@end ifinfo
@ifinfo
-This file documents the GNU linker LD.
+This file documents the @sc{gnu} linker LD.
-Copyright (C) 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
+Copyright (C) 1991, 92, 93, 94, 95, 1996 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
@sp 1
@subtitle @code{ld} version 2
@subtitle January 1994
-@author Steve Chamberlain and Roland Pesch
+@author Steve Chamberlain
@author Cygnus Support
@page
@tex
{\parskip=0pt
\hfill Cygnus Support\par
-\hfill steve\@cygnus.com, pesch\@cygnus.com\par
+\hfill steve\@cygnus.com, doc\@cygnus.com\par
\hfill {\it Using LD, the GNU linker}\par
\hfill Edited by Jeffrey Osier (jeffrey\@cygnus.com)\par
-\hfill and Roland Pesch (pesch\@cygnus.com)\par
}
\global\parindent=0pt % Steve likes it this way.
@end tex
@vskip 0pt plus 1filll
-Copyright @copyright{} 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
+Copyright @copyright{} 1991, 92, 93, 94, 95, 1996 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
@ifinfo
@node Top
@top Using ld
-This file documents the GNU linker ld.
+This file documents the @sc{gnu} linker ld.
@menu
* Overview:: Overview
@end ifclear
@c Following blank line required for remaining bug in makeinfo conds/menus
+* Reporting Bugs:: Reporting Bugs
* MRI:: MRI Compatible Script Files
* Index:: Index
@end menu
@node Overview
@chapter Overview
-@cindex GNU linker
+@cindex @sc{gnu} linker
@cindex what is this?
@code{ld} combines a number of object and archive files, relocates
their data and ties up symbol references. Usually the last step in
available kind of object file. @xref{BFD}, for more information.
@end ifclear
-Aside from its flexibility, the GNU linker is more helpful than other
+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
@node Invocation
@chapter Invocation
-The GNU linker @code{ld} is meant to cover a broad range of situations,
+The @sc{gnu} linker @code{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.
@cindex command line
@cindex options
-Here is a summary of the options you can use on the @code{ld} command
-line:
-
-@c FIXME! -relax only avail h8/300, i960. Conditionals screwed in examples.
-@smallexample
-ld [ -o @var{output} ] @var{objfile}@dots{}
- [ -A@var{architecture} ] [ -b @var{input-format} ]
- [ -Bstatic ] [ -Bdynamic ] [ -Bsymbolic ]
- [ -c @var{MRI-commandfile} ] [ -d | -dc | -dp ]
- [ -defsym @var{symbol}=@var{expression} ]
- [ -dynamic-linker @var{file} ] [ -embedded-relocs ]
- [ -e @var{entry} ] [ -F ] [ -F @var{format} ]
- [ -format @var{input-format} ] [ -g ] [ -G @var{size} ] [ -help ]
- [ -i ] [ -l@var{archive} ] [ -L@var{searchdir} ] [ -M ]
- [ -Map @var{mapfile} ] [ -m @var{emulation} ] [ -N | -n ]
- [ -noinhibit-exec ] [ -no-keep-memory ] [ -oformat @var{output-format} ]
- [ -R @var{filename} ] [ -relax ] [ -retain-symbols-file @var{filename} ]
- [ -r | -Ur ] [ -rpath @var{dir} ] [ -S ] [ -s ] [ -soname @var{name} ]
- [ -shared ] [ -sort-common ] [ -stats ] [ -T @var{commandfile} ]
- [ -Ttext @var{org} ] [ -Tdata @var{org} ]
- [ -Tbss @var{org} ] [ -t ] [ -traditional-format ]
- [ -u @var{symbol}] [-V] [-v] [ -verbose] [ -version ]
- [ -warn-common ] [ -warn-once ] [ -y @var{symbol} ] [ -X ] [-x ]
- [ -( [ archives ] -) ] [ --start-group [ archives ] --end-group ]
- [ -split-by-reloc @var{count} ] [ -split-by-file ] [ --whole-archive ]
-@end smallexample
-
-This plethora of command-line options may seem intimidating, but in
-actual practice few of them are used in any particular context.
+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
object files on a standard, supported Unix system. On such a system, to
link a file @code{hello.o}:
-@example
+@smallexample
ld -o @var{output} /lib/crt0.o hello.o -lc
-@end example
+@end smallexample
This tells @code{ld} to produce a file called @var{output} as the
result of linking the file @code{/lib/crt0.o} with @code{hello.o} and
directories. (See the discussion of the @samp{-l} option below.)
The command-line options to @code{ld} may be specified in any order, and
-may be repeated at will. Repeating most options with a
-different argument will either have no further effect, or override prior
+may be repeated at will. Repeating most options with a different
+argument will either have no further effect, or override prior
occurrences (those further to the left on the command line) of that
-option.
-
-@ifclear SingleFormat
-The exceptions---which may meaningfully be used more than once---are
-@samp{-A}, @samp{-b} (or its synonym @samp{-format}), @samp{-defsym},
-@samp{-L}, @samp{-l}, @samp{-R}, @samp{-u}, and @samp{-(} (or its
-synonym @samp{--start-group})..
-@end ifclear
-@ifset SingleFormat
-The exceptions---which may meaningfully be used more than once---are
-@samp{-A}, @samp{-defsym}, @samp{-L}, @samp{-l}, @samp{-R}, @samp{-u},
-and @samp{-(} (or its synonym @samp{--start-group}).
-@end ifset
+option. Options which may be meaningfully specified more than once are
+noted in the descriptions below.
@cindex object files
-The list of object files to be linked together, shown as @var{objfile}@dots{},
-may follow, precede, or be mixed in with command-line options, except that
-an @var{objfile} argument may not be placed between an option and
-its argument.
+Non-option arguments are objects files which are to be linked together.
+They may follow, precede, or be mixed in with command-line options,
+except that an object file argument may not be placed between an option
+and its argument.
Usually the linker is invoked with at least one object file, but you can
specify other forms of binary input files using @samp{-l}, @samp{-R},
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. @xref{Commands}.
+@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.
+@xref{Commands}.
For options whose names are a single letter,
option arguments must either follow the option letter without intervening
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
+@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
of multiple-letter options are accepted.
@table @code
+@kindex -a@var{keyword}
+@item -a@var{keyword}
+This option is supported for HP/UX compatibility. The @var{keyword}
+argument must be one of the strings @samp{archive}, @samp{shared}, or
+@samp{default}. @samp{-aarchive} is functionally equivalent to
+@samp{-Bstatic}, and the other two keywords are functionally equivalent
+to @samp{-Bdynamic}. This option may be used any number of times.
+
@ifset I960
@cindex architectures
@kindex -A@var{arch}
@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
@var{architecture} argument identifies the particular architecture in
@ifclear SingleFormat
@cindex binary input format
@kindex -b @var{format}
+@kindex --format=@var{format}
@cindex input format
-@item -b @var{input-format}
@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
@samp{-b} option to specify the binary format for input object files
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
-formats with @samp{objdump -i}.) @w{@samp{-format @var{input-format}}}
-has the same effect, as does the script command @code{TARGET}.
+formats with @samp{objdump -i}.)
@xref{BFD}.
You may want to use this option if you are linking files with an unusual
Commands}.
@end ifclear
-@kindex -Bstatic
-@item -Bstatic
-Do not link against shared libraries. This is only meaningful on
-platforms for which shared libraries are supported.
-
-@kindex -Bdynamic
-@item -Bdynamic
-Link against dynamic libraries. This is only meaningful on platforms
-for which shared libraries are supported. This option is normally the
-default on such platforms.
-
-@kindex -Bsymbolic
-@item -Bsymbolic
-When creating a shared library, bind references to global symbols to the
-definition within the shared library, if any. Normally, it is possible
-for a program linked against a shared library to override the definition
-within the shared library. This option is only meaningful on ELF
-platforms which support shared libraries.
