@setfilename standards.info
@settitle GNU Coding Standards
@c This date is automagically updated when you save this file:
-@set lastupdate February 14, 2002
+@set lastupdate July 22, 2007
@c %**end of header
-@ifnottex
-@format
-START-INFO-DIR-ENTRY
-* Standards: (standards). GNU coding standards.
-END-INFO-DIR-ENTRY
-@end format
-@end ifnottex
+@dircategory GNU organization
+@direntry
+* Standards: (standards). GNU coding standards.
+@end direntry
@c @setchapternewpage odd
@setchapternewpage off
@iftex
@set CHAPTER chapter
@end iftex
-@ifnottex
+@ifinfo
@set CHAPTER node
-@end ifnottex
+@end ifinfo
-@ifnottex
-GNU Coding Standards
-Copyright (C) 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
+@copying
+The GNU coding standards, last updated @value{lastupdate}.
+
+Copyright @copyright{} 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
+2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007 Free Software
+Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
-under the terms of the GNU Free Documentation License, Version 1.1
+under the terms of the GNU Free Documentation License, Version 1.2
or any later version published by the Free Software Foundation;
with no Invariant Sections, with no
Front-Cover Texts, and with no Back-Cover Texts.
A copy of the license is included in the section entitled ``GNU
Free Documentation License''.
-@end ifnottex
+@end copying
@titlepage
@title GNU Coding Standards
@author Richard Stallman, et al.
@author last updated @value{lastupdate}
@page
-
@vskip 0pt plus 1filll
-Copyright @copyright{} 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
-
-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 no Invariant Sections, with no
-Front-Cover Texts, and with no Back-Cover Texts.
-A copy of the license is included in the section entitled ``GNU
-Free Documentation License''.
+@insertcopying
@end titlepage
+@contents
+
@ifnottex
@node Top, Preface, (dir), (dir)
@top Version
-Last updated @value{lastupdate}.
+@insertcopying
@end ifnottex
@menu
-* Preface:: About the GNU Coding Standards
-* Legal Issues:: Keeping Free Software Free
-* Design Advice:: General Program Design
-* Program Behavior:: Program Behavior for All Programs
-* Writing C:: Making The Best Use of C
-* Documentation:: Documenting Programs
-* Managing Releases:: The Release Process
-* References:: References to Non-Free Software or Documentation
-* Copying This Manual:: How to Make Copies of This Manual
-* Index::
+* Preface:: About the GNU Coding Standards.
+* Legal Issues:: Keeping free software free.
+* Design Advice:: General program design.
+* Program Behavior:: Program behavior for all programs
+* Writing C:: Making the best use of C.
+* Documentation:: Documenting programs.
+* Managing Releases:: The release process.
+* References:: Mentioning non-free software or documentation.
+* GNU Free Documentation License:: Copying and sharing this manual.
+* Index::
@end menu
@cindex where to obtain @code{standards.texi}
@cindex downloading this manual
If you did not obtain this file directly from the GNU project and
-recently, please check for a newer version. You can ftp the GNU
-Coding Standards from any GNU FTP host in the directory
-@file{/pub/gnu/standards/}. The GNU Coding Standards are available
-there in several different formats: @file{standards.text},
-@file{standards.info}, and @file{standards.dvi}, as well as the
-Texinfo ``source'' which is divided in two files:
-@file{standards.texi} and @file{make-stds.texi}. The GNU Coding
-Standards are also available on the GNU World Wide Web server:
-@uref{http://www.gnu.org/prep/standards_toc.html}.
+recently, please check for a newer version. You can get the GNU
+Coding Standards from the GNU web server in many
+different formats, including the Texinfo source, PDF, HTML, DVI, plain
+text, and more, at: @uref{http://www.gnu.org/prep/standards/}.
Corrections or suggestions for this document should be sent to
@email{bug-standards@@gnu.org}. If you make a suggestion, please include a
you don't have those files, please mail your suggestion anyway.
These standards cover the minimum of what is important when writing a
-GNU package. Likely, the needs for additional standards will come up.
+GNU package. Likely, the need for additional standards will come up.
Sometimes, you might suggest that such standards be added to this
document. If you think your standards would be generally useful, please
do suggest them.
to document them as much as possible. That way, your program will be
more maintainable by others.
+The GNU Hello program serves as an example of how to follow the GNU
+coding standards for a trivial program.
+@uref{http://www.gnu.org/software/hello/hello.html}.
+
@node Legal Issues
@chapter Keeping Free Software Free
@cindex legal aspects
-This @value{CHAPTER} discusses how you can make sure that GNU software
+This chapter discusses how you can make sure that GNU software
avoids legal difficulties, and other related issues.
@menu
-* Reading Non-Free Code:: Referring to Proprietary Programs
-* Contributions:: Accepting Contributions
-* Trademarks:: How We Deal with Trademark Issues
+* Reading Non-Free Code:: Referring to proprietary programs.
+* Contributions:: Accepting contributions.
+* Trademarks:: How we deal with trademark issues.
@end menu
@node Reading Non-Free Code
For example, Unix utilities were generally optimized to minimize
memory use; if you go for speed instead, your program will be very
-different. You could keep the entire input file in core and scan it
+different. You could keep the entire input file in memory and scan it
there instead of using stdio. Use a smarter algorithm discovered more
recently than the Unix program. Eliminate use of temporary files. Do
it in one pass instead of two (we did this in the assembler).
You don't need papers for changes of a few lines here or there, since
they are not significant for copyright purposes. Also, you don't need
papers if all you get from the suggestion is some ideas, not actual code
-which you use. For example, if someone send you one implementation, but
+which you use. For example, if someone sent you one implementation, but
you write a different implementation of the same idea, you don't need to
get papers.
We have more detailed advice for maintainers of programs; if you have
reached the stage of actually maintaining a program for GNU (whether
-released or not), please ask us for a copy.
+released or not), please ask us for a copy. It is also available
+online for your perusal: @uref{http://www.gnu.org/prep/maintain/}.
@node Trademarks
@section Trademarks
Trademark acknowledgements are the statements that such-and-such is a
trademark of so-and-so. The GNU Project has no objection to the basic
-idea of trademarks, but these acknowledgements feel like kowtowing, so
-we don't use them. There is no legal requirement for them.
+idea of trademarks, but these acknowledgements feel like kowtowing,
+and there is no legal requirement for them, so we don't use them.
What is legally required, as regards other people's trademarks, is to
-avoid using them in ways which a reader might read as naming or labeling
-our own programs or activities. For example, since ``Objective C'' is
-(or at least was) a trademark, we made sure to say that we provide a
-``compiler for the Objective C language'' rather than an ``Objective C
-compiler''. The latter is meant to be short for the former, but it does
-not explicitly state the relationship, so it could be misinterpreted as
-using ``Objective C'' as a label for the compiler rather than for the
-language.
+avoid using them in ways which a reader might reasonably understand as
+naming or labeling our own programs or activities. For example, since
+``Objective C'' is (or at least was) a trademark, we made sure to say
+that we provide a ``compiler for the Objective C language'' rather
+than an ``Objective C compiler''. The latter would have been meant as
+a shorter way of saying the former, but it does not explicitly state
+the relationship, so it could be misinterpreted as using ``Objective
+C'' as a label for the compiler rather than for the language.
