@end ifset
version @value{VERSION}.
-Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000,
+Copyright @copyright{} 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
@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, 2008, 2009 Free Software Foundation, Inc.
+Copyright @copyright{} 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
+1999, 2000, 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 1.3
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
@samp{-Bstatic}, and the other two keywords are functionally equivalent
to @samp{-Bdynamic}. This option may be used any number of times.
+@kindex --audit @var{AUDITLIB}
+@item --audit @var{AUDITLIB}
+Adds @var{AUDITLIB} to the @code{DT_AUDIT} entry of the dynamic section.
+@var{AUDITLIB} is not checked for existence, nor will it use the DT_SONAME
+specified in the library. If specified multiple times @code{DT_AUDIT}
+will contain a colon separated list of audit interfaces to use. If the linker
+finds an object with an audit entry while searching for shared libraries,
+it will add a corresponding @code{DT_DEPAUDIT} entry in the output file.
+This option is only meaningful on ELF platforms supporting the rtld-audit
+interface.
+
@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
script command @code{FORCE_COMMON_ALLOCATION} has the same effect.
@xref{Miscellaneous Commands}.
+@kindex --depaudit @var{AUDITLIB}
+@kindex -P @var{AUDITLIB}
+@item --depaudit @var{AUDITLIB}
+@itemx -P @var{AUDITLIB}
+Adds @var{AUDITLIB} to the @code{DT_DEPAUDIT} entry of the dynamic section.
+@var{AUDITLIB} is not checked for existence, nor will it use the DT_SONAME
+specified in the library. If specified multiple times @code{DT_DEPAUDIT}
+will contain a colon separated list of audit interfaces to use. This
+option is only meaningful on ELF platforms supporting the rtld-audit interface.
+The -P option is provided for Solaris compatibility.
+
@cindex entry point, from command line
@kindex -e @var{entry}
@kindex --entry=@var{entry}
@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.
@kindex --nmagic
@item -n
@itemx --nmagic
-Turn off page alignment of sections, and mark the output as
-@code{NMAGIC} if possible.
+Turn off page alignment of sections, and disable linking against shared
+libraries. If the output format supports Unix style magic numbers,
+mark the output as @code{NMAGIC}.
@kindex -N
@kindex --omagic
@item --as-needed
@itemx --no-as-needed
This option affects ELF DT_NEEDED tags for dynamic libraries mentioned
-on the command line after the @option{--as-needed} option. Normally,
+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 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.
+needed or not. @option{--as-needed} causes a DT_NEEDED tag to only be
+emitted for a library that satisfies an undefined symbol reference
+from a regular object file or, if the library is not found in the
+DT_NEEDED lists of other libraries linked up to that point, an
+undefined symbol reference from another dynamic library.
@option{--no-as-needed} restores the default behaviour.
@kindex --add-needed
@kindex --no-add-needed
@item --add-needed
@itemx --no-add-needed
-This option affects the treatment of dynamic libraries from ELF
-DT_NEEDED tags in dynamic libraries mentioned on the command line after
-the @option{--no-add-needed} option. Normally, the linker will add
-a DT_NEEDED tag for each dynamic library from DT_NEEDED tags.
-@option{--no-add-needed} causes DT_NEEDED tags will never be emitted
-for those libraries from DT_NEEDED tags. @option{--add-needed} restores
-the default behaviour.
+These two options have been deprecated because of the similarity of
+their names to the @option{--as-needed} and @option{--no-as-needed}
+options. They have been replaced by @option{--copy-dt-needed-entries}
+and @option{--no-copy-dt-needed-entries}.
@kindex -assert @var{keyword}
@item -assert @var{keyword}
force checking in that case by using the @option{--check-sections}
option.
+@kindex --copy-dt-needed-entries
+@kindex --no-copy-dt-needed-entries
+@item --copy-dt-needed-entries
+@itemx --no-copy-dt-needed-entries
+This option affects the treatment of dynamic libraries referred to
+by DT_NEEDED tags @emph{inside} ELF dynamic libraries mentioned on the
+command line. Normally the linker will add a DT_NEEDED tag to the
+output binary for each library mentioned in a DT_NEEDED tag in an
+input dynamic library. With @option{--no-copy-dt-needed-entries}
+specified on the command line however any dynamic libraries that
+follow it will have their DT_NEEDED entries ignored. The default
+behaviour can be restored with @option{--copy-dt-needed-entries}.
