\input texinfo
@setfilename ld.info
+@c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
+@c 2001, 2002 Free Software Foundation, Inc.
@syncodeindex ky cp
@include configdoc.texi
@c (configdoc.texi is generated by the Makefile)
@c @smallbook
+@macro gcctabopt{body}
+@code{\body\}
+@end macro
+
+@c man begin NAME
+@ifset man
+@c Configure for the generation of man pages
+@set UsesEnvVars
+@set GENERIC
+@set A29K
+@set ARC
+@set ARM
+@set D10V
+@set D30V
+@set H8/300
+@set H8/500
+@set HPPA
+@set I370
+@set I80386
+@set I860
+@set I960
+@set M32R
+@set M68HC11
+@set M680X0
+@set MCORE
+@set MIPS
+@set MMIX
+@set PDP11
+@set PJ
+@set SH
+@set SPARC
+@set C54X
+@set V850
+@set VAX
+@end ifset
+@c man end
+
@ifinfo
@format
START-INFO-DIR-ENTRY
@ifinfo
This file documents the @sc{gnu} linker LD version @value{VERSION}.
-Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000 Free Software Foundation, Inc.
+Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000,
+2001, 2002 Free Software Foundation, Inc.
@ignore
@end tex
@vskip 0pt plus 1filll
-Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000 Free Software Foundation, Inc.
+@c man begin COPYRIGHT
+Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001 Free Software Foundation, Inc.
- Permission is granted to copy, distribute and/or modify this document
- under the terms of the GNU Free Documentation License, Version 1.1
- or any later version published by the Free Software Foundation;
- with no Invariant Sections, with no Front-Cover Texts, and with no
- Back-Cover Texts. A copy of the license is included in the
- section entitled "GNU Free Documentation License".
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.1
+or any later version published by the Free Software Foundation;
+with no Invariant Sections, with no Front-Cover Texts, and with no
+Back-Cover Texts. A copy of the license is included in the
+section entitled "GNU Free Documentation License".
+@c man end
@end titlepage
@end iftex
@cindex @sc{gnu} linker
@cindex what is this?
-@code{ld} combines a number of object and archive files, relocates
+
+@ifset man
+@c man begin SYNOPSIS
+ld [@b{options}] @var{objfile} @dots{}
+@c man end
+
+@c man begin SEEALSO
+ar(1), nm(1), objcopy(1), objdump(1), readelf(1) and
+the Info entries for @file{binutils} and
+@file{ld}.
+@c man end
+@end ifset
+
+@c man begin DESCRIPTION
+
+@command{ld} combines a number of object and archive files, relocates
their data and ties up symbol references. Usually the last step in
-compiling a program is to run @code{ld}.
+compiling a program is to run @command{ld}.
-@code{ld} accepts Linker Command Language files written in
+@command{ld} accepts Linker Command Language files written in
a superset of AT&T's Link Editor Command Language syntax,
to provide explicit and total control over the linking process.
+@ifset man
+@c For the man only
+This man page does not describe the command language; see the
+@command{ld} entry in @code{info}, or the manual
+ld: the GNU linker, for full details on the command language and
+on other aspects of the GNU linker.
+@end ifset
+
@ifclear SingleFormat
-This version of @code{ld} uses the general purpose BFD libraries
-to operate on object files. This allows @code{ld} to read, combine, and
+This version of @command{ld} uses the general purpose BFD libraries
+to operate on object files. This allows @command{ld} to read, combine, and
write object files in many different formats---for example, COFF or
@code{a.out}. Different formats may be linked together to produce any
available kind of object file. @xref{BFD}, for more information.
Aside from its flexibility, the @sc{gnu} linker is more helpful than other
linkers in providing diagnostic information. Many linkers abandon
execution immediately upon encountering an error; whenever possible,
-@code{ld} continues executing, allowing you to identify other errors
+@command{ld} continues executing, allowing you to identify other errors
(or, in some cases, to get an output file in spite of the error).
+@c man end
+
@node Invocation
@chapter Invocation
-The @sc{gnu} linker @code{ld} is meant to cover a broad range of situations,
+@c man begin DESCRIPTION
+
+The @sc{gnu} linker @command{ld} is meant to cover a broad range of situations,
and to be as compatible as possible with other linkers. As a result,
you have many choices to control its behavior.
+@c man end
+
@ifset UsesEnvVars
@menu
* Options:: Command Line Options
@cindex command line
@cindex options
+
+@c man begin OPTIONS
+
The linker supports a plethora of command-line options, but in actual
practice few of them are used in any particular context.
@cindex standard Unix system
-For instance, a frequent use of @code{ld} is to link standard Unix
+For instance, a frequent use of @command{ld} is to link standard Unix
object files on a standard, supported Unix system. On such a system, to
link a file @code{hello.o}:
ld -o @var{output} /lib/crt0.o hello.o -lc
@end smallexample
-This tells @code{ld} to produce a file called @var{output} as the
+This tells @command{ld} to produce a file called @var{output} as the
result of linking the file @code{/lib/crt0.o} with @code{hello.o} and
the library @code{libc.a}, which will come from the standard search
directories. (See the discussion of the @samp{-l} option below.)
-Some of the command-line options to @code{ld} may be specified at any
+Some of the command-line options to @command{ld} may be specified at any
point in the command line. However, options which refer to files, such
as @samp{-l} or @samp{-T}, cause the file to be read at the point at
which the option appears in the command line, relative to the object
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 should only be used to augment the main
-linker script; if you want to use some command that logically can only
-appear once, such as the @code{SECTIONS} or @code{MEMORY} command, you
-must replace the default linker script using the @samp{-T} option.
+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}.
For options whose names are a single letter,
option that requires them.
For options whose names are multiple letters, either one dash or two can
-precede the option name; for example, @samp{--oformat} and
-@samp{--oformat} are equivalent. Arguments to multiple-letter options
-must either be separated from the option name by an equals sign, or be
-given as separate arguments immediately following the option that
-requires them. For example, @samp{--oformat srec} and
-@samp{--oformat=srec} are equivalent. Unique abbreviations of the names
-of multiple-letter options are accepted.
+precede the option name; for example, @samp{-trace-symbol} and
+@samp{--trace-symbol} are equivalent. Note - there is one exception to
+this rule. Multiple letter options that start with a lower case 'o' can
+only be preceeded by two dashes. This is to reduce confusion with the
+@samp{-o} option. So for example @samp{-omagic} sets the output file
+name to @samp{magic} whereas @samp{--omagic} sets the NMAGIC flag on the
+output.
+
+Arguments to multiple-letter options must either be separated from the
+option name by an equals sign, or be given as separate arguments
+immediately following the option that requires them. For example,
+@samp{--trace-symbol foo} and @samp{--trace-symbol=foo} are equivalent.
+Unique abbreviations of the names of multiple-letter options are
+accepted.
Note - if the linker is being invoked indirectly, via a compiler driver
(eg @samp{gcc}) then all the linker command line options should be
Here is a table of the generic command line switches accepted by the GNU
linker:
-@table @code
+@table @gcctabopt
@kindex -a@var{keyword}
@item -a@var{keyword}
This option is supported for HP/UX compatibility. The @var{keyword}
@item -A@var{architecture}
@kindex --architecture=@var{arch}
@itemx --architecture=@var{architecture}
-In the current release of @code{ld}, this option is useful only for the
-Intel 960 family of architectures. In that @code{ld} configuration, the
+In the current release of @command{ld}, this option is useful only for the
+Intel 960 family of architectures. In that @command{ld} configuration, the
@var{architecture} argument identifies the particular architecture in
the 960 family, enabling some safeguards and modifying the
-archive-library search path. @xref{i960,,@code{ld} and the Intel 960
+archive-library search path. @xref{i960,,@command{ld} and the Intel 960
family}, for details.
-Future releases of @code{ld} may support similar functionality for
+Future releases of @command{ld} may support similar functionality for
other architecture families.
@end ifset
@cindex input format
@item -b @var{input-format}
@itemx --format=@var{input-format}
-@code{ld} may be configured to support more than one kind of object
-file. If your @code{ld} is configured this way, you can use the
+@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{-b} option to specify the binary format for input object files
-that follow this option on the command line. Even when @code{ld} is
+that follow this option on the command line. Even when @command{ld} is
configured to support alternative object formats, you don't usually need
-to specify this, as @code{ld} should be configured to expect as a
+to specify this, as @command{ld} should be configured to expect as a
default input format the most usual format on each machine.
@var{input-format} is a text string, the name of a particular format
supported by the BFD libraries. (You can list the available binary
binary format. You can also use @samp{-b} to switch formats explicitly (when
linking object files of different formats), by including
@samp{-b @var{input-format}} before each group of object files in a
-particular format.
+particular format.
The default format is taken from the environment variable
@code{GNUTARGET}.
@xref{Environment}.
@end ifset
You can also define the input format from a script, using the command
-@code{TARGET}; see @ref{Format Commands}.
+@code{TARGET};
+@ifclear man
+see @ref{Format Commands}.
