changing the GNAT compiler to Use::
-* Adding/Changing a Library Path::
-* Removing a Library Path::
-* List Current Configuration::
-@end menu
-
-@noindent
-This tool can be used to switch from one compiler to another and to manage
-the list of directories where GNAT must look to find packages. It is
-also a convenient way to do network installation of GNAT.
-
-The form of the @code{gnatreg} command is
-
-@smallexample
-$ gnatreg [@var{-hqcarf}] parameter
-@end smallexample
-
-@noindent
-Commons options are
-
-@table @code
-
-@item -h
-print a usage message.
-
-@item -q
-quiet/terse - display nothing, just do the job.
-
-@item -f
-force mode - create the registry keys if they do not
-exist. @code{gnatreg} will exit with an error if this option is omitted
-and some registry keys are not setup correctly.
-
-@end table
-
-@subsection Changing the GNAT compiler to use
-
-@smallexample
-$ gnatreg c:\gnatpro
-@end smallexample
-
-@noindent
-This will setup the registry to use the GNAT compiler that has been
-installed under c:\gnatpro. @code{gnatreg} check that this directory contain
-effectively a GNAT compiler. If you want to setup a network installation
-and if GNAT has never been installed on this computer you'll have to use
-the -f option.
-
-@subsection Adding/Changing a library path
-
-@smallexample
-$ gnatreg -a COMPNT=c:\ada\components
-@end smallexample
-
-@noindent
-Add the directory c:\ada\components to the list of standards libraries. When
-running gnatmake the option -Ic:\ada\components is added automatically to the
-command line.
-
-The directory c:\ada\components is associated with the name COMPNT. This
-name will be used to remove the library path.
-
-@subsection Removing a library path
-
-@smallexample
-$ gnatreg -r COMPNT
-@end smallexample
-
-@noindent
-Remove the library path named COMPNT.
-
-@subsection List current configuration
-
-@smallexample
-$ gnatreg -c
-@end smallexample
-
-@noindent
-@code{gnatreg} will display the GNAT and AdaGIDE path used and
-all the standards libraries and their associated names that have been set.
-
-@end ignore
-@end ifset
-
-@ifset vxworks
-@node VxWorks Topics
-@chapter VxWorks Topics
-
-@noindent
-This chapter describes topics that are specific to the GNAT for VxWorks
-configurations.
-
-@menu
-* Kernel Configuration for VxWorks::
-* Kernel Compilation Issues for VxWorks::
-* Handling Relocation Issues for PowerPc Targets::
-* Support for Software Floating Point on PowerPC Processors::
-* Interrupt Handling for VxWorks::
-* Simulating Command Line Arguments for VxWorks::
-* Debugging Issues for VxWorks::
-* Using GNAT from the Tornado 2 Project Facility::
-* Frequently Asked Questions for VxWorks::
-@end menu
-
-@node Kernel Configuration for VxWorks
-@section Kernel Configuration for VxWorks
-
-@noindent
-When configuring your VxWorks kernel we recommend including the target
-shell. If you omit it from the configuration, you may get undefined
-symbols at load time, e.g.
-
-@smallexample
--> ld < hello.exe
-Loading hello.exe
-Undefined symbols:
-mkdir
-@end smallexample
-
-@noindent
-Generally, such undefined symbols are harmless since these are used by
-optional parts of the GNAT run time. However if running your application
-generates a VxWorks exception or illegal instruction, you should reconfigure
-your kernel to resolve these symbols.
-
-@node Kernel Compilation Issues for VxWorks
-@section Kernel Compilation Issues for VxWorks
-
-@noindent
-If you plan to link an Ada module with a Tornado 2 Kernel, follow these steps.
-(Note that these recommendations apply to @file{cygnus-2.7.2-960126},
-shipped with Tornado 2 as the C compiler toolchain.)
-
-@itemize @bullet
-@item
-Compile your Ada module without linking it with the VxWorks Library:
-@smallexample
-gnatmake foo.adb -largs -nostdlib
-@end smallexample
-
-@item
-Edit your makefile and add on the @code{LIBS} line the exact path and name
-of the GCC library file provided with GNAT.
-@smallexample
-LIBS = $(WIND_BASE)/target/lib/libPPC604gnuvx.a \
-/opt/gnu/gnat/lib/gcc-lib/powerpc-wrs-vxworks/2.8.1/libgcc.a
-@end smallexample
-
-@noindent
-To know the exact name and location of this file, type
-@code{<arch>-gcc -print-libgcc-file-name} in a console. Note that this version of GCC is the
-one provided with GNAT.
-@smallexample
-~ >powerpc-wrs-vxworks-gcc -print-libgcc-file-name
-/opt/gnu/gnat/lib/gcc-lib/powerpc-wrs-vxworks/2.8.1/libgcc.a
-@end smallexample
-@end itemize
-
-
-@node Handling Relocation Issues for PowerPc Targets
-@section Handling Relocation Issues for PowerPc Targets
-@cindex Relocation issues for PowerPc VxWorks targets
-@cindex PowerPc VxWorks, relocation issues
-@cindex VxWorks PowerPc, relocation issues
-
-@noindent
-Under certain circumstances, loading a program onto a PowerPC
-board will fail with the message
-@emph{Relocation value does not fit in 24 bits}.
-
-For some background on this issue, please refer to WRS' SPRs
-6040, 20257, and 22767.
-In summary,
-VxWorks on the PowerPC follows the variation of the SVR4 ABI known
-as the Embedded ABI (@emph{EABI}).
-@cindex Embedded ABI (for VxWorks on PowerPc)
-@cindex EABI (for VxWorks on PowerPc)
-In order to save space and time in
-embedded applications, the EABI specifies that the default for
-subprogram calls should be the branch instruction with relative
-addressing using an immediate operand. The immediate operand
-to this instruction (relative address) is 24 bits wide. It
-is sign extended and 2#00# is appended for the last 2 bits (all
-instructions must be on a 4 byte boundary).
-The resulting
-26 bit offset means that the target of the branch must be within
-+/- 32 Mbytes of the relative branch instruction. When VxWorks
-is loading a program it completes the linking phase by
-resolving all of the unresolved references in the object being
-loaded. When one of those references is a relative address in
-a branch instruction, and the linker determines that the target
-is more than 32 Mbytes away from the branch, the error occurs.
-
-This only happens when the BSP is configured to use
-more than 32 MBytes of memory. The VxWorks kernel is loaded into
-low memory addresses, and the error usually occurs when the target
-loader is used (because it loads objects into high memory, and thus
-calls from the program to the VxWorks kernel can be too far).
-@cindex VxWorks kernel (relocation issues on PowerPc)
-
-One way to solve this problem is to use the Tornado
-host loader; this will place programs in low memory, close to the kernel.
-
-Another approach is to make use of the @code{-mlongcall} option to the
-compiler;
-@cindex @code{-mlongcall} (gcc)
-GNAT has incorporated WRS'
-gcc modification that implements this option.
-If a subprogram call is
-compiled with the @code{-mlongcall} option, then the generated code
-constructs an absolute address in a register and uses a branch
-instruction with absolute addressing mode.
-
-Starting with release 3.15, the GNAT runtime libraries that are
-distributed are compiled with the @code{-mlongcall} option. In many
-cases the use of these libraries is sufficient to avoid the
-relocation problem, since it is the runtime library that contains
-calls to the VxWorks kernel that need to span the address space gap.
-If you are using an earlier GNAT release or a manually-built runtime,
-you should recompile the GNAT runtime library with @code{-mlongcall};
-you can use the
-@file{Makefile.adalib} file from the @file{adalib} directory.
-
-Application code may need to be compiled with @code{-mlongcall} if there
-are calls directly to the kernel, the application is very large,
-or in some specialized linking/loading scenarios.
-
-You can compile individual files with @code{-mlongcall} by placing this
-option on the @code{gcc} command line (for brevity we are omitting the
-@code{powerpc-wrs-vxworks-} prefix on the commands shown in this
-paragraph).
-If you provide @code{-mlongcall} as an option for @code{gnatmake}, it will be
-passed to all invocations of @code{gcc} that @code{gnatmake} directly performs.
-Note that one other compilation is made by @code{gnatlink}, on the file created
-by @code{gnatbind} for the elaboration package body
-(see @ref{Binding Using gnatbind}).