-
@kindex -c @var{MRI-cmdfile}
+@kindex --mri-script=@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
files written in an alternate, restricted command language, described in
@ref{MRI,,MRI Compatible Script Files}. Introduce MRI script files with
@cindex common allocation
@kindex -d
-@item -d
@kindex -dc
-@itemx -dc
@kindex -dp
+@item -d
+@itemx -dc
@itemx -dp
These three options are equivalent; multiple forms are supported for
compatibility with other linkers. They
@code{FORCE_COMMON_ALLOCATION} has the same effect. @xref{Option
Commands}.
-@cindex symbols, from command line
-@kindex -defsym @var{symbol}=@var{exp}
-@item -defsym @var{symbol}=@var{expression}
-Create a global symbol in the output file, containing the absolute
-address given by @var{expression}. You may use this option as many
-times as necessary to define multiple symbols in the command line. A
-limited form of arithmetic is supported for the @var{expression} in this
-context: you may give a hexadecimal constant or the name of an existing
-symbol, or use @code{+} and @code{-} to add or subtract hexadecimal
-constants or symbols. If you need more elaborate expressions, consider
-using the linker command language from a script (@pxref{Assignment, ,
-Assignment: Symbol Definitions}). @emph{Note:} there should be no
-white space between @var{symbol}, the equals sign (``@key{=}''), and
-@var{expression}.
-
-@ifset GENERIC
-@cindex dynamic linker, from command line
-@kindex -dynamic-linker @var{file}
-@item -dynamic-linker @var{file}
-Set the name of the dynamic linker. This is only meaningful when
-generating dynamically linked ELF executables. The default dynamic
-linker is normally correct; don't use this unless you know what you are
-doing.
-@end ifset
-
-@cindex MIPS embedded PIC code
-@kindex -embedded-relocs
-@item -embedded-relocs
-This option is only meaningful when linking MIPS embedded PIC code,
-generated by the -membedded-pic option to the GNU compiler and
-assembler. It causes the linker to create a table which may be used at
-runtime to relocate any data which was statically initialized to pointer
-values. See the code in testsuite/ld-empic for details.
-
@cindex entry point, from command line
@kindex -e @var{entry}
+@kindex --entry=@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. @xref{Entry Point}, for a
discussion of defaults and other ways of specifying the
entry point.
-@ifclear SingleFormat
+@cindex dynamic symbol table
+@kindex -E
+@kindex --export-dynamic
+@item -E
+@itemx --export-dynamic
+When creating a dynamically linked executable, add all symbols to the
+dynamic symbol table. Normally, the dynamic symbol table contains only
+symbols which are used by a dynamic object. This option is needed for
+some uses of @code{dlopen}.
+
+@kindex -f
+@kindex --auxiliary
+@item -f
+@itemx --auxiliary @var{name}
+When creating an ELF shared object, set the internal DT_AUXILIARY field
+to the specified name. This tells the dynamic linker that the symbol
+table of the shared object should be used as an auxiliary filter on the
+symbol table of the shared object @var{name}.
+
+If you later link a program against this filter object, then, when you
+run the program, the dynamic linker will see the DT_AUXILIARY field. If
+the dynamic linker resolves any symbols from the filter object, it will
+first check whether there is a definition in the shared object
+@var{name}. If there is one, it will be used instead of the definition
+in the filter object. The shared object @var{name} need not exist.
+Thus the shared object @var{name} may be used to provide an alternative
+implementation of certain functions, perhaps for debugging or for
+machine specific performance.
+
@kindex -F
-@item -F
-@itemx -F@var{format}
-Ignored. Some older linkers used this option throughout a compilation
+@kindex --filter
+@item -F @var{name}
+@itemx --filter @var{name}
+When creating an ELF shared object, set the internal DT_FILTER field to
+the specified name. This tells the dynamic linker that the symbol table
+of the shared object which is being created should be used as a filter
+on the symbol table of the shared object @var{name}.
+
+If you later link a program against this filter object, then, when you
+run the program, the dynamic linker will see the DT_FILTER field. The
+dynamic linker will resolve symbols according to the symbol table of the
+filter object as usual, but it will actually link to the definitions
+found in the shared object @var{name}. Thus the filter object can be
+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
toolchain for specifying object-file format for both input and output
-object files. The mechanisms @code{ld} uses for this purpose (the
-@samp{-b} or @samp{-format} options for input files, @samp{-oformat}
-option or the @code{TARGET} command in linker scripts for output files,
-the @code{GNUTARGET} environment variable) are more flexible, but
-@code{ld} accepts the @samp{-F} option for compatibility with scripts
-written to call the old linker.
-
-@kindex -format
-@item -format @var{input-format}
-Synonym for @samp{-b @var{input-format}}.
-@end ifclear
+object files. The @sc{gnu} linker uses other mechanisms for this
+purpose: the @code{-b}, @code{--format}, @code{--oformat} options, the
+@code{TARGET} command in linker scripts, and the @code{GNUTARGET}
+environment variable. The @sc{gnu} linker will ignore the @code{-F}
+option when not creating an ELF shared object.
+
+@kindex --force-exe-suffix
+@item --force-exe-suffix
+Make sure that an output file has a .exe suffix.
+
+If a successfully built fully linked output file does not have a
+@code{.exe} or @code{.dll} suffix, this option forces the linker to copy
+the output file to one of the same name with a @code{.exe} suffix. This
+option is useful when using unmodified Unix makefiles on a Microsoft
+Windows host, since some versions of Windows won't run an image unless
+it ends in a @code{.exe} suffix.
@kindex -g
@item -g
Ignored. Provided for compatibility with other tools.
@kindex -G
+@kindex --gpsize
@cindex object size
@item -G@var{value}
-@itemx -G @var{value}
+@itemx --gpsize=@var{value}
Set the maximum size of objects to be optimized using the GP register to
-@var{size} under MIPS ECOFF. Ignored for other object file formats.
+@var{size}. This is only meaningful for object file formats such as
+MIPS ECOFF which supports putting large and small objects into different
+sections. This is ignored for other object file formats.
-@cindex help
-@cindex usage
-@kindex -help
-@item -help
-Print a summary of the command-line options on the standard output and exit.
+@cindex runtime library name
+@kindex -h@var{name}
+@kindex -soname=@var{name}
+@item -h@var{name}
+@itemx -soname=@var{name}
+When creating an ELF shared object, set the internal DT_SONAME field to
+the specified name. When an executable is linked with a shared object
+which has a DT_SONAME field, then when the executable is run the dynamic
+linker will attempt to load the shared object specified by the DT_SONAME
+field rather than the using the file name given to the linker.
@kindex -i
@cindex incremental link
@cindex archive files, from cmd line
@kindex -l@var{archive}
-@item -l@var{ar}
-Add archive file @var{archive} to the list of files to link. This
+@kindex --library=@var{archive}
+@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
-path-list for occurrences of @code{lib@var{ar}.a} for every @var{archive}
-specified.
+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
+libraries with extensions other than @code{.a}. Specifically, on ELF
+and SunOS systems, @code{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.
+
+The linker will search an archive only once, at the location where it is
+specified on the command line. If the archive defines a symbol which
+was undefined in some object which appeared before the archive on the
+command line, the linker will include the appropriate file(s) from the
+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
+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
+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}
-@itemx -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
-option any number of times.
+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
+order in which the options appear.
@ifset UsesEnvVars
The default set of paths searched (without being specified with
@end ifset
The paths can also be specified in a link script with the
-@code{SEARCH_DIR} command.
-
-@cindex link map
-@kindex -M
-@item -M
-Print (to the standard output) a link map---diagnostic information
-about where symbols are mapped by @code{ld}, and information on global
-common storage allocation.