+@end ifclear
@end ifclear
@kindex -c @var{MRI-cmdfile}
@cindex compatibility, MRI
@item -c @var{MRI-commandfile}
@itemx --mri-script=@var{MRI-commandfile}
-For compatibility with linkers produced by MRI, @code{ld} accepts script
+For compatibility with linkers produced by MRI, @command{ld} accepts script
files written in an alternate, restricted command language, described in
-@ref{MRI,,MRI Compatible Script Files}. Introduce MRI script files with
+@ifclear man
+@ref{MRI,,MRI Compatible Script Files}.
+@end ifclear
+@ifset man
+the MRI Compatible Script Files section of GNU ld documentation.
+@end ifset
+Introduce MRI script files with
the option @samp{-c}; use the @samp{-T} option to run linker
-scripts written in the general-purpose @code{ld} scripting language.
-If @var{MRI-cmdfile} does not exist, @code{ld} looks for it in the directories
+scripts written in the general-purpose @command{ld} scripting language.
+If @var{MRI-cmdfile} does not exist, @command{ld} looks for it in the directories
specified by any @samp{-L} options.
@cindex common allocation
@kindex -d
@kindex -dc
@kindex -dp
-@item -d
+@item -d
@itemx -dc
@itemx -dp
These three options are equivalent; multiple forms are supported for
@cindex entry point, from command line
@kindex -e @var{entry}
@kindex --entry=@var{entry}
-@item -e @var{entry}
+@item -e @var{entry}
@itemx --entry=@var{entry}
Use @var{entry} as the explicit symbol for beginning execution of your
program, rather than the default entry point. If there is no symbol
dynamic object, then you will probably need to use this option when
linking the program itself.
+You can also use the version script to control what symbols should
+be added to the dynamic symbol table if the output format supports it.
+See the description of @samp{--version-script} in @ref{VERSION}.
+
@cindex big-endian objects
@cindex endianness
@kindex -EB
used to select a subset of the symbols provided by the object
@var{name}.
-Some older linkers used the @code{-F} option throughout a compilation
+Some older linkers used the @option{-F} option throughout a compilation
toolchain for specifying object-file format for both input and output
object files. The @sc{gnu} linker uses other mechanisms for this
-purpose: the @code{-b}, @code{--format}, @code{--oformat} options, the
+purpose: the @option{-b}, @option{--format}, @option{--oformat} options, the
@code{TARGET} command in linker scripts, and the @code{GNUTARGET}
-environment variable. The @sc{gnu} linker will ignore the @code{-F}
+environment variable. The @sc{gnu} linker will ignore the @option{-F}
option when not creating an ELF shared object.
@cindex finalization function
@item -l@var{archive}
@itemx --library=@var{archive}
Add archive file @var{archive} to the list of files to link. This
-option may be used any number of times. @code{ld} will search its
+option may be used any number of times. @command{ld} will search its
path-list for occurrences of @code{lib@var{archive}.a} for every
@var{archive} specified.
-On systems which support shared libraries, @code{ld} may also search for
+On systems which support shared libraries, @command{ld} may also search for
libraries with extensions other than @code{.a}. Specifically, on ELF
-and SunOS systems, @code{ld} will search a directory for a library with
+and SunOS systems, @command{ld} will search a directory for a library with
an extension of @code{.so} before searching for one with an extension of
@code{.a}. By convention, a @code{.so} extension indicates a shared
library.
archive. However, an undefined symbol in an object appearing later on
the command line will not cause the linker to search the archive again.
-See the @code{-(} option for a way to force the linker to search
+See the @option{-(} option for a way to force the linker to search
archives multiple times.
You may list the same archive multiple times on the command line.
@ifset GENERIC
This type of archive searching is standard for Unix linkers. However,
-if you are using @code{ld} on AIX, note that it is different from the
+if you are using @command{ld} on AIX, note that it is different from the
behaviour of the AIX linker.
@end ifset
@cindex search directory, from cmd line
@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 @code{ld} will search
-for archive libraries and @code{ld} control scripts. You may use this
+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
option any number of times. The directories are searched in the order
in which they are specified on the command line. Directories specified
on the command line are searched before the default directories. All
-@code{-L} options apply to all @code{-l} options, regardless of the
+@option{-L} options apply to all @option{-l} options, regardless of the
order in which the options appear.
@ifset UsesEnvVars
The default set of paths searched (without being specified with
-@samp{-L}) depends on which emulation mode @code{ld} is using, and in
+@samp{-L}) depends on which emulation mode @command{ld} is using, and in
some cases also on how it was configured. @xref{Environment}.
@end ifset
@item -n
@itemx --nmagic
Turn off page alignment of sections, and mark the output as
-@code{NMAGIC} if possible.
+@code{NMAGIC} if possible.
@kindex -N
@kindex --omagic
@cindex read/write from cmd line
@cindex OMAGIC
-@item -N
+@item -N
@itemx --omagic
Set the text and data sections to be readable and writable. Also, do
not page-align the data segment. If the output format supports Unix
@cindex naming the output file
@item -o @var{output}
@itemx --output=@var{output}
-Use @var{output} as the name for the program produced by @code{ld}; if this
+Use @var{output} as the name for the program produced by @command{ld}; if this
option is not specified, the name @file{a.out} is used by default. The
script command @code{OUTPUT} can also specify the output file name.
@kindex -O @var{level}
@cindex generating optimized output
@item -O @var{level}
-If @var{level} is a numeric values greater than zero @code{ld} optimizes
+If @var{level} is a numeric values greater than zero @command{ld} optimizes
the output. This might take significantly longer and therefore probably
should only be enabled for the final binary.
order to perform correct modifications of executables. This results
in larger executables.
+This option is currently only supported on ELF platforms.
+
@cindex partial link
@cindex relocatable output
@kindex -r
@item -r
@itemx --relocateable
Generate relocatable output---i.e., generate an output file that can in
-turn serve as input to @code{ld}. This is often called @dfn{partial
+turn serve as input to @command{ld}. This is often called @dfn{partial
linking}. As a side effect, in environments that support standard Unix
magic numbers, this option also sets the output file's magic number to
@code{OMAGIC}.
-@c ; see @code{-N}.
+@c ; see @option{-N}.
If this option is not specified, an absolute file is produced. When
linking C++ programs, this option @emph{will not} resolve references to
constructors; to do that, use @samp{-Ur}.
+When an input file does not have the same format as the output file,
+partial linking is only supported if that input file does not contain any
+relocations. Different output formats can have further restrictions; for
+example some @code{a.out}-based formats do not support partial linking
+with input files in other formats at all.
+
This option does the same thing as @samp{-i}.
@kindex -R @var{file}
to refer symbolically to absolute locations of memory defined in other
programs. You may use this option more than once.
-For compatibility with other ELF linkers, if the @code{-R} option is
+For compatibility with other ELF linkers, if the @option{-R} option is
followed by a directory name, rather than a file name, it is treated as
-the @code{-rpath} option.
+the @option{-rpath} option.
@kindex -s
@kindex --strip-all
@cindex strip all symbols
-@item -s
+@item -s
@itemx --strip-all
Omit all symbol information from the output file.
@kindex -S
@kindex --strip-debug
@cindex strip debugger symbols
-@item -S
+@item -S
@itemx --strip-debug
Omit debugger symbol information (but not all symbols) from the output file.
@kindex -t
@kindex --trace
@cindex input files, displaying
-@item -t
+@item -t
@itemx --trace
-Print the names of the input files as @code{ld} processes them.
+Print the names of the input files as @command{ld} processes them.
@kindex -T @var{script}
@kindex --script=@var{script}
@item -T @var{scriptfile}
@itemx --script=@var{scriptfile}
Use @var{scriptfile} as the linker script. This script replaces
-@code{ld}'s default linker script (rather than adding to it), so
+@command{ld}'s default linker script (rather than adding to it), so
@var{commandfile} must specify everything necessary to describe the
-output file. You must use this option if you want to use a command
-which can only appear once in a linker script, such as the
-@code{SECTIONS} or @code{MEMORY} command. @xref{Scripts}. If
-@var{scriptfile} does not exist in the current directory, @code{ld}
-looks for it in the directories specified by any preceding @samp{-L}
-options. Multiple @samp{-T} options accumulate.
+output file. @xref{Scripts}. If @var{scriptfile} does not exist in
+the current directory, @code{ld} looks for it in the directories
+specified by any preceding @samp{-L} options. Multiple @samp{-T}
+options accumulate.
@kindex -u @var{symbol}
@kindex --undefined=@var{symbol}
@kindex -Ur
@cindex constructors
-@item -Ur
+@item -Ur
For anything other than C++ programs, this option is equivalent to
@samp{-r}: it generates relocatable output---i.e., an output file that can in
-turn serve as input to @code{ld}. When linking C++ programs, @samp{-Ur}
+turn serve as input to @command{ld}. When linking C++ programs, @samp{-Ur}
@emph{does} resolve references to constructors, unlike @samp{-r}.
