\input texinfo
@setfilename ld.info
@c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
-@c 2001, 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
+@c 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
+@c Free Software Foundation, Inc.
@syncodeindex ky cp
@c man begin INCLUDE
@include configdoc.texi
@set HPPA
@set I960
@set M68HC11
+@set M68K
@set MMIX
@set MSP430
@set POWERPC
version @value{VERSION}.
Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000,
-2001, 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
+2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 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 1.3
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
@vskip 0pt plus 1filll
@c man begin COPYRIGHT
Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001,
-2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
+2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 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 1.3
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
version @value{VERSION}.
This document is distributed under the terms of the GNU Free
-Documentation License. A copy of the license is included in the
-section entitled ``GNU Free Documentation License''.
+Documentation License version 1.3. A copy of the license is included
+in the section entitled ``GNU Free Documentation License''.
@menu
* Overview:: Overview
@ifset M68HC11
* M68HC11/68HC12:: ld and the Motorola 68HC11 and 68HC12 families
@end ifset
+@ifset M68K
+* M68K:: ld and Motorola 68K family
+@end ifset
@ifset POWERPC
* PowerPC ELF32:: ld and PowerPC 32-bit ELF Support
@end ifset
linker script or the one specified by using @samp{-T}). This feature
permits the linker to link against a file which appears to be an object
or an archive, but actually merely defines some symbol values, or uses
-@code{INPUT} or @code{GROUP} to load other objects. Note that
-specifying a script in this way merely augments the main linker script;
-use the @samp{-T} option to replace the default linker script entirely.
-@xref{Scripts}.
+@code{INPUT} or @code{GROUP} to load other objects. Specifying a
+script in this way merely augments the main linker script, with the
+extra commands placed after the main script; use the @samp{-T} option
+to replace the default linker script entirely, but note the effect of
+the @code{INSERT} command. @xref{Scripts}.
For options whose names are a single letter,
option arguments must either follow the option letter without intervening
compiler driver) like this:
@smallexample
- gcc -Wl,--startgroup foo.o bar.o -Wl,--endgroup
+ gcc -Wl,--start-group foo.o bar.o -Wl,--end-group
@end smallexample
This is important, because otherwise the compiler driver program may
-silently drop the linker options, resulting in a bad link.
+silently drop the linker options, resulting in a bad link. Confusion
+may also arise when passing options that require values through a
+driver, as the use of a space between option and argument acts as
+a separator, and causes the driver to pass only the option to the linker
+and the argument to the compiler. In this case, it is simplest to use
+the joined forms of both single- and multiple-letter options, such as:
+
+@smallexample
+ gcc foo.o bar.o -Wl,-eENTRY -Wl,-Map=a.map
+@end smallexample
Here is a table of the generic command line switches accepted by the GNU
linker:
@table @gcctabopt
@include at-file.texi
-@kindex -a@var{keyword}
-@item -a@var{keyword}
+@kindex -a @var{keyword}
+@item -a @var{keyword}
This option is supported for HP/UX compatibility. The @var{keyword}
argument must be one of the strings @samp{archive}, @samp{shared}, or
@samp{default}. @samp{-aarchive} is functionally equivalent to
@ifset I960
@cindex architectures
-@kindex -A@var{arch}
-@item -A@var{architecture}
+@kindex -A @var{arch}
+@item -A @var{architecture}
@kindex --architecture=@var{arch}
@itemx --architecture=@var{architecture}
In the current release of @command{ld}, this option is useful only for the
@kindex --exclude-libs
@item --exclude-libs @var{lib},@var{lib},...
Specifies a list of archive libraries from which symbols should not be automatically
-exported. The library names may be delimited by commas or colons. Specifying
+exported. The library names may be delimited by commas or colons. Specifying
@code{--exclude-libs ALL} excludes symbols in all archive libraries from
automatic export. This option is available only for the i386 PE targeted
port of the linker and for ELF targeted ports. For i386 PE, symbols
option. For ELF targeted ports, symbols affected by this option will
be treated as hidden.
+@kindex --exclude-modules-for-implib
+@item --exclude-modules-for-implib @var{module},@var{module},...
+Specifies a list of object files or archive members, from which symbols
+should not be automatically exported, but which should be copied wholesale
+into the import library being generated during the link. The module names
+may be delimited by commas or colons, and must match exactly the filenames
+used by @command{ld} to open the files; for archive members, this is simply
+the member name, but for object files the name listed must include and
+match precisely any path used to specify the input file on the linker's
+command-line. This option is available only for the i386 PE targeted port
+of the linker. Symbols explicitly listed in a .def file are still exported,
+regardless of this option.
+
@cindex dynamic symbol table
@kindex -E
@kindex --export-dynamic
+@kindex --no-export-dynamic
@item -E
@itemx --export-dynamic
-When creating a dynamically linked executable, add all symbols to the
-dynamic symbol table. The dynamic symbol table is the set of symbols
-which are visible from dynamic objects at run time.
+@itemx --no-export-dynamic
+When creating a dynamically linked executable, using the @option{-E}
+option or the @option{--export-dynamic} option causes the linker to add
+all symbols to the dynamic symbol table. The dynamic symbol table is the
+set of symbols which are visible from dynamic objects at run time.
-If you do not use this option, the dynamic symbol table will normally
-contain only those symbols which are referenced by some dynamic object
-mentioned in the link.
+If you do not use either of these options (or use the
+@option{--no-export-dynamic} option to restore the default behavior), the
+dynamic symbol table will normally contain only those symbols which are
+referenced by some dynamic object mentioned in the link.
If you use @code{dlopen} to load a dynamic object which needs to refer
back to the symbols defined by the program, rather than some other
be added to the dynamic symbol table if the output format supports it.
See the description of @samp{--dynamic-list}.
+Note that this option is specific to ELF targeted ports. PE targets
+support a similar function to export all symbols from a DLL or EXE; see
+the description of @samp{--export-all-symbols} below.
+
@ifclear SingleFormat
@cindex big-endian objects
@cindex endianness
Link little-endian objects. This affects the default output format.
@end ifclear
-@kindex -f
-@kindex --auxiliary
-@item -f
-@itemx --auxiliary @var{name}
+@kindex -f @var{name}
+@kindex --auxiliary=@var{name}
+@item -f @var{name}
+@itemx --auxiliary=@var{name}
When creating an ELF shared object, set the internal DT_AUXILIARY field
to the specified name. This tells the dynamic linker that the symbol
table of the shared object should be used as an auxiliary filter on the
This option may be specified more than once. The DT_AUXILIARY entries
will be created in the order in which they appear on the command line.