+
+Please don't use ``win'' as an abbreviation for Microsoft Windows in
+GNU software or documentation. In hacker terminology, calling
+something a ``win'' is a form of praise. If you wish to praise
+Microsoft Windows when speaking on your own, by all means do so, but
+not in GNU software. Usually we write the name ``Windows'' in full,
+but when brevity is very important (as in file names and sometimes
+symbol names), we abbreviate it to ``w''. For instance, the files and
+functions in Emacs that deal with Windows start with @samp{w32}.
@node Design Advice
@chapter General Program Design
@cindex program design
-This @value{CHAPTER} discusses some of the issues you should take into
+This chapter discusses some of the issues you should take into
account when designing your program.
@c Standard or ANSI C
@c A major revision of the C Standard appeared in 1999.
@menu
-* Source Language:: Which languges to use.
-* Compatibility:: Compatibility with other implementations
-* Using Extensions:: Using non-standard features
-* Standard C:: Using Standard C features
-* Conditional Compilation:: Compiling Code Only If A Conditional is True
+* Source Language:: Which languages to use.
+* Compatibility:: Compatibility with other implementations.
+* Using Extensions:: Using non-standard features.
+* Standard C:: Using standard C features.
+* Conditional Compilation:: Compiling code only if a conditional is true.
@end menu
@node Source Language
@section Which Languages to Use
-@cindex programming languges
+@cindex programming languages
When you want to use a language that gets compiled and runs at high
speed, the best language to use is C. Using another language is like
technique.
@cindex GUILE
-The standard extensibility interpreter for GNU software is GUILE, which
-implements the language Scheme (an especially clean and simple dialect
-of Lisp). @uref{http://www.gnu.org/software/guile/}. We don't reject
-programs written in other ``scripting languages'' such as Perl and
-Python, but using GUILE is very important for the overall consistency of
-the GNU system.
+The standard extensibility interpreter for GNU software is GUILE
+(@uref{http://www.gnu.org/software/guile/}), which implements the
+language Scheme (an especially clean and simple dialect of Lisp). We
+don't reject programs written in other ``scripting languages'' such as
+Perl and Python, but using GUILE is very important for the overall
+consistency of the GNU system.
@node Compatibility
@section Compatibility with Other Implementations
...
@end smallexample
+@noindent
instead of:
@smallexample
A modern compiler such as GCC will generate exactly the same code in
both cases, and we have been using similar techniques with good success
-in several projects.
+in several projects. Of course, the former method assumes that
+@code{HAS_FOO} is defined as either 0 or 1.
While this is not a silver bullet solving all portability problems,
-following this policy would have saved the GCC project alone many person
-hours if not days per year.
+and is not always appropriate, following this policy would have saved
+GCC developers many hours, or even days, per year.
In the case of function-like macros like @code{REVERSIBLE_CC_MODE} in
GCC which cannot be simply used in @code{if( ...)} statements, there is
@node Program Behavior
@chapter Program Behavior for All Programs
-This @value{CHAPTER} describes conventions for writing robust
+This chapter describes conventions for writing robust
software. It also describes general standards for error messages, the
command line interface, and how libraries should behave.
@menu
-* Semantics:: Writing robust programs
-* Libraries:: Library behavior
-* Errors:: Formatting error messages
-* User Interfaces:: Standards about interfaces generally
-* Graphical Interfaces:: Standards for graphical interfaces
-* Command-Line Interfaces:: Standards for command line interfaces
-* Option Table:: Table of long options
-* Memory Usage:: When and how to care about memory needs
-* File Usage:: Which files to use, and where
+* Non-GNU Standards:: We consider standards such as POSIX;
+ we don't "obey" them.
+* Semantics:: Writing robust programs.
+* Libraries:: Library behavior.
+* Errors:: Formatting error messages.
+* User Interfaces:: Standards about interfaces generally.
+* Graphical Interfaces:: Standards for graphical interfaces.
+* Command-Line Interfaces:: Standards for command line interfaces.
+* Option Table:: Table of long options.
+* Memory Usage:: When and how to care about memory needs.
+* File Usage:: Which files to use, and where.
@end menu
+@node Non-GNU Standards
+@section Non-GNU Standards
+
+The GNU Project regards standards published by other organizations as
+suggestions, not orders. We consider those standards, but we do not
+``obey'' them. In developing a GNU program, you should implement
+an outside standard's specifications when that makes the GNU system
+better overall in an objective sense. When it doesn't, you shouldn't.
+
+In most cases, following published standards is convenient for
+users---it means that their programs or scripts will work more
+portably. For instance, GCC implements nearly all the features of
+Standard C as specified by that standard. C program developers would
+be unhappy if it did not. And GNU utilities mostly follow
+specifications of POSIX.2; shell script writers and users would be
+unhappy if our programs were incompatible.
+
+But we do not follow either of these specifications rigidly, and there
+are specific points on which we decided not to follow them, so as to
+make the GNU system better for users.
+
+For instance, Standard C says that nearly all extensions to C are
+prohibited. How silly! GCC implements many extensions, some of which
+were later adopted as part of the standard. If you want these
+constructs to give an error message as ``required'' by the standard,
+you must specify @samp{--pedantic}, which was implemented only so that
+we can say ``GCC is a 100% implementation of the standard,'' not
+because there is any reason to actually use it.
+
+POSIX.2 specifies that @samp{df} and @samp{du} must output sizes by
+default in units of 512 bytes. What users want is units of 1k, so
+that is what we do by default. If you want the ridiculous behavior
+``required'' by POSIX, you must set the environment variable
+@samp{POSIXLY_CORRECT} (which was originally going to be named
+@samp{POSIX_ME_HARDER}).
+
+GNU utilities also depart from the letter of the POSIX.2 specification
+when they support long-named command-line options, and intermixing
+options with ordinary arguments. This minor incompatibility with
+POSIX is never a problem in practice, and it is very useful.
+
+In particular, don't reject a new feature, or remove an old one,
+merely because a standard says it is ``forbidden'' or ``deprecated.''
+
@node Semantics
@section Writing Robust Programs
@end example
@noindent
-If you want to mention the column number, use this format:
+If you want to mention the column number, use one of these formats:
@example
@var{source-file-name}:@var{lineno}:@var{column}: @var{message}
+@var{source-file-name}:@var{lineno}.@var{column}: @var{message}
+
@end example
@noindent
numbers assuming that space and all ASCII printing characters have
equal width, and assuming tab stops every 8 columns.
+The error message can also give both the starting and ending positions
+of the erroneous text. There are several formats so that you can
+avoid redundant information such as a duplicate line number.
+Here are the possible formats:
+
+@example
+@var{source-file-name}:@var{lineno-1}.@var{column-1}-@var{lineno-2}.@var{column-2}: @var{message}
+@var{source-file-name}:@var{lineno-1}.@var{column-1}-@var{column-2}: @var{message}
+@var{source-file-name}:@var{lineno-1}-@var{lineno-2}: @var{message}
+@end example
+
+@noindent
+When an error is spread over several files, you can use this format:
+
+@example
+@var{file-1}:@var{lineno-1}.@var{column-1}-@var{file-2}:@var{lineno-2}.@var{column-2}: @var{message}
+@end example
+
Error messages from other noninteractive programs should look like this:
@example
would do best to print error messages using the noninteractive style.)
The string @var{message} should not begin with a capital letter when
-it follows a program name and/or file name. Also, it should not end
-with a period.
+it follows a program name and/or file name, because that isn't the
+beginning of a sentence. (The sentence conceptually starts at the
+beginning of the line.) Also, it should not end with a period.