It does not work to use @samp{-Ur} on files that were themselves linked
with @samp{-Ur}; once the constructor table has been built, it cannot
be added to. Use @samp{-Ur} only for the last partial link, and
@samp{-r} for the others.
-@kindex --unique
-@item --unique
-Creates a separate output section for every orphan input section. This
-option prevents the normal merging of orphan input sections with the same
-name. An orphan section is one not specifically mentioned in a linker
-script, so this option along with a custom linker script allows any
-selection of input sections to be merged while others are kept separate.
+@kindex --unique[=@var{SECTION}]
+@item --unique[=@var{SECTION}]
+Creates a separate output section for every input section matching
+@var{SECTION}, or if the optional wildcard @var{SECTION} argument is
+missing, for every orphan input section. An orphan section is one not
+specifically mentioned in a linker script. You may use this option
+multiple times on the command line; It prevents the normal merging of
+input sections with the same name, overriding output section assignments
+in a linker script.
@kindex -v
@kindex -V
@item -v
@itemx --version
@itemx -V
-Display the version number for @code{ld}. The @code{-V} option also
+Display the version number for @command{ld}. The @option{-V} option also
lists the supported emulations.
@kindex -x
@kindex --discard-locals
@cindex local symbols, deleting
@cindex L, deleting symbols beginning
-@item -X
+@item -X
@itemx --discard-locals
Delete all temporary local symbols. For most targets, this is all local
symbols whose names begin with @samp{L}.
@item -z @var{keyword}
The recognized keywords are @code{initfirst}, @code{interpose},
@code{loadfltr}, @code{nodefaultlib}, @code{nodelete}, @code{nodlopen},
-@code{nodump}, @code{now} and @code{origin}. The other keywords are
+@code{nodump}, @code{now}, @code{origin}, @code{combreloc}, @code{nocombreloc}
+and @code{nocopyreloc}.
+The other keywords are
ignored for Solaris compatibility. @code{initfirst} marks the object
to be initialized first at runtime before any other objects.
@code{interpose} marks the object that its symbol table interposes
@code{nodump} marks the object can not be dumped by @code{dldump}.
@code{now} marks the object with the non-lazy runtime binding.
@code{origin} marks the object may contain $ORIGIN.
+@code{defs} disallows undefined symbols.
+@code{combreloc} combines multiple reloc sections and sorts them
+to make dynamic symbol lookup caching possible.
+@code{nocombreloc} disables multiple reloc sections combining.
+@code{nocopyreloc} disables production of copy relocs.
@kindex -(
@cindex groups of archives
default on such platforms. The different variants of this option are
for compatibility with various systems. You may use this option
multiple times on the command line: it affects library searching for
-@code{-l} options which follow it.
+@option{-l} options which follow it.
+
+@kindex -Bgroup
+@item -Bgroup
+Set the @code{DF_1_GROUP} flag in the @code{DT_FLAGS_1} entry in the dynamic
+section. This causes the runtime linker to handle lookups in this
+object and its dependencies to be performed only inside the group.
+@option{--no-undefined} is implied. This option is only meaningful on ELF
+platforms which support shared libraries.
@kindex -Bstatic
@kindex -dn
@kindex -non_shared
@kindex -static
-@item -Bstatic
+@item -Bstatic
@itemx -dn
@itemx -non_shared
@itemx -static
platforms for which shared libraries are supported. The different
variants of this option are for compatibility with various systems. You
may use this option multiple times on the command line: it affects
-library searching for @code{-l} options which follow it.
+library searching for @option{-l} options which follow it.
@kindex -Bsymbolic
@item -Bsymbolic
symbol is defined, the first file listed is the location of the
definition. The remaining files contain references to the symbol.
+@cindex common allocation
+@kindex --no-define-common
+@item --no-define-common
+This option inhibits the assignment of addresses to common symbols.
+The script command @code{INHIBIT_COMMON_ALLOCATION} has the same effect.
+@xref{Miscellaneous Commands}.
+
+The @samp{--no-define-common} option allows decoupling
+the decision to assign addresses to Common symbols from the choice
+of the output file type; otherwise a non-Relocatable output type
+forces assigning addresses to Common symbols.
+Using @samp{--no-define-common} allows Common symbols that are referenced
+from a shared library to be assigned addresses only in the main program.
+This eliminates the unused duplicate space in the shared library,
+and also prevents any possible confusion over resolving to the wrong
+duplicate when there are many dynamic modules with specialized search
+paths for runtime symbol resolution.
+
@cindex symbols, from command line
@kindex --defsym @var{symbol}=@var{exp}
@item --defsym @var{symbol}=@var{expression}
and other output. When the linker is told to demangle, it tries to
present symbol names in a readable fashion: it strips leading
underscores if they are used by the object file format, and converts C++
-mangled symbol names into user readable names. Different compilers have
-different mangling styles. The optional demangling style argument can be used
-to choose an appropriate demangling style for your compiler. The linker will
+mangled symbol names into user readable names. Different compilers have
+different mangling styles. The optional demangling style argument can be used
+to choose an appropriate demangling style for your compiler. The linker will
demangle by default unless the environment variable @samp{COLLECT_NO_DEMANGLE}
is set. These options may be used to override the default.
@cindex dynamic linker, from command line
+@kindex -I@var{file}
@kindex --dynamic-linker @var{file}
@item --dynamic-linker @var{file}
Set the name of the dynamic linker. This is only meaningful when
runtime to relocate any data which was statically initialized to pointer
values. See the code in testsuite/ld-empic for details.
+
+@kindex --fatal-warnings
+@item --fatal-warnings
+Treat all warnings as errors.
+
@kindex --force-exe-suffix
@item --force-exe-suffix
Make sure that an output file has a .exe suffix.
@cindex memory usage
@kindex --no-keep-memory
@item --no-keep-memory
-@code{ld} normally optimizes for speed over memory usage by caching the
-symbol tables of input files in memory. This option tells @code{ld} to
+@command{ld} normally optimizes for speed over memory usage by caching the
+symbol tables of input files in memory. This option tells @command{ld} to
instead optimize for memory usage, by rereading the symbol tables as
-necessary. This may be required if @code{ld} runs out of memory space
+necessary. This may be required if @command{ld} runs out of memory space
while linking a large executable.
@kindex --no-undefined
+@kindex -z defs
@item --no-undefined
+@itemx -z defs
Normally when creating a non-symbolic shared library, undefined symbols
-are allowed and left to be resolved by the runtime loader. This option
+are allowed and left to be resolved by the runtime loader. These options
disallows such undefined symbols.
+@kindex --allow-shlib-undefined
+@item --allow-shlib-undefined
+Allow undefined symbols in shared objects even when --no-undefined is
+set. The net result will be that undefined symbols in regular objects
+will still trigger an error, but undefined symbols in shared objects
+will be ignored. The implementation of no_undefined makes the
+assumption that the runtime linker will choke on undefined symbols.
+However there is at least one system (BeOS) where undefined symbols in
+shared libraries is normal since the kernel patches them at load time to
+select which function is most appropriate for the current architecture.
+I.E. dynamically select an appropriate memset function. Apparently it
+is also normal for HPPA shared libraries to have undefined symbols.
+
@kindex --no-warn-mismatch
@item --no-warn-mismatch
-Normally @code{ld} will give an error if you try to link together input
+Normally @command{ld} will give an error if you try to link together input
files that are mismatched for some reason, perhaps because they have
been compiled for different processors or for different endiannesses.
-This option tells @code{ld} that it should silently permit such possible
+This option tells @command{ld} that it should silently permit such possible
errors. This option should only be used with care, in cases when you
have taken some special action that ensures that the linker errors are
inappropriate.
@kindex --no-whole-archive
@item --no-whole-archive
-Turn off the effect of the @code{--whole-archive} option for subsequent
+Turn off the effect of the @option{--whole-archive} option for subsequent
archive files.
@cindex output file after errors
errors during the link process; it exits without writing an output file
when it issues any error whatsoever.
+@kindex -nostdlib
+@item -nostdlib
+Only search library directories explicitly specified on the
+command line. Library directories specified in linker scripts
+(including linker scripts specified on the command line) are ignored.
+
@ifclear SingleFormat
@kindex --oformat
@item --oformat @var{output-format}
-@code{ld} may be configured to support more than one kind of object
-file. If your @code{ld} is configured this way, you can use the
+@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
-object file. Even when @code{ld} is configured to support alternative
-object formats, you don't usually need to specify this, as @code{ld}
+object file. Even when @command{ld} is configured to support alternative
+object formats, you don't usually need to specify this, as @command{ld}
should be configured to produce as a default output format the most
usual format on each machine. @var{output-format} is a text string, the
name of a particular format supported by the BFD libraries. (You can
@cindex synthesizing linker
@cindex relaxing addressing modes
@item --relax
-An option with machine dependent effects.
+An option with machine dependent effects.
@ifset GENERIC
This option is only supported on a few targets.