-@kindex -F
-@kindex --filter
+@kindex -F @var{name}
+@kindex --filter=@var{name}
@item -F @var{name}
-@itemx --filter @var{name}
+@itemx --filter=@var{name}
When creating an ELF shared object, set the internal DT_FILTER field to
the specified name. This tells the dynamic linker that the symbol table
of the shared object which is being created should be used as a filter
creating an ELF shared object.
@cindex finalization function
-@kindex -fini
-@item -fini @var{name}
+@kindex -fini=@var{name}
+@item -fini=@var{name}
When creating an ELF executable or shared object, call NAME when the
executable or shared object is unloaded, by setting DT_FINI to the
address of the function. By default, the linker uses @code{_fini} as
@item -g
Ignored. Provided for compatibility with other tools.
-@kindex -G
-@kindex --gpsize
+@kindex -G @var{value}
+@kindex --gpsize=@var{value}
@cindex object size
-@item -G@var{value}
+@item -G @var{value}
@itemx --gpsize=@var{value}
Set the maximum size of objects to be optimized using the GP register to
@var{size}. This is only meaningful for object file formats such as
sections. This is ignored for other object file formats.
@cindex runtime library name
-@kindex -h@var{name}
+@kindex -h @var{name}
@kindex -soname=@var{name}
-@item -h@var{name}
+@item -h @var{name}
@itemx -soname=@var{name}
When creating an ELF shared object, set the internal DT_SONAME field to
the specified name. When an executable is linked with a shared object
Perform an incremental link (same as option @samp{-r}).
@cindex initialization function
-@kindex -init
-@item -init @var{name}
+@kindex -init=@var{name}
+@item -init=@var{name}
When creating an ELF executable or shared object, call NAME when the
executable or shared object is loaded, by setting DT_INIT to the address
of the function. By default, the linker uses @code{_init} as the
function to call.
@cindex archive files, from cmd line
-@kindex -l@var{namespec}
+@kindex -l @var{namespec}
@kindex --library=@var{namespec}
-@item -l@var{namespec}
+@item -l @var{namespec}
@itemx --library=@var{namespec}
Add the archive or object file specified by @var{namespec} to the
list of files to link. This option may be used any number of times.
If @var{namespec} is of the form @file{:@var{filename}}, @command{ld}
-will search the library path for a file called @var{filename}, otherise it
+will search the library path for a file called @var{filename}, otherwise it
will search the library path for a file called @file{lib@var{namespec}.a}.
On systems which support shared libraries, @command{ld} may also search for
@end ifset
@cindex search directory, from cmd line
-@kindex -L@var{dir}
+@kindex -L @var{dir}
@kindex --library-path=@var{dir}
-@item -L@var{searchdir}
+@item -L @var{searchdir}
@itemx --library-path=@var{searchdir}
Add path @var{searchdir} to the list of paths that @command{ld} will search
for archive libraries and @command{ld} control scripts. You may use this
in which they are specified on the command line. Directories specified
on the command line are searched before the default directories. All
@option{-L} options apply to all @option{-l} options, regardless of the
-order in which the options appear.
+order in which the options appear. @option{-L} options do not affect
+how @command{ld} searches for a linker script unless @option{-T}
+option is specified.
If @var{searchdir} begins with @code{=}, then the @code{=} will be replaced
by the @dfn{sysroot prefix}, a path specified when the linker is configured.
@cindex emulation
@kindex -m @var{emulation}
-@item -m@var{emulation}
+@item -m @var{emulation}
Emulate the @var{emulation} linker. You can list the available
emulations with the @samp{--verbose} or @samp{-V} options.
on the command line after the @option{--as-needed} option. Normally,
the linker will add a DT_NEEDED tag for each dynamic library mentioned
on the command line, regardless of whether the library is actually
-needed. @option{--as-needed} causes DT_NEEDED tags to only be emitted
-for libraries that satisfy some symbol reference from regular objects
-which is undefined at the point that the library was linked.
+needed. @option{--as-needed} causes a DT_NEEDED tag to only be emitted
+for a library that satisfies a symbol reference from regular objects
+which is undefined at the point that the library was linked, or, if
+the library is not found in the DT_NEEDED lists of other libraries
+linked up to that point, a reference from another dynamic library.
@option{--no-as-needed} restores the default behaviour.
@kindex --add-needed
suitable error messages. The linker does know about, and does make
allowances for sections in overlays. The default behaviour can be
restored by using the command line switch @option{--check-sections}.
+Section overlap is not usually checked for relocatable links. You can
+force checking in that case by using the @option{--check-sections}
+option.
@cindex cross reference table
@kindex --cref
paths for runtime symbol resolution.
@cindex symbols, from command line
-@kindex --defsym @var{symbol}=@var{exp}
-@item --defsym @var{symbol}=@var{expression}
+@kindex --defsym=@var{symbol}=@var{exp}
+@item --defsym=@var{symbol}=@var{expression}
Create a global symbol in the output file, containing the absolute
address given by @var{expression}. You may use this option as many
times as necessary to define multiple symbols in the command line. A
@cindex dynamic linker, from command line
@kindex -I@var{file}
-@kindex --dynamic-linker @var{file}
-@item --dynamic-linker @var{file}
+@kindex --dynamic-linker=@var{file}
+@item -I@var{file}
+@itemx --dynamic-linker=@var{file}
Set the name of the dynamic linker. This is only meaningful when
generating dynamically linked ELF executables. The default dynamic
linker is normally correct; don't use this unless you know what you are
doing.
-
@kindex --fatal-warnings
+@kindex --no-fatal-warnings
@item --fatal-warnings
-Treat all warnings as errors.
+@itemx --no-fatal-warnings
+Treat all warnings as errors. The default behaviour can be restored
+with the option @option{--no-fatal-warnings}.
@kindex --force-exe-suffix
@item --force-exe-suffix
@item --gc-sections
@itemx --no-gc-sections
Enable garbage collection of unused input sections. It is ignored on
-targets that do not support this option. This option is not compatible
-with @samp{-r} or @samp{--emit-relocs}. The default behaviour (of not
+targets that do not support this option. The default behaviour (of not
performing this garbage collection) can be restored by specifying
@samp{--no-gc-sections} on the command line.