-
-@cindex link map
-@kindex -Map
-@item -Map @var{mapfile}
-Print to the file @var{mapfile} a link map---diagnostic information
-about where symbols are mapped by @code{ld}, and information on global
-common storage allocation.
+@code{SEARCH_DIR} command. Directories specified this way are searched
+at the point in which the linker script appears in the command line.
@cindex emulation
@kindex -m @var{emulation}
@item -m@var{emulation}
-@itemx -m @var{emulation}
Emulate the @var{emulation} linker. You can list the available
emulations with the @samp{--verbose} or @samp{-V} options. The default
depends on how your @code{ld} was configured.
+@cindex link map
+@kindex -M
+@kindex --print-map
+@item -M
+@itemx --print-map
+Print (to the standard output) a link map---diagnostic information about
+where symbols are mapped by @code{ld}, and information on global common
+storage allocation.
+
+@kindex -n
+@cindex read-only text
+@cindex NMAGIC
+@kindex --nmagic
+@item -n
+@itemx --nmagic
+Set the text segment to be read only, and mark the output as
+@code{NMAGIC} if possible.
+
@kindex -N
+@kindex --omagic
@cindex read/write from cmd line
-@kindex OMAGIC
+@cindex OMAGIC
@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
style magic numbers, mark the output as @code{OMAGIC}.
-@kindex -n
-@cindex read-only text
-@kindex NMAGIC
-@item -n
-Set the text segment to be read only, and mark the output as
-@code{NMAGIC} if possible.
+@kindex -o @var{output}
+@kindex --output=@var{output}
+@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
+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.
-@item -noinhibit-exec
-@cindex output file after errors
-@kindex -noinhibit-exec
-Retain the executable output file whenever it is still usable.
-Normally, the linker will not produce an output file if it encounters
-errors during the link process; it exits without writing an output file
-when it issues any error whatsoever.
+@cindex partial link
+@cindex relocatable output
+@kindex -r
+@kindex --relocateable
+@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
+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}.
+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}.
+
+This option does the same thing as @samp{-i}.
+
+@kindex -R @var{file}
+@kindex --just-symbols=@var{file}
+@cindex symbol-only input
+@item -R @var{filename}
+@itemx --just-symbols=@var{filename}
+Read symbol names and their addresses from @var{filename}, but do not
+relocate it or include it in the output. This allows your output 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
+followed by a directory name, rather than a file name, it is treated as
+the @code{-rpath} option.
+
+@kindex -s
+@kindex --strip-all
+@cindex strip all symbols
+@item -s
+@itemx --strip-all
+Omit all symbol information from the output file.
+
+@kindex -S
+@kindex --strip-debug
+@cindex strip debugger symbols
+@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
+@itemx --trace
+Print the names of the input files as @code{ld} processes them.
+
+@kindex -T @var{script}
+@kindex --script=@var{script}
+@cindex script files
+@item -T @var{commandfile}
+@itemx --script=@var{commandfile}
+Read link commands from the file @var{commandfile}. These commands
+replace @code{ld}'s default link script (rather than adding to it), so
+@var{commandfile} must specify everything necessary to describe the
+target format. 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{Commands}. If
+@var{commandfile} does not exist, @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}
+@cindex undefined symbol
+@item -u @var{symbol}
+@itemx --undefined=@var{symbol}
+Force @var{symbol} to be entered in the output file as an undefined symbol.
+Doing this may, for example, trigger linking of additional modules from
+standard libraries. @samp{-u} may be repeated with different option
+arguments to enter additional undefined symbols.
+@c Nice idea, but no such command: This option is equivalent
+@c to the @code{EXTERN} linker command.
+
+@kindex -v
+@kindex -V
+@kindex --version
+@cindex version
+@item -v
+@itemx --version
+@itemx -V
+Display the version number for @code{ld}. The @code{-V} option also
+lists the supported emulations.
+
+@kindex -x
+@kindex --discard-all
+@cindex deleting local symbols
+@item -x
+@itemx --discard-all
+Delete all local symbols.
+
+@kindex -X
+@kindex --discard-locals
+@cindex local symbols, deleting
+@cindex L, deleting symbols beginning
+@item -X
+@itemx --discard-locals
+Delete all temporary local symbols. For most targets, this is all local
+symbols whose names begin with @samp{L}.
+
+@kindex -y @var{symbol}
+@kindex --trace-symbol=@var{symbol}
+@cindex symbol tracing
+@item -y @var{symbol}
+@itemx --trace-symbol=@var{symbol}
+Print the name of each linked file in which @var{symbol} appears. This
+option may be given any number of times. On many systems it is necessary
+to prepend an underscore.
+
+This option is useful when you have an undefined symbol in your link but
+don't know where the reference is coming from.
+
+@kindex -Y @var{path}
+@item -Y @var{path}
+Add @var{path} to the default library search path. This option exists
+for Solaris compatibility.
+
+@kindex -z @var{keyword}
+@item -z @var{keyword}
+This option is ignored for Solaris compatibility.
+
+@kindex -(
+@cindex groups of archives
+@item -( @var{archives} -)
+@itemx --start-group @var{archives} --end-group
+The @var{archives} should be a list of archive files. They may be
+either explicit file names, or @samp{-l} options.
+
+The specified archives are searched repeatedly until no new undefined
+references are created. Normally, an archive is searched only once in
+the order that it is specified on the command line. If a symbol in that
+archive is needed to resolve an undefined symbol referred to by an
+object in an archive that appears later on the command line, the linker
+would not be able to resolve that reference. By grouping the archives,
+they all be searched repeatedly until all possible references are
+resolved.
+
+Using this option has a significant performance cost. It is best to use
+it only when there are unavoidable circular references between two or
+more archives.
+
+@kindex -assert @var{keyword}
+@item -assert @var{keyword}
+This option is ignored for SunOS compatibility.
+
+@kindex -Bdynamic
+@kindex -dy
+@kindex -call_shared
+@item -Bdynamic
+@itemx -dy
+@itemx -call_shared
+Link against dynamic libraries. This is only meaningful on platforms
+for which shared libraries are supported. This option is normally the
+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.
+
+@kindex -Bstatic
+@kindex -dn
+@kindex -non_shared
+@kindex -static
+@item -Bstatic
+@itemx -dn
+@itemx -non_shared
+@itemx -static
+Do not link against shared libraries. This is only meaningful on
+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.
+
+@kindex -Bsymbolic
+@item -Bsymbolic
+When creating a shared library, bind references to global symbols to the
+definition within the shared library, if any. Normally, it is possible
+for a program linked against a shared library to override the definition
+within the shared library. This option is only meaningful on ELF
+platforms which support shared libraries.
+
+@cindex cross reference table
+@kindex --cref
+@item --cref
+Output a cross reference table. If a linker map file is being
+generated, the cross reference table is printed to the map file.
+Otherwise, it is printed on the standard output.
+
+The format of the table is intentionally simple, so that it may be
+easily processed by a script if necessary. The symbols are printed out,
+sorted by name. For each symbol, a list of file names is given. If the
+symbol is defined, the first file listed is the location of the
+definition. The remaining files contain references to the symbol.
+
+@cindex symbols, from command line
+@kindex --defsym @var{symbol}=@var{exp}
+@item --defsym @var{symbol}=@var{expression}
+Create a global symbol in the output file, containing the absolute
+address given by @var{expression}. You may use this option as many
+times as necessary to define multiple symbols in the command line. A
+limited form of arithmetic is supported for the @var{expression} in this
+context: you may give a hexadecimal constant or the name of an existing
+symbol, or use @code{+} and @code{-} to add or subtract hexadecimal
+constants or symbols. If you need more elaborate expressions, consider
+using the linker command language from a script (@pxref{Assignment, ,
+Assignment: Symbol Definitions}). @emph{Note:} there should be no
+white space between @var{symbol}, the equals sign (``@key{=}''), and
+@var{expression}.