-Passing @code{-mlongcall} to @code{gnatlink}, either directly
-on the @code{gnatlink} command line or by including @code{-mlongcall} in the
-@code{-largs} list of @code{gnatmake}, will direct @code{gnatlink} to compile the
-binder file with the @code{-mlongcall} option.
-
-To see the effect of @code{-mlongcall}, consider the following small example:
-
-@smallexample
- procedure Proc is
- procedure Imported_Proc;
- pragma Import (Ada, Imported_Proc);
- begin
- Imported_Proc;
- end;
-@end smallexample
-
-@noindent
-If you compile @code{Proc} with the default options (no @code{-mlongcall}), the following code is generated:
-
-@smallexample
- _ada_proc:
- ...
- bl imported_proc
- ...
-@end smallexample
-
-@noindent
-In contrast, here is the result with the @code{-mlongcall} option:
-
-@smallexample
- _ada_proc:
- ...
- addis 9,0,imported_proc@@ha
- addi 0,9,imported_proc@@l
- mtlr 0
- blrl
- ...
-@end smallexample
-
-
-@node Support for Software Floating Point on PowerPC Processors
-@section Support for Software Floating Point on PowerPC Processors
-
-@noindent
-The PowerPC 860 processor does not have hardware floating-point support.
-In order to build and run GNAT modules properly, you need to install and
-invoke software-emulated floating-point support as follows:
-
-@itemize @bullet
-@item
-At installation time:
-@itemize @bullet
-@item
-Create a file @file{ada_object_path} under the directory
-@file{BASE\lib\gcc-lib\powerpc-wrs-vxworks\2.8.1}
-(by default @file{BASE}=@file{c:\gnatpro})
-containing the following line:
-@smallexample
-rts-soft-float\adalib
-@end smallexample
-
-@item
-Create a file @file{ada_source_path} under the directory
-@file{BASE\lib\gcc-lib\powerpc-wrs-vxworks\2.8.1}
-(by default @file{BASE}=@file{c:\gnatpro})
-containing the following line:
-@smallexample
-rts-soft-float\adainclude
-@end smallexample
-@end itemize
-
-@item
-When using the compiler, specify @option{-msoft-float}
-as a compiler and a linker option, e.g.:
-@smallexample
-$powerpc-wrs-vxworks-gnatmake -msoft-float module -largs -msoft-float
-@end smallexample
-@end itemize
-
-
-@node Interrupt Handling for VxWorks
-@section Interrupt Handling for VxWorks
-
-@noindent
-GNAT offers a range of options for hardware interrupt handling. In rough
-order of latency and lack of restrictions:
-
-@itemize @bullet
-@item Directly vectored interrupt procedure handlers
-@item Directly vectored interrupt procedures that signal a task using
-a suspension object
-@item Ada 95 protected procedure handlers for interrupts
-@item Ada 83 style interrupt entry handlers for interrupts
-@end itemize
-
-@noindent
-In general, the range of possible solutions trades off latency versus
-restrictions in the handler code. Restrictions in direct vectored
-interrupt handlers are documented in the @cite{VxWorks Programmer's Guide}.
-Protected procedure handlers have only the
-restriction that no potentially blocking operations are performed within
-the handler. Interrupt entries have no restrictions. We recommend the
-use of the protected procedure mechanism as providing the best balance
-of these considerations for most applications.
-
-All handler types must explicitly perform any required hardware cleanups,
-such as issuing an end-of-interrupt if necessary.
-
-For VxWorks/AE, applications that handle interrupts must be loaded into
-the kernel protection domain.
-
-@itemize @bullet
-@item Direct Vectored Interrupt Routines
-
-@noindent
-This approach provides the lowest interrupt latency, but has the most
-restrictions on what VxWorks and Ada runtime calls can be made, as well
-as on what Ada entities are accessible to the handler code. Such handlers
-are most useful when there are stringent latency requirements, and very
-little processing is to be performed in the handler. Access to the
-necessary VxWorks routines for setting up such handlers is provided in
-the package @code{Interfaces.VxWorks}.
-
-VxWorks restrictions are described in the @cite{VxWorks Programmer's Manual}.
-Note in particular that floating point context is not automatically saved and
-restored when interrupts are vectored to the handler. If the handler is
-to execute floating point instructions, the statements involved must be
-bracketed by a pair of calls to @code{fppSave} and @code{fppRestore} defined
-in @code{Interfaces.VxWorks}.
-
-In general, it is a good idea to save and restore the handler that was
-installed prior to application startup. The routines @code{intVecGet}
-and @code{intVecSet} are used for this purpose. The Ada handler code
-is installed into the vector table using routine @code{intConnect},
-which generates wrapper code to save and restore registers.
-
-Example:
-
-@smallexample
-with Interfaces.VxWorks; use Interfaces.VxWorks;
-with System;
-
-package P is
-
- Count : Natural := 0;
- pragma Atomic (Count);
-
- -- Interrupt level used by this example
- Level : constant := 1;
-
- -- Be sure to use a reasonable interrupt number for the target
- -- board! Refer to the BSP for details.
- Interrupt : constant := 16#14#;
-
- procedure Handler (Parameter : System.Address);
-
-end P;
-
-package body P is
-
- procedure Handler (parameter : System.Address) is
- S : Status;
- begin
- Count := Count + 1;
- -- Acknowledge interrupt. Not necessary for all interrupts.
- S := sysBusIntAck (intLevel => Level);
- end Handler;
-end P;
-
-with Interfaces.VxWorks; use Interfaces.VxWorks;
-with Ada.Text_IO; use Ada.Text_IO;
-
-with P; use P;
-procedure Useint is
- task T;
-
- S : Status;
-
- task body T is
- begin
- for I in 1 .. 10 loop
- Put_Line ("Generating an interrupt...");
- delay 1.0;
-
- -- Generate interrupt, using interrupt number
- S := sysBusIntGen (Level, Interrupt);
- end loop;
- end T;
-
- -- Save old handler
- Old_Handler : VOIDFUNCPTR := intVecGet (INUM_TO_IVEC (Interrupt));
-begin
- S := intConnect (INUM_TO_IVEC (Interrupt), Handler'Access);
- S := sysIntEnable (intLevel => Level);
-
- for I in 1 .. 10 loop
- delay 2.0;
- Put_Line ("value of count:" & P.Count'Img);
- end loop;
-
- -- Restore previous handler
- S := sysIntDisable (intLevel => Level);
- intVecSet (INUM_TO_IVEC (Interrupt), Old_Handler);
-end Useint;
-@end smallexample
-
-@item Direct Vectored Interrupt Routines
-
-@noindent
-A variation on the direct vectored routine that allows for less restrictive
-handler code is to separate the interrupt processing into two levels.
-
-The first level is the same as in the previous section. Here we perform
-simple hardware actions and signal a task pending on a Suspension_Object
-(defined in @code{Ada.Synchronous_Task_Control}) to perform the more complex
-and time-consuming operations. The routine @code{Set_True} signals a task
-whose body loops and pends on the suspension object using @code{Suspend_Until_True}.
-The suspension object is declared in a scope global to both the handler and
-the task. This approach can be thought of as a slightly higher-level
-application of the @code{C} example using a binary semaphore given in the
-VxWorks Programmer's Manual. In fact, the implementation of
-@code{Ada.Synchronous_Task_Control} is a very thin wrapper around a VxWorks
-binary semaphore.
-
-This approach has a latency between the direct vectored approach and the
-protected procedure approach. There are no restrictions in the Ada task
-code, while the handler code has the same restrictions as any other
-direct interrupt handler.