+
+This option also has an effect on the resolution of symbols in dynamic
+libraries. With the default setting dynamic libraries mentioned on
+the command line will be recursively searched, following their
+DT_NEEDED tags to other libraries, in order to resolve symbols
+required by the output binary. With
+@option{--no-copy-dt-needed-entries} specified however the searching
+of dynamic libraries that follow it will stop with the dynamic
+library itself. No DT_NEEDED links will be traversed to resolve
+symbols.
+
@cindex cross reference table
@kindex --cref
@item --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
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
+@samp{-r}). In this case the root of symbols kept must be explicitly
specified either by an @samp{--entry} or @samp{--undefined} option or by
a @code{ENTRY} command in the linker script.
@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.
(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
@kindex --relax
@cindex synthesizing linker
@cindex relaxing addressing modes
+@cindex --no-relax
@item --relax
+@itemx --no-relax
An option with machine dependent effects.
@ifset GENERIC
This option is only supported on a few targets.
@xref{PowerPC ELF32,,@command{ld} and PowerPC 32-bit ELF Support}.
@end ifset
-On some platforms, the @samp{--relax} option performs global
-optimizations that become possible when the linker resolves addressing
-in the program, such as relaxing address modes and synthesizing new
-instructions in the output object file.
+On some platforms the @samp{--relax} option performs target specific,
+global optimizations that become possible when the linker resolves
+addressing in the program, such as relaxing address modes,
+synthesizing new instructions, selecting shorter version of current
+instructions, and combinig constant values.
On some platforms these link time global optimizations may make symbolic
debugging of the resulting executable impossible.
@ifset GENERIC
-This is known to be
-the case for the Matsushita MN10200 and MN10300 family of processors.
+This is known to be the case for the Matsushita MN10200 and MN10300
+family of processors.
@end ifset
@ifset GENERIC
but ignored.
@end ifset
+On platforms where @samp{--relax} is accepted the option
+@samp{--no-relax} can be used to disable the feature.
+
@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.
shared library if the @option{-e} option is not used and there are
undefined symbols in the link.
-@item --sort-common [= ascending | descending]
@kindex --sort-common
+@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,
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
+@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}
-@itemx -Ttext-segment @var{org}
+@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 --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
mismatches are considered to be errors.
[This option is specific to the i386 PE targeted port of the linker]
+@kindex --leading-underscore
+@kindex --no-leading-underscore
+@item --leading-underscore
+@itemx --no-leading-underscore
+For most targets default symbol-prefix is an underscore and is defined
+in target's description. By this option it is possible to
+disable/enable the default underscore symbol-prefix.
+
@cindex DLLs, creating
@kindex --export-all-symbols
@item --export-all-symbols
exported. The symbol names may be delimited by commas or colons.
[This option is specific to the i386 PE targeted port of the linker]
+@kindex --exclude-all-symbols
+@item --exclude-all-symbols
+Specifies no symbols should be automatically exported.
+[This option is specific to the i386 PE targeted port of the linker]
+
@kindex --file-alignment
@item --file-alignment
Specify the file alignment. Sections in the file will always begin at
@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
* 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
@item
the @code{ENTRY(@var{symbol})} command in a linker script;
@item
-the value of the symbol @code{start}, if defined;
+the value of a target specific symbol, if it is defined; For many
+targets this is @code{start}, but PE and BeOS based systems for example
+check a list of possible entry symbols, matching the first one found.
@item
the address of the first byte of the @samp{.text} section, if present;
@item
@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.
@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
@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
of the linker script. It is not put into the output file. Program
header names are stored in a separate name space, and will not conflict
with symbol names, file names, or section names. Each program header
-must have a distinct name.