+
+@cindex dynamic linker, from command line
+@kindex --dynamic-linker @var{file}
+@item --dynamic-linker @var{file}
+Set the name of the dynamic linker. This is only meaningful when
+generating dynamically linked ELF executables. The default dynamic
+linker is normally correct; don't use this unless you know what you are
+doing.
+
+@cindex big-endian objects
+@cindex endianness
+@kindex -EB
+@item -EB
+Link big-endian objects. This affects the default output format.
+
+@cindex little-endian objects
+@kindex -EL
+@item -EL
+Link little-endian objects. This affects the default output format.
+
+@cindex MIPS embedded PIC code
+@kindex --embedded-relocs
+@item --embedded-relocs
+This option is only meaningful when linking MIPS embedded PIC code,
+generated by the -membedded-pic option to the @sc{gnu} compiler and
+assembler. It causes the linker to create a table which may be used at
+runtime to relocate any data which was statically initialized to pointer
+values. See the code in testsuite/ld-empic for details.
+
+@cindex help
+@cindex usage
+@kindex --help
+@item --help
+Print a summary of the command-line options on the standard output and exit.
+
+@cindex link map
+@kindex -Map
+@item -Map @var{mapfile}
+Print to the file @var{mapfile} a link map---diagnostic information
+about where symbols are mapped by @code{ld}, and information on global
+common storage allocation.
-@item -no-keep-memory
@cindex memory usage
-@kindex -no-keep-memory
+@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
instead optimize for memory usage, by rereading the symbol tables as
necessary. This may be required if @code{ld} runs out of memory space
while linking a large executable.
-@item -o @var{output}
-@kindex -o @var{output}
-@cindex naming the output file
-Use @var{output} as the name for the program produced by @code{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 --no-whole-archive
+@item --no-whole-archive
+Turn off the effect of the @code{--whole-archive} option for subsequent
+archive files.
+
+@cindex output file after errors
+@kindex --noinhibit-exec
+@item --noinhibit-exec
+Retain the executable output file whenever it is still usable.
+Normally, the linker will not produce an output file if it encounters
+errors during the link process; it exits without writing an output file
+when it issues any error whatsoever.
@ifclear SingleFormat
-@kindex -oformat
-@item -oformat @var{output-format}
+@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
-@samp{-oformat} option to specify the binary format for the output
+@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}
should be configured to produce as a default output format the most
this option overrides it. @xref{BFD}.
@end ifclear
-@item -R @var{filename}
-@kindex -R @var{file}
-@cindex symbol-only input
-Read symbol names and their addresses from @var{filename}, but do not
-relocate it or include it in the output. This allows your output file
-to refer symbolically to absolute locations of memory defined in other
-programs.
-
-@kindex -relax
+@kindex -qmagic
+@item -qmagic
+This option is ignored for Linux compatibility.
+
+@kindex -Qy
+@item -Qy
+This option is ignored for SVR4 compatibility.
+
+@kindex --relax
@cindex synthesizing linker
@cindex relaxing addressing modes
-@item -relax
+@item --relax
An option with machine dependent effects.
@ifset GENERIC
-Currently this option is only supported on the H8/300 and the Intel 960.
+This option is only supported on a few targets.
@end ifset
@ifset H8300
@xref{H8/300,,@code{ld} and the H8/300}.
@xref{i960,, @code{ld} and the Intel 960 family}.
@end ifset
-On some platforms, the @samp{-relax} option performs global optimizations that
-become possible when the linker resolves addressing in the program, such
-as relaxing address modes and synthesizing new instructions in the
-output object file.
+On some platforms, the @samp{--relax} option performs global
+optimizations that become possible when the linker resolves addressing
+in the program, such as relaxing address modes and synthesizing new
+instructions in the output object file.
@ifset GENERIC
-On platforms where this is not supported, @samp{-relax} is accepted, but
-ignored.
+On platforms where this is not supported, @samp{--relax} is accepted,
+but ignored.
@end ifset
-@item -retain-symbols-file @var{filename}
@cindex retaining specified symbols
@cindex stripping all but some symbols
@cindex symbols, retaining selectively
+@item --retain-symbols-file @var{filename}
Retain @emph{only} the symbols listed in the file @var{filename},
discarding all others. @var{filename} is simply a flat file, with one
symbol name per line. This option is especially useful in environments
where a large global symbol table is accumulated gradually, to conserve
run-time memory.
-@samp{-retain-symbols-file} does @emph{not} discard undefined symbols,
+@samp{--retain-symbols-file} does @emph{not} discard undefined symbols,
or symbols needed for relocations.
-You may only specify @samp{-retain-symbols-file} once in the command
+You may only specify @samp{--retain-symbols-file} once in the command
line. It overrides @samp{-s} and @samp{-S}.
@ifset GENERIC
@item -rpath @var{dir}
@cindex runtime library search path
@kindex -rpath
-Add a directory to the runtime library search path. This is only
-meaningful when linking an ELF executable with shared objects. All
--rpath arguments are concatenated and passed to the runtime linker,
-which uses them to locate shared objects at runtime.
+Add a directory to the runtime library search path. This is used when
+linking an ELF executable with shared objects. All @code{-rpath}
+arguments are concatenated and passed to the runtime linker, which uses
+them to locate shared objects at runtime. The @code{-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
+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
+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
+filesystems.
+
+For compatibility with other ELF linkers, if the @code{-R} option is
+followed by a directory name, rather than a file name, it is treated as
+the @code{-rpath} option.
@end ifset
-@cindex partial link
-@cindex relocatable output
-@kindex -r
-@item -r
-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
-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}.
-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}.
-
-This option does the same thing as @samp{-i}.
-
-@kindex -S
-@cindex strip debugger symbols
-@item -S
-Omit debugger symbol information (but not all symbols) from the output file.
-
-@kindex -s
-@cindex strip all symbols
-@item -s
-Omit all symbol information from the output file.
-
@ifset GENERIC
-@item -soname @var{name}
-@cindex runtime library name
-@kindex -soname
-When creating an ELF shared object, set the internal DT_SONAME field to
-the specified name. When an executable is linked with a shared object
-which has a DT_SONAME field, then when the executable is run the dynamic
-linker will attempt to load the shared object specified by the DT_SONAME
-field rather than the using the file name given to the linker.
+@cindex link-time runtime library search path
+@kindex -rpath-link
+@item -rpath-link @var{DIR}
+When using ELF or SunOS, one shared library may require another. This
+happens when an @code{ld -shared} link includes a shared library as one
+of the input files.
+
+When the linker encounters such a dependency when doing a non-shared,
+non-relocateable 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
+specifies the first set of directories to search. The
+@code{-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.
+
+The linker uses the following search paths to locate required shared
+libraries.
+@enumerate
+@item
+Any directories specified by @code{-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
+at link time.
+@item
+On an ELF system, if the @code{-rpath} and @code{rpath-link} options
+were not used, search the contents of the environment variable
+@code{LD_RUN_PATH}.
+@item
+On SunOS, if the @code{-rpath} option was not used, search any
+directories specified using @code{-L} options.
+@item
+For a native linker, the contents of the environment variable
+@code{LD_LIBRARY_PATH}.
+@item
+The default directories, normally @file{/lib} and @file{/usr/lib}.
+@end enumerate
+
+If the required shared library is not found, the linker will issue a
+warning and continue with the link.
@end ifset
+@kindex -shared
+@kindex -Bshareable
@item -shared
+@itemx -Bshareable
@cindex shared libraries
-@kindex -shared
-Create a shared library. This is currently only supported on ELF
-platforms.
-
-@item -sort-common
-@kindex -sort-common
-Normally, when @code{ld} places the global common symbols in the
-appropriate output sections, it sorts them by size. First come all the
-one byte symbols, then all the two bytes, then all the four bytes, and
-then everything else. This is to prevent gaps between symbols due to
-alignment constraints. This option disables that sorting.