-
-Example:
-
-@smallexample
-with System;
-package Sem_Handler is
-
- Count : Natural := 0;
- pragma Atomic (Count);
-
- -- Interrupt level used by this example
- Level : constant := 1;
- Interrupt : constant := 16#14#;
-
- -- Interrupt handler providing "immediate" handling
- procedure Handler (Param : System.Address);
-
- -- Task whose body provides "deferred" handling
- task Receiver is
- pragma Interrupt_Priority
- (System.Interrupt_Priority'First + Level + 1);
- end Receiver;
-
-end Sem_Handler;
-
-with Ada.Synchronous_Task_Control; use Ada.Synchronous_Task_Control;
-with Interfaces.VxWorks; use Interfaces.VxWorks;
-package body Sema_Handler is
-
- SO : Suspension_Object;
-
- task body Receiver is
- begin
- loop
- -- Wait for notification from immediate handler
- Suspend_Until_True (SO);
-
- -- Interrupt processing
- Count := Count + 1;
- end loop;
- end Receiver;
-
- procedure Handler (Param : System.Address) is
- S : STATUS;
- begin
- -- Hardware cleanup, if necessary
- S := sysBusIntAck (Level);
-
- -- Signal the task
- Set_True (SO);
- end Handler;
-
-end Sem_Handler;
-
-with Interfaces.VxWorks; use Interfaces.VxWorks;
-with Ada.Text_IO; use Ada.Text_IO;
-with Sem_Handler; use Sem_Handler;
-procedure Useint is
-
- S : STATUS;
-
- task T;
-
- task body T is
- begin
- for I in 1 .. 10 loop
- Put_Line ("Generating an interrupt...");
- delay 1.0;
-
- -- Generate interrupt, using interrupt number
- S := sysBusIntGen (Level, Interrupt);
- end loop;
- end T;
-
- -- Save old handler
- Old_Handler : VOIDFUNCPTR := intVecGet (INUM_TO_IVEC (Interrupt));
-begin
- S := intConnect (INUM_TO_IVEC (Interrupt), Handler'Access);
- S := sysIntEnable (intLevel => Level);
-
- for I in 1 .. 10 loop
- delay 2.0;
- Put_Line ("value of Count:" & Sem_Handler.Count'Img);
- end loop;
-
- -- Restore handler
- S := sysIntDisable (intLevel => Level);
- intVecSet (INUM_TO_IVEC (Interrupt), Old_Handler);
- abort Receiver;
-end Useint;
-@end smallexample
-
-@item Protected Procedure Handlers for Interrupts
-
-@noindent
-This is the recommended default mechanism for interrupt handling.
-It essentially wraps the hybrid handler / task mechanism in a higher-level
-abstraction, and provides a good balance between latency and capability.
-
-Vectored interrupts are designated by their interrupt number, starting from
-0 and ranging to the number of entries in the interrupt vector table - 1.
-
-In the GNAT VxWorks implementation, the following priority mappings are used:
-@itemize @bullet
-@item Normal task priorities are in the range 0 .. 245.
-@item Interrupt priority 246 is used by the GNAT @code{Interrupt_Manager}
-task.
-@item Interrupt priority 247 is used for vectored interrupts
-that do not correspond to those generated via an interrupt controller.
-@item Interrupt priorities 248 .. 255 correspond to PIC interrupt levels
-0 .. 7.
-@item Priority 256 is reserved to the VxWorks kernel.
-@end itemize
-
-Except for reserved priorities, the above are recommendations for setting the
-ceiling priority of a protected object that handles interrupts, or the
-priority of a task with interrupt entries. It's a very good idea to follow
-these recommendations for vectored interrupts that come in through the PIC
-as it will determine the priority of execution of the code in the protected
-procedure or interrupt entry.
-
-No vectored interrupt numbers are reserved in this implementation, because
-dedicated interrupts are determined by the board support package. Obviously,
-careful consideration of the hardware is necessary when handling interrupts.
-The VxWorks BSP for the board is the definitive reference for interrupt
-assignments.
-
-Example:
-
-@smallexample
-package PO_Handler is
-
- -- Interrupt level used by this example
- Level : constant := 1;
-
- Interrupt : constant := 16#14#;
-
- protected Protected_Handler is
- procedure Handler;
- pragma Attach_Handler (Handler, Interrupt);
-
- function Count return Natural;
-
- pragma Interrupt_Priority (248);
- private
- The_Count : Natural := 0;
- end Protected_Handler;
-
-end PO_Handler;
-
-with Interfaces.VxWorks; use Interfaces.VxWorks;
-package body PO_Handler is
-
- protected body Protected_Handler is
-
- procedure Handler is
- S : Status;
- begin
- -- Hardware cleanup if necessary
- S := sysBusIntAck (Level);
-
- -- Interrupt processing
- The_Count := The_Count + 1;
- end Handler;
-
- function Count return Natural is
- begin
- return The_Count;
- end Count;
- end Protected_Handler;
-
-end PO_Handler;
-
-with Interfaces.VxWorks; use Interfaces.VxWorks;
-with Ada.Text_IO; use Ada.Text_IO;
-
-with PO_Handler; use PO_Handler;
-procedure Useint is
-
- task T;
-
- S : STATUS;
-
- task body T is
- begin
- for I in 1 .. 10 loop
- Put_Line ("Generating an interrupt...");
- delay 1.0;
-
- -- Generate interrupt, using interrupt number
- S := sysBusIntGen (Level, Interrupt);
- end loop;
- end T;
-
-begin
- S := sysIntEnable (intLevel => Level);
-
- for I in 1 .. 10 loop
- delay 2.0;
- Put_Line ("value of count:" & Protected_Handler.Count'Img);
- end loop;
-
- S := sysIntDisable (intLevel => Level);
-end Useint;
-@end smallexample
-
-@noindent
-This is obviously significantly higher-level and easier to write than the
-previous examples.
-
-@item Ada 83 Style Interrupt Entries
-
-GNAT provides a full implementation of the Ada 83 interrupt entry mechanism
-for vectored interrupts. However, due to latency issues,
-we only recommend using these for backward compatibility. The comments in
-the previous section regarding interrupt priorities and reserved interrupts
-apply here.
-
-In order to associate an interrupt with an entry, GNAT provides the
-standard Ada convenience routine @code{Ada.Interrupts.Reference}. It is used
-as follows:
-
-@smallexample
-Interrupt_Address : constant System.Address :=
- Ada.Interrupts.Reference (Int_Num);
-
-task Handler_Task is
- pragma Interrupt_Priority (248); -- For instance
- entry Handler;
- for Handler'Address use Interrupt_Address;
-end Handler_Task;
-@end smallexample
-
-@noindent
-Since there is no restriction within an interrupt entry on blocking operations,
-be sure to perform any hardware interrupt controller related operations before
-executing a call that could block within the entry's accept statements. It
-is assumed that interrupt entries are always open alternatives when they
-appear within a selective wait statement. The presence of a guard gives
-undefined behavior.
-
-Example:
-
-@smallexample
-with Ada.Interrupts;
-with System;
-package Task_Handler is
-
- -- Interrupt level used by this example
- Level : constant := 1;
-
- Interrupt : constant := 16#14#;
-
- Interrupt_Address : constant System.Address :=
- Ada.Interrupts.Reference (Int_Num);
-
- task Handler_Task is
- pragma Interrupt_Priority (248); -- For instance
- entry Handler;
- for Handler'Address use Interrupt_Address;
-
- entry Count (Value : out Natural);
- end Handler_Task;
-end Task_Handler;
-
-with Interfaces.VxWorks; use Interfaces.VxWorks;
-package body Task_Handler is
-
- task body Handler_Task is
- The_Count : Natural := 0;
- S : STATUS;
- begin
- loop
- select
- accept Handler do
- -- Hardware cleanup if necessary
- S := sysBusIntAck (Level);
-
- -- Interrupt processing
- The_Count := The_Count + 1;
- end Handler;
- or
- accept Count (Value : out Natural) do
- Value := The_Count;
- end Count;
- end select;
- end loop;
- end Handler_Task;
-
-end Handler_Task;
-
-with Interfaces.VxWorks; use Interfaces.VxWorks;
-with Ada.Text_IO; use Ada.Text_IO;
-
-with Handler_Task; use Handler_Task;
-procedure Useint is
-
- task T;
-
- S : STATUS;
- Current_Count : Natural := 0;
-
- task body T is
- begin
- for I in 1 .. 10 loop
- Put_Line ("Generating an interrupt...");
- delay 1.0;
-
- -- Generate interrupt, using interrupt number
- S := sysBusIntGen (Level, Interrupt);
- end loop;
- end T;
-
-begin
- S := sysIntEnable (intLevel => Level);
-
- for I in 1 .. 10 loop
- delay 2.0;
- Handler_Task.Count (Current_Count);
- Put_Line ("value of count:" & Current_Count'Img);
- end loop;
-
- S := sysIntDisable (intLevel => Level);
- abort Handler_Task;
-end Useint;
-@end smallexample
-@end itemize
-
-
-@node Simulating Command Line Arguments for VxWorks
-@section Simulating Command Line Arguments for VxWorks
-
-@noindent
-The GNAT implementation of @code{Ada.Command_Line} relies on the standard C
-symbols @code{argv} and @code{argc}. The model for invoking "programs" under
-VxWorks does not provide these symbols. The typical method for invoking a
-program under VxWorks is to call the @code{sp} function in order to spawn a
-thread in which to execute a designated function (in GNAT, this is the implicit
-main generated by gnatbind. @code{sp} provides the capability to push a variable
-number of arguments onto the stack when the function is invoked. But this does
-not work for the implicit Ada main, because it has no way of knowing how many
-arguments might be required. This eliminates the possibility to use
-@code{Ada.Command_Line}.