Error messages from interactive programs, and other messages such as
usage messages, should start with a capital letter. But they should not
like @code{ls} except that its default output format is always
multi-column format.
+
@node Graphical Interfaces
@section Standards for Graphical Interfaces
@cindex graphical user interface
-@cindex gtk
+@cindex gtk+
When you write a program that provides a graphical user interface,
-please make it work with X Windows and the GTK toolkit unless the
+please make it work with X Windows and the GTK+ toolkit unless the
functionality specifically requires some alternative (for example,
``displaying jpeg images while in console mode'').
doing the work to provide the functionality and the graphical interface,
these won't be much extra work.
+
@node Command-Line Interfaces
@section Standards for Command Line Interfaces
@cindex command-line interface
(preferably @samp{-o} or @samp{--output}). Even if you allow an output
file name as an ordinary argument for compatibility, try to provide an
option as another way to specify it. This will lead to more consistency
-among GNU utilities, and fewer idiosyncracies for users to remember.
+among GNU utilities, and fewer idiosyncrasies for users to remember.
@cindex standard command-line options
+@cindex options, standard command-line
+@cindex CGI programs, standard options for
+@cindex PATH_INFO, specifying standard options as
All programs should support two standard options: @samp{--version}
-and @samp{--help}.
+and @samp{--help}. CGI programs should accept these as command-line
+options, and also if given as the @env{PATH_INFO}; for instance,
+visiting @url{http://example.org/p.cgi/--help} in a browser should
+output the same information as invoking @samp{p.cgi --help} from the
+command line.
-@table @code
-@cindex @samp{--version} option
-@item --version
-This option should direct the program to print information about its name,
-version, origin and legal status, all on standard output, and then exit
-successfully. Other options and arguments should be ignored once this
-is seen, and the program should not perform its normal function.
+@menu
+* --version:: The standard output for --version.
+* --help:: The standard output for --help.
+@end menu
+
+@node --version
+@subsection @option{--version}
+
+@cindex @samp{--version} output
+
+The standard @code{--version} option should direct the program to
+print information about its name, version, origin and legal status,
+all on standard output, and then exit successfully. Other options and
+arguments should be ignored once this is seen, and the program should
+not perform its normal function.
@cindex canonical name of a program
@cindex program's canonical name
program's version number, you can mention the package version number
just before the close-parenthesis.
-If you @strong{need} to mention the version numbers of libraries which
+If you @emph{need} to mention the version numbers of libraries which
are distributed separately from the package which contains this program,
you can do so by printing an additional line of version info for each
library you want to mention. Use the same format for these lines as for
copyright notice. If more than one copyright notice is called for, put
each on a separate line.
-Next should follow a brief statement that the program is free software,
-and that users are free to copy and change it on certain conditions. If
-the program is covered by the GNU GPL, say so here. Also mention that
-there is no warranty, to the extent permitted by law.
+Next should follow a line stating the license, preferably using one of
+abbrevations below, and a brief statement that the program is free
+software, and that users are free to copy and change it. Also mention
+that there is no warranty, to the extent permitted by law. See
+recommended wording below.
It is ok to finish the output with a list of the major authors of the
program, as a way of giving credit.
Here's an example of output that follows these rules:
@smallexample
-GNU Emacs 19.34.5
-Copyright (C) 1996 Free Software Foundation, Inc.
-GNU Emacs comes with NO WARRANTY,
-to the extent permitted by law.
-You may redistribute copies of GNU Emacs
-under the terms of the GNU General Public License.
-For more information about these matters,
-see the files named COPYING.
+GNU hello 2.3
+Copyright (C) 2007 Free Software Foundation, Inc.
+License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
+This is free software: you are free to change and redistribute it.
+There is NO WARRANTY, to the extent permitted by law.
@end smallexample
You should adapt this to your program, of course, filling in the proper
which changes were made---there's no need to list the years for previous
versions' changes. You don't have to mention the name of the program in
these notices, if that is inconvenient, since it appeared in the first
-line.
+line. (The rules are different for copyright notices in source files;
+@pxref{Copyright Notices,,,maintain,Information for GNU Maintainers}.)
Translations of the above lines must preserve the validity of the
copyright notices (@pxref{Internationalization}). If the translation's
character set supports it, the @samp{(C)} should be replaced with the
copyright symbol, as follows:
-@ifinfo
-(the official copyright symbol, which is the letter C in a circle);
-@end ifinfo
-@ifnotinfo
+@ifinfo
+(the official copyright symbol, which is the letter C in a circle);
+@end ifinfo
+@ifnotinfo
@copyright{}
-@end ifnotinfo
+@end ifnotinfo
Write the word ``Copyright'' exactly like that, in English. Do not
translate it into another language. International treaties recognize
the English word ``Copyright''; translations into other languages do not
have legal significance.
+Finally, here is the table of our suggested license abbreviations.
+Any abbreviation can be followed by @samp{v@var{version}[+]}, meaning
+that particular version, or later versions with the @samp{+}, as shown
+above.
-@cindex @samp{--help} option
-@item --help
-This option should output brief documentation for how to invoke the
-program, on standard output, then exit successfully. Other options and
-arguments should be ignored once this is seen, and the program should
-not perform its normal function.
+In the case of exceptions for extra permissions with the GPL, we use
+@samp{/} for a separator; the version number can follow the license
+abbreviation as usual, as in the examples below.
+
+@table @asis
+@item GPL
+GNU General Public License, @url{http://www.gnu.org/licenses/gpl.html}.
+
+@item LGPL
+GNU Lesser General Public License, @url{http://www.gnu.org/licenses/lgpl.html}.
+
+@item GPL/Guile
+GNU GPL with the exception for Guile; for example, GPLv3+/Guile means
+the GNU GPL version 3 or later, with the extra exception for Guile.
+
+GNU GPL with the exception for Ada.
+
+@item Apache
+The Apache Software Foundation license,
+@url{http://www.apache.org/licenses}.
+
+@item Artistic
+The Artistic license used for Perl, @url{http://www.perlfoundation.org/legal}.
+
+@item Expat
+The Expat license, @url{http://www.jclark.com/xml/copying.txt}.
+
+@item MPL
+The Mozilla Public License, @url{http://www.mozilla.org/MPL/}.
+
+@item OBSD
+The original (4-clause) BSD license, incompatible with the GNU GPL
+@url{http://www.xfree86.org/3.3.6/COPYRIGHT2.html#6}.
+
+@item PHP
+The license used for PHP, @url{http://www.php.net/license/}.
+
+@item public domain
+The non-license that is being in the public domain,
+@url{http://www.gnu.org/licenses/license-list.html#PublicDomain}.
+
+@item Python
+The license for Python, @url{http://www.python.org/2.0.1/license.html}.
+
+@item RBSD
+The revised (3-clause) BSD, compatible with the GNU GPL,
+@url{http://www.xfree86.org/3.3.6/COPYRIGHT2.html#5}.
+
+@item X11
+The simple non-copyleft license used for most versions of the X Window
+system, @url{http://www.xfree86.org/3.3.6/COPYRIGHT2.html#3}.
+
+@item Zlib
+The license for Zlib, @url{http://www.gzip.org/zlib/zlib_license.html}.
+
+@end table
+
+More information about these licenses and many more are on the GNU
+licensing web pages,
+@url{http://www.gnu.org/licenses/license-list.html}.