-
-@item -split-by-reloc @var{count}
-@kindex split
-Trys to creates extra sections in the output file so that no single output section
-in the file contains more than @var{count} relocations. This
-is useful when generating huge relocatable for downloading into
-certain real time kernels with the COFF object file format; since
-COFF cannot represent more than 65535 relocations in a single section.
-Note that this will fail to work with object file formats which do not
-support arbitrary sections. The linker will not split up individual input
-sections for redistribution, so if a single input section contains
+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
+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
+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
+everything else. This is to prevent gaps between symbols due to
+alignment constraints.
+
+@kindex --split-by-file
+@item --split-by-file
+Similar to @code{--split-by-reloc} but creates a new output section for
+each input file.
+
+@kindex --split-by-reloc
+@item --split-by-reloc @var{count}
+Trys to creates extra sections in the output file so that no single
+output section in the file contains more than @var{count} relocations.
+This is useful when generating huge relocatable for downloading into
+certain real time kernels with the COFF object file format; since COFF
+cannot represent more than 65535 relocations in a single section. Note
+that this will fail to work with object file formats which do not
+support arbitrary sections. The linker will not split up individual
+input sections for redistribution, so if a single input section contains
more than @var{count} relocations one output section will contain that
many relocations.
-@item -split-by-file
-@kindex split
-Similar to -split-by-reloc but creates a new output section for each
-input file.
-
-@item -stats
-Compute and display statistics about the operation of the linker,
-such as execution time and memory usage.
-
-@item -Tbss @var{org}
-@kindex -Tbss @var{org}
-@itemx -Tdata @var{org}
-@kindex -Tdata @var{org}
-@itemx -Ttext @var{org}
-@kindex -Ttext @var{org}
-@cindex segment origins, cmd line
-Use @var{org} as the starting address for---respectively---the
-@code{bss}, @code{data}, or the @code{text} segment of the output file.
-@var{org} must be a single hexadecimal integer;
-for compatibility with other linkers, you may omit the leading
-@samp{0x} usually associated with hexadecimal values.
-
-@item -T @var{commandfile}
-@itemx -T@var{commandfile}
-@kindex -T @var{script}
-@cindex script files
-Read link commands from the file @var{commandfile}. These commands
-replace @code{ld}'s default link script (rather than adding
-to it), so @var{commandfile} must specify everything necessary to describe
-the target format. @xref{Commands}. If @var{commandfile} does not
-exist, @code{ld} looks for it in the directories specified by any
-preceding @samp{-L} options. Multiple @samp{-T} options accumulate.
+@kindex --stats
+@item --stats
+Compute and display statistics about the operation of the linker, such
+as execution time and memory usage.
-@kindex -t
-@cindex verbose
-@cindex input files, displaying
-@item -t
-Print the names of the input files as @code{ld} processes them.
-
-@kindex -traditional-format
+@kindex --traditional-format
@cindex traditional format
-@item -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
use the traditional format instead.
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 @code{ld} to not
combine duplicate entries.
-@item -u @var{symbol}
-@kindex -u @var{symbol}
-@cindex undefined symbol
-Force @var{symbol} to be entered in the output file as an undefined symbol.
-Doing this may, for example, trigger linking of additional modules from
-standard libraries. @samp{-u} may be repeated with different option
-arguments to enter additional undefined symbols.
-@c Nice idea, but no such command: This option is equivalent
-@c to the @code{EXTERN} linker command.
+@kindex -Tbss @var{org}
+@kindex -Tdata @var{org}
+@kindex -Ttext @var{org}
+@cindex segment origins, cmd line
+@item -Tbss @var{org}
+@itemx -Tdata @var{org}
+@itemx -Ttext @var{org}
+Use @var{org} as the starting address for---respectively---the
+@code{bss}, @code{data}, or the @code{text} segment of the output file.
+@var{org} must be a single hexadecimal integer;
+for compatibility with other linkers, you may omit the leading
+@samp{0x} usually associated with hexadecimal values.
@kindex -Ur
@cindex constructors
@samp{-r} for the others.
@kindex --verbose
-@cindex version
+@cindex verbose
@item --verbose
Display the version number for @code{ld} and list the linker emulations
-supported. Display which input files can and cannot be opened.
-
-@kindex -v
-@kindex -V
-@cindex version
-@item -v
-@itemx -V
-Display the version number for @code{ld}. The @code{-V} option also
-lists the supported emulations.
-
-@item -version
-@kindex -version
-Display the version number for @code{ld} and exit.
+supported. Display which input files can and cannot be opened. Display
+the linker script if using a default builtin script.
-@item -warn-common
-@kindex -warn-comon
+@kindex --warn-comon
@cindex warnings, on combining symbols
@cindex combining symbols, warnings on
+@item --warn-common
Warn when a common symbol is combined with another common symbol or with
a symbol definition. Unix linkers allow this somewhat sloppy practice,
but linkers on some other operating systems do not. This option allows
a definition of the same variable.
@end table
-The @samp{-warn-common} option can produce five kinds of warnings. Each
-warning consists of a pair of lines: the first describes the symbol just
-encountered, and the second describes the previous symbol encountered
-with the same name. One or both of the two symbols will be a common
-symbol.
+The @samp{--warn-common} option can produce five kinds of warnings.
+Each warning consists of a pair of lines: the first describes the symbol
+just encountered, and the second describes the previous symbol
+encountered with the same name. One or both of the two symbols will be
+a common symbol.
@enumerate
@item
@end smallexample
@end enumerate
-@kindex -warn-once
+@kindex --warn-constructors
+@item --warn-constructors
+Warn if any global constructors are used. This is only useful for a few
+object file formats. For formats like COFF or ELF, the linker can not
+detect the use of global constructors.
+
+@kindex --warn-multiple-gp
+@item --warn-multiple-gp
+Warn if multiple global pointer values are required in the output file.
+This is only meaningful for certain processors, such as the Alpha.
+Specifically, some processors put large-valued constants in a special
+section. A special register (the global pointer) points into the middle
+of this section, so that constants can be loaded efficiently via a
+base-register relative addressing mode. Since the offset in
+base-register relative mode is fixed and relatively small (e.g., 16
+bits), this limits the maximum size of the constant pool. Thus, in
+large programs, it is often necessary to use multiple global pointer
+values in order to be able to address all possible constants. This
+option causes a warning to be issued whenever this case occurs.
+
+@kindex --warn-once
@cindex warnings, on undefined symbols
@cindex undefined symbols, warnings on
-@item -warn-once
+@item --warn-once
Only warn once for each undefined symbol, rather than once per module
which refers to it.
+@kindex --warn-section-align
+@cindex warnings, on section alignment
+@cindex section alignment, warnings on
+@item --warn-section-align
+Warn if the address of an output section is changed because of
+alignment. Typically, the alignment will be set by an input section.
+The address will only be changed if it not explicitly specified; that
+is, if the @code{SECTIONS} command does not specify a start address for
+the section (@pxref{SECTIONS}).
+
@kindex --whole-archive
@cindex including an entire archive
-For each archive mentioned on the command line, 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.
-
-@kindex -X
-@cindex local symbols, deleting
-@cindex L, deleting symbols beginning
-@item -X
-Delete all temporary local symbols. For most targets, this is all local
-symbols whose names begin with @samp{L}.
-
-@kindex -x
-@cindex deleting local symbols
-@item -x
-Delete all local symbols.
+@item --whole-archive
+For each archive mentioned on the command line after the
+@code{--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.
+
+@kindex --wrap
+@item --wrap @var{symbol}
+Use a wrapper function for @var{symbol}. Any undefined reference to
+@var{symbol} will be resolved to @code{__wrap_@var{symbol}}. Any
+undefined reference to @code{__real_@var{symbol}} will be resolved to
+@var{symbol}.