-
-One way to solve this problem is to define symbols in the VxWorks environment,
-then import them into the Ada application. For example, we could define the
-following package that imports two symbols, one an int and the other a string:
-
-@smallexample
-with Interfaces.C.Strings;
-use Interfaces.C.Strings;
-package Args is
- -- Define and import a variable for each argument
- Int_Arg : Interfaces.C.Int;
- String_Arg : Chars_Ptr;
-private
- pragma Import (C, Int_Arg, "intarg");
- pragma Import (C, String_Arg, "stringarg");
-end Args;
-@end smallexample
-
-@noindent
-An Ada unit could then use the two imported variables @code{Int_Arg} and
-@code{String_Arg} as follows:
-
-@smallexample
-with Args; use Args;
-with Interfaces.C.Strings;
-use Interfaces.C, Interfaces.C.Strings;
-with Ada.Text_IO; use Ada.Text_IO;
-procedure Argtest is
-begin
- Put_Line (Int'Image (Int_Arg));
- Put_Line (Value (String_Arg));
-end Argtest;
-@end smallexample
-
-@noindent
-When invoking the application from the shell, one will then set the values
-to be imported, and spawn the application, as follows:
-
-@smallexample
--> intarg=10
--> stringarg="Hello"
--> sp (argtest)
-@end smallexample
-
-
-@node Debugging Issues for VxWorks
-@section Debugging Issues for VxWorks
-
-@noindent
-The debugger can be launched directly from the Tornado environment or from @code{glide}
-through its graphical interface: @code{gvd}. It can also be used
-directly in text mode as shown below:
-@noindent
-The command to run @code{GDB} in text mode is
-
-@smallexample
-$ @i{target}-gdb
-@end smallexample
-
-@noindent
-where @i{target} is the name of target of the cross GNAT
-compiler. In contrast with native @code{gdb}, it is not useful to give the name of
-the program to debug on the command line. Before starting a debugging
-session, one needs to connect to the VxWorks-configured board and load
-the relocatable object produced by @code{gnatlink}. This can be achieved
-by the following commands:
-
-@smallexample
-(vxgdb) target wtx myboard
-(vxgdb) load program
-@end smallexample
-
-@noindent
-where @code{myboard} is the host name or IP number of the target board, and
-@code{wtx} is the name of debugging protocol used to communicate
-with the VxWorks board. Early versions of VxWorks, up tp 5.2, only
-support the @code{<vxworks>} protocol whereas starting with VxWorks 5.3
-and Tornado, another protocol called @code{<wtx>} was made available. The
-choice of the protocol can be made when configuring the VxWorks
-kernel itself. When available, the @code{<wtx>} is greatly preferable
-and actually the only supported protocol with GNAT. When the debugger
-is launched directly from Tornado, the proper @code{target} command
-is automatically generated by the environment.
-
-The GNAT debugger can be used for debugging multitasking programs in two
-different modes and some minimal understanding of these modes is
-necessary in order to use the debugger effectively. The two modes are:
-
-@itemize @bullet
-@item Monotask mode: attach to, and debug, a single task.
-This mode is equivalent to the capabilities offered by CrossWind. The
-debugger interacts with a single task, while not affecting other tasks
-(insofar as possible). This is the DEFAULT mode.
-
-@item Multitask mode:
-The debugger has control over all Ada tasks in an application. It is
-possible to gather information about all application tasks, and to
-switch from one to another within a single debugging session.
-@end itemize
-
-@noindent
-It is not advised to switch between the two modes within a debugging
-session. A third mode called System mode is also available and can be
-used in place of the Multitask mode. Consult the Tornado documentation
-for this.
-
-Among the criteria for selecting the appropriate mode is the effect of
-task synchronization on the application's behavior. Debugging a
-tasking application affects the timing of the application; minimizing
-such effects may be critical in certain situations. The two modes have
-different effects: monotask mode only affects the attached task:
-others will run normally (if possible). Multitask mode stops all tasks
-at each breakpoint and restarts them on single-step, next, finish or
-continue; this may help avoid deadlocks in the presence of task
-synchronization despite the inherent latency of stopping and
-restarting the tasks.
-
-@subsection Using the debugger in monotask mode
-
-@noindent
-There are two ways to begin your debugging session:
-
-@itemize @bullet
-@item The program is already running on the board.
-
-@noindent
-The sequence of commands to use this mode is:
-@itemize @bullet
-@item Launch GVD (possibly from the Tornado menu)
-
-@noindent
-Verify that the debugger has access to the debug information of both
-your program and the kernel. The Console window should have a message
-"Looking for all loaded modules:" followed by the names of the modules
-on the board and "ok". If you have some error messages here instead of
-"ok", the debugging session may not work as expected.
-
-@item Attach to the desired task using
-@smallexample
- File --> Attach...
-@end smallexample
-@noindent
-This task is stopped by the debugger. Other tasks continue to operate
-normally (unless they are blocked by synchronization with the stopped
-task). The source window should display the code on which the task has
-been stopped, and if the stack display is enabled, it should reflect
-the stack of the task.
-@end itemize
-
-@item The program hasn't been loaded yet on the board
-@itemize @bullet
-@item Launch GVD (possibly from the Tornado menu)
-@item Load your program to the board:
-@smallexample
-File --> Open Program...
-@end smallexample
-
-@noindent
-GVD should display:
-@smallexample
-Downloading your_program ...done.
-Reading symbols from your_program...expanding to full symbols...done.
-@end smallexample
-
-@item Set breakpoints in your program.
-
-@noindent
-WARNING: they must be set in the main task (if your program runs
-several tasks)
-
-@item Run your program using one of the three methods below:
-@itemize @bullet
-@item
-Click on button <run> or <start>
-
-@item Menu
-@smallexample
-Program --> Run/Start
-@end smallexample
-
-@item
-Type in GVD's Console window
-@smallexample
-(gdb) run your_program
-@end smallexample
-@end itemize
-@end itemize
-
-@item Whichever method you chose to start your debugging session,
-you can use the following commands at this point:
-@itemize @bullet
-@item Browse sources and set breakpoints
-@item Examine the call stack (Data --> call stack)
-@item Go "up" and "down" in the call stack ("up" & "down" buttons)
-@item Examine data
-(Data --> Display local variables, or any of the other methods for viewing data in GVD)
-@item Continue/finish
-@end itemize
-
-Next/step/finish will only work if the top frame in the call stack has
-debug information. This is almost never the case when first attaching
-to the task since the task is usually stopped by the attach operation
-in the GNAT runtime. You can verify which frames of the call stack
-have debug information by:
-@smallexample
-Data --> call stack
-<right Button> (contextual menu inside the call stack window)
- add "file location"
-@end smallexample
-
-@noindent
-If the current frame does not have a "file location", then there is no
-debug information for the frame. We strongly recommended that you set
-breakpoints in the source where debug information can be found and
-"continue" until a breakpoint is reached before using
-"next/step". Another convenient possibility is to use the "continue
-until" capability available from the contextual menu of the Source
-window.
-
-You can also examine the state of other tasks using
-@smallexample
-Data -> tasks
-@end smallexample
-
-@noindent
-but you can't "switch" to another task by clicking on the
-elements of the task list. If you try to, you will get an error
-message in GVD's console:
-@smallexample
-"Task switching is not allowed when multi-tasks mode is not active"
-@end smallexample
-
-@noindent
-Once you have completed your debugging session on the attached
-task, you can detach from the task:
-@smallexample
-File --> detach
-@end smallexample
-
-@noindent
-The task resumes normal execution at this stage. WARNING: when you
-detach from a task, be sure that you are in a frame where there is
-debug information. Otherwise, the task won't resume properly. You can
-then start another attach/detach cycle if you wish.
-
-Note that it is possible to launch several GVD sessions and
-simultaneously attach each to a distinct task in monotask mode:
-@smallexample
-File --> New Debugger... (uncheck the box: Replace Current Debugger)
-File --> Attach... (in the new window)
-File --> detach
-@end smallexample
-@end itemize
-
-
-@subsection Using the debugger in Multitask mode
-
-@noindent
-The steps are as follows
-
-@itemize @bullet
-@item
-Launch GVD (possibly from the Tornado menu)
-
-@noindent
-There are two possibilities:
-@itemize @bullet
-@item
-If the program is already loaded on the target board, you need only verify
-that debug information has been found by the debugger as described
-above.