+
+
+@node --help
+@subsection @option{--help}
+
+@cindex @samp{--help} output
+
+The standard @code{--help} option should output brief documentation
+for how to invoke the program, on standard output, then exit
+successfully. Other options and arguments should be ignored once this
+is seen, and the program should not perform its normal function.
@cindex address for bug reports
@cindex bug reports
@example
Report bugs to @var{mailing-address}.
@end example
-@end table
+
@node Option Table
@section Table of Long Options
Used in @code{su}.
@item machine
-No listing of which programs already use this;
-someone should check to
-see if any actually do, and tell @email{gnu@@gnu.org}.
+Used in @code{uname}.
@item macro-name
@samp{-M} in @code{ptx}.
@item no-sort
@samp{-p} in @code{nm}.
+@item no-splash
+Don't print a startup splash screen.
+
@item no-split
Used in @code{makeinfo}.
@samp{-q} in Make.
@item quiet
-Used in many programs to inhibit the usual output. @strong{Note:} every
+Used in many programs to inhibit the usual output. Every
program accepting @samp{--quiet} should accept @samp{--silent} as a
synonym.
@item silent
Used in many programs to inhibit the usual output.
-@strong{Note:} every program accepting
+Every program accepting
@samp{--silent} should accept @samp{--quiet} as a synonym.
@item size
@item socket
Specify a file descriptor for a network server to use for its socket,
instead of opening and binding a new socket. This provides a way to
-run, in a nonpriveledged process, a server that normally needs a
+run, in a non-privileged process, a server that normally needs a
reserved port number.
@item sort
If a program typically uses just a few meg of memory, don't bother making any
effort to reduce memory usage. For example, if it is impractical for
other reasons to operate on files more than a few meg long, it is
-reasonable to read entire input files into core to operate on them.
+reasonable to read entire input files into memory to operate on them.
However, for programs such as @code{cat} or @code{tail}, that can
usefully operate on very large files, it is important to avoid using a
If a program works by lines and could be applied to arbitrary
user-supplied input files, it should keep only a line in memory, because
this is not very hard and users will want to be able to operate on input
-files that are bigger than will fit in core all at once.
+files that are bigger than will fit in memory all at once.
If your program creates complicated data structures, just make them in
-core and give a fatal error if @code{malloc} returns zero.
+memory and give a fatal error if @code{malloc} returns zero.
@node File Usage
@section File Usage
@node Writing C
@chapter Making The Best Use of C
-This @value{CHAPTER} provides advice on how best to use the C language
+This chapter provides advice on how best to use the C language
when writing GNU software.
@menu
-* Formatting:: Formatting Your Source Code
-* Comments:: Commenting Your Work
-* Syntactic Conventions:: Clean Use of C Constructs
-* Names:: Naming Variables, Functions, and Files
-* System Portability:: Portability between different operating systems
-* CPU Portability:: Supporting the range of CPU types
-* System Functions:: Portability and ``standard'' library functions
-* Internationalization:: Techniques for internationalization
+* Formatting:: Formatting your source code.
+* Comments:: Commenting your work.
+* Syntactic Conventions:: Clean use of C constructs.
+* Names:: Naming variables, functions, and files.
+* System Portability:: Portability among different operating systems.
+* CPU Portability:: Supporting the range of CPU types.
+* System Functions:: Portability and ``standard'' library functions.
+* Internationalization:: Techniques for internationalization.
+* Character Set:: Use ASCII by default.
+* Quote Characters:: Use `...' in the C locale.
* Mmap:: How you can safely use @code{mmap}.
@end menu
@cindex open brace
@cindex braces, in C source
It is important to put the open-brace that starts the body of a C
-function in column zero, and avoid putting any other open-brace or
-open-parenthesis or open-bracket in column zero. Several tools look
-for open-braces in column zero to find the beginnings of C functions.
-These tools will not work on code not formatted that way.
+function in column one, so that they will start a defun. Several
+tools look for open-braces in column one to find the beginnings of C
+functions. These tools will not work on code not formatted that way.
+
+Avoid putting open-brace, open-parenthesis or open-bracket in column
+one when they are inside a function, so that they won't start a defun.
+The open-brace that starts a @code{struct} body can go in column one
+if you find it useful to treat that definition as a defun.
It is also important for function definitions to start the name of the
-function in column zero. This helps people to search for function
+function in column one. This helps people to search for function
definitions, and may also help certain tools recognize them. Thus,
-the proper format is this:
+using Standard C syntax, the format is this:
@example
static char *
-concat (s1, s2) /* Name starts in column zero here */
- char *s1, *s2;
-@{ /* Open brace in column zero here */
+concat (char *s1, char *s2)
+@{
@dots{}
@}
@end example
@noindent
-or, if you want to use Standard C syntax, format the definition like
+or, if you want to use traditional C syntax, format the definition like
this:
@example
static char *
-concat (char *s1, char *s2)
-@{
+concat (s1, s2) /* Name starts in column one here */
+ char *s1, *s2;
+@{ /* Open brace in column one here */
@dots{}
@}
@end example
@cindex commenting
Every program should start with a comment saying briefly what it is for.
-Example: @samp{fmt - filter for simple filling of text}.
+Example: @samp{fmt - filter for simple filling of text}. This comment
+should be at the top of the source file containing the @samp{main}
+function of the program.
+
+Also, please write a brief comment at the start of each source file,
+with the file name and a line or two about the overall purpose of the
+file.
Please write the comments in a GNU program in English, because English
is the one language that nearly all programmers in all countries can
@cindex temporary variables
It used to be common practice to use the same local variables (with
names like @code{tem}) over and over for different values within one
-function. Instead of doing this, it is better declare a separate local
+function. Instead of doing this, it is better to declare a separate local
variable for each distinct purpose, and give it a name which is
meaningful. This not only makes programs easier to understand, it also
facilitates optimization by good compilers. You can also move the
same declaration. Instead, declare the structure tag separately
and then use it to declare the variables or typedefs.
-Try to avoid assignments inside @code{if}-conditions. For example,
-don't write this:
+Try to avoid assignments inside @code{if}-conditions (assignments
+inside @code{while}-conditions are ok). For example, don't write
+this:
@example
if ((foo = (char *) malloc (sizeof *foo)) == 0)
@cindex file-name limitations
@pindex doschk
You might want to make sure that none of the file names would conflict
-the files were loaded onto an MS-DOS file system which shortens the
+if the files were loaded onto an MS-DOS file system which shortens the
names. You can use the program @code{doschk} to test for this.
Some GNU programs were designed to limit themselves to file names of 14
when there is a higher-level alternative (@code{readdir}).
@cindex non-@sc{posix} systems, and portability
-As for systems that are not like Unix, such as MSDOS, Windows, the
-Macintosh, VMS, and MVS, supporting them is often a lot of work. When
-that is the case, it is better to spend your time adding features that
-will be useful on GNU and GNU/Linux, rather than on supporting other
-incompatible systems.
+As for systems that are not like Unix, such as MSDOS, Windows, VMS, MVS,
+and older Macintosh systems, supporting them is often a lot of work.
+When that is the case, it is better to spend your time adding features
+that will be useful on GNU and GNU/Linux, rather than on supporting
+other incompatible systems.
+
+If you do support Windows, please do not abbreviate it as ``win''. In
+hacker terminology, calling something a ``win'' is a form of praise.