+
+This can be used to provide a wrapper for a system function. The
+wrapper function should be called @code{__wrap_@var{symbol}}. If it
+wishes to call the system function, it should call
+@code{__real_@var{symbol}}.
+
+Here is a trivial example:
-@item -y @var{symbol}
-@kindex -y @var{symbol}
-@cindex symbol tracing
-Print the name of each linked file in which @var{symbol} appears. This
-option may be given any number of times. On many systems it is necessary
-to prepend an underscore.
-
-This option is useful when you have an undefined symbol in your link but
-don't know where the reference is coming from.
+@smallexample
+void *
+__wrap_malloc (int c)
+@{
+ printf ("malloc called with %ld\n", c);
+ return __real_malloc (c);
+@}
+@end smallexample
-@item -( @var{archives} -)
-@itemx --start-group @var{archives} --end-group
-@kindex -(
-@cindex groups of archives
-The @var{archives} should be a list of archive files. They may be
-either explicit file names, or @samp{-l} options.
+If you link other code with this file using @code{--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.
-The specified archives are searched repeatedly until no new undefined
-references are created. Normally, an archive is searched only once in
-the order that it is specified on the command line. If a symbol in that
-archive is needed to resolve an undefined symbol referred to by an
-object in an archive that appears later on the command line, the linker
-would not be able to resolve that reference. By grouping the archives,
-they all be searched repeatedly until all possible references are
-resolved.
+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,
+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}.
-Using this option has a significant performance cost. It is best to use
-it only when there are unavoidable circular references between two or
-more archives.
@end table
@ifset UsesEnvVars
@kindex GNUTARGET
@cindex default input format
@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
+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
-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 there is no method
-of ensuring that the magic number used to specify object-file formats is
-unique. However, the configuration procedure for BFD on each system
-places the conventional format for that system first in the search-list,
-so ambiguities are resolved in favor of convention.
+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
+there is no method of ensuring that the magic number used to specify
+object-file formats is unique. However, the configuration procedure for
+BFD on each system places the conventional format for that system first
+in the search-list, so ambiguities are resolved in favor of convention.
@end ifset
@node Commands
placement of common blocks
@end itemize
-You may supply a command file (also known as a link script) to the
+You may supply a command file (also known as a linker script) to the
linker either explicitly through the @samp{-T} option, or implicitly as
-an ordinary file. If the linker opens a file which it cannot recognize
-as a supported object or archive format, it reports an error.
+an ordinary file. Normally you should use the @samp{-T} option. An
+implicit linker script should only be used when you want to augment,
+rather than replace, the default linker script; typically an implicit
+linker script would consist only of @code{INPUT} or @code{GROUP}
+commands.
+
+If the linker opens a file which it cannot recognize as a supported
+object or archive format, nor as a linker script, it reports an error.
@menu
* Scripts:: Linker Scripts
* Expressions:: Expressions
* MEMORY:: MEMORY Command
* SECTIONS:: SECTIONS Command
+* PHDRS:: PHDRS Command
* Entry Point:: The Entry Point
* Option Commands:: Option Commands
@end menu
* Evaluation:: Evaluation
* Assignment:: Assignment: Defining Symbols
* Arithmetic Functions:: Built-In Functions
+* Semicolons:: Semicolon Usage
@end menu
@node Integers
@cindex octal integers
An octal integer is @samp{0} followed by zero or more of the octal
digits (@samp{01234567}).
-@example
+@smallexample
_as_octal = 0157255;
-@end example
+@end smallexample
@cindex decimal integers
A decimal integer starts with a non-zero digit followed by zero or
more digits (@samp{0123456789}).
-@example
+@smallexample
_as_decimal = 57005;
-@end example
+@end smallexample
@cindex hexadecimal integers
@kindex 0x
A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
-@example
+@smallexample
_as_hex = 0xdead;
-@end example
+@end smallexample
@cindex negative integers
To write a negative integer, use
-the prefix operator @samp{-}; @pxref{Operators}.
-@example
+the prefix operator @samp{-} (@pxref{Operators}).
+@smallexample
_as_neg = -57005;
-@end example
+@end smallexample
@cindex scaled integers
@cindex K and M integer suffixes
@c END TEXI2ROFF-KILL
respectively. For example, the following all refer to the same quantity:
-@example
+@smallexample
_fourk_1 = 4K;
_fourk_2 = 4096;
_fourk_3 = 0x1000;
-@end example
+@end smallexample
@node Symbols
@subsection Symbol Names
and hyphens. Unquoted symbol names must not conflict with any
keywords. You can specify a symbol which contains odd characters or has
the same name as a keyword, by surrounding the symbol name in double quotes:
-@example
+@smallexample
"SECTION" = 9;
"with a space" = "also with a space" + 10;
-@end example
+@end smallexample
Since symbols can contain many non-alphabetic characters, it is safest
to delimit symbols with spaces. For example, @samp{A-B} is one symbol,
@cindex holes
This may be used to create holes in the output section. The location
counter may never be moved backwards.
-@example
+@smallexample
SECTIONS
@{
output :
file3(.text)
@} = 0x1234;
@}
-@end example
+@end smallexample
@noindent
In the previous example, @code{file1} is located at the beginning of the
output section, then there is a 1000 byte gap. Then @code{file2}
@vfill
@end iftex
-@need 5000
+@need 2000
@node Operators
@subsection Operators
@cindex Operators for arithmetic
@c TEXI2ROFF-KILL
@ifinfo
@c END TEXI2ROFF-KILL
-@example
+@smallexample
precedence associativity Operators Notes
(highest)
1 left ! - ~ (1)
10 right ? :
11 right &= += -= *= /= (2)
(lowest)
-@end example
+@end smallexample
Notes:
(1) Prefix operators
-(2) @xref{Assignment}
+(2) @xref{Assignment}.
@c TEXI2ROFF-KILL
@end ifinfo
@tex
\vskip \baselineskip
-%"lispnarrowing" is the extra indent used generally for @example
+%"lispnarrowing" is the extra indent used generally for smallexample
\hskip\lispnarrowing\vbox{\offinterlineskip
\hrule
\halign
section definition by using the absolute assignment function
@code{ABSOLUTE}. For example, to create an absolute symbol whose address
is the last byte of an output section named @code{.data}:
-@example
+@smallexample
SECTIONS@{ @dots{}
.data :
@{
_edata = ABSOLUTE(.) ;
@}
@dots{} @}
-@end example
+@end smallexample
The linker tries to put off the evaluation of an assignment until all
the terms in the source expression are known (@pxref{Evaluation}). For
counter @dfn{dot}, @samp{.} must be evaluated during allocation. If the
result of an expression is required, but the value is not available,
then an error results. For example, a script like the following
-@example
+@smallexample
SECTIONS @{ @dots{}
text 9+this_isnt_constant :
@{ @dots{}
@}
@dots{} @}
-@end example
+@end smallexample
@kindex Non constant expression
@noindent
will cause the error message ``@code{Non constant expression for initial
The command language includes a number of built-in
functions for use in link script expressions.
@table @code
-@item ABSOLUTE(@var{exp})
@kindex ABSOLUTE(@var{exp})
@cindex expression, absolute
+@item ABSOLUTE(@var{exp})
Return the absolute (non-relocatable, as opposed to non-negative) value
of the expression @var{exp}. Primarily useful to assign an absolute
value to a symbol within a section definition, where symbol values are
normally section-relative.