-
-@item
-Otherwise, load the program on the board using
-@smallexample
-File --> Open program
-@end smallexample
-@end itemize
-
-@item Set breakpoints in the desired parts of the program
-
-@item Start the program
-
-@noindent
-The simplest way to start the debugger in multitask mode is to use the
-menu
-@smallexample
-Program --> Run/Start
-@end smallexample
-
-@noindent
-and check the box "enable vxWorks multi-tasks mode".
-You can also use the following gdb commands in the console window
-@smallexample
- (gdb) set multi-tasks-mode on
- (gdb) run your_program
-@end smallexample
-
-@item Debug the stopped program
-
-@noindent
-Once stopped at a breakpoint
-(or if you pressed the "stop" button), you can use all the standard
-commands listed for monotask mode + task switching (using Data -->
-tasks). Using next/step under this mode is possible with the same
-restrictions as for monotask mode, but is not recommended because all
-tasks are restarted, leading to the possibility that a different task
-hits a breakpoint before the stepping operation has completed. Such
-an occurrence can result in a confusing state for both the user and
-the debugger. So we strongly suggest the use of only breakpoints and
-"continue" in this mode.
-@end itemize
-
-A final reminder: whatever the mode, whether you are debugging or not,
-the program has to be reloaded before each new execution, so that data
-initialized by the loader is set correctly. For instance, if you wish
-to restart the same execution of the same program, you can use the
-following sequence of gdb commands in the console window:
-@smallexample
-(gdb) detach
-(gdb) unload your_program(.exe)
-(gdb) load your_program(.exe)
-(gdb) run your_program
-@end smallexample
-
-
-@node Using GNAT from the Tornado 2 Project Facility
-@section Using GNAT from the Tornado 2 Project Facility
-@cindex Tornado II Project
-
-@menu
-* The GNAT Toolchain as Used from the Tornado 2 Project Facility::
-* Building a Simple Application::
-* Mixing C and Ada Code in a Tornado 2 Project::
-* Compilation Switches::
-* Autoscale and Minimal Kernel Configuration::
-* Adapting BSPs to GNAT::
-* Using GNAT Project Files in a Tornado 2 Project::
-@end menu
-
-@noindent
-This section describes how to add an Ada module in a Tornado project
-using the Tornado 2 Project facility described in
-@cite{Tornado User's Guide}, Chapter 4.
-All recommendations apply for both 'Downloadable Modules' and 'Kernel'
-project types.
-
-
-@node The GNAT Toolchain as Used from the Tornado 2 Project Facility
-@subsection The GNAT Toolchain as Used from the Tornado 2 Project Facility
-
-@noindent
-Tornado 2 allows you to integrate third-party C toolchains.
-(@cite{Tornado 2 API Programmer's Guide}, Chapter 7).
-Thus the GNAT toolchain will be seen as a new C toolchain when used from
-the Tornado 2 Project Facility. For each processor you can compile for,
-you will find a <proc>gnat toolchain, e.g. PPC604gnat. These toolchains will
-allow you to include Ada modules into your projects, and simply build them.
-
-The name of the so-called C compiler is @emph{cc_gnat_<arch>}, the name
-of the 'linker' is @emph{ld_gnat_<arch>}, where <arch> is an architecture; e.g.,
-PPC. These scripts will call the correct executables during the compilation or
-link processes, thus the C compiler, the C linker, or the GNAT toolchain,
-depending on the context.
-
-
-@node Building a Simple Application
-@subsection Building a Simple Application
-
-@noindent
-First, create a new project, using one of the gnat toolchains.
-
-To add an Ada source file to the current project, just click on
-@code{Project -> Add/Include}, browse to the relevant file, and include it.
-The Ada source file included should be the Ada entry point. Only
-one Ada entry point is allowed in a project. Any other required Ada source
-files will be automatically compiled and linked by the underlying tools.
-
-You can now compile the project, @code{Build->Rebuild all}.
-A log of the compilation process can be found in the build directory, in
-@file{gnatbuild.log}. It contains all the calls executed by the scripts, and
-associated information.
-
-
-@node Mixing C and Ada Code in a Tornado 2 Project
-@subsection Mixing C and Ada Code in a Tornado 2 Project
-
-@noindent
-You can mix C and Ada code in your projects. Your source files and the build
-options should comply with the recommendations from the section
-@cite{Interfacing to C}.
-This means that you can have several or no C source files, and one or no Ada entry
-point in your Tornado 2 Project.
-
-
-@node Compilation Switches
-@subsection Compilation Switches
-@noindent
-Once you have included all your source files, you may modify some compilation
-and linking options.
-To pass specific options to the GNAT toolchain, go to the Project's build
-settings, on the @code{C/C++ Compiler} tab, and add your arguments in the
-input window.
-
-You must comply with several rules to pass arguments to GNAT.
-Arguments to be passed should be
-
-@itemize @bullet
-
-@item after any arguments passed to the C toolchain.
-
-@item prefixed depending on the tool that uses them, with the following syntax
-
-@itemize @bullet
-@item @code{-cargs @emph{gnatmake-options}} to pass arguments to gnatmake
-@item @code{-bargs @emph{gnatbind-options}} to pass arguments to gnatbind
-@item @code{-largs @emph{gnatlink-options}} to pass arguments to gnatlink
-@end itemize
-@end itemize
-
-@noindent
-You will find more information on the compilation process of Ada source files
-in the section @cite{The GNAT Compilation Model}.
-For a list of all available switches, refer to the sections describing
-@code{gnatmake}, @code{gnatbind} and @code{gnatlink}.
-
-Here is an example that passes the option @code{-v} to the GNAT compiler :
-@smallexample
--g -mstrict-align -prjtype $(PRJ_TYPE) -ansi -nostdinc -DRW_MULTI_THREAD -D_REENTRANT
--fvolatile -fno-builtin -fno-for-scope -I. -I/usr/windppc-2.0/target/h -DCPU=PPC604
--cargs -v
-@end smallexample
-
-@noindent
-Here is an example that passes the option @code{-v} to the GNAT compiler, binder and linker,
-and @code{-v} and @code{-g} to the compiler :
-@smallexample
--g -mstrict-align -prjtype $(PRJ_TYPE) -ansi -nostdinc -DRW_MULTI_THREAD -D_REENTRANT
--fvolatile -fno-builtin -fno-for-scope -I. -I/usr/windppc-2.0/target/h -DCPU=PPC604
--cargs -v -g -O2 -bargs -v -largs -v
-@end smallexample
-
-@noindent
-In both examples, the following arguments have been automatically added by the Project
-Facility, and will be used by the C compiler.
-@smallexample
--g -mstrict-align -prjtype $(PRJ_TYPE) -ansi -nostdinc -DRW_MULTI_THREAD -D_REENTRANT
--fvolatile -fno-builtin -fno-for-scope -I. -I/usr/windppc-2.0/target/h -DCPU=PPC604
-@end smallexample
-
-@noindent
-Note: The @code{-prjtype $(PRJ_TYPE)} option present in a few input
-boxes is used by the GNAT toolchain. It is required for the compilation
-process. You should not remove it from any input box.
-
-
-@node Autoscale and Minimal Kernel Configuration
-@subsection Autoscale and Minimal Kernel Configuration
-
-@noindent
-The Autoscale feature, present in the Project Facility can be used on your
-VxWorks Kernel projects to determine the minimum set of components required
-for your kernel to work.
-(Please refer to the @cite{Tornado II User's Guide} Section 4.4 for more details.)
-This feature is also available for projects involving Ada code. Just click on
-@code{Project->Autoscale} to launch a check and determine the minimal kernel
-configuration.
-
-
-@node Adapting BSPs to GNAT
-@subsection Adapting BSPs to GNAT
-
-@noindent
-To use your Board Support Packages with the GNAT toolchain, you will have to adapt them,
-either manually or using the @code{adaptbsp4gnat} script.
-This procedure is described in the @cite{Tornado API Programmer's Guide},
-Chapter 7.
-Here is a summary of this setup, depending on the context.