+must have a distinct name. The headers are processed in order and it
+is usual for them to map to sections in ascending load address order.
Certain program header types describe segments of memory which the
system loader will load from the file. In the linker script, you
@kindex FILEHDR
@kindex PHDRS
-You may use the @code{FILEHDR} and @code{PHDRS} keywords appear after
+You may use the @code{FILEHDR} and @code{PHDRS} keywords after
the program header type to further describe the contents of the segment.
The @code{FILEHDR} keyword means that the segment should include the ELF
file header. The @code{PHDRS} keyword means that the segment should
-include the ELF program headers themselves.
+include the ELF program headers themselves. If applied to a loadable
+segment (@code{PT_LOAD}), all prior loadable segments must have one of
+these keywords.
The @var{type} may be one of the following. The numbers indicate the
value of the keyword.
bar1; bar2;
extern "C++" @{
ns::*;
- "int f(int, double)";
- @}
+ "f(int, double)";
+ @};
@} VERS_1.2;
@end smallexample
The supported @samp{lang}s are @samp{C}, @samp{C++}, and @samp{Java}.
The linker will iterate over the list of symbols at the link time and
demangle them according to @samp{lang} before matching them to the
-patterns specified in @samp{version-script-commands}.
+patterns specified in @samp{version-script-commands}. The default
+@samp{lang} is @samp{C}.
Demangled names may contains spaces and other special characters. As
described above, you can use a glob pattern to match demangled names,
@menu
* Constants:: Constants
+* Symbolic Constants:: Symbolic constants
* Symbols:: Symbol Names
* Orphan Sections:: Orphan Sections
* Location Counter:: The Location Counter
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
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.
+
+@kindex --merge-exidx-entries
+@kindex --no-merge-exidx-entries
+The @samp{--no-merge-exidx-entries} switch disables the merging of adjacent exidx entries in debuginfo.
+
@ifclear GENERIC
@lowersections
@end ifclear
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 before the first
+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
@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 --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:
_bar = bar
another_foo = abc.dll.afoo
var1 DATA
+doo = foo == foo2
+eoo DATA == var1
@end example
-This example defines a DLL with a non-default base address and five
+This example defines a DLL with a non-default base address and seven
symbols in the export table. The third exported symbol @code{_bar} is an
alias for the second. The fourth symbol, @code{another_foo} is resolved
by "forwarding" to another module and treating it as an alias for
@code{afoo} exported from the DLL @samp{abc.dll}. The final symbol
-@code{var1} is declared to be a data object.
+@code{var1} is declared to be a data object. The @samp{doo} symbol in
+export library is an alias of @samp{foo}, which gets the string name
+in export table @samp{foo2}. The @samp{eoo} symbol is an data export
+symbol, which gets in export table the name @samp{var1}.
The optional @code{LIBRARY <name>} command indicates the @emph{internal}
name of the output DLL. If @samp{<name>} does not include a suffix,
EXPORTS
( ( ( <name1> [ = <name2> ] )
| ( <name1> = <module-name> . <external-name>))
- [ @@ <integer> ] [NONAME] [DATA] [CONSTANT] [PRIVATE] ) *
+ [ @@ <integer> ] [NONAME] [DATA] [CONSTANT] [PRIVATE] [== <name3>] ) *
@end example
Declares @samp{<name1>} as an exported symbol from the DLL, or declares
@samp{<name1>} as a "forward" alias for the symbol
@samp{<external-name>} in the DLL @samp{<module-name>}.
Optionally, the symbol may be exported by the specified ordinal
-@samp{<integer>} alias.
+@samp{<integer>} alias. The optional @samp{<name3>} is the to be used
+string in import/export table for the symbol.
The optional keywords that follow the declaration indicate:
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
@cindex Xtensa options
@table @option
-@kindex --no-relax
-@item --no-relax
-Since the Xtensa version of @code{ld} enables the @option{--relax} option
-by default, the @option{--no-relax} option is provided to disable
-relaxation.
-
@item --size-opt
When optimizing indirect calls to direct calls, optimize for code size
more than performance. With this option, the linker will not insert