+@samp{--gc-sections} decides which input sections are used by
+examining symbols and relocations. The section containing the entry
+symbol and all sections containing symbols undefined on the
+command-line will be kept, as will sections containing symbols
+referenced by dynamic objects. Note that when building shared
+libraries, the linker must assume that any visible symbol is
+referenced. Once this initial set of sections has been determined,
+the linker recursively marks as used any section referenced by their
+relocations. See @samp{--entry} and @samp{--undefined}.
+
+This option can be set when doing a partial link (enabled with option
+@samp{-r}). In this case the root of symbols kept must be explicitely
+specified either by an @samp{--entry} or @samp{--undefined} option or by
+a @code{ENTRY} command in the linker script.
+
@kindex --print-gc-sections
@kindex --no-print-gc-sections
@cindex garbage collection
@item --target-help
Print a summary of all target specific options on the standard output and exit.
-@kindex -Map
-@item -Map @var{mapfile}
+@kindex -Map=@var{mapfile}
+@item -Map=@var{mapfile}
Print a link map to the file @var{mapfile}. See the description of the
@option{-M} option, above.
@kindex --no-allow-shlib-undefined
@item --allow-shlib-undefined
@itemx --no-allow-shlib-undefined
-Allows (the default) or disallows undefined symbols in shared libraries.
+Allows or disallows undefined symbols in shared libraries.
This switch is similar to @option{--no-undefined} except that it
determines the behaviour when the undefined symbols are in a
shared library rather than a regular object file. It does not affect
how undefined symbols in regular object files are handled.
-The reason that @option{--allow-shlib-undefined} is the default is that
-the shared library being specified at link time may not be the same as
-the one that is available at load time, so the symbols might actually be
-resolvable at load time. Plus there are some systems, (eg BeOS) where
-undefined symbols in shared libraries is normal. (The kernel patches
-them at load time to select which function is most appropriate
-for the current architecture. This is used for example to dynamically
-select an appropriate memset function). Apparently it is also normal
-for HPPA shared libraries to have undefined symbols.
+The default behaviour is to report errors for any undefined symbols
+referenced in shared libraries if the linker is being used to create
+an executable, but to allow them if the linker is being used to create
+a shared library.
+
+The reasons for allowing undefined symbol references in shared
+libraries specified at link time are that:
+
+@itemize @bullet
+@item
+A shared library specified at link time may not be the same as the one
+that is available at load time, so the symbol might actually be
+resolvable at load time.
+@item
+There are some operating systems, eg BeOS and HPPA, where undefined
+symbols in shared libraries are normal.
+
+The BeOS kernel for example patches shared libraries at load time to
+select whichever function is most appropriate for the current
+architecture. This is used, for example, to dynamically select an
+appropriate memset function.
+@end itemize
@kindex --no-undefined-version
@item --no-undefined-version
(including linker scripts specified on the command line) are ignored.
@ifclear SingleFormat
-@kindex --oformat
-@item --oformat @var{output-format}
+@kindex --oformat=@var{output-format}
+@item --oformat=@var{output-format}
@command{ld} may be configured to support more than one kind of object
file. If your @command{ld} is configured this way, you can use the
@samp{--oformat} option to specify the binary format for the output
@cindex retaining specified symbols
@cindex stripping all but some symbols
@cindex symbols, retaining selectively
-@item --retain-symbols-file @var{filename}
+@kindex --retain-symbols-file=@var{filename}
+@item --retain-symbols-file=@var{filename}
Retain @emph{only} the symbols listed in the file @var{filename},
discarding all others. @var{filename} is simply a flat file, with one
symbol name per line. This option is especially useful in environments
line. It overrides @samp{-s} and @samp{-S}.
@ifset GENERIC
-@item -rpath @var{dir}
+@item -rpath=@var{dir}
@cindex runtime library search path
-@kindex -rpath
+@kindex -rpath=@var{dir}
Add a directory to the runtime library search path. This is used when
linking an ELF executable with shared objects. All @option{-rpath}
arguments are concatenated and passed to the runtime linker, which uses
@ifset GENERIC
@cindex link-time runtime library search path
-@kindex -rpath-link
-@item -rpath-link @var{DIR}
+@kindex -rpath-link=@var{dir}
+@item -rpath-link=@var{dir}
When using ELF or SunOS, one shared library may require another. This
happens when an @code{ld -shared} link includes a shared library as one
of the input files.
by native linkers and cross linkers which have been configured with
the @option{--with-sysroot} option.
@item
-On an ELF system, if the @option{-rpath} and @code{rpath-link} options
-were not used, search the contents of the environment variable
-@code{LD_RUN_PATH}. It is for the native linker only.
+On an ELF system, for native linkers, if the @option{-rpath} and
+@option{-rpath-link} options were not used, search the contents of the
+environment variable @code{LD_RUN_PATH}.
@item
On SunOS, if the @option{-rpath} option was not used, search any
directories specified using @option{-L} options.
@item
-For a native linker, the contents of the environment variable
-@code{LD_LIBRARY_PATH}.
+For a native linker, the search the contents of the environment
+variable @code{LD_LIBRARY_PATH}.
@item
For a native ELF linker, the directories in @code{DT_RUNPATH} or
@code{DT_RPATH} of a shared library are searched for shared
shared library if the @option{-e} option is not used and there are
undefined symbols in the link.
-@item --sort-common
@kindex --sort-common
-This option tells @command{ld} to sort the common symbols by size when it
-places them in the appropriate output sections. First come all the one
-byte symbols, then all the two byte, then all the four byte, and then
-everything else. This is to prevent gaps between symbols due to
-alignment constraints.
-
-@kindex --sort-section name
-@item --sort-section name
+@item --sort-common
+@itemx --sort-common=ascending
+@itemx --sort-common=descending
+This option tells @command{ld} to sort the common symbols by alignment in
+ascending or descending order when it places them in the appropriate output
+sections. The symbol alignments considered are sixteen-byte or larger,
+eight-byte, four-byte, two-byte, and one-byte. This is to prevent gaps
+between symbols due to alignment constraints. If no sorting order is
+specified, then descending order is assumed.
+
+@kindex --sort-section=name
+@item --sort-section=name
This option will apply @code{SORT_BY_NAME} to all wildcard section
patterns in the linker script.
-@kindex --sort-section alignment
-@item --sort-section alignment
+@kindex --sort-section=alignment
+@item --sort-section=alignment
This option will apply @code{SORT_BY_ALIGNMENT} to all wildcard section
patterns in the linker script.