@end ifset
@ifset H8300
-@xref{H8/300,,@code{ld} and the H8/300}.
+@xref{H8/300,,@command{ld} and the H8/300}.
@end ifset
@ifset I960
-@xref{i960,, @code{ld} and the Intel 960 family}.
+@xref{i960,, @command{ld} and the Intel 960 family}.
@end ifset
@cindex runtime library search path
@kindex -rpath
Add a directory to the runtime library search path. This is used when
-linking an ELF executable with shared objects. All @code{-rpath}
+linking an ELF executable with shared objects. All @option{-rpath}
arguments are concatenated and passed to the runtime linker, which uses
-them to locate shared objects at runtime. The @code{-rpath} option is
+them to locate shared objects at runtime. The @option{-rpath} option is
also used when locating shared objects which are needed by shared
objects explicitly included in the link; see the description of the
-@code{-rpath-link} option. If @code{-rpath} is not used when linking an
+@option{-rpath-link} option. If @option{-rpath} is not used when linking an
ELF executable, the contents of the environment variable
@code{LD_RUN_PATH} will be used if it is defined.
-The @code{-rpath} option may also be used on SunOS. By default, on
+The @option{-rpath} option may also be used on SunOS. By default, on
SunOS, the linker will form a runtime search patch out of all the
-@code{-L} options it is given. If a @code{-rpath} option is used, the
-runtime search path will be formed exclusively using the @code{-rpath}
-options, ignoring the @code{-L} options. This can be useful when using
-gcc, which adds many @code{-L} options which may be on NFS mounted
+@option{-L} options it is given. If a @option{-rpath} option is used, the
+runtime search path will be formed exclusively using the @option{-rpath}
+options, ignoring the @option{-L} options. This can be useful when using
+gcc, which adds many @option{-L} options which may be on NFS mounted
filesystems.
-For compatibility with other ELF linkers, if the @code{-R} option is
+For compatibility with other ELF linkers, if the @option{-R} option is
followed by a directory name, rather than a file name, it is treated as
-the @code{-rpath} option.
+the @option{-rpath} option.
@end ifset
@ifset GENERIC
When the linker encounters such a dependency when doing a non-shared,
non-relocatable link, it will automatically try to locate the required
shared library and include it in the link, if it is not included
-explicitly. In such a case, the @code{-rpath-link} option
+explicitly. In such a case, the @option{-rpath-link} option
specifies the first set of directories to search. The
-@code{-rpath-link} option may specify a sequence of directory names
+@option{-rpath-link} option may specify a sequence of directory names
either by specifying a list of names separated by colons, or by
appearing multiple times.
libraries.
@enumerate
@item
-Any directories specified by @code{-rpath-link} options.
+Any directories specified by @option{-rpath-link} options.
@item
-Any directories specified by @code{-rpath} options. The difference
-between @code{-rpath} and @code{-rpath-link} is that directories
-specified by @code{-rpath} options are included in the executable and
-used at runtime, whereas the @code{-rpath-link} option is only effective
+Any directories specified by @option{-rpath} options. The difference
+between @option{-rpath} and @option{-rpath-link} is that directories
+specified by @option{-rpath} options are included in the executable and
+used at runtime, whereas the @option{-rpath-link} option is only effective
at link time. It is for the native linker only.
@item
-On an ELF system, if the @code{-rpath} and @code{rpath-link} options
+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.
@item
-On SunOS, if the @code{-rpath} option was not used, search any
-directories specified using @code{-L} options.
+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}.
@cindex shared libraries
Create a shared library. This is currently only supported on ELF, XCOFF
and SunOS platforms. On SunOS, the linker will automatically create a
-shared library if the @code{-e} option is not used and there are
+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 @code{ld} to sort the common symbols by size when it
+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 bytes, then all the four bytes, and then
+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 --split-by-file
@item --split-by-file [@var{size}]
-Similar to @code{--split-by-reloc} but creates a new output section for
+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 --traditional-format
@cindex traditional format
@item --traditional-format
-For some targets, the output of @code{ld} is different in some ways from
-the output of some existing linker. This switch requests @code{ld} to
+For some targets, the output of @command{ld} is different in some ways from
+the output of some existing linker. This switch requests @command{ld} to
use the traditional format instead.
@cindex dbx
-For example, on SunOS, @code{ld} combines duplicate entries in the
+For example, on SunOS, @command{ld} combines duplicate entries in the
symbol string table. This can reduce the size of an output file with
full debugging information by over 30 percent. Unfortunately, the SunOS
@code{dbx} program can not read the resulting program (@code{gdb} has no
-trouble). The @samp{--traditional-format} switch tells @code{ld} to not
+trouble). The @samp{--traditional-format} switch tells @command{ld} to not
combine duplicate entries.
@kindex --section-start @var{sectionname}=@var{org}
@cindex verbose
@item --dll-verbose
@itemx --verbose
-Display the version number for @code{ld} and list the linker emulations
+Display the version number for @command{ld} and list the linker emulations
supported. Display which input files can and cannot be opened. Display
-the linker script if using a default builtin script.
+the linker script being used by the linker.
@kindex --version-script=@var{version-scriptfile}
@cindex version script, symbol versions
is only meaningful on ELF platforms which support shared libraries.
@xref{VERSION}.
-@kindex --warn-comon
+@kindex --warn-common
@cindex warnings, on combining symbols
@cindex combining symbols, warnings on
@item --warn-common
@cindex including an entire archive
@item --whole-archive
For each archive mentioned on the command line after the
-@code{--whole-archive} option, include every object file in the archive
+@option{--whole-archive} option, include every object file in the archive
in the link, rather than searching the archive for the required object
files. This is normally used to turn an archive file into a shared
library, forcing every object to be included in the resulting shared
library. This option may be used more than once.
+Two notes when using this option from gcc: First, gcc doesn't know
+about this option, so you have to use @option{-Wl,-whole-archive}.
+Second, don't forget to use @option{-Wl,-no-whole-archive} after your
+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}
Use a wrapper function for @var{symbol}. Any undefined reference to
@}
@end smallexample
-If you link other code with this file using @code{--wrap malloc}, then
+If you link other code with this file using @option{--wrap malloc}, then
all calls to @code{malloc} will call the function @code{__wrap_malloc}
instead. The call to @code{__real_malloc} in @code{__wrap_malloc} will
call the real @code{malloc} function.
You may wish to provide a @code{__real_malloc} function as well, so that
-links without the @code{--wrap} option will succeed. If you do this,
+links without the @option{--wrap} option will succeed. If you do this,
you should not put the definition of @code{__real_malloc} in the same
file as @code{__wrap_malloc}; if you do, the assembler may resolve the
call before the linker has a chance to wrap it to @code{malloc}.
@itemx --disable-new-dtags
This linker can create the new dynamic tags in ELF. But the older ELF
systems may not understand them. If you specify
-@code{--enable-new-dtags}, the dynamic tags will be created as needed.
-If you specify @code{--disable-new-dtags}, no new dynamic tags will be
+@option{--enable-new-dtags}, the dynamic tags will be created as needed.
+If you specify @option{--disable-new-dtags}, no new dynamic tags will be
created. By default, the new dynamic tags are not created. Note that
those options are only available for ELF systems.
@end table
+@c man end
+
@subsection Options specific to i386 PE targets
-The i386 PE linker supports the @code{-shared} option, which causes
+@c man begin OPTIONS
+
+The i386 PE linker supports the @option{-shared} option, which causes
the output to be a dynamically linked library (DLL) instead of a
normal executable. You should name the output @code{*.dll} when you
use this option. In addition, the linker fully supports the standard
PE target. Options that take values may be separated from their
values by either a space or an equals sign.
-@table @code
+@table @gcctabopt
@kindex --add-stdcall-alias
@item --add-stdcall-alias
@kindex --dll
@item --dll
Create a DLL instead of a regular executable. You may also use
-@code{-shared} or specify a @code{LIBRARY} in a given @code{.def}
+@option{-shared} or specify a @code{LIBRARY} in a given @code{.def}
file.
@kindex --enable-stdcall-fixup
to the function @code{_bar}. When the linker does this, it prints a
warning, since it normally should have failed to link, but sometimes
import libraries generated from third-party dlls may need this feature
-to be usable. If you specify @code{--enable-stdcall-fixup}, this
+to be usable. If you specify @option{--enable-stdcall-fixup}, this
feature is fully enabled and warnings are not printed. If you specify
-@code{--disable-stdcall-fixup}, this feature is disabled and such
+@option{--disable-stdcall-fixup}, this feature is disabled and such
mismatches are considered to be errors.
@cindex DLLs, creating
explicitly exported via DEF files or implicitly exported via function
attributes, the default is to not export anything else unless this
option is given. Note that the symbols @code{DllMain@@12},
-@code{DllEntryPoint@@0}, and @code{impure_ptr} will not be automatically
-exported.