-
-@itemize @bullet
-@item To do the adaptation manually:
-
-@itemize @bullet
-
-@item Copy your BSP directory contents into a new directory
-
-@item Go to this directory
-
-@item Edit the file @file{Makefile},
-
-@itemize @bullet
-@item Set tool to gnat, @code{TOOL=gnat}
-
-@item Reverse the order of the following lines
-@itemize @bullet
-@item @code{include $(TGT_DIR)/h/make/make.$(CPU)$(TOOL)}
-@item @code{include $(TGT_DIR)/h/make/defs.$(WIND_HOST_TYPE)}
-@end itemize
-
-@end itemize
-
-@end itemize
-
-@item To do the adaptation automatically, you may use the @code{adaptbsp4gnat}
-script. Its syntax is @code{adaptbsp4gnat <path_to_bsp>}.
-
-@noindent
-This script follows the different steps described above to perform the
-adaptation.
-The name of the new bsp is given after the modification. By default, if
-@file{<bsp>} is the name of your BSP, @file{<bsp>-gnat}, will be the name of
-the BSP created.
-@end itemize
-
-
-@node Using GNAT Project Files in a Tornado 2 Project
-@subsection Using GNAT Project Files in a Tornado 2 Project
-
-@noindent
-You can use GNAT Project files to compile your Ada files.
-To do so, you need to use the @option{-Pproject_file.gpr} option from @command{gnatmake}.
-The path to the project file can be either absolute, or relative to the build
-directory, i.e. where the executable will be placed (e.g. @file{~/myproject/PPC604gnat}).
-Your project file should set the @code{Object_Dir} variable to a specific
-value.
-@smallexample
-project Sample is
-
- Target := external ("TARGET_DIR");
- for Object_Dir use Target;
-
-end Sample;
-@end smallexample
-
-
-@node Frequently Asked Questions for VxWorks
-@section Frequently Asked Questions for VxWorks
-
-@itemize @bullet
-
-@item
-When I run my program twice on the board, it does not work, why?
-
-@noindent
-Usually, Ada programs require elaboration and finalization, so the
-compiler creates a wrapper procedure whose name is the same as the Ada
-name of the main subprogram, which takes care of calling the elaboration
-and finalization routines before and after your program. But the static
-part of the elaboration is taken care of while loading the program
-itself and thus if you launch it twice this part of the elaboration will
-not be performed. This affects the proper elaboration of the
-GNAT runtime and thus it is mandatory to reload your program before
-relaunching it.
-
-@item
-Can I load a collection of subprograms rather than a standalone program?
-
-@noindent
-It is possible to write Ada programs with multiple entry points which
-can be called from the VxWorks shell; you just need to consider your
-main program as the VxWorks shell itself and generate an Ada subsystem
-callable from outside @xref{Binding with Non-Ada Main Programs}. If you
-use this method, you need to call @code{adainit} manually before calling
-any Ada entry point.
-
-@item
-When I use the @code{break exception} command, I get the message
-@code{"exception" is not a function}, why?
-
-You are not in the proper language mode. Issue the command:
-@smallexample
-(vxgdb) set language ada
-@end smallexample
-
-@item
-When I load a large application from the VxWorks shell using the "ld"
-command, the load hangs and never finishes. How can I load large
-executables?
-
-This is a classic VxWorks problem when using the default "rsh" communication
-method. Using NFS instead should work. Use the @code{nfsShowMount} command to
-verify that your program is in a NFS mounted directory.
-
-@item
-When I load a large application from the debugger using the wtx target
-connection, the load never finishes, why?
-
-Make sure that the memory cache size parameter of the target server is
-large enough. (@code{target -m big_enough_size}, or Memory cache size box in GUI.)
-See @cite{Tornado 1.01 API Programming Guide}, Section 3.6.2.
-
-@item
-When I spawn my program under the VxWorks shell, interactive input does
-not work, why?
-
-Only programs directly launched from the shell can have interactive
-input. For a program spawned with the @code{sp} or @code{taskSpawn}
-command, you need to have file redirection for input:
-@smallexample
--> # here you can have interactive input
--> main
--> # here you cannot
--> sp main
--> # neither here
--> taskSpawn("ess",100,0,8000000,main)
--> # but you can input from a file:
--> taskSpawn("Bae",100,0,8000000,main) < input_file
-@end smallexample
-@end itemize
-
-
-@node LynxOS Topics
-@chapter LynxOS Topics
-@noindent
-This chapter describes topics that are specific to the GNAT for LynxOS
-cross configurations.
-
-@menu
-* Getting Started with GNAT on LynxOS::
-* Kernel Configuration for LynxOS::
-* Patch Level Issues for LynxOS::
-* Debugging Issues for LynxOS::
-* An Example Debugging Session for LynxOS::
-@end menu
-
-@node Getting Started with GNAT on LynxOS
-@section Getting Started with GNAT on LynxOS
-
-@noindent
-This section is a starting point for using GNAT to develop and
-execute Ada 95 programs for LynuxWorks' LynxOS target environment from a
-Unix host environment.
-We assume that you know how to use GNAT in a native environment
-and how to start a telnet or other login session to connect to your LynxOS board.
-
-To compile code for a LynxOS system running on a PowerPC
-board, the basic compiler command is
-@command{powerpc-xcoff-lynxos-gcc}.
-
-With GNAT, the easiest way to build the basic @code{Hello World} program is
-with @code{gnatmake}. For the LynxOS PowerPC target this would look
-like:
-
-@smallexample
-$ powerpc-xcoff-lynxos-gnatmake hello
-@i{powerpc-xcoff-lynxos-gcc -c hello.adb
-powerpc-xcoff-lynxos-gnatbind -x hello.ali
-powerpc-xcoff-lynxos-gnatlink hello.ali}
-@end smallexample
-
-@noindent
-(The first line is the command entered by the user -- the subseqent three
-are the programs run by @code{gnatmake}.)
-
-This creates the executable @command{hello}" which you then need to load on the
-board (using ftp or an NFS directory for example) to run it.
-
-
-@node Kernel Configuration for LynxOS
-@section Kernel Configuration for LynxOS
-
-@noindent
-The appropriate configuration for your LynxOS kernel depends
-on the target system and the requirements of your application. GNAT itself
-adds no additional demands; however in some situations it may be appropriate
-to increase the conservative
-resource assumptions made by the default configuration.
-
-Kernel parameters limiting the maximum number of file descriptors,
-kernel and user threads, synchronization objects, etc., may be set in the
-file @file{uparam.h}. You may also wish to modify the file
-@file{/etc/starttab}, which places limits on data, stack, and core file
-size. See the documentation provided by LynuxWorks for more information.
-
-
-@node Patch Level Issues for LynxOS
-@section Patch Level Issues for LynxOS
-
-@noindent
-The GNAT runtime requires that your system run at patch level 040 or
-later. Please see the file @file{PatchCompatibility.txt} from the
-distribution for more information.
-
-
-@node Debugging Issues for LynxOS
-@section Debugging Issues for LynxOS
-
-@noindent
-GNAT's debugger is based on the same GNU gdb technology as the debugger
-provided by LynxOS, though with a great number of extensions and
-enhancements to support the Ada language and GNAT. The LynxOS
-documentation is relevant to understanding how to get the debugger
-started if you run into difficulties.
-
-To demonstrate a debugging session, we will use a slightly more complex
-program called @file{demo1.adb}, which can be found in the @file{examples}
-directory of the GNAT distribution. This program is compiled with
-debugging information as follows:
-
-@smallexample
-$ powerpc-xcoff-lynxos-gnatmake -g demo1
-powerpc-xcoff-lynxos-gcc -c -g demo1.adb
-powerpc-xcoff-lynxos-gcc -c -g gen_list.adb
-powerpc-xcoff-lynxos-gcc -c -g instr.adb
-powerpc-xcoff-lynxos-gnatbind -x demo1.ali
-powerpc-xcoff-lynxos-gnatlink -g demo1.ali
-@end smallexample
-
-@noindent
-Once the executable is created, copy it to your working directory on the
-board. In this directory, you will have to launch the gdb server and
-choose a free port number on your TCP/IP socket. Presuming the Internet
-hostname of the board is @file{myboard} and the port chosen is 2345,
-issue the following command:
-
-@smallexample
-myboard> gdbserver myboard:2345 demo1
-@end smallexample
-
-@noindent
-Then return to your host environment.