@kindex --split-by-file
-@item --split-by-file [@var{size}]
+@item --split-by-file[=@var{size}]
Similar to @option{--split-by-reloc} but creates a new output section for
each input file when @var{size} is reached. @var{size} defaults to a
size of 1 if not given.
@kindex --split-by-reloc
-@item --split-by-reloc [@var{count}]
+@item --split-by-reloc[=@var{count}]
Tries to creates extra sections in the output file so that no single
output section in the file contains more than @var{count} relocations.
This is useful when generating huge relocatable files for downloading into
Compute and display statistics about the operation of the linker, such
as execution time and memory usage.
-@kindex --sysroot
+@kindex --sysroot=@var{directory}
@item --sysroot=@var{directory}
Use @var{directory} as the location of the sysroot, overriding the
configure-time default. This option is only supported by linkers
trouble). The @samp{--traditional-format} switch tells @command{ld} to not
combine duplicate entries.
-@kindex --section-start @var{sectionname}=@var{org}
-@item --section-start @var{sectionname}=@var{org}
+@kindex --section-start=@var{sectionname}=@var{org}
+@item --section-start=@var{sectionname}=@var{org}
Locate a section in the output file at the absolute
address given by @var{org}. You may use this option as many
times as necessary to locate multiple sections in the command
should be no white space between @var{sectionname}, the equals
sign (``@key{=}''), and @var{org}.
-@kindex -Tbss @var{org}
-@kindex -Tdata @var{org}
-@kindex -Ttext @var{org}
+@kindex -Tbss=@var{org}
+@kindex -Tdata=@var{org}
+@kindex -Ttext=@var{org}
@cindex segment origins, cmd line
-@item -Tbss @var{org}
-@itemx -Tdata @var{org}
-@itemx -Ttext @var{org}
-Same as --section-start, with @code{.bss}, @code{.data} or
+@item -Tbss=@var{org}
+@itemx -Tdata=@var{org}
+@itemx -Ttext=@var{org}
+Same as @option{--section-start}, with @code{.bss}, @code{.data} or
@code{.text} as the @var{sectionname}.
+@kindex -Ttext-segment=@var{org}
+@item -Ttext-segment=@var{org}
+@cindex text segment origin, cmd line
+When creating an ELF executable or shared object, it will set the address
+of the first byte of the text segment.
+
@kindex --unresolved-symbols
@item --unresolved-symbols=@var{method}
Determine how to handle unresolved symbols. There are four possible
@kindex --version-script=@var{version-scriptfile}
@cindex version script, symbol versions
-@itemx --version-script=@var{version-scriptfile}
+@item --version-script=@var{version-scriptfile}
Specify the name of a version script to the linker. This is typically
used when creating shared libraries to specify additional information
about the version hierarchy for the library being created. This option
-is only meaningful on ELF platforms which support shared libraries.
-@xref{VERSION}.
+is only fully supported on ELF platforms which support shared libraries;
+see @ref{VERSION}. It is partially supported on PE platforms, which can
+use version scripts to filter symbol visibility in auto-export mode: any
+symbols marked @samp{local} in the version script will not be exported.
+@xref{WIN32}.
@kindex --warn-common
@cindex warnings, on combining symbols
@item --warn-shared-textrel
Warn if the linker adds a DT_TEXTREL to a shared object.
+@kindex --warn-alternate-em
+@item --warn-alternate-em
+Warn if an object has alternate ELF machine code.
+
@kindex --warn-unresolved-symbols
@item --warn-unresolved-symbols
If the linker is going to report an unresolved symbol (see the option
list of archives, because gcc will add its own list of archives to
your link and you may not want this flag to affect those as well.
-@kindex --wrap
-@item --wrap @var{symbol}
+@kindex --wrap=@var{symbol}
+@item --wrap=@var{symbol}
Use a wrapper function for @var{symbol}. Any undefined reference to
@var{symbol} will be resolved to @code{__wrap_@var{symbol}}. Any
undefined reference to @code{__real_@var{symbol}} will be resolved to
file.
[This option is specific to the i386 PE targeted port of the linker]
+@kindex --enable-long-section-names
+@kindex --disable-long-section-names
+@item --enable-long-section-names
+@itemx --disable-long-section-names
+The PE variants of the Coff object format add an extension that permits
+the use of section names longer than eight characters, the normal limit
+for Coff. By default, these names are only allowed in object files, as
+fully-linked executable images do not carry the Coff string table required
+to support the longer names. As a GNU extension, it is possible to
+allow their use in executable images as well, or to (probably pointlessly!)
+disallow it in object files, by using these two options. Executable images
+generated with these long section names are slightly non-standard, carrying
+as they do a string table, and may generate confusing output when examined
+with non-GNU PE-aware tools, such as file viewers and dumpers. However,
+GDB relies on the use of PE long section names to find Dwarf-2 debug
+information sections in an executable image at runtime, and so if neither
+option is specified on the command-line, @command{ld} will enable long
+section names, overriding the default and technically correct behaviour,
+when it finds the presence of debug information while linking an executable
+image and not stripping symbols.
+[This option is valid for all PE targeted ports of the linker]
+
@kindex --enable-stdcall-fixup
@kindex --disable-stdcall-fixup
@item --enable-stdcall-fixup
to be made writable. This does not conform to the PE-COFF format
specification published by Microsoft.
+Note - use of the 'auto-import' extension will also cause read only
+data which would normally be placed into the .rdata section to be
+placed into the .data section instead. This is in order to work
+around a problem with consts that is described here:
+http://www.cygwin.com/ml/cygwin/2004-09/msg01101.html
+
Using 'auto-import' generally will 'just work' -- but sometimes you may
see this message:
@var{which}.
[This option is specific to the i386 PE targeted port of the linker]
+The following options set flags in the @code{DllCharacteristics} field
+of the PE file header:
+[These options are specific to PE targeted ports of the linker]
+
+@kindex --dynamicbase
+@item --dynamicbase
+The image base address may be relocated using address space layout
+randomization (ASLR). This feature was introduced with MS Windows
+Vista for i386 PE targets.
+
+@kindex --forceinteg
+@item --forceinteg
+Code integrity checks are enforced.
+
+@kindex --nxcompat
+@item --nxcompat
+The image is compatible with the Data Execution Prevention.
+This feature was introduced with MS Windows XP SP2 for i386 PE targets.