+You're free to praise Microsoft Windows on your own if you want, but
+please don't do this in GNU packages. Instead of abbreviating
+``Windows'' to ``un'', you can write it in full or abbreviate it to
+``woe'' or ``w''. In GNU Emacs, for instance, we use @samp{w32} in
+file names of Windows-specific files, but the macro for Windows
+conditionals is called @code{WINDOWSNT}.
It is a good idea to define the ``feature test macro''
@code{_GNU_SOURCE} when compiling your C files. When you compile on GNU
@end example
1989 Standard C requires this to work, and we know of only one
-counterexample: 64-bit programs on Microsoft Windows IA-64. We will
+counterexample: 64-bit programs on Microsoft Windows. We will
leave it to those who want to port GNU programs to that environment
to figure out how to do it.
@example
int c;
@dots{}
-while ((c = getchar()) != EOF)
- write(file_descriptor, &c, 1);
+while ((c = getchar ()) != EOF)
+ write (file_descriptor, &c, 1);
@end example
-When calling functions, you need not worry about the difference between
-pointers of various types, or between pointers and integers. On most
-machines, there's no difference anyway. As for the few machines where
-there is a difference, all of them support Standard C prototypes, so you can
-use prototypes (perhaps conditionalized to be active only in Standard C)
-to make the code work on those systems.
+@noindent Instead, use @code{unsigned char} as follows. (The @code{unsigned}
+is for portability to unusual systems where @code{char} is signed and
+where there is integer overflow checking.)
-In certain cases, it is ok to pass integer and pointer arguments
-indiscriminately to the same function, and use no prototype on any
-system. For example, many GNU programs have error-reporting functions
-that pass their arguments along to @code{printf} and friends:
+@example
+int c;
+while ((c = getchar ()) != EOF)
+ @{
+ unsigned char u = c;
+ write (file_descriptor, &u, 1);
+ @}
+@end example
+
+It used to be ok to not worry about the difference between pointers
+and integers when passing arguments to functions. However, on most
+modern 64-bit machines pointers are wider than @code{int}.
+Conversely, integer types like @code{long long int} and @code{off_t}
+are wider than pointers on most modern 32-bit machines. Hence it's
+often better nowadays to use prototypes to define functions whose
+argument types are not trivial.
+
+In particular, if functions accept varying argument counts or types
+they should be declared using prototypes containing @samp{...} and
+defined using @file{stdarg.h}. For an example of this, please see the
+@uref{http://www.gnu.org/software/gnulib/, Gnulib} error module, which
+declares and defines the following function:
@example
-error (s, a1, a2, a3)
- char *s;
- char *a1, *a2, *a3;
-@{
- fprintf (stderr, "error: ");
- fprintf (stderr, s, a1, a2, a3);
-@}
+/* Print a message with `fprintf (stderr, FORMAT, ...)';
+ if ERRNUM is nonzero, follow it with ": " and strerror (ERRNUM).
+ If STATUS is nonzero, terminate the program with `exit (STATUS)'. */
+
+void error (int status, int errnum, const char *format, ...);
@end example
-@noindent
-In practice, this works on all machines, since a pointer is generally
-the widest possible kind of argument; it is much simpler than any
-``correct'' alternative. Be sure @emph{not} to use a prototype for such
-functions.
+A simple way to use the Gnulib error module is to obtain the two
+source files @file{error.c} and @file{error.h} from the Gnulib library
+source code repository at
+@uref{http://savannah.gnu.org/cgi-bin/viewcvs/gnulib/gnulib/lib/}.
+Here's a sample use:
+
+@example
+#include "error.h"
+#include <errno.h>
+#include <stdio.h>
-If you have decided to use Standard C, then you can instead define
-@code{error} using @file{stdarg.h}, and pass the arguments along to
-@code{vfprintf}.
+char *program_name = "myprogram";
+
+FILE *
+xfopen (char const *name)
+@{
+ FILE *fp = fopen (name, "r");
+ if (! fp)
+ error (1, errno, "cannot read %s", name);
+ return fp;
+@}
+@end example
@cindex casting pointers to integers
Avoid casting pointers to integers if you can. Such casts greatly
name} for the package. The text domain name is used to separate the
translations for this package from the translations for other packages.
Normally, the text domain name should be the same as the name of the
-package---for example, @samp{fileutils} for the GNU file utilities.
+package---for example, @samp{coreutils} for the GNU core utilities.
@cindex message text, and internationalization
To enable gettext to work well, avoid writing code that makes
Here is an example of what not to do:
+@smallexample
+printf ("%s is full", capacity > 5000000 ? "disk" : "floppy disk");
+@end smallexample
+
+If you apply gettext to all strings, like this,
+
+@smallexample
+printf (gettext ("%s is full"),
+ capacity > 5000000 ? gettext ("disk") : gettext ("floppy disk"));
+@end smallexample
+
+@noindent
+the translator will hardly know that "disk" and "floppy disk" are meant to
+be substituted in the other string. Worse, in some languages (like French)
+the construction will not work: the translation of the word "full" depends
+on the gender of the first part of the sentence; it happens to be not the
+same for "disk" as for "floppy disk".
+
+Complete sentences can be translated without problems:
+
+@example
+printf (capacity > 5000000 ? gettext ("disk is full")
+ : gettext ("floppy disk is full"));
+@end example
+
+A similar problem appears at the level of sentence structure with this
+code:
+
+@example
+printf ("# Implicit rule search has%s been done.\n",
+ f->tried_implicit ? "" : " not");
+@end example
+
+@noindent
+Adding @code{gettext} calls to this code cannot give correct results for
+all languages, because negation in some languages requires adding words
+at more than one place in the sentence. By contrast, adding
+@code{gettext} calls does the job straightforwardly if the code starts
+out like this:
+
+@example
+printf (f->tried_implicit
+ ? "# Implicit rule search has been done.\n",
+ : "# Implicit rule search has not been done.\n");
+@end example
+
+Another example is this one:
+
@example
printf ("%d file%s processed", nfiles,
nfiles != 1 ? "s" : "");
@end example
@noindent
-The problem with that example is that it assumes that plurals are made
+The problem with this example is that it assumes that plurals are made
by adding `s'. If you apply gettext to the format string, like this,
@example
@noindent
the message can use different words, but it will still be forced to use
-`s' for the plural. Here is a better way:
+`s' for the plural. Here is a better way, with gettext being applied to
+the two strings independently:
@example
-printf ((nfiles != 1 ? "%d files processed"
- : "%d file processed"),
+printf ((nfiles != 1 ? gettext ("%d files processed")
+ : gettext ("%d file processed")),
nfiles);
@end example
@noindent
-This way, you can apply gettext to each of the two strings
-independently:
+But this still doesn't work for languages like Polish, which has three
+plural forms: one for nfiles == 1, one for nfiles == 2, 3, 4, 22, 23, 24, ...
+and one for the rest. The GNU @code{ngettext} function solves this problem:
@example
-printf ((nfiles != 1 ? gettext ("%d files processed")
- : gettext ("%d file processed")),
+printf (ngettext ("%d files processed", "%d file processed", nfiles),
nfiles);
@end example
-@noindent
-This can be any method of forming the plural of the word for ``file'', and
-also handles languages that require agreement in the word for
-``processed''.