+@code{DllEntryPoint@@0}, @code{DllMainCRTStartup@@12}, and
+@code{impure_ptr} will not be automatically
+exported. Also, symbols imported from other DLLs will not be
+re-exported, nor will symbols specifying the DLL's internal layout
+such as those beginning with @code{_head_} or ending with
+@code{_iname}. In addition, no symbols from @code{libgcc},
+@code{libstd++}, @code{libmingw32}, or @code{crtX.o} will be exported.
+Symbols whose names begin with @code{__rtti_} or @code{__builtin_} will
+not be exported, to help with C++ DLLs. Finally, there is an
+extensive list of cygwin-private symbols that are not exported
+(obviously, this applies on when building DLLs for cygwin targets).
+These cygwin-excludes are: @code{_cygwin_dll_entry@@12},
+@code{_cygwin_crt0_common@@8}, @code{_cygwin_noncygwin_dll_entry@@12},
+@code{_fmode}, @code{_impure_ptr}, @code{cygwin_attach_dll},
+@code{cygwin_premain0}, @code{cygwin_premain1}, @code{cygwin_premain2},
+@code{cygwin_premain3}, and @code{environ}.
@kindex --exclude-symbols
@item --exclude-symbols @var{symbol},@var{symbol},...
library with @code{dlltool} or may be used as a reference to
automatically or implicitly exported symbols.
+@cindex DLLs, creating
+@kindex --out-implib
+@item --out-implib @var{file}
+The linker will create the file @var{file} which will contain an
+import lib corresponding to the DLL the linker is generating. This
+import lib (which should be called @code{*.dll.a} or @code{*.a}
+may be used to link clients against the generated DLL; this behavior
+makes it possible to skip a separate @code{dlltool} import library
+creation step.
+
+@kindex --enable-auto-image-base
+@item --enable-auto-image-base
+Automatically choose the image base for DLLs, unless one is specified
+using the @code{--image-base} argument. By using a hash generated
+from the dllname to create unique image bases for each DLL, in-memory
+collisions and relocations which can delay program execution are
+avoided.
+
+@kindex --disable-auto-image-base
+@item --disable-auto-image-base
+Do not automatically generate a unique image base. If there is no
+user-specified image base (@code{--image-base}) then use the platform
+default.
+
+@cindex DLLs, linking to
+@kindex --dll-search-prefix
+@item --dll-search-prefix @var{string}
+When linking dynamically to a dll without an import library, i
+search for @code{<string><basename>.dll} in preference to
+@code{lib<basename>.dll}. This behavior allows easy distinction
+between DLLs built for the various "subplatforms": native, cygwin,
+uwin, pw, etc. For instance, cygwin DLLs typically use
+@code{--dll-search-prefix=cyg}.
+
+@kindex --enable-auto-import
+@item --enable-auto-import
+Do sophisticated linking of @code{_symbol} to @code{__imp__symbol} for
+DATA imports from DLLs, and create the necessary thunking symbols when
+building the DLLs with those DATA exports. This generally will 'just
+work' -- but sometimes you may see this message:
+
+"variable '<var>' can't be auto-imported. Please read the
+documentation for ld's @code{--enable-auto-import} for details."
+
+This message occurs when some (sub)expression accesses an address
+ultimately given by the sum of two constants (Win32 import tables only
+allow one). Instances where this may occur include accesses to member
+fields of struct variables imported from a DLL, as well as using a
+constant index into an array variable imported from a DLL. Any
+multiword variable (arrays, structs, long long, etc) may trigger
+this error condition. However, regardless of the exact data type
+of the offending exported variable, ld will always detect it, issue
+the warning, and exit.
+
+There are several ways to address this difficulty, regardless of the
+data type of the exported variable:
+
+One solution is to force one of the 'constants' to be a variable --
+that is, unknown and un-optimizable at compile time. For arrays,
+there are two possibilities: a) make the indexee (the array's address)
+a variable, or b) make the 'constant' index a variable. Thus:
+
+@example
+extern type extern_array[];
+extern_array[1] -->
+ @{ volatile type *t=extern_array; t[1] @}
+@end example
+
+or
+
+@example
+extern type extern_array[];
+extern_array[1] -->
+ @{ volatile int t=1; extern_array[t] @}
+@end example
+
+For structs (and most other multiword data types) the only option
+is to make the struct itself (or the long long, or the ...) variable:
+
+@example
+extern struct s extern_struct;
+extern_struct.field -->
+ @{ volatile struct s *t=&extern_struct; t->field @}
+@end example
+
+or
+
+@example
+extern long long extern_ll;
+extern_ll -->
+ @{ volatile long long * local_ll=&extern_ll; *local_ll @}
+@end example
+
+A second method of dealing with this difficulty is to abandon
+'auto-import' for the offending symbol and mark it with
+@code{__declspec(dllimport)}. However, in practice that
+requires using compile-time #defines to indicate whether you are
+building a DLL, building client code that will link to the DLL, or
+merely building/linking to a static library. In making the choice
+between the various methods of resolving the 'direct address with
+constant offset' problem, you should consider typical real-world usage:
+
+Original:
+@example
+--foo.h
+extern int arr[];
+--foo.c
+#include "foo.h"
+void main(int argc, char **argv)@{
+ printf("%d\n",arr[1]);
+@}
+@end example
+
+Solution 1:
+@example
+--foo.h
+extern int arr[];
+--foo.c
+#include "foo.h"
+void main(int argc, char **argv)@{
+ /* This workaround is for win32 and cygwin; do not "optimize" */
+ volatile int *parr = arr;
+ printf("%d\n",parr[1]);
+@}
+@end example
+
+Solution 2:
+@example
+--foo.h
+/* Note: auto-export is assumed (no __declspec(dllexport)) */
+#if (defined(_WIN32) || defined(__CYGWIN__)) && \
+ !(defined(FOO_BUILD_DLL) || defined(FOO_STATIC))
+#define FOO_IMPORT __declspec(dllimport)
+#else
+#define FOO_IMPORT
+#endif
+extern FOO_IMPORT int arr[];
+--foo.c
+#include "foo.h"
+void main(int argc, char **argv)@{
+ printf("%d\n",arr[1]);
+@}
+@end example
+
+A third way to avoid this problem is to re-code your
+library to use a functional interface rather than a data interface
+for the offending variables (e.g. set_foo() and get_foo() accessor
+functions).
+
+@kindex --disable-auto-import
+@item --disable-auto-import
+Do not attempt to do sophisticalted linking of @code{_symbol} to
+@code{__imp__symbol} for DATA imports from DLLs.
+
+@kindex --enable-extra-pe-debug
+@item --enable-extra-pe-debug
+Show additional debug info related to auto-import symbol thunking.
+
@kindex --section-alignment
@item --section-alignment
Sets the section alignment. Sections in memory will always begin at
@item --stack @var{reserve}
@itemx --stack @var{reserve},@var{commit}
Specify the amount of memory to reserve (and optionally commit) to be
-used as stack for this program. The default is 32Mb reserved, 4K
+used as stack for this program. The default is 2Mb reserved, 4K
committed.
@kindex --subsystem
@end table
+@c man end
+
@ifset UsesEnvVars
@node Environment
@section Environment Variables
-You can change the behavior of @code{ld} with the environment variables
+@c man begin ENVIRONMENT
+
+You can change the behavior of @command{ld} with the environment variables
@code{GNUTARGET}, @code{LDEMULATION}, and @code{COLLECT_NO_DEMANGLE}.
@kindex GNUTARGET
@code{GNUTARGET} determines the input-file object format if you don't
use @samp{-b} (or its synonym @samp{--format}). Its value should be one
of the BFD names for an input format (@pxref{BFD}). If there is no
-@code{GNUTARGET} in the environment, @code{ld} uses the natural format
+@code{GNUTARGET} in the environment, @command{ld} uses the natural format
of the target. If @code{GNUTARGET} is set to @code{default} then BFD
attempts to discover the input format by examining binary input files;
this method often succeeds, but there are potential ambiguities, since
the @samp{-m} option is not used, and the @code{LDEMULATION} environment
variable is not defined, the default emulation depends upon how the
linker was configured.
-@end ifset
@kindex COLLECT_NO_DEMANGLE
@cindex demangling, default
may be overridden by the @samp{--demangle} and @samp{--no-demangle}
options.
+@c man end
+@end ifset
+
@node Scripts
@chapter Linker Scripts
entry point by trying each of the following methods in order, and
stopping when one of them succeeds:
@itemize @bullet
-@item
+@item
the @samp{-e} @var{entry} command-line option;
-@item
+@item
the @code{ENTRY(@var{symbol})} command in a linker script;
-@item
+@item
the value of the symbol @code{start}, if defined;
-@item
+@item
the address of the first byte of the @samp{.text} section, if present;
-@item
+@item
The address @code{0}.
@end itemize
@cindex including a linker script
Include the linker script @var{filename} at this point. The file will
be searched for in the current directory, and in any directory specified
-with the @code{-L} option. You can nest calls to @code{INCLUDE} up to
+with the @option{-L} option. You can nest calls to @code{INCLUDE} up to
10 levels deep.