-@item ADDR(@var{section})
@kindex ADDR(@var{section})
@cindex section address
+@item ADDR(@var{section})
Return the absolute address of the named @var{section}. Your script must
previously have defined the location of that section. In the following
example, @code{symbol_1} and @code{symbol_2} are assigned identical
values:
-@example
+@smallexample
+@group
SECTIONS@{ @dots{}
.output1 :
@{
symbol_2 = start_of_output_1;
@}
@dots{} @}
-@end example
+@end group
+@end smallexample
+
+@kindex LOADADDR(@var{section})
+@cindex section load address
+@item LOADADDR(@var{section})
+Return the absolute load address of the named @var{section}. This is
+normally the same as @code{ADDR}, but it may be different if the
+@code{AT} keyword is used in the section definition (@pxref{Section
+Options}).
-@item ALIGN(@var{exp})
@kindex ALIGN(@var{exp})
@cindex rounding up location counter
+@item ALIGN(@var{exp})
Return the result of the current location counter (@code{.}) aligned to
the next @var{exp} boundary. @var{exp} must be an expression whose
value is a power of two. This is equivalent to
-@example
+@smallexample
(. + @var{exp} - 1) & ~(@var{exp} - 1)
-@end example
+@end smallexample
@code{ALIGN} doesn't change the value of the location counter---it just
does arithmetic on it. As an example, to align the output @code{.data}
section to the next @code{0x2000} byte boundary after the preceding
section and to set a variable within the section to the next
@code{0x8000} boundary after the input sections:
-@example
+@smallexample
+@group
SECTIONS@{ @dots{}
.data ALIGN(0x2000): @{
*(.data)
variable = ALIGN(0x8000);
@}
@dots{} @}
-@end example
+@end group
+@end smallexample
@noindent
The first use of @code{ALIGN} in this example specifies the location of
a section because it is used as the optional @var{start} attribute of a
The built-in @code{NEXT} is closely related to @code{ALIGN}.
-@item DEFINED(@var{symbol})
@kindex DEFINED(@var{symbol})
@cindex symbol defaults
+@item DEFINED(@var{symbol})
Return 1 if @var{symbol} is in the linker global symbol table and is
defined, otherwise return 0. You can use this function to provide default
values for symbols. For example, the following command-file fragment shows how
existed, its value is preserved:
@smallexample
+@group
SECTIONS@{ @dots{}
.text : @{
begin = DEFINED(begin) ? begin : . ;
@dots{}
@}
@dots{} @}
+@end group
@end smallexample
-@item NEXT(@var{exp})
@kindex NEXT(@var{exp})
@cindex unallocated address, next
+@item NEXT(@var{exp})
Return the next unallocated address that is a multiple of @var{exp}.
This function is closely related to @code{ALIGN(@var{exp})}; unless you
use the @code{MEMORY} command to define discontinuous memory for the
output file, the two functions are equivalent.
-@item SIZEOF(@var{section})
@kindex SIZEOF(@var{section})
@cindex section size
+@item SIZEOF(@var{section})
Return the size in bytes of the named @var{section}, if that section has
been allocated. In the following example, @code{symbol_1} and
@code{symbol_2} are assigned identical values:
@c What does it return if the section hasn't been allocated? 0?
-@example
+@smallexample
+@group
SECTIONS@{ @dots{}
.output @{
.start = . ;
symbol_1 = .end - .start ;
symbol_2 = SIZEOF(.output);
@dots{} @}
+@end group
+@end smallexample
-@end example
-
-@item SIZEOF_HEADERS
@kindex SIZEOF_HEADERS
@cindex header size
-@itemx sizeof_headers
@kindex sizeof_headers
+@item SIZEOF_HEADERS
+@itemx sizeof_headers
Return the size in bytes of the output file's headers. You can use this number
as the start address of the first section, if you choose, to facilitate
paging.
+@kindex MAX
+@item MAX(@var{exp1}, @var{exp2})
+Returns the maximum of @var{exp1} and @var{exp2}.
+
+@kindex MIN
+@item MIN(@var{exp1}, @var{exp2})
+Returns the minimum of @var{exp1} and @var{exp2}.
+
+@end table
+
+@node Semicolons
+@subsection Semicolons
+
+Semicolons (``@key{;}'') are required in the following places. In all
+other places they can appear for aesthetic reasons but are otherwise ignored.
+
+@table @code
+@item Assignment
+Semicolons must appear at the end of assignment expressions.
+@xref{Assignment}
+
+@item PHDRS
+Semicolons must appear at the end of a @code{PHDRS} statement.
+@xref{PHDRS}
@end table
@node MEMORY
command; however, you can define as many blocks of memory within it as
you wish. The syntax is:
-@example
+@smallexample
+@group
MEMORY
@{
@var{name} (@var{attr}) : ORIGIN = @var{origin}, LENGTH = @var{len}
@dots{}
@}
-@end example
+@end group
+@end smallexample
@table @code
@cindex naming memory regions
@item @var{name}
allocation---one starting at 0 for 256 kilobytes, and the other
starting at @code{0x40000000} for four megabytes:
-@example
+@smallexample
+@group
MEMORY
@{
rom : ORIGIN = 0, LENGTH = 256K
ram : org = 0x40000000, l = 4M
@}
-@end example
+@end group
+@end smallexample
Once you have defined a region of memory named @var{mem}, you can direct
specific output sections there by using a command ending in
You can also use the first two operations---defining the entry point and
defining symbols---outside the @code{SECTIONS} command: @pxref{Entry
-Point}, and @pxref{Assignment}. They are permitted here as well for
+Point}, and @ref{Assignment}. They are permitted here as well for
your convenience in reading the script, so that symbols and the entry
point can be defined at meaningful points in your output-file layout.
* Section Placement:: Section Placement
* Section Data Expressions:: Section Data Expressions
* Section Options:: Optional Section Attributes
+* Overlays:: Overlays
@end menu
@node Section Definition
fill pattern, and target memory region. Most of
these specifications are optional; the simplest form of a section
definition is
-@example
+@smallexample
SECTIONS @{ @dots{}
@var{secname} : @{
@var{contents}
@}
@dots{} @}
-@end example
+@end smallexample
@cindex naming output sections
@noindent
@var{secname} is the name of the output section, and @var{contents} a
@code{ld} symbol name syntax must be quoted.
@xref{Symbols, , Symbol Names}.
+The special @var{secname} @samp{/DISCARD/} may be used to discard input
+sections. Any sections which are assigned to an output section named
+@samp{/DISCARD/} are not included in the final link output.
+
The linker will not create output sections which do not have any
contents. This is for convenience when referring to input sections that
may or may not exist. For example,
-@example
-.foo @{ *(.foo @}
-@end example
+@smallexample
+.foo @{ *(.foo) @}
+@end smallexample
will only create a @samp{.foo} section in the output file if there is a
@samp{.foo} section in at least one input file.
The @var{contents} of a section definition may include any of the
following kinds of statement. You can include as many of these as you
like in a single section definition, separated from one another by
-whitespace.
+whitespace.
@table @code
@kindex @var{filename}
only those sections which have not yet been allocated are used.
To specify a list of particular files by name:
-@example
+@smallexample
.data : @{ afile.o bfile.o cfile.o @}
-@end example
+@end smallexample
@noindent
The example also illustrates that multiple statements can be included in
the contents of a section definition, since each file name is a separate
@kindex @var{filename}(@var{section})
@cindex files and sections, section defn
@item @var{filename}( @var{section} )
-@itemx @var{filename}( @var{section}, @var{section}, @dots{} )
+@itemx @var{filename}( @var{section} , @var{section}, @dots{} )
@itemx @var{filename}( @var{section} @var{section} @dots{} )
You can name one or more sections from your input files, for
insertion in the current output section. If you wish to specify a list
For example, to copy sections @code{1} through @code{4} from an Oasys file
into the @code{.text} section of an @code{a.out} file, and sections @code{13}
and @code{14} into the @code{.data} section:
-@example
+@smallexample
+@group
SECTIONS @{
.text :@{
*("1" "2" "3" "4")
*("13" "14")
@}
@}
-@end example
+@end group
+@end smallexample
@cindex @code{[@var{section}@dots{}]}, not supported
@samp{[ @var{section} @dots{} ]} used to be accepted as an alternate way
input file's format.