-A similar problem appears at the level of sentence structure with this
-code:
+@node Character Set
+@section Character Set
+@cindex character set
+@cindex encodings
+@cindex ASCII characters
+@cindex non-ASCII characters
-@example
-printf ("# Implicit rule search has%s been done.\n",
- f->tried_implicit ? "" : " not");
-@end example
+Sticking to the ASCII character set (plain text, 7-bit characters) is
+preferred in GNU source code comments, text documents, and other
+contexts, unless there is good reason to do something else because of
+the application domain. For example, if source code deals with the
+French Revolutionary calendar, it is OK if its literal strings contain
+accented characters in month names like ``Flor@'eal''. Also, it is OK
+to use non-ASCII characters to represent proper names of contributors in
+change logs (@pxref{Change Logs}).
-@noindent
-Adding @code{gettext} calls to this code cannot give correct results for
-all languages, because negation in some languages requires adding words
-at more than one place in the sentence. By contrast, adding
-@code{gettext} calls does the job straightfowardly if the code starts
-out like this:
+If you need to use non-ASCII characters, you should normally stick with
+one encoding, as one cannot in general mix encodings reliably.
+
+
+@node Quote Characters
+@section Quote Characters
+@cindex quote characters
+@cindex locale-specific quote characters
+@cindex left quote
+@cindex grave accent
+
+In the C locale, GNU programs should stick to plain ASCII for quotation
+characters in messages to users: preferably 0x60 (@samp{`}) for left
+quotes and 0x27 (@samp{'}) for right quotes. It is ok, but not
+required, to use locale-specific quotes in other locales.
+
+The @uref{http://www.gnu.org/software/gnulib/, Gnulib} @code{quote} and
+@code{quotearg} modules provide a reasonably straightforward way to
+support locale-specific quote characters, as well as taking care of
+other issues, such as quoting a filename that itself contains a quote
+character. See the Gnulib documentation for usage details.
+
+In any case, the documentation for your program should clearly specify
+how it does quoting, if different than the preferred method of @samp{`}
+and @samp{'}. This is especially important if the output of your
+program is ever likely to be parsed by another program.
+
+Quotation characters are a difficult area in the computing world at
+this time: there are no true left or right quote characters in Latin1;
+the @samp{`} character we use was standardized there as a grave
+accent. Moreover, Latin1 is still not universally usable.
+
+Unicode contains the unambiguous quote characters required, and its
+common encoding UTF-8 is upward compatible with Latin1. However,
+Unicode and UTF-8 are not universally well-supported, either.
+
+This may change over the next few years, and then we will revisit
+this.
-@example
-printf (f->tried_implicit
- ? "# Implicit rule search has been done.\n",
- : "# Implicit rule search has not been done.\n");
-@end example
@node Mmap
@section Mmap
* Manual Credits:: Giving credit to documentation contributors.
* Printed Manuals:: Mentioning the printed manual.
* NEWS File:: NEWS files supplement manuals.
-* Change Logs:: Recording Changes
+* Change Logs:: Recording changes.
* Man Pages:: Man pages are secondary.
* Reading other Manuals:: How far you can go in learning
from other manuals.
converted automatically into Texinfo. It is ok to produce the Texinfo
documentation by conversion this way, as long as it gives good results.
-Programmers often find it most natural to structure the documentation
-following the structure of the implementation, which they know. But
-this structure is not necessarily good for explaining how to use the
-program; it may be irrelevant and confusing for a user.
-
-At every level, from the sentences in a paragraph to the grouping of
-topics into separate manuals, the right way to structure documentation
-is according to the concepts and questions that a user will have in mind
-when reading it. Sometimes this structure of ideas matches the
+Make sure your manual is clear to a reader who knows nothing about the
+topic and reads it straight through. This means covering basic topics
+at the beginning, and advanced topics only later. This also means
+defining every specialized term when it is first used.
+
+Programmers tend to carry over the structure of the program as the
+structure for its documentation. But this structure is not
+necessarily good for explaining how to use the program; it may be
+irrelevant and confusing for a user.
+
+Instead, the right way to structure documentation is according to the
+concepts and questions that a user will have in mind when reading it.
+This principle applies at every level, from the lowest (ordering
+sentences in a paragraph) to the highest (ordering of chapter topics
+within the manual). Sometimes this structure of ideas matches the
structure of the implementation of the software being documented---but
-often they are different. Often the most important part of learning to
-write good documentation is learning to notice when you are structuring
-the documentation like the implementation, and think about better
-alternatives.
+often they are different. An important part of learning to write good
+documentation is to learn to notice when you have unthinkingly
+structured the documentation like the implementation, stop yourself,
+and look for better alternatives.
For example, each program in the GNU system probably ought to be
documented in one manual; but this does not mean each program should
The manual which discusses a program should certainly document all of
the program's command-line options and all of its commands. It should
-give examples of their use. But don't organize the manual as a list of
-features. Instead, organize it logically, by subtopics. Address the
-questions that a user will ask when thinking about the job that the
-program does.
+give examples of their use. But don't organize the manual as a list
+of features. Instead, organize it logically, by subtopics. Address
+the questions that a user will ask when thinking about the job that
+the program does. Don't just tell the reader what each feature can
+do---say what jobs it is good for, and show how to use it for those
+jobs. Explain what is recommended usage, and what kinds of usage
+users should avoid.
In general, a GNU manual should serve both as tutorial and reference.
It should be set up for convenient access to each topic through Info,
the program. One combined Index should do for a short manual, but
sometimes for a complex package it is better to use multiple indices.
The Texinfo manual includes advice on preparing good index entries, see
-@ref{Index Entries, , Making Index Entries, texinfo, The GNU Texinfo
-Manual}, and see @ref{Indexing Commands, , Defining the Entries of an
-Index, texinfo, The GNU Texinfo manual}.
+@ref{Index Entries, , Making Index Entries, texinfo, GNU Texinfo}, and
+see @ref{Indexing Commands, , Defining the Entries of an
+Index, texinfo, GNU Texinfo}.
Don't use Unix man pages as a model for how to write GNU documentation;
most of them are terse, badly structured, and give inadequate
different from what we use in GNU manuals.
Please include an email address in the manual for where to report
-bugs @emph{in the manual}.
+bugs @emph{in the text of the manual}.
Please do not use the term ``pathname'' that is used in Unix
documentation; use ``file name'' (two words) instead. We use the term
``path'' only for search paths, which are lists of directory names.
-Please do not use the term ``illegal'' to refer to erroneous input to a
-computer program. Please use ``invalid'' for this, and reserve the term
-``illegal'' for activities punishable by law.
+Please do not use the term ``illegal'' to refer to erroneous input to
+a computer program. Please use ``invalid'' for this, and reserve the
+term ``illegal'' for activities prohibited by law.
+
+Please do not write @samp{()} after a function name just to indicate
+it is a function. @code{foo ()} is not a function, it is a function
+call with no arguments.
@node Doc Strings and Manuals
@section Doc Strings and Manuals
variables. The previous descriptions of functions and variables in the
section will also have given information about the topic. A description
written to stand alone would repeat some of that information; this
-redundance looks bad. Meanwhile, the informality that is acceptable in
+redundancy looks bad. Meanwhile, the informality that is acceptable in
a documentation string is totally unacceptable in a manual.
The only good way to use documentation strings in writing a good manual
@samp{@var{program} Invocation} or @samp{Invoking @var{program}}. This
node (together with its subnodes, if any) should describe the program's
command line arguments and how to run it (the sort of information people
-would look in a man page for). Start with an @samp{@@example}
+would look for in a man page). Start with an @samp{@@example}
containing a template for all the options and arguments that the program
uses.
history of how the conflicting concepts arose and who they came from.