@item INPUT(@var{file}, @var{file}, @dots{})
search path. See the description of @samp{-L} in @ref{Options,,Command
Line Options}.
-If you use @samp{INPUT (-l@var{file})}, @code{ld} will transform the
+If you use @samp{INPUT (-l@var{file})}, @command{ld} will transform the
name to @code{lib@var{file}.a}, as with the command line argument
@samp{-l}.
@cindex archive search path in linker script
@cindex search path in linker script
The @code{SEARCH_DIR} command adds @var{path} to the list of paths where
-@code{ld} looks for archive libraries. Using
+@command{ld} looks for archive libraries. Using
@code{SEARCH_DIR(@var{path})} is exactly like using @samp{-L @var{path}}
on the command line (@pxref{Options,,Command Line Options}). If both
are used, then the linker will search both paths. Paths specified using
@kindex FORCE_COMMON_ALLOCATION
@cindex common allocation in linker script
This command has the same effect as the @samp{-d} command-line option:
-to make @code{ld} assign space to common symbols even if a relocatable
+to make @command{ld} assign space to common symbols even if a relocatable
output file is specified (@samp{-r}).
+@item INHIBIT_COMMON_ALLOCATION
+@kindex INHIBIT_COMMON_ALLOCATION
+@cindex common allocation in linker script
+This command has the same effect as the @samp{--no-define-common}
+command-line option: to make @code{ld} omit the assignment of addresses
+to common symbols even for a non-relocatable output file.
+
@item NOCROSSREFS(@var{section} @var{section} @dots{})
@kindex NOCROSSREFS(@var{sections})
@cindex cross references
-This command may be used to tell @code{ld} to issue an error about any
+This command may be used to tell @command{ld} to issue an error about any
references among certain output sections.
In certain types of programs, particularly on embedded systems when
a function defined in the other section.
The @code{NOCROSSREFS} command takes a list of output section names. If
-@code{ld} detects any cross references between the sections, it reports
+@command{ld} detects any cross references between the sections, it reports
an error and returns a non-zero exit status. Note that the
@code{NOCROSSREFS} command uses output section names, not input section
names.
*(.text)
_etext = .;
@}
- _bdata = (. + 3) & ~ 4;
+ _bdata = (. + 3) & ~ 3;
.data : @{ *(.data) @}
@}
@end smallexample
@subsection Output section description
The full description of an output section looks like this:
@smallexample
-@group
+@group
@var{section} [@var{address}] [(@var{type})] : [AT(@var{lma})]
@{
@var{output-section-command}
@noindent
The difference between these is the order in which the @samp{.text} and
@samp{.rdata} input sections will appear in the output section. In the
-first example, they will be intermingled. In the second example, all
+first example, they will be intermingled, appearing in the same order as
+they are found in the linker input. In the second example, all
@samp{.text} input sections will appear first, followed by all
@samp{.rdata} input sections.
@cindex KEEP
@cindex garbage collection
When link-time garbage collection is in use (@samp{--gc-sections}),
-it is often useful to mark sections that should not be eliminated.
+it is often useful to mark sections that should not be eliminated.
This is accomplished by surrounding an input section's wildcard entry
with @code{KEEP()}, as in @code{KEEP(*(.init))} or
@code{KEEP(SORT(*)(.ctors))}.
@}
@}
@end group
-@end smallexample
+@end smallexample
@node Output Section Data
@subsection Output section data
current section. It is followed by an expression in parentheses. Any
otherwise unspecified regions of memory within the section (for example,
gaps left due to the required alignment of input sections) are filled
-with the two least significant bytes of the expression, repeated as
+with the value of the expression, repeated as
necessary. A @code{FILL} statement covers memory locations after the
point at which it occurs in the section definition; by including more
than one @code{FILL} statement, you can have different fill patterns in
different parts of an output section.
This example shows how to fill unspecified regions of memory with the
-value @samp{0x9090}:
+value @samp{0x90}:
@smallexample
-FILL(0x9090)
+FILL(0x90909090)
@end smallexample
The @code{FILL} command is similar to the @samp{=@var{fillexp}} output
section attribute (@pxref{Output Section Fill}), but it only affects the
part of the section following the @code{FILL} command, rather than the
entire section. If both are used, the @code{FILL} command takes
-precedence.
+precedence. See (@pxref{Output Section Fill}) for details on the fill
+expression.
@node Output Section Keywords
@subsection Output section keywords
We showed above that the full description of an output section looked
like this:
@smallexample
-@group
+@group
@var{section} [@var{address}] [(@var{type})] : [AT(@var{lma})]
@{
@var{output-section-command}
@var{output-section-command}. In this section we will describe the
remaining section attributes.
-@menu
+@menu
* Output Section Type:: Output section type
* Output Section LMA:: Output section LMA
* Output Section Region:: Output section region
SECTIONS
@{
.text 0x1000 : @{ *(.text) _etext = . ; @}
- .mdata 0x2000 :
+ .mdata 0x2000 :
AT ( ADDR (.text) + SIZEOF (.text) )
@{ _data = . ; *(.data); _edata = . ; @}
.bss 0x3000 :
@samp{=@var{fillexp}}. @var{fillexp} is an expression
(@pxref{Expressions}). Any otherwise unspecified regions of memory
within the output section (for example, gaps left due to the required
-alignment of input sections) will be filled with the two least
-significant bytes of the value, repeated as necessary.
+alignment of input sections) will be filled with the value, repeated as
+necessary. If the fill expression is a simple hex number, ie. a string
+of hex digit starting with "0x" and without a trailing "k" or "M", then
+an arbitrarily long sequence of hex digits can be used to specify the
+fill pattern; Leading zeros become part of the pattern too. For all
+other cases, including extra parentheses or a unary '+', the fill
+pattern is the four least significant bytes of the value of the
+expression. In all cases, the number is big-endian.
You can also change the fill value with a @code{FILL} command in the
output section commands; see @ref{Output Section Data}.
Here is a simple example:
@smallexample
@group
-SECTIONS @{ .text : @{ *(.text) @} =0x9090 @}
+SECTIONS @{ .text : @{ *(.text) @} =0x90909090 @}
@end group
@end smallexample
you wish. The syntax is:
@smallexample
@group
-MEMORY
+MEMORY
@{
@var{name} [(@var{attr})] : ORIGIN = @var{origin}, LENGTH = @var{len}
@dots{}
@smallexample
@group
-MEMORY
+MEMORY
@{
rom (rx) : ORIGIN = 0, LENGTH = 256K
ram (!rx) : org = 0x40000000, l = 4M
global:
foo1;
local:
- old*;
- original*;
- new*;
+ old*;
+ original*;
+ new*;
@};
VERS_1.2 @{
version node defined is @samp{VERS_1.1}; it has no other dependencies.
The script binds the symbol @samp{foo1} to @samp{VERS_1.1}. It reduces
a number of symbols to local scope so that they are not visible outside
-of the shared library.
+of the shared library; this is done using wildcard patterns, so that any
+symbol whose name begins with @samp{old}, @samp{original}, or @samp{new}
+is matched. The wildcard patterns available are the same as those used
+in the shell when matching filenames (also known as ``globbing'').
Next, the version script defines node @samp{VERS_1.2}. This node
depends upon @samp{VERS_1.1}. The script binds the symbol @samp{foo2}
could just as well have appeared in between @samp{1.1} and @samp{1.2}.
However, this would be a confusing way to write a version script.
+Node name can be omited, provided it is the only version node
+in the version script. Such version script doesn't assign any versions to
+symbols, only selects which symbols will be globally visible out and which
+won't.
+
+@smallexample
+@{ global: foo; bar; local: *; @}
+@end smallexample
+
When you link an application against a shared library that has versioned
symbols, the application itself knows which version of each symbol it
requires, and it also knows which version nodes it needs from each
(i.e. @samp{old_foo}), or you can use the @samp{.symver} directive to
specifically bind to an external version of the function in question.
+You can also specify the language in the version script:
+
+@smallexample
+VERSION extern "lang" @{ version-script-commands @}
+@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}.
+
@node Expressions
@section Expressions in Linker Scripts
@cindex expressions
file2(.text)
. += 1000;
file3(.text)
- @} = 0x1234;
+ @} = 0x12345678;
@}
@end smallexample
@noindent
located at the beginning of the output section @samp{output}. It is
followed by a 1000 byte gap. Then the @samp{.text} section from
@file{file2} appears, also with a 1000 byte gap following before the
-@samp{.text} section from @file{file3}. The notation @samp{= 0x1234}
+@samp{.text} section from @file{file3}. The notation @samp{= 0x12345678}
specifies what data to write in the gaps (@pxref{Output Section Fill}).
@cindex dot inside sections
(lowest)
@end smallexample
Notes:
-(1) Prefix operators
+(1) Prefix operators
(2) @xref{Assignments}.