+
+@kindex --no-isolation
+@item --no-isolation
+Although the image understands isolation, do not isolate the image.
+
+@kindex --no-seh
+@item --no-seh
+The image does not use SEH. No SE handler may be called from
+this image.
+
+@kindex --no-bind
+@item --no-bind
+Do not bind this image.
+
+@kindex --wdmdriver
+@item --wdmdriver
+The driver uses the MS Windows Driver Model.
+
+@kindex --tsaware
+@item --tsaware
+The image is Terminal Server aware.
+
@end table
@c man end
@c man end
@end ifset
+@ifset M68K
+@subsection Options specific to Motorola 68K target
+
+@c man begin OPTIONS
+
+The following options are supported to control handling of GOT generation
+when linking for 68K targets.
+
+@table @gcctabopt
+
+@kindex --got
+@item --got=@var{type}
+This option tells the linker which GOT generation scheme to use.
+@var{type} should be one of @samp{single}, @samp{negative},
+@samp{multigot} or @samp{target}. For more information refer to the
+Info entry for @file{ld}.
+
+@end table
+
+@c man end
+@end ifset
+
@ifset UsesEnvVars
@node Environment
@section Environment Variables
* Format Commands:: Commands dealing with object file formats
@end ifclear
+* REGION_ALIAS:: Assign alias names to memory regions
* Miscellaneous Commands:: Other linker script commands
@end menu
with the @option{-L} option. You can nest calls to @code{INCLUDE} up to
10 levels deep.
+You can place @code{INCLUDE} directives at the top level, in @code{MEMORY} or
+@code{SECTIONS} commands, or in output section descriptions.
+
@item INPUT(@var{file}, @var{file}, @dots{})
@itemx INPUT(@var{file} @var{file} @dots{})
@kindex INPUT(@var{files})
@end table
@end ifclear
+@node REGION_ALIAS
+@subsection Assign alias names to memory regions
+@kindex REGION_ALIAS(@var{alias}, @var{region})
+@cindex region alias
+@cindex region names
+
+Alias names can be added to existing memory regions created with the
+@ref{MEMORY} command. Each name corresponds to at most one memory region.
+
+@smallexample
+REGION_ALIAS(@var{alias}, @var{region})
+@end smallexample
+
+The @code{REGION_ALIAS} function creates an alias name @var{alias} for the
+memory region @var{region}. This allows a flexible mapping of output sections
+to memory regions. An example follows.
+
+Suppose we have an application for embedded systems which come with various
+memory storage devices. All have a general purpose, volatile memory @code{RAM}
+that allows code execution or data storage. Some may have a read-only,
+non-volatile memory @code{ROM} that allows code execution and read-only data
+access. The last variant is a read-only, non-volatile memory @code{ROM2} with
+read-only data access and no code execution capability. We have four output
+sections:
+
+@itemize @bullet
+@item
+@code{.text} program code;
+@item
+@code{.rodata} read-only data;
+@item
+@code{.data} read-write initialized data;
+@item
+@code{.bss} read-write zero initialized data.
+@end itemize
+
+The goal is to provide a linker command file that contains a system independent
+part defining the output sections and a system dependent part mapping the
+output sections to the memory regions available on the system. Our embedded
+systems come with three different memory setups @code{A}, @code{B} and
+@code{C}:
+@multitable @columnfractions .25 .25 .25 .25
+@item Section @tab Variant A @tab Variant B @tab Variant C
+@item .text @tab RAM @tab ROM @tab ROM
+@item .rodata @tab RAM @tab ROM @tab ROM2
+@item .data @tab RAM @tab RAM/ROM @tab RAM/ROM2
+@item .bss @tab RAM @tab RAM @tab RAM
+@end multitable
+The notation @code{RAM/ROM} or @code{RAM/ROM2} means that this section is
+loaded into region @code{ROM} or @code{ROM2} respectively. Please note that
+the load address of the @code{.data} section starts in all three variants at
+the end of the @code{.rodata} section.
+
+The base linker script that deals with the output sections follows. It
+includes the system dependent @code{linkcmds.memory} file that describes the
+memory layout:
+@smallexample
+INCLUDE linkcmds.memory
+
+SECTIONS
+ @{
+ .text :
+ @{
+ *(.text)
+ @} > REGION_TEXT
+ .rodata :
+ @{
+ *(.rodata)
+ rodata_end = .;
+ @} > REGION_RODATA
+ .data : AT (rodata_end)
+ @{
+ data_start = .;
+ *(.data)
+ @} > REGION_DATA
+ data_size = SIZEOF(.data);
+ data_load_start = LOADADDR(.data);
+ .bss :
+ @{
+ *(.bss)
+ @} > REGION_BSS
+ @}
+@end smallexample
+
+Now we need three different @code{linkcmds.memory} files to define memory
+regions and alias names. The content of @code{linkcmds.memory} for the three
+variants @code{A}, @code{B} and @code{C}:
+@table @code
+@item A
+Here everything goes into the @code{RAM}.
+@smallexample
+MEMORY
+ @{
+ RAM : ORIGIN = 0, LENGTH = 4M
+ @}
+
+REGION_ALIAS("REGION_TEXT", RAM);
+REGION_ALIAS("REGION_RODATA", RAM);
+REGION_ALIAS("REGION_DATA", RAM);
+REGION_ALIAS("REGION_BSS", RAM);
+@end smallexample
+@item B
+Program code and read-only data go into the @code{ROM}. Read-write data goes
+into the @code{RAM}. An image of the initialized data is loaded into the
+@code{ROM} and will be copied during system start into the @code{RAM}.
+@smallexample
+MEMORY
+ @{
+ ROM : ORIGIN = 0, LENGTH = 3M
+ RAM : ORIGIN = 0x10000000, LENGTH = 1M
+ @}
+
+REGION_ALIAS("REGION_TEXT", ROM);
+REGION_ALIAS("REGION_RODATA", ROM);
+REGION_ALIAS("REGION_DATA", RAM);
+REGION_ALIAS("REGION_BSS", RAM);
+@end smallexample
+@item C
+Program code goes into the @code{ROM}. Read-only data goes into the
+@code{ROM2}. Read-write data goes into the @code{RAM}. An image of the
+initialized data is loaded into the @code{ROM2} and will be copied during
+system start into the @code{RAM}.