@menu
-* Change Log Concepts::
-* Style of Change Logs::
-* Simple Changes::
-* Conditional Changes::
+* Change Log Concepts::
+* Style of Change Logs::
+* Simple Changes::
+* Conditional Changes::
* Indicating the Part Changed::
@end menu
you add a function, because there should be a comment before the
function definition to explain what it does.
+In the past, we recommended not mentioning changes in non-software
+files (manuals, help files, etc.) in change logs. However, we've been
+advised that it is a good idea to include them, for the sake of
+copyright records.
+
However, sometimes it is useful to write one line to describe the
overall purpose of a batch of changes.
@cindex change logs, style
Here are some simple examples of change log entries, starting with the
-header line that says who made the change and when, followed by
-descriptions of specific changes. (These examples are drawn from Emacs
-and GCC.)
+header line that says who made the change and when it was installed,
+followed by descriptions of specific changes. (These examples are
+drawn from Emacs and GCC.)
@example
1998-08-17 Richard Stallman <rms@@gnu.org>
(Fexecute_extended_command): Deal with `keymap' property.
@end example
+When you install someone else's changes, put the contributor's name in
+the change log entry rather than in the text of the entry. In other
+words, write this:
+
+@example
+2002-07-14 John Doe <jdoe@@gnu.org>
+
+ * sewing.c: Make it sew.
+@end example
+
+@noindent
+rather than this:
+
+@example
+2002-07-14 Usual Maintainer <usual@@gnu.org>
+
+ * sewing.c: Make it sew. Patch by jdoe@@gnu.org.
+@end example
+
+As for the date, that should be the date you applied the change.
+
@node Simple Changes
@subsection Simple Changes
entry for the file, without mentioning the functions. Just ``Doc
fixes'' is enough for the change log.
-There's no need to make change log entries for documentation files.
-This is because documentation is not susceptible to bugs that are hard
-to fix. Documentation does not consist of parts that must interact in a
-precisely engineered fashion. To correct an error, you need not know
-the history of the erroneous passage; it is enough to compare what the
-documentation says with the way the program actually works.
+There's no technical need to make change log entries for documentation
+files. This is because documentation is not susceptible to bugs that
+are hard to fix. Documentation does not consist of parts that must
+interact in a precisely engineered fashion. To correct an error, you
+need not know the history of the erroneous passage; it is enough to
+compare what the documentation says with the way the program actually
+works.
+
+However, you should keep change logs for documentation files when the
+project gets copyright assignments from its contributors, so as to
+make the records of authorship more accurate.
@node Conditional Changes
@subsection Conditional Changes
is more authoritative. The note should say how to access the Texinfo
documentation.
+Be sure that man pages include a copyright statement and free
+license. The simple all-permissive license is appropriate for simple
+man pages:
+
+@example
+Copying and distribution of this file, with or without modification,
+are permitted in any medium without royalty provided the copyright
+notice and this notice are preserved.
+@end example
+
+For long man pages, with enough explanation and documentation that
+they can be considered true manuals, use the GFDL (@pxref{License for
+Manuals}).
+
+Finally, the GNU help2man program
+(@uref{http://www.gnu.org/software/help2man/}) is one way to automate
+generation of a man page, in this case from @option{--help} output.
+This is sufficient in many cases.
+
@node Reading other Manuals
@section Reading other Manuals
all GNU software.
@menu
-* Configuration:: How Configuration Should Work
-* Makefile Conventions:: Makefile Conventions
-* Releases:: Making Releases
+* Configuration:: How configuration of GNU packages should work.
+* Makefile Conventions:: Makefile conventions.
+* Releases:: Making releases
@end menu
@node Configuration
@var{cpu}-@var{company}-@var{system}
@end example
-For example, a Sun 3 might be @samp{m68k-sun-sunos4.1}.
+For example, an Athlon-based GNU/Linux system might be
+@samp{i686-pc-linux-gnu}.
The @code{configure} script needs to be able to decode all plausible
-alternatives for how to describe a machine. Thus, @samp{sun3-sunos4.1}
-would be a valid alias. For many programs, @samp{vax-dec-ultrix} would
-be an alias for @samp{vax-dec-bsd}, simply because the differences
-between Ultrix and @sc{bsd} are rarely noticeable, but a few programs
-might need to distinguish them.
-@c Real 4.4BSD now runs on some Suns.
-
-There is a shell script called @file{config.sub} that you can use
-as a subroutine to validate system types and canonicalize aliases.
+alternatives for how to describe a machine. Thus,
+@samp{athlon-pc-gnu/linux} would be a valid alias. There is a shell
+script called
+@uref{http://savannah.gnu.org/@/cgi-bin/@/viewcvs/@/*checkout*/@/config/@/config/@/config.sub,
+@file{config.sub}} that you can use as a subroutine to validate system
+types and canonicalize aliases.
+
+The @code{configure} script should also take the option
+@option{--build=@var{buildtype}}, which should be equivalent to a
+plain @var{buildtype} argument. For example, @samp{configure
+--build=i686-pc-linux-gnu} is equivalent to @samp{configure
+i686-pc-linux-gnu}. When the build type is not specified by an option
+or argument, the @code{configure} script should normally guess it using
+the shell script
+@uref{http://savannah.gnu.org/@/cgi-bin/@/viewcvs/@/*checkout*/@/config/@/config/@/config.guess,
+@file{config.guess}}.
@cindex optional features, configure-time
Other options are permitted to specify in more detail the software
-or hardware present on the machine, and include or exclude optional
-parts of the package:
+or hardware present on the machine, to include or exclude optional parts
+of the package, or to adjust the name of some tools or arguments to them:
@table @samp
@item --enable-@var{feature}@r{[}=@var{parameter}@r{]}
Do not use a @samp{--with} option to specify the file name to use to
find certain files. That is outside the scope of what @samp{--with}
options are for.
+
+@item @var{variable}=@var{value}
+Set the value of the variable @var{variable} to @var{value}. This is
+used to override the default values of commands or arguments in the
+build process. For example, the user could issue @samp{configure
+CFLAGS=-g CXXFLAGS=-g} to build with debugging information and without
+the default optimization.
+
+Specifying variables as arguments to @code{configure}, like this:
+@example
+./configure CC=gcc
+@end example
+is preferable to setting them in environment variables:
+@example
+CC=gcc ./configure
+@end example
+as it helps to recreate the same configuration later with
+@file{config.status}.
@end table
-All @code{configure} scripts should accept all of these ``detail''
-options, whether or not they make any difference to the particular
-package at hand. In particular, they should accept any option that
-starts with @samp{--with-} or @samp{--enable-}. This is so users will
-be able to configure an entire GNU source tree at once with a single set
-of options.
+All @code{configure} scripts should accept all of the ``detail''
+options and the variable settings, whether or not they make any
+difference to the particular package at hand. In particular, they
+should accept any option that starts with @samp{--with-} or
+@samp{--enable-}. This is so users will be able to configure an
+entire GNU source tree at once with a single set of options.
You will note that the categories @samp{--with-} and @samp{--enable-}
are narrow: they @strong{do not} provide a place for any sort of option
system as both the host and the target, thus producing a program which
works for the same type of machine that it runs on.
+To compile a program to run on a host type that differs from the build
+type, use the configure option @option{--host=@var{hosttype}}, where
+@var{hosttype} uses the same syntax as @var{buildtype}. The host type
+normally defaults to the build type.
