\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 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 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 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
@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
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
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
+@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
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:
@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})
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
match all files except the ones specified in the EXCLUDE_FILE list. For
example:
@smallexample
-(*(EXCLUDE_FILE (*crtend.o *otherfile.o) .ctors))
+*(EXCLUDE_FILE (*crtend.o *otherfile.o) .ctors)
@end smallexample
will cause all .ctors sections from all files except @file{crtend.o} and
@file{otherfile.o} to be included.
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
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
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 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