@end table
-For example, the following command script arranges the output file into
-three consecutive sections, named @code{.text}, @code{.data}, and
+In any place where you may use a specific file or section name, you may
+also use a wildcard pattern. The linker handles wildcards much as the
+Unix shell does. A @samp{*} character matches any number of characters.
+A @samp{?} character matches any single character. The sequence
+@samp{[@var{chars}]} will match a single instance of any of the
+@var{chars}; the @samp{-} character may be used to specify a range of
+characters, as in @samp{[a-z]} to match any lower case letter. A
+@samp{\} character may be used to quote the following character.
+
+When a file name is matched with a wildcard, the wildcard characters
+will not match a @samp{/} character (used to separate directory names on
+Unix). A pattern consisting of a single @samp{*} character is an
+exception; it will always match any file name. In a section name, the
+wildcard characters will match a @samp{/} character.
+
+Wildcards only match files which are explicitly specified on the command
+line. The linker does not search directories to expand wildcards.
+However, if you specify a simple file name---a name with no wildcard
+characters---in a linker script, and the file name is not also specified
+on the command line, the linker will attempt to open the file as though
+it appeared on the command line.
+
+In the following example, the command script arranges the output file
+into three consecutive sections, named @code{.text}, @code{.data}, and
@code{.bss}, taking the input for each from the correspondingly named
sections of all the input files:
-@example
+@smallexample
+@group
SECTIONS @{
.text : @{ *(.text) @}
.data : @{ *(.data) @}
.bss : @{ *(.bss) *(COMMON) @}
@}
-@end example
+@end group
+@end smallexample
The following example reads all of the sections from file @code{all.o}
and places them at the start of output section @code{outputa} which
All of the remaining @code{.input1} and @code{.input2} sections from any
files are written to output section @code{outputc}.
-@example
+@smallexample
+@group
SECTIONS @{
outputa 0x10000 :
@{
*(.input2)
@}
@}
-@end example
+@end group
+@end smallexample
+
+This example shows how wildcard patterns might be used to partition
+files. All @code{.text} sections are placed in @code{.text}, and all
+@code{.bss} sections are placed in @code{.bss}. For all files beginning
+with an upper case character, the @code{.data} section is placed into
+@code{.DATA}; for all other files, the @code{.data} section is placed
+into @code{.data}.
+
+@smallexample
+@group
+SECTIONS @{
+ .text : @{ *(.text) @}
+ .DATA : @{ [A-Z]*(.data) @}
+ .data : @{ *(.data) @}
+ .bss : @{ *(.bss) @}
+@}
+@end group
+@end smallexample
@node Section Data Expressions
@subsection Section Data Expressions
The foregoing statements arrange, in your output file, data originating
from your input files. You can also place data directly in an output
section from the link command script. Most of these additional
-statements involve expressions; @pxref{Expressions}. Although these
+statements involve expressions (@pxref{Expressions}). Although these
statements are shown separately here for ease of presentation, no such
segregation is needed within a section definition in the @code{SECTIONS}
command; you can intermix them freely with any of the statements we've
data written from that input file. For instance, with @code{a.out}
files it is conventional to have a symbol for each input file. You can
accomplish this by defining the output @code{.text} section as follows:
-@example
+@smallexample
+@group
SECTIONS @{
.text 0x2020 :
@{
@}
@dots{}
@}
-@end example
+@end group
+@end smallexample
If @code{sample.ld} is a file containing this script, and @code{a.o},
@code{b.o}, @code{c.o}, and @code{d.o} are four input files with
contents like the following---
-@example
+@smallexample
+@group
/* a.c */
afunction() @{ @}
int adata=1;
int abss;
-@end example
+@end group
+@end smallexample
@noindent
@samp{ld -M -T sample.ld a.o b.o c.o d.o} would create a map like this,
containing symbols matching the object file names:
-@example
+@smallexample
00000000 A __DYNAMIC
00004020 B _abss
00004000 D _adata
00002038 t b.o
00002050 t c.o
00002068 t d.o
-@end example
+@end smallexample
@kindex @var{symbol} = @var{expression} ;
@kindex @var{symbol} @var{f}= @var{expression} ;
definition, the value is relative to the beginning of the section
(@pxref{Assignment}). If you write
-@example
+@smallexample
+@group
SECTIONS @{
abs = 14 ;
@dots{}
abs2 = 14 + ADDR(.data);
@dots{}
@}
-@end example
+@end group
+@end smallexample
@c FIXME: Try above example!
@noindent
appropriate for the output file format (@pxref{BFD}).
@end ifclear
-@item FILL(@var{expression})
@kindex FILL(@var{expression})
@cindex holes, filling
@cindex unspecified memory
+@item FILL(@var{expression})
Specify the ``fill pattern'' for the current section. Any otherwise
unspecified regions of memory within the section (for example, regions
you skip over by assigning a new value to the location counter @samp{.})
optional portions:
@smallexample
+@group
SECTIONS @{
@dots{}
@var{secname} @var{start} BLOCK(@var{align}) (NOLOAD) : AT ( @var{ldadr} )
- @{ @var{contents} @} >@var{region} =@var{fill}
+ @{ @var{contents} @} >@var{region} :@var{phdr} =@var{fill}
@dots{}
@}
+@end group
@end smallexample
@var{secname} and @var{contents} are required. @xref{Section
-Definition}, and @pxref{Section Placement} for details on
+Definition}, and @ref{Section Placement}, for details on
@var{contents}. The remaining elements---@var{start},
@code{BLOCK(@var{align)}}, @code{(NOLOAD)}, @code{AT ( @var{ldadr} )},
-@code{>@var{region}}, and @code{=@var{fill}}---are all optional.
+@code{>@var{region}}, @code{:@var{phdr}}, and @code{=@var{fill}}---are
+all optional.
@table @code
@cindex start address, section
example generates section @var{output} at location
@code{0x40000000}:
-@example
+@smallexample
+@group
SECTIONS @{
@dots{}
output 0x40000000: @{
@}
@dots{}
@}
-@end example
+@end group
+@end smallexample
@kindex BLOCK(@var{align})
@cindex section alignment
@code{ROM} segment is addressed at memory location @samp{0} and does not
need to be loaded into each object file:
-@example
+@smallexample
+@group
SECTIONS @{
ROM 0 (NOLOAD) : @{ @dots{} @}
@dots{}
@}
-@end example
+@end group
+@end smallexample
@kindex AT ( @var{ldadr} )
@cindex specify load address
@code{0x2000}:
@smallexample
+@group
SECTIONS
@{
.text 0x1000 : @{ *(.text) _etext = . ; @}
.bss 0x3000 :
@{ _bstart = . ; *(.bss) *(COMMON) ; _bend = . ;@}
@}
+@end group
@end smallexample
The run-time initialization code (for C programs, usually @code{crt0})
address:
@smallexample
+@group
char *src = _etext;
char *dst = _data;
/* Zero bss */
for (dst = _bstart; dst< _bend; dst++)
*dst = 0;
+@end group
@end smallexample
@kindex >@var{region}
Assign this section to a previously defined region of memory.
@xref{MEMORY}.
+@kindex :@var{phdr}
+@cindex section, assigning to program header
+@cindex program headers and sections
+@item :@var{phdr}
+Assign this section to a segment described by a program header.
+@xref{PHDRS}. If a section is assigned to one or more segments, then
+all subsequent allocated sections will be assigned to those segments as
+well, unless they use an explicitly @code{:@var{phdr}} modifier. To
+prevent a section from being assigned to a segment when it would
+normally default to one, use @code{:NONE}.
+
@kindex =@var{fill}
@cindex section fill pattern
@cindex fill pattern, entire section
@end table