-
-The graphical debugger interface, @command{gvd}, supports both native
-and cross environments at the same time. @command{gvd} can be launched from
-@command{Glide} (see @file{README.Glide} for more information on customizing
-@command{Glide} for LynxOS) or it can be launched from the command line as
-follows:
-
-@smallexample
-$ gvd --debugger powerpc-xcoff-lynxos-gdb
-@end smallexample
-
-@noindent
-Then to attach to the target, enter in @command{gvd}'s command line window:
-
-@smallexample
-(gdb) target remote myboard:2345
-@end smallexample
-
-@noindent
-For more information see the GVD documentation.
-
-The comments below concern debugging directly from the command line but
-they also apply to @command{gvd}, though in most cases an equivalent
-graphical command is also available.
-
-To run the cross debugger from the command line without the visual
-interface use the command @code{powerpc-xcoff-lynxos-gdb}.
-
-You will see something like:
-
-@smallexample
-GNU gdb 4.17.gnat.3.14a1
-Copyright 1998 Free Software Foundation, Inc.
-GDB is free software, covered by the GNU General Public License, and you are
-welcome to change it and/or distribute copies of it under certain conditions.
-Type "show copying" to see the conditions.
-There is absolutely no warranty for GDB. Type "show warranty" for details.
-This GDB was configured as "--host=sparc-sun-solaris2.5.1 --target=powerpc-xc
-off-lynxos".
-(gdb)
-@end smallexample
-
-@noindent
-Where @command{(gdb)} is the debugger's prompt. The first thing to do at the
-prompt from within @command{gdb} is to load the symbol table from the
-executable:
-
-@smallexample
-(gdb) file demo1
-Reading symbols from demo1...done.
-(gdb)
-@end smallexample
-
-@noindent
-You then have to attach to the server running on the board. Issue the command:
-
-@smallexample
-(gdb) target remote myboard:2345
-@end smallexample
-
-@noindent
-After the server has been started and attached from the host, the program is
-running on the target but has halted execution at the very beginning.
-The following commands set a breakpoint and continue execution:
-
-@smallexample
-(gdb) break demo1.adb:37
-Breakpoint 1 at 0x100064d0: file demo1.adb, line 37.
-(gdb) cont
-Continuing.
-
-Breakpoint 1, demo1 () at demo1.adb:37
-37 Set_Name (Fuel, "Fuel");
-(gdb)
-@end smallexample
-
-@noindent
-Here the execution has stopped at the breakpoint set above. Now
-you can use the standard @code{gdb} commands to examine the stack and
-program variables.
-
-Note that once execution has completed, the server on the board must be
-restarted before a new debugging session may begin.
-
-@node An Example Debugging Session for LynxOS
-@section An Example Debugging Session for LynxOS
-
-@noindent
-Carrying on a little further with the debugging session, the following
-example illustrates some of the usual debugging commands for moving
-around and seeing where you are:
-
-@smallexample
-(gdb) next
-38 Set_Name (Water, "Water");
-(gdb) bt
-#0 demo1 () at demo1.adb:38
-#1 0x10001218 in main (argc=1, argv=2147483640, envp=2147483520) at
-b~demo1.adb:118
-#2 0x10017538 in runmainthread ()
-#3 0x10001048 in __start ()
-(gdb) up
-#1 0x10001218 in main (argc=1, argv=2147483640, envp=2147483520) at
-b~demo1.adb:118
-118 Ada_Main_Program;
-(gdb) down
-#0 demo1 () at demo1.adb:38
-38 Set_Name (Water, "Water");
-(gdb)
-@end smallexample
-
-@noindent
-To examine and modify variables (of a tagged type here):
-
-@smallexample
-(gdb) print speed
-$1 = (name => "Speed ", value => -286331154)
-(gdb) ptype speed
-type = new instr.instrument with record
- value: instr.speed;
-end record
-(gdb) speed.value := 3
-$2 = 3
-(gdb) print speed
-$3 = (name => "Speed ", value => 3)
-(gdb) info local
-speed = (name => "Speed ", value => 3)
-fuel = (name => "Fuel ", value => -286331154)
-oil = (name => ' ' <repeats 14 times>, value => -286331154, size => 20,
- fill => 42 '*', empty => 46 '.')
-water = (name => ' ' <repeats 14 times>, value => -286331154, size => 20,
- fill => 42 '*', empty => 46 '.')
-time = (name => ' ' <repeats 14 times>, seconds => 0, minutes => 0, hours =>
-0)
-chrono = (name => ' ' <repeats 14 times>, seconds => 0, minutes => 0,
- hours => 0)
-db = (access demo1.dash_board.internal) 0x0
-(gdb)
-@end smallexample
-
-@noindent
-And finally letting the program it run to completion:
-
-@smallexample
-(gdb) c
-Continuing.
-
-Program exited normally.
-(gdb)
-@end smallexample
-@end ifset
-
-
-@node Performance Considerations
-@chapter Performance Considerations
-@cindex Performance
-
-@noindent
-The GNAT system provides a number of options that allow a trade-off
-between
-
-@itemize @bullet
-@item
-performance of the generated code
-
-@item
-speed of compilation
-
-@item
-minimization of dependences and recompilation
-
-@item
-the degree of run-time checking.
-@end itemize
-
-@noindent
-The defaults (if no options are selected) aim at improving the speed
-of compilation and minimizing dependences, at the expense of performance
-of the generated code:
-
-@itemize @bullet
-@item
-no optimization
-
-@item
-no inlining of subprogram calls
-
-@item
-all run-time checks enabled except overflow and elaboration checks
-@end itemize
-
-@noindent
-These options are suitable for most program development purposes. This
-chapter describes how you can modify these choices, and also provides
-some guidelines on debugging optimized code.
-
-@menu
-* Controlling Run-Time Checks::
-* Optimization Levels::
-* Debugging Optimized Code::
-* Inlining of Subprograms::
-@ifset vms
-* Coverage Analysis::
-@end ifset
-@end menu
-
-@node Controlling Run-Time Checks
-@section Controlling Run-Time Checks
-
-@noindent
-By default, GNAT generates all run-time checks, except arithmetic overflow
-checking for integer operations and checks for access before elaboration on
-subprogram calls. The latter are not required in default mode, because all
-necessary checking is done at compile time.
-@cindex @option{-gnatp} (@code{gcc})
-@cindex @option{-gnato} (@code{gcc})
-Two gnat switches, @option{-gnatp} and @option{-gnato} allow this default to
-be modified. @xref{Run-Time Checks}.
-
-Our experience is that the default is suitable for most development
-purposes.
-
-We treat integer overflow specially because these
-are quite expensive and in our experience are not as important as other
-run-time checks in the development process. Note that division by zero
-is not considered an overflow check, and divide by zero checks are
-generated where required by default.
-
-Elaboration checks are off by default, and also not needed by default, since
-GNAT uses a static elaboration analysis approach that avoids the need for
-run-time checking. This manual contains a full chapter discussing the issue
-of elaboration checks, and if the default is not satisfactory for your use,
-you should read this chapter.
-
-For validity checks, the minimal checks required by the Ada Reference
-Manual (for case statements and assignments to array elements) are on
-by default. These can be suppressed by use of the @option{-gnatVn} switch.
-Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
-is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
-it may be reasonable to routinely use @option{-gnatVn}. Validity checks
-are also suppressed entirely if @option{-gnatp} is used.
-
-@cindex Overflow checks
-@cindex Checks, overflow
-@findex Suppress
-@findex Unsuppress
-@cindex pragma Suppress
-@cindex pragma Unsuppress
-Note that the setting of the switches controls the default setting of
-the checks. They may be modified using either @code{pragma Suppress} (to
-remove checks) or @code{pragma Unsuppress} (to add back suppressed
-checks) in the program source.
-
-@node Optimization Levels
-@section Optimization Levels
-@cindex @code{^-O^/OPTIMIZE^} (@code{gcc})
-
-@noindent
-The default is optimization off. This results in the fastest compile
-times, but GNAT makes absolutely no attempt to optimize, and the
-generated programs are considerably larger and slower than when
-optimization is enabled. You can use the
-@ifclear vms
-@code{-O@var{n}} switch, where @var{n} is an integer from 0 to 3,
-@end ifclear
-@ifset vms
-@code{^-O^/OPTIMIZE^}
-@end ifset
-on the @code{gcc} command line to control the optimization level:
-
-@table @code
-@item -O0
-no optimization (the default)
-
-@item -O1
-medium level optimization
-
-@item -O2
-full optimization
-
-@item -O3
-full optimization, and also attempt automatic inlining of small
-subprograms within a unit (@pxref{Inlining of Subprograms}).