@c TEXI2ROFF-KILL
@end ifinfo
height2pt&\omit&&\omit&&\omit&\cr
&highest&&&&&\cr
% '176 is tilde, '~' in tt font
-&1&&left&&\qquad- \char'176\ !\qquad\dag&\cr
+&1&&left&&\qquad- \char'176\ !\qquad\dag&\cr
&2&&left&&* / \%&\cr
&3&&left&&+ -&\cr
&4&&left&&>> <<&\cr
@group
SECTIONS
@{
- .text 9+this_isnt_constant :
+ .text 9+this_isnt_constant :
@{ *(.text) @}
@}
@end group
@group
SECTIONS @{ @dots{}
.output1 :
- @{
+ @{
start_of_output_1 = ABSOLUTE(.);
@dots{}
@}
scripts. It is most often seen when setting the address of an output
section.
+@item DATA_SEGMENT_ALIGN(@var{maxpagesize}, @var{commonpagesize})
+@kindex DATA_SEGMENT_ALIGN(@var{maxpagesize}, @var{commonpagesize})
+This is equivalent to either
+@smallexample
+(ALIGN(@var{maxpagesize}) + (. & (@var{maxpagesize} - 1)))
+@end smallexample
+or
+@smallexample
+(ALIGN(@var{maxpagesize}) + (. & (@var{maxpagesize} - @var{commonpagesize})))
+@end smallexample
+@noindent
+depending on whether the latter uses fewer @var{commonpagesize} sized pages
+for the data segment (area between the result of this expression and
+@code{DATA_SEGMENT_END}) than the former or not.
+If the latter form is used, it means @var{commonpagesize} bytes of runtime
+memory will be saved at the expense of up to @var{commonpagesize} wasted
+bytes in the on-disk file.
+
+This expression can only be used directly in @code{SECTIONS} commands, not in
+any output section descriptions and only once in the linker script.
+@var{commonpagesize} should be less or equal to @var{maxpagesize} and should
+be the system page size the object wants to be optimized for (while still
+working on system page sizes up to @var{maxpagesize}).
+
+@noindent
+Example:
+@smallexample
+ . = DATA_SEGMENT_ALIGN(0x10000, 0x2000);
+@end smallexample
+
+@item DATA_SEGMENT_END(@var{exp})
+@kindex DATA_SEGMENT_END(@var{exp})
+This defines the end of data segment for @code{DATA_SEGMENT_ALIGN}
+evaluation purposes.
+
+@smallexample
+ . = DATA_SEGMENT_END(.);
+@end smallexample
+
@item DEFINED(@var{symbol})
@kindex DEFINED(@var{symbol})
@cindex symbol defaults
@chapter Machine Dependent Features
@cindex machine dependencies
-@code{ld} has additional features on some platforms; the following
-sections describe them. Machines where @code{ld} has no additional
+@command{ld} has additional features on some platforms; the following
+sections describe them. Machines where @command{ld} has no additional
functionality are not listed.
@menu
* i960:: @code{ld} and the Intel 960 family
* ARM:: @code{ld} and the ARM family
* HPPA ELF32:: @code{ld} and HPPA 32-bit ELF
+@ifset MMIX
+* MMIX:: @code{ld} and MMIX
+@end ifset
@ifset TICOFF
-* TI COFF:: @code{ld} and TI COFF
+* TI COFF:: @command{ld} and TI COFF
@end ifset
@end menu
@end ifset
@end ifclear
@node H8/300
-@section @code{ld} and the H8/300
+@section @command{ld} and the H8/300
@cindex H8/300 support
-For the H8/300, @code{ld} can perform these global optimizations when
+For the H8/300, @command{ld} can perform these global optimizations when
you specify the @samp{--relax} command-line option.
@table @emph
@cindex relaxing on H8/300
@item relaxing address modes
-@code{ld} finds all @code{jsr} and @code{jmp} instructions whose
+@command{ld} finds all @code{jsr} and @code{jmp} instructions whose
targets are within eight bits, and turns them into eight-bit
program-counter relative @code{bsr} and @code{bra} instructions,
respectively.
@cindex synthesizing on H8/300
@item synthesizing instructions
@c FIXME: specifically mov.b, or any mov instructions really?
-@code{ld} finds all @code{mov.b} instructions which use the
+@command{ld} finds all @code{mov.b} instructions which use the
sixteen-bit absolute address form, but refer to the top
page of memory, and changes them to use the eight-bit address form.
(That is: the linker turns @samp{mov.b @code{@@}@var{aa}:16} into
@c This stuff is pointless to say unless you're especially concerned
@c with Hitachi chips; don't enable it for generic case, please.
@node Hitachi
-@chapter @code{ld} and other Hitachi chips
+@chapter @command{ld} and other Hitachi chips
-@code{ld} also supports the H8/300H, the H8/500, and the Hitachi SH. No
+@command{ld} also supports the H8/300H, the H8/500, and the Hitachi SH. No
special features, commands, or command-line options are required for
these chips.
@end ifset
@end ifclear
@node i960
-@section @code{ld} and the Intel 960 family
+@section @command{ld} and the Intel 960 family
@cindex i960 support
libraries specific to each particular architecture, by including in the
search loop names suffixed with the string identifying the architecture.
-For example, if your @code{ld} command line included @w{@samp{-ACA}} as
+For example, if your @command{ld} command line included @w{@samp{-ACA}} as
well as @w{@samp{-ltry}}, the linker would look (in its built-in search
paths, and in any paths you specify with @samp{-L}) for a library with
the names
use will add another pair of name variants to search for when @w{@samp{-l}}
specifies a library.
-@cindex @code{--relax} on i960
+@cindex @option{--relax} on i960
@cindex relaxing on i960
-@code{ld} supports the @samp{--relax} option for the i960 family. If
-you specify @samp{--relax}, @code{ld} finds all @code{balx} and
+@command{ld} supports the @samp{--relax} option for the i960 family. If
+you specify @samp{--relax}, @command{ld} finds all @code{balx} and
@code{calx} instructions whose targets are within 24 bits, and turns
them into 24-bit program-counter relative @code{bal} and @code{cal}
-instructions, respectively. @code{ld} also turns @code{cal}
+instructions, respectively. @command{ld} also turns @code{cal}
instructions into @code{bal} instructions when it determines that the
target subroutine is a leaf routine (that is, the target subroutine does
not itself call any subroutines).
@end ifclear
@node ARM
-@section @code{ld}'s support for interworking between ARM and Thumb code
+@section @command{ld}'s support for interworking between ARM and Thumb code
@cindex ARM interworking support
@kindex --support-old-code
-For the ARM, @code{ld} will generate code stubs to allow functions calls
+For the ARM, @command{ld} will generate code stubs to allow functions calls
betweem ARM and Thumb code. These stubs only work with code that has
been compiled and assembled with the @samp{-mthumb-interwork} command
line option. If it is necessary to link with old ARM object files or
@cindex entry point, thumb
@kindex --thumb-entry=@var{entry}
The @samp{--thumb-entry} switch is a duplicate of the generic
-@samp{--entry} switch, in that it sets the program's starting address.
+@samp{--entry} switch, in that it sets the program's starting address.
But it also sets the bottom bit of the address, so that it can be
branched to using a BX instruction, and the program will start
executing in Thumb mode straight away.
@node HPPA ELF32
-@section @code{ld} and HPPA 32-bit ELF support
+@section @command{ld} and HPPA 32-bit ELF support
@cindex HPPA multiple sub-space stubs
@kindex --multi-subspace
-When generating a shared library, @code{ld} will by default generate
+When generating a shared library, @command{ld} will by default generate
import stubs suitable for use with a single sub-space application.
-The @samp{--multi-subspace} switch causes @code{ld} to generate export
+The @samp{--multi-subspace} switch causes @command{ld} to generate export
stubs, and different (larger) import stubs suitable for use with
multiple sub-spaces.
@cindex HPPA stub grouping
@kindex --stub-group-size=@var{N}
-Long branch stubs and import/export stubs are placed by @code{ld} in
+Long branch stubs and import/export stubs are placed by @command{ld} in
stub sections located between groups of input sections.
@samp{--stub-group-size} specifies the maximum size of a group of input
sections handled by one stub section. Since branch offsets are signed,
A negative value for @samp{N} chooses this scheme, ensuring that
branches to stubs always use a negative offset. Two special values of
@samp{N} are recognized, @samp{1} and @samp{-1}. These both instruct
-@code{ld} to automatically size input section groups for the branch types
+@command{ld} to automatically size input section groups for the branch types
detected, with the same behaviour regarding stub placement as other
positive or negative values of @samp{N} respectively.
create a larger group (of one section). If input sections are too
large, it may not be possible for a branch to reach its stub.
+@ifset MMIX
+@node MMIX
+@section @code{ld} and MMIX
+For MMIX, there is choice of generating @code{ELF} object files or
+@code{mmo} object files when linking. The simulator @code{mmix}
+understands the @code{mmo} format. The binutils @code{objcopy} utility
+can translate between the two formats.
+
+There is one special section, the @samp{.MMIX.reg_contents} section.