+
To configure a cross-compiler, cross-assembler, or what have you, you
should specify a target different from the host, using the configure
option @samp{--target=@var{targettype}}. The syntax for
look like this:
@example
-./configure @var{hosttype} --target=@var{targettype}
+./configure --host=@var{hosttype} --target=@var{targettype}
@end example
+The target type normally defaults to the host type.
Programs for which cross-operation is not meaningful need not accept the
@samp{--target} option, because configuring an entire operating system for
cross-operation is not a meaningful operation.
-Bootstrapping a cross-compiler requires compiling it on a machine other
-than the host it will run on. Compilation packages accept a
-configuration option @samp{--build=@var{buildtype}} for specifying the
-configuration on which you will compile them, but the configure script
-should normally guess the build machine type (using
-@file{config.guess}), so this option is probably not necessary. The
-host and target types normally default from the build type, so in
-bootstrapping a cross-compiler you must specify them both explicitly.
-
Some programs have ways of configuring themselves automatically. If
your program is set up to do this, your @code{configure} script can simply
ignore most of its arguments.
@section Making Releases
@cindex packaging
+You should identify each release with a pair of version numbers, a
+major version and a minor. We have no objection to using more than
+two numbers, but it is very unlikely that you really need them.
+
Package the distribution of @code{Foo version 69.96} up in a gzipped tar
file with the name @file{foo-69.96.tar.gz}. It should unpack into a
subdirectory named @file{foo-69.96}.
Make sure that all the files in the distribution are world-readable.
-Make sure that no file name in the distribution is more than 14
-characters long. Likewise, no file created by building the program
-should have a name longer than 14 characters. The reason for this is
-that some systems adhere to a foolish interpretation of the @sc{posix}
-standard, and refuse to open a longer name, rather than truncating as
-they did in the past.
-
Don't include any symbolic links in the distribution itself. If the tar
file contains symbolic links, then people cannot even unpack it on
systems that don't support symbolic links. Also, don't use multiple
A GNU program should not recommend use of any non-free program. We
can't stop some people from writing proprietary programs, or stop
-other people from using them, but we can and should avoid helping to
+other people from using them, but we can and should refuse to
advertise them to new potential customers. Proprietary software is a
social and ethical problem, and the point of GNU is to solve that
problem.
+The GNU definition of free software is found on the GNU web site at
+@url{http://www.gnu.org/philosophy/free-sw.html}, and the definition
+of free documentation is found at
+@url{http://www.gnu.org/philosophy/free-doc.html}. A list of
+important licenses and whether they qualify as free is in
+@url{http://www.gnu.org/@/licenses/@/license-list.html}. The terms
+``free'' and ``non-free'', used in this document, refer to that
+definition. If it is not clear whether a license qualifies as free
+under this definition, please ask the GNU Project by writing to
+@email{licensing@@gnu.org}. We will answer, and if the license is an
+important one, we will add it to the list.
+
When a non-free program or system is well known, you can mention it in
passing---that is harmless, since users who might want to use it
probably already know about it. For instance, it is fine to explain
-how to build your package on top of some non-free operating system, or
-how to use it together with some widely used non-free program.
+how to build your package on top of some widely used non-free
+operating system, or how to use it together with some widely used
+non-free program.
However, you should give only the necessary information to help those
who already use the non-free program to use your program with
enhances your program, or that its existence is in any way a good
thing. The goal should be that people already using the proprietary
program will get the advice they need about how to use your free
-program, while people who don't already use the proprietary program
-will not see anything to lead them to take an interest in it.
+program with it, while people who don't already use the proprietary
+program will not see anything to lead them to take an interest in it.
If a non-free program or system is obscure in your program's domain,
your program should not mention or support it at all, since doing so
your program. (You cannot hope to find many additional users among
the users of Foobar if the users of Foobar are few.)
+Sometimes a program is free software in itself but depends on a
+non-free platform in order to run. For instance, many Java programs
+depend on the parts of Sun's Java implementation which are not yet
+free software, and won't run on the GNU Java Compiler (which does not
+yet have all the features) or won't run with the GNU Java libraries.
+We hope this particular problem will be gone in a few months, when Sun
+makes the standard Java libraries free software, but of course the
+general principle remains: you should not recommend programs that
+depend on non-free software to run.
+
+Some free programs encourage the use of non-free software. A typical
+example is @command{mplayer}. It is free software in itself, and the
+free code can handle some kinds of files. However, @command{mplayer}
+recommends use of non-free codecs for other kinds of files, and users
+that install @command{mplayer} are very likely to install those codecs
+along with it. To recommend @command{mplayer} is, in effect, to
+recommend the non-free codecs. We must not do that, so we cannot
+recommend @command{mplayer} either.
+
+In general, you should also not recommend programs that themselves
+strongly recommend the use of non-free software.
+
A GNU package should not refer the user to any non-free documentation
for free software. Free documentation that can be included in free
-operating systems is essential for completing the GNU system, so it is
-a major focus of the GNU Project; to recommend use of documentation
-that we are not allowed to use in GNU would undermine the efforts to
-get documentation that we can include. So GNU packages should never
-recommend non-free documentation.
+operating systems is essential for completing the GNU system, or any
+free operating system, so it is a major focus of the GNU Project; to
+recommend use of documentation that we are not allowed to use in GNU
+would weaken the impetus for the community to produce documentation
+that we can include. So GNU packages should never recommend non-free
+documentation.
-@node Copying This Manual
-@appendix Copying This Manual
+By contrast, it is ok to refer to journal articles and textbooks in
+the comments of a program for explanation of how it functions, even
+though they be non-free. This is because we don't include such things
+in the GNU system even if we are allowed to---they are outside the
+scope of an operating system project.
-@menu
-* GNU Free Documentation License:: License for copying this manual
-@end menu
+Referring to a web site that describes or recommends a non-free
+program is in effect promoting that software, so please do not make
+links (or mention by name) web sites that contain such material. This
+policy is relevant particularly for the web pages for a GNU package.
+
+Following links from nearly any web site can lead to non-free
+software; this is an inescapable aspect of the nature of the web, and
+in itself is no objection to linking to a site. As long as the site
+does not itself recommend a non-free program, there is no need be
+concerned about the sites it links to for other reasons.
+Thus, for example, you should not make a link to AT&T's web site,
+because that recommends AT&T's non-free software packages; you should
+not make a link to a site that links to AT&T's site saying it is a
+place to get a non-free program; but if a site you want to link to
+refers to AT&T's web site in some other context (such as long-distance
+telephone service), that is not a problem.
+
+
+@node GNU Free Documentation License
+@appendix GNU Free Documentation License
+
+@cindex FDL, GNU Free Documentation License
@include fdl.texi
@node Index
@unnumbered Index
@printindex cp
-@contents
-
@bye
-@c Local variables:
-@c eval: (add-hook 'write-file-hooks 'time-stamp)
-@c time-stamp-start: "@set lastupdate "
-@c time-stamp-end: "$"
-@c time-stamp-format: "%:b %:d, %:y"
-@c compile-command: "make just-standards"
-@c End:
+
+Local variables:
+eval: (add-hook 'write-file-hooks 'time-stamp)
+time-stamp-start: "@set lastupdate "
+time-stamp-end: "$"
+time-stamp-format: "%:b %:d, %:y"
+compile-command: "make just-standards"
+End:
projects / msp430-binutils.git / blobdiff