\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
@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
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
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
@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
shared library if the @option{-e} option is not used and there are
undefined symbols in the link.
-@item --sort-common
+@item --sort-common [= ascending | descending]
@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.
+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
Same as --section-start, with @code{.bss}, @code{.data} or
@code{.text} as the @var{sectionname}.
+@kindex -Ttext-segment @var{org}
+@itemx -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
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.
+[This option is valid for all PE targeted ports of the linker]
+
@kindex --enable-stdcall-fixup
@kindex --disable-stdcall-fixup
@item --enable-stdcall-fixup
@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
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})
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
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
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 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
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
@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 before 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.
@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
@end itemize
If, however, @samp{--export-all-symbols} is not given explicitly on the
@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 / deliverable / binutils-gdb.git / blobdiff