+@smallexample
+MEMORY
+ @{
+ ROM : ORIGIN = 0, LENGTH = 2M
+ ROM2 : ORIGIN = 0x10000000, LENGTH = 1M
+ RAM : ORIGIN = 0x20000000, LENGTH = 1M
+ @}
+
+REGION_ALIAS("REGION_TEXT", ROM);
+REGION_ALIAS("REGION_RODATA", ROM2);
+REGION_ALIAS("REGION_DATA", RAM);
+REGION_ALIAS("REGION_BSS", RAM);
+@end smallexample
+@end table
+
+It is possible to write a common system initialization routine to copy the
+@code{.data} section from @code{ROM} or @code{ROM2} into the @code{RAM} if
+necessary:
+@smallexample
+#include <string.h>
+
+extern char data_start [];
+extern char data_size [];
+extern char data_load_start [];
+
+void copy_data(void)
+@{
+ if (data_start != data_load_start)
+ @{
+ memcpy(data_start, data_load_start, (size_t) data_size);
+ @}
+@}
+@end smallexample
+
@node Miscellaneous Commands
@subsection Other Linker Script Commands
There are a few other linker scripts commands.
command-line option: to make @code{ld} omit the assignment of addresses
to common symbols even for a non-relocatable output file.
+@item INSERT [ AFTER | BEFORE ] @var{output_section}
+@kindex INSERT
+@cindex insert user script into default script
+This command is typically used in a script specified by @samp{-T} to
+augment the default @code{SECTIONS} with, for example, overlays. It
+inserts all prior linker script statements after (or before)
+@var{output_section}, and also causes @samp{-T} to not override the
+default linker script. The exact insertion point is as for orphan
+sections. @xref{Location Counter}. The insertion happens after the
+linker has mapped input sections to output sections. Prior to the
+insertion, since @samp{-T} scripts are parsed before the default
+linker script, statements in the @samp{-T} script occur before the
+default linker script statements in the internal linker representation
+of the script. In particular, input section assignments will be made
+to @samp{-T} output sections before those in the default script. Here
+is an example of how a @samp{-T} script using @code{INSERT} might look:
+
+@smallexample
+SECTIONS
+@{
+ OVERLAY :
+ @{
+ .ov1 @{ ov1*(.text) @}
+ .ov2 @{ ov2*(.text) @}
+ @}
+@}
+INSERT AFTER .text;
+@end smallexample
+
@item NOCROSSREFS(@var{section} @var{section} @dots{})
@kindex NOCROSSREFS(@var{sections})
@cindex cross references
@smallexample
@group
@var{section} [@var{address}] [(@var{type})] :
- [AT(@var{lma})] [ALIGN(@var{section_align})] [SUBALIGN(@var{subsection_align})]
+ [AT(@var{lma})]
+ [ALIGN(@var{section_align})]
+ [SUBALIGN(@var{subsection_align})]
+ [@var{constraint}]
@{
@var{output-section-command}
@var{output-section-command}
aligned upward to the specified value.
Specifying @var{address} for a section will change the value of the
-location counter.
+location counter, provided that the section is non-empty. (Empty
+sections are ignored).
@node Input Section
@subsection Input Section Description
data.o(.data)
@end smallexample
+You can also specify files within archives by writing a pattern
+matching the archive, a colon, then the pattern matching the file,
+with no whitespace around the colon.
+
+@table @samp
+@item archive:file
+matches file within archive
+@item archive:
+matches the whole archive
+@item :file
+matches file but not one in an archive
+@end table
+
+Either one or both of @samp{archive} and @samp{file} can contain shell
+wildcards. On DOS based file systems, the linker will assume that a
+single letter followed by a colon is a drive specifier, so
+@samp{c:myfile.o} is a simple file specification, not @samp{myfile.o}
+within an archive called @samp{c}. @samp{archive:file} filespecs may
+also be used within an @code{EXCLUDE_FILE} list, but may not appear in
+other linker script contexts. For instance, you cannot extract a file
+from an archive by using @samp{archive:file} in an @code{INPUT}
+command.
+
If you use a file name without a list of sections, then all sections in
the input file will be included in the output section. This is not
commonly done, but it may by useful on occasion. For example:
data.o
@end smallexample
-When you use a file name which does not contain any wild card
+When you use a file name which is not an @samp{archive:file} specifier
+and does not contain any wild card
characters, the linker will first see if you also specified the file
name on the linker command line or in an @code{INPUT} command. If you
did not, the linker will attempt to open the file as an input file, as
@cindex output section attributes
We showed above that the full description of an output section looked
like this:
+
@smallexample
@group
@var{section} [@var{address}] [(@var{type})] :
- [AT(@var{lma})] [ALIGN(@var{section_align})] [SUBALIGN(@var{subsection_align})]
+ [AT(@var{lma})]
+ [ALIGN(@var{section_align})]
+ [SUBALIGN(@var{subsection_align})]
+ [@var{constraint}]
@{
@var{output-section-command}
@var{output-section-command}
@} [>@var{region}] [AT>@var{lma_region}] [:@var{phdr} :@var{phdr} @dots{}] [=@var{fillexp}]
@end group
@end smallexample
+
We've already described @var{section}, @var{address}, and
@var{output-section-command}. In this section we will describe the
remaining section attributes.
* Output Section LMA:: Output section LMA
* Forced Output Alignment:: Forced Output Alignment
* Forced Input Alignment:: Forced Input Alignment
+* Output Section Constraint:: Output section constraint
* Output Section Region:: Output section region
* Output Section Phdr:: Output section phdr
* Output Section Fill:: Output section fill
SUBALIGN. The value specified overrides any alignment given by input
sections, whether larger or smaller.
+@node Output Section Constraint
+@subsubsection Output Section Constraint
+@kindex ONLY_IF_RO
+@kindex ONLY_IF_RW
+@cindex constraints on output sections
+You can specify that an output section should only be created if all
+of its input sections are read-only or all of its input sections are
+read-write by using the keyword @code{ONLY_IF_RO} and
+@code{ONLY_IF_RW} respectively.
+
@node Output Section Region
@subsubsection Output Section Region
@kindex >@var{region}
region. The region name has no meaning outside of the linker script.
Region names are stored in a separate name space, and will not conflict
with symbol names, file names, or section names. Each memory region
-must have a distinct name.
+must have a distinct name within the @code{MEMORY} command. However you can
+add later alias names to existing memory regions with the @ref{REGION_ALIAS}
+command.
@cindex memory region attributes
The @var{attr} string is an optional list of attributes that specify
specifically bound to a version node, it will effectively bind it to an
unspecified base version of the library. You can bind all otherwise
unspecified symbols to a given version node by using @samp{global: *;}
-somewhere in the version script.