+Contents in this section is assumed to correspond to that of global
+registers, and symbols referring to it are translated to special symbols,
+equal to registers. In a final link, the start address of the
+@samp{.MMIX.reg_contents} section corresponds to the first allocated
+global register multiplied by 8. Register @code{$255} is not included in
+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.
+
+Initial and trailing multiples of zero-valued 32-bit words in a section,
+are left out from an mmo file.
+@end ifset
+
@ifset TICOFF
@node TI COFF
-@section @code{ld}'s support for various TI COFF versions
+@section @command{ld}'s support for various TI COFF versions
@cindex TI COFF versions
@kindex --format=@var{version}
The @samp{--format} switch allows selection of one of the various
TI COFF versions. The latest of this writing is 2; versions 0 and 1 are
also supported. The TI COFF versions also vary in header byte-order
-format; @code{ld} will read any version or byte order, but the output
+format; @command{ld} will read any version or byte order, but the output
header format depends on the default specified by the specific target.
@end ifset
@node Reporting Bugs
@chapter Reporting Bugs
-@cindex bugs in @code{ld}
-@cindex reporting bugs in @code{ld}
+@cindex bugs in @command{ld}
+@cindex reporting bugs in @command{ld}
-Your bug reports play an essential role in making @code{ld} reliable.
+Your bug reports play an essential role in making @command{ld} reliable.
Reporting a bug may help you by bringing a solution to your problem, or
it may not. But in any case the principal function of a bug report is
-to help the entire community by making the next version of @code{ld}
+to help the entire community by making the next version of @command{ld}
work better. Bug reports are your contribution to the maintenance of
-@code{ld}.
+@command{ld}.
In order for a bug report to serve its purpose, you must include the
information that enables us to fix the bug.
@cindex crash of linker
@item
If the linker gets a fatal signal, for any input whatever, that is a
-@code{ld} bug. Reliable linkers never crash.
+@command{ld} bug. Reliable linkers never crash.
@cindex error on valid input
@item
-If @code{ld} produces an error message for valid input, that is a bug.
+If @command{ld} produces an error message for valid input, that is a bug.
@cindex invalid input
@item
-If @code{ld} does not produce an error message for invalid input, that
+If @command{ld} does not produce an error message for invalid input, that
may be a bug. In the general case, the linker can not verify that
object files are correct.
@item
If you are an experienced user of linkers, your suggestions for
-improvement of @code{ld} are welcome in any case.
+improvement of @command{ld} are welcome in any case.
@end itemize
@node Bug Reporting
@section How to report bugs
@cindex bug reports
-@cindex @code{ld} bugs, reporting
+@cindex @command{ld} bugs, reporting
A number of companies and individuals offer support for @sc{gnu}
-products. If you obtained @code{ld} from a support organization, we
+products. If you obtained @command{ld} from a support organization, we
recommend you contact that organization first.
You can find contact information for many support companies and
individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
distribution.
-Otherwise, send bug reports for @code{ld} to
-@samp{bug-gnu-utils@@gnu.org}.
+Otherwise, send bug reports for @command{ld} to
+@samp{bug-binutils@@gnu.org}.
The fundamental principle of reporting bugs usefully is this:
@strong{report all the facts}. If you are not sure whether to state a
@itemize @bullet
@item
-The version of @code{ld}. @code{ld} announces it if you start it with
+The version of @command{ld}. @command{ld} announces it if you start it with
the @samp{--version} argument.
Without this, we will not know whether there is any point in looking for
-the bug in the current version of @code{ld}.
+the bug in the current version of @command{ld}.
@item
-Any patches you may have applied to the @code{ld} source, including any
+Any patches you may have applied to the @command{ld} source, including any
patches made to the @code{BFD} library.
@item
version number.
@item
-What compiler (and its version) was used to compile @code{ld}---e.g.
+What compiler (and its version) was used to compile @command{ld}---e.g.
``@code{gcc-2.7}''.
@item
A description of what behavior you observe that you believe is
incorrect. For example, ``It gets a fatal signal.''
-Of course, if the bug is that @code{ld} gets a fatal signal, then we
+Of course, if the bug is that @command{ld} gets a fatal signal, then we
will certainly notice it. But if the bug is incorrect output, we might
not notice unless it is glaringly wrong. You might as well not give us
a chance to make a mistake.
Even if the problem you experience is a fatal signal, you should still
say so explicitly. Suppose something strange is going on, such as, your
-copy of @code{ld} is out of synch, or you have encountered a bug in the
+copy of @command{ld} is out of synch, or you have encountered a bug in the
C library on your system. (This has happened!) Your copy might crash
and ours would not. If you told us to expect a crash, then when ours
fails to crash, we would know that the bug was not happening for us. If
any conclusion from our observations.
@item
-If you wish to suggest changes to the @code{ld} source, send us context
+If you wish to suggest changes to the @command{ld} source, send us context
diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or
@samp{-p} option. Always send diffs from the old file to the new file.
-If you even discuss something in the @code{ld} source, refer to it by
+If you even discuss something in the @command{ld} source, refer to it by
context, not by line number.
The line numbers in our development sources will not match those in your
a patch is all we need. We might see problems with your patch and decide
to fix the problem another way, or we might not understand it at all.
-Sometimes with a program as complicated as @code{ld} it is very hard to
+Sometimes with a program as complicated as @command{ld} it is very hard to
construct an example that will make the program follow a certain path
through the code. If you do not send us the example, we will not be
able to construct one, so we will not be able to verify that the bug is
@node MRI
@appendix MRI Compatible Script Files
@cindex MRI compatibility
-To aid users making the transition to @sc{gnu} @code{ld} from the MRI
-linker, @code{ld} can use MRI compatible linker scripts as an
+To aid users making the transition to @sc{gnu} @command{ld} from the MRI
+linker, @command{ld} can use MRI compatible linker scripts as an
alternative to the more general-purpose linker scripting language
described in @ref{Scripts}. MRI compatible linker scripts have a much
simpler command set than the scripting language otherwise used with
-@code{ld}. @sc{gnu} @code{ld} supports the most commonly used MRI
+@command{ld}. @sc{gnu} @command{ld} supports the most commonly used MRI
linker commands; these commands are described here.
In general, MRI scripts aren't of much use with the @code{a.out} object
Each command in an MRI-compatible script occupies its own line; each
command line starts with the keyword that identifies the command (though
blank lines are also allowed for punctuation). If a line of an
-MRI-compatible script begins with an unrecognized keyword, @code{ld}
+MRI-compatible script begins with an unrecognized keyword, @command{ld}
issues a warning message, but continues processing the script.
Lines beginning with @samp{*} are comments.
@cindex @code{ABSOLUTE} (MRI)
@item ABSOLUTE @var{secname}
@itemx ABSOLUTE @var{secname}, @var{secname}, @dots{} @var{secname}
-Normally, @code{ld} includes in the output file all sections from all
+Normally, @command{ld} includes in the output file all sections from all
the input files. However, in an MRI-compatible script, you can use the
@code{ABSOLUTE} command to restrict the sections that will be present in
your output program. If the @code{ABSOLUTE} command is used at all in a
@cindex @code{FORMAT} (MRI)
@item FORMAT @var{output-format}
Similar to the @code{OUTPUT_FORMAT} command in the more general linker
-language, but restricted to one of these output formats:
+language, but restricted to one of these output formats:
@enumerate
-@item
+@item
S-records, if @var{output-format} is @samp{S}
@item
@cindex @code{LIST} (MRI)
@item LIST @var{anything}@dots{}
Print (to the standard output file) a link map, as produced by the
-@code{ld} command-line option @samp{-M}.
+@command{ld} command-line option @samp{-M}.
The keyword @code{LIST} may be followed by anything on the
same line, with no change in its effect.
@item LOAD @var{filename}
@itemx LOAD @var{filename}, @var{filename}, @dots{} @var{filename}
Include one or more object file @var{filename} in the link; this has the
-same effect as specifying @var{filename} directly on the @code{ld}
+same effect as specifying @var{filename} directly on the @command{ld}
command line.
@cindex @code{NAME} (MRI)
@item NAME @var{output-name}
-@var{output-name} is the name for the program produced by @code{ld}; the
+@var{output-name} is the name for the program produced by @command{ld}; the
MRI-compatible command @code{NAME} is equivalent to the command-line
option @samp{-o} or the general script language command @code{OUTPUT}.
@cindex @code{ORDER} (MRI)
@item ORDER @var{secname}, @var{secname}, @dots{} @var{secname}
@itemx ORDER @var{secname} @var{secname} @var{secname}
-Normally, @code{ld} orders the sections in its output file in the
+Normally, @command{ld} orders the sections in its output file in the
order in which they first appear in the input files. In an MRI-compatible
script, you can override this ordering with the @code{ORDER} command. The
sections you list with @code{ORDER} will appear first in your output
@cindex GNU Free Documentation License
GNU Free Documentation License
-
+
Version 1.1, March 2000
Copyright (C) 2000 Free Software Foundation, Inc.
59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
-
+
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
@contents
@bye
-
-