-@end table
-
-Higher optimization levels perform more global transformations on the
-program and apply more expensive analysis algorithms in order to generate
-faster and more compact code. The price in compilation time, and the
-resulting improvement in execution time,
-both depend on the particular application and the hardware environment.
-You should experiment to find the best level for your application.
-
-Note: Unlike some other compilation systems, @code{gcc} has
-been tested extensively at all optimization levels. There are some bugs
-which appear only with optimization turned on, but there have also been
-bugs which show up only in @emph{unoptimized} code. Selecting a lower
-level of optimization does not improve the reliability of the code
-generator, which in practice is highly reliable at all optimization
-levels.
-
-Note regarding the use of @code{-O3}: The use of this optimization level
-is generally discouraged with GNAT, since it often results in larger
-executables which run more slowly. See further discussion of this point
-in @pxref{Inlining of Subprograms}.
-
-@node Debugging Optimized Code
-@section Debugging Optimized Code
-
-@noindent
-Since the compiler generates debugging tables for a compilation unit before
-it performs optimizations, the optimizing transformations may invalidate some
-of the debugging data. You therefore need to anticipate certain
-anomalous situations that may arise while debugging optimized code. This
-section describes the most common cases.
-
-@enumerate
-@item
-@i{The "hopping Program Counter":} Repeated 'step' or 'next' commands show the PC
-bouncing back and forth in the code. This may result from any of the following
-optimizations:
-
-@itemize @bullet
-@item
-@i{Common subexpression elimination:} using a single instance of code for a
-quantity that the source computes several times. As a result you
-may not be able to stop on what looks like a statement.
-
-@item
-@i{Invariant code motion:} moving an expression that does not change within a
-loop, to the beginning of the loop.
-
-@item
-@i{Instruction scheduling:} moving instructions so as to
-overlap loads and stores (typically) with other code, or in
-general to move computations of values closer to their uses. Often
-this causes you to pass an assignment statement without the assignment
-happening and then later bounce back to the statement when the
-value is actually needed. Placing a breakpoint on a line of code
-and then stepping over it may, therefore, not always cause all the
-expected side-effects.
-@end itemize
-
-@item
-@i{The "big leap":} More commonly known as @i{cross-jumping}, in which two
-identical pieces of code are merged and the program counter suddenly
-jumps to a statement that is not supposed to be executed, simply because
-it (and the code following) translates to the same thing as the code
-that @emph{was} supposed to be executed. This effect is typically seen in
-sequences that end in a jump, such as a @code{goto}, a @code{return}, or
-a @code{break} in a C @code{switch} statement.
-
-@item
-@i{The "roving variable":} The symptom is an unexpected value in a variable.
-There are various reasons for this effect:
-
-@itemize @bullet
-@item
-In a subprogram prologue, a parameter may not yet have been moved to its
-"home".
-
-@item
-A variable may be dead, and its register re-used. This is
-probably the most common cause.
-
-@item
-As mentioned above, the assignment of a value to a variable may
-have been moved.
-
-@item
-A variable may be eliminated entirely by value propagation or
-other means. In this case, GCC may incorrectly generate debugging
-information for the variable
-@end itemize
-
-@noindent
-In general, when an unexpected value appears for a local variable or parameter
-you should first ascertain if that value was actually computed by
-your program, as opposed to being incorrectly reported by the debugger.
-Record fields or
-array elements in an object designated by an access value
-are generally less of a problem, once you have ascertained that the access value
-is sensible.
-Typically, this means checking variables in the preceding code and in the
-calling subprogram to verify that the value observed is explainable from other
-values (one must apply the procedure recursively to those
-other values); or re-running the code and stopping a little earlier
-(perhaps before the call) and stepping to better see how the variable obtained
-the value in question; or continuing to step @emph{from} the point of the
-strange value to see if code motion had simply moved the variable's
-assignments later.
-@end enumerate
-
-@node Inlining of Subprograms
-@section Inlining of Subprograms
-
-@noindent
-A call to a subprogram in the current unit is inlined if all the
-following conditions are met:
-
-@itemize @bullet
-@item
-The optimization level is at least @code{-O1}.
-
-@item
-The called subprogram is suitable for inlining: It must be small enough
-and not contain nested subprograms or anything else that @code{gcc}
-cannot support in inlined subprograms.
-
-@item
-The call occurs after the definition of the body of the subprogram.
-
-@item
-@cindex pragma Inline
-@findex Inline
-Either @code{pragma Inline} applies to the subprogram or it is
-small and automatic inlining (optimization level @code{-O3}) is
-specified.
-@end itemize
-
-@noindent
-Calls to subprograms in @code{with}'ed units are normally not inlined.
-To achieve this level of inlining, the following conditions must all be
-true:
-
-@itemize @bullet
-@item
-The optimization level is at least @code{-O1}.
-
-@item
-The called subprogram is suitable for inlining: It must be small enough
-and not contain nested subprograms or anything else @code{gcc} cannot
-support in inlined subprograms.
-
-@item
-The call appears in a body (not in a package spec).
-
-@item
-There is a @code{pragma Inline} for the subprogram.
-
-@item
-@cindex @option{-gnatn} (@code{gcc})
-The @code{^-gnatn^/INLINE^} switch
-is used in the @code{gcc} command line
-@end itemize
-
-Note that specifying the @option{-gnatn} switch causes additional
-compilation dependencies. Consider the following:
-
-@smallexample
-@group
-@cartouche
-@b{package} R @b{is}
- @b{procedure} Q;
- @b{pragma} Inline (Q);
-@b{end} R;
-@b{package body} R @b{is}
- ...
-@b{end} R;
-
-@b{with} R;
-@b{procedure} Main @b{is}
-@b{begin}
- ...
- R.Q;
-@b{end} Main;
-@end cartouche
-@end group
-@end smallexample
-
-@noindent
-With the default behavior (no @option{-gnatn} switch specified), the
-compilation of the @code{Main} procedure depends only on its own source,
-@file{main.adb}, and the spec of the package in file @file{r.ads}. This
-means that editing the body of @code{R} does not require recompiling
-@code{Main}.
-
-On the other hand, the call @code{R.Q} is not inlined under these
-circumstances. If the @option{-gnatn} switch is present when @code{Main}
-is compiled, the call will be inlined if the body of @code{Q} is small
-enough, but now @code{Main} depends on the body of @code{R} in
-@file{r.adb} as well as on the spec. This means that if this body is edited,
-the main program must be recompiled. Note that this extra dependency
-occurs whether or not the call is in fact inlined by @code{gcc}.
-
-The use of front end inlining with @option{-gnatN} generates similar
-additional dependencies.
-
-@cindex @code{^-fno-inline^/INLINE=SUPPRESS^} (@code{gcc})
-Note: The @code{^-fno-inline^/INLINE=SUPPRESS^} switch
-can be used to prevent
-all inlining. This switch overrides all other conditions and ensures
-that no inlining occurs. The extra dependences resulting from
-@option{-gnatn} will still be active, even if
-this switch is used to suppress the resulting inlining actions.
-
-Note regarding the use of @code{-O3}: There is no difference in inlining
-behavior between @code{-O2} and @code{-O3} for subprograms with an explicit
-pragma @code{Inline} assuming the use of @option{-gnatn}
-or @option{-gnatN} (the switches that activate inlining). If you have used
-pragma @code{Inline} in appropriate cases, then it is usually much better
-to use @code{-O2} and @option{-gnatn} and avoid the use of @code{-O3} which
-in this case only has the effect of inlining subprograms you did not
-think should be inlined. We often find that the use of @code{-O3} slows
-down code by performing excessive inlining, leading to increased instruction
-cache pressure from the increased code size. So the bottom line here is
-that you should not automatically assume that @code{-O3} is better than
-@code{-O2}, and indeed you should use @code{-O3} only if tests show that
-it actually improves performance.
-
-@ifset vms
-@node Coverage Analysis
-@section Coverage Analysis
-
-@noindent
-GNAT supports the Digital Performance Coverage Analyzer (PCA), which allows
-the user to determine the distribution of execution time across a program,
-@pxref{Profiling} for details of usage.
-@end ifset
-
-@include fdl.texi
-@c GNU Free Documentation License
-
-@node Index,,GNU Free Documentation License, Top
-@unnumbered Index
-
-@printindex cp
-
-@contents
-
-@bye
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