+somewhere in the version script. Note that it's slightly crazy to use
+wildcards in a global spec except on the last version node. Global
+wildcards elsewhere run the risk of accidentally adding symbols to the
+set exported for an old version. That's wrong since older versions
+ought to have a fixed set of symbols.
The names of the version nodes have no specific meaning other than what
they might suggest to the person reading them. The @samp{2.0} version
@menu
* Constants:: Constants
+* Symbolic Constants:: Symbolic constants
* Symbols:: Symbol Names
* Orphan Sections:: Orphan Sections
* Location Counter:: The Location Counter
As in C, the linker considers an integer beginning with @samp{0} to be
octal, and an integer beginning with @samp{0x} or @samp{0X} to be
-hexadecimal. The linker considers other integers to be decimal.
+hexadecimal. Alternatively the linker accepts suffixes of @samp{h} or
+@samp{H} for hexadeciaml, @samp{o} or @samp{O} for octal, @samp{b} or
+@samp{B} for binary and @samp{d} or @samp{D} for decimal. Any integer
+value without a prefix or a suffix is considered to be decimal.
@cindex scaled integers
@cindex K and M integer suffixes
${\rm 1024}$ or ${\rm 1024}^2$
@end tex
@c END TEXI2ROFF-KILL
-respectively. For example, the following all refer to the same quantity:
+respectively. For example, the following
+all refer to the same quantity:
+
@smallexample
_fourk_1 = 4K;
_fourk_2 = 4096;
_fourk_3 = 0x1000;
+_fourk_4 = 10000o;
+@end smallexample
+
+Note - the @code{K} and @code{M} suffixes cannot be used in
+conjunction with the base suffixes mentioned above.
+
+@node Symbolic Constants
+@subsection Symbolic Constants
+@cindex symbolic constants
+@kindex CONSTANT
+It is possible to refer to target specific constants via the use of
+the @code{CONSTANT(@var{name})} operator, where @var{name} is one of:
+
+@table @code
+@item MAXPAGESIZE
+@kindex MAXPAGESIZE
+The target's maximum page size.
+
+@item COMMONPAGESIZE
+@kindex COMMONPAGESIZE
+The target's default page size.
+@end table
+
+So for example:
+
+@smallexample
+ .text ALIGN (CONSTANT (MAXPAGESIZE)) : @{ *(.text) @}
@end smallexample
+will create a text section aligned to the largest page boundary
+supported by the target.
+
@node Symbols
@subsection Symbol Names
@cindex symbol names
For ELF targets, the attribute of the section includes section type as
well as section flag.
+If an orphaned section's name is representable as a C identifier then
+the linker will automatically @pxref{PROVIDE} two symbols:
+__start_SECNAME and __end_SECNAME, where SECNAME is the name of the
+section. These indicate the start address and end address of the
+orphaned section respectively. Note: most section names are not
+representable as C identifiers because they contain a @samp{.}
+character.
+
@node Location Counter
@subsection The Location Counter
@kindex .
@ifset HPPA
* HPPA ELF32:: @command{ld} and HPPA 32-bit ELF
@end ifset
+@ifset M68K
+* M68K:: @command{ld} and the Motorola 68K family
+@end ifset
@ifset MMIX
* MMIX:: @command{ld} and MMIX
@end ifset
target subroutine is a leaf routine (that is, the target subroutine does
not itself call any subroutines).
+@cindex Cortex-A8 erratum workaround
+@kindex --fix-cortex-a8
+@kindex --no-fix-cortex-a8
+The @samp{--fix-cortex-a8} switch enables a link-time workaround for an erratum in certain Cortex-A8 processors. The workaround is enabled by default if you are targeting the ARM v7-A architecture profile. It can be enabled otherwise by specifying @samp{--fix-cortex-a8}, or disabled unconditionally by specifying @samp{--no-fix-cortex-a8}.
+
+The erratum only affects Thumb-2 code. Please contact ARM for further details.
+
@ifclear GENERIC
@lowersections
@end ifclear
case when a pointer to a function is taken. The pointer will in fact
point to the function trampoline.
-@cindex PIC_VENEER
-@kindex --pic-veneer
-The @samp{--pic-veneer} switch makes the linker use PIC sequences for
-ARM/Thumb interworking veneers, even if the rest of the binary
-is not PIC. This avoids problems on uClinux targets where
-@samp{--emit-relocs} is used to generate relocatable binaries.
-
@ifclear GENERIC
@lowersections
@end ifclear
branched to using a BX instruction, and the program will start
executing in Thumb mode straight away.
+@cindex PE import table prefixing
+@kindex --use-nul-prefixed-import-tables
+The @samp{--use-nul-prefixed-import-tables} switch is specifying, that
+the import tables idata4 and idata5 have to be generated with a zero
+elememt prefix for import libraries. This is the old style to generate
+import tables. By default this option is turned off.
+
@cindex BE8
@kindex --be8
The @samp{--be8} switch instructs @command{ld} to generate BE8 format
In the former case, the switch should not be used, and @samp{R_ARM_V4BX}
relocations are ignored.
+@cindex FIX_V4BX_INTERWORKING
+@kindex --fix-v4bx-interworking
+Replace @code{BX rM} instructions identified by @samp{R_ARM_V4BX}
+relocations with a branch to the following veneer:
+
+@smallexample
+TST rM, #1
+MOVEQ PC, rM
+BX Rn
+@end smallexample
+
+This allows generation of libraries/applications that work on ARMv4 cores
+and are still interworking safe. Note that the above veneer clobbers the
+condition flags, so may cause incorrect progrm behavior in rare cases.
+
@cindex USE_BLX
@kindex --use-blx
The @samp{--use-blx} switch enables the linker to use ARM/Thumb
@cindex NO_ENUM_SIZE_WARNING
@kindex --no-enum-size-warning
-The @samp{--no-enum-size-warning} switch prevents the linker from
+The @option{--no-enum-size-warning} switch prevents the linker from
warning when linking object files that specify incompatible EABI
enumeration size attributes. For example, with this switch enabled,
linking of an object file using 32-bit enumeration values with another
using enumeration values fitted into the smallest possible space will
not be diagnosed.
+@cindex NO_WCHAR_SIZE_WARNING
+@kindex --no-wchar-size-warning
+The @option{--no-wchar-size-warning} switch prevents the linker from
+warning when linking object files that specify incompatible EABI
+@code{wchar_t} size attributes. For example, with this switch enabled,
+linking of an object file using 32-bit @code{wchar_t} values with another
+using 16-bit @code{wchar_t} values will not be diagnosed.
+
+@cindex PIC_VENEER
+@kindex --pic-veneer
+The @samp{--pic-veneer} switch makes the linker use PIC sequences for
+ARM/Thumb interworking veneers, even if the rest of the binary
+is not PIC. This avoids problems on uClinux targets where
+@samp{--emit-relocs} is used to generate relocatable binaries.
+
+@cindex STUB_GROUP_SIZE
+@kindex --stub-group-size=@var{N}
+The linker will automatically generate and insert small sequences of
+code into a linked ARM ELF executable whenever an attempt is made to
+perform a function call to a symbol that is too far away. The
+placement of these sequences of instructions - called stubs - is
+controlled by the command line option @option{--stub-group-size=N}.
+The placement is important because a poor choice can create a need for
+duplicate stubs, increasing the code sizw. The linker will try to
+group stubs together in order to reduce interruptions to the flow of
+code, but it needs guidance as to how big these groups should be and
+where they should be placed.
+
+The value of @samp{N}, the parameter to the
+@option{--stub-group-size=} option controls where the stub groups are
+placed. If it is negative then all stubs are placed after the first
+branch that needs them. If it is positive then the stubs can be
+placed either before or after the branches that need them. If the
+value of @samp{N} is 1 (either +1 or -1) then the linker will choose
+exactly where to place groups of stubs, using its built in heuristics.
+A value of @samp{N} greater than 1 (or smaller than -1) tells the
+linker that a single group of stubs can service at most @samp{N} bytes
+from the input sections.
+
+The default, if @option{--stub-group-size=} is not specified, is
+@samp{N = +1}.
+
+Farcalls stubs insertion is fully supported for the ARM-EABI target
+only, because it relies on object files properties not present
+otherwise.
+
@ifclear GENERIC
@lowersections
@end ifclear
@end ifclear
@end ifset
+@ifset M68K
+@ifclear GENERIC
+@raisesections
+@end ifclear
+
+@node M68K
+@section @command{ld} and the Motorola 68K family
+
+@cindex Motorola 68K GOT generation
+@kindex --got=@var{type}
+The @samp{--got=@var{type}} option lets you choose the GOT generation scheme.
+The choices are @samp{single}, @samp{negative}, @samp{multigot} and
+@samp{target}. When @samp{target} is selected the linker chooses
+the default GOT generation scheme for the current target.
+@samp{single} tells the linker to generate a single GOT with
+entries only at non-negative offsets.
+@samp{negative} instructs the linker to generate a single GOT with
+entries at both negative and positive offsets. Not all environments
+support such GOTs.
+@samp{multigot} allows the linker to generate several GOTs in the
+output file. All GOT references from a single input object
+file access the same GOT, but references from different input object
+files might access different GOTs. Not all environments support such GOTs.
+
+@ifclear GENERIC
+@lowersections
+@end ifclear
+@end ifset
+
@ifset MMIX
@ifclear GENERIC
@raisesections
this section; it is always set to the program entry, which is at the
symbol @code{Main} for @code{mmo} files.
-Symbols with the prefix @code{__.MMIX.start.}, for example
-@code{__.MMIX.start..text} and @code{__.MMIX.start..data} are special;
-there must be only one each, even if they are local. The default linker
-script uses these to set the default start address of a section.
+Global symbols with the prefix @code{__.MMIX.start.}, for example
+@code{__.MMIX.start..text} and @code{__.MMIX.start..data} are special.
+The default linker script uses these to set the default start address
+of a section.
Initial and trailing multiples of zero-valued 32-bit words in a section,
are left out from an mmo file.
@samp{--relax} enables the generation of trampolines that can access
the entire 32-bit address space. These trampolines are inserted at
section boundaries, so may not themselves be reachable if an input
-section exceeds 33M in size.
+section exceeds 33M in size. You may combine @samp{-r} and
+@samp{--relax} to add trampolines in a partial link. In that case
+both branches to undefined symbols and inter-section branches are also
+considered potentially out of range, and trampolines inserted.
@cindex PowerPC ELF32 options
@table @option
@item --no-opd-optimize
PowerPC64 @command{ld} normally removes @code{.opd} section entries
corresponding to deleted link-once functions, or functions removed by
-the action of @samp{--gc-sections} or linker scrip @code{/DISCARD/}.
+the action of @samp{--gc-sections} or linker script @code{/DISCARD/}.
Use this option to disable @code{.opd} optimization.
@cindex PowerPC64 OPD spacing
@item --export-all-symbols [This is the default]
@item --exclude-symbols
@item --exclude-libs
+@item --exclude-modules-for-implib
+@item --version-script
@end itemize
-If, however, @samp{--export-all-symbols} is not given explicitly on the
+When auto-export is in operation, @command{ld} will export all the non-local
+(global and common) symbols it finds in a DLL, with the exception of a few
+symbols known to belong to the system's runtime and libraries. As it will
+often not be desirable to export all of a DLL's symbols, which may include
+private functions that are not part of any public interface, the command-line
+options listed above may be used to filter symbols out from the list for
+exporting. The @samp{--output-def} option can be used in order to see the
+final list of exported symbols with all exclusions taken into effect.
+
+If @samp{--export-all-symbols} is not given explicitly on the
command line, then the default auto-export behavior will be @emph{disabled}
if either of the following are true:
As a GNU extension, weak symbols that do not specify an alternate symbol
are supported. If the symbol is undefined when linking, the symbol
uses a default value.
+
+@cindex aligned common symbols
+@item aligned common symbols
+As a GNU extension to the PE file format, it is possible to specify the
+desired alignment for a common symbol. This information is conveyed from
+the assembler or compiler to the linker by means of GNU-specific commands
+carried in the object file's @samp{.drectve} section, which are recognized
+by @command{ld} and respected when laying out the common symbols. Native
+tools will be able to process object files employing this GNU extension,
+but will fail to respect the alignment instructions, and may issue noisy
+warnings about unknown linker directives.
@end table
@ifclear GENERIC
@var{secname}, only the @emph{first} sets the start address.
@end table
+@node GNU Free Documentation License
+@appendix GNU Free Documentation License
@include fdl.texi
@node LD Index
projects / msp430-binutils.git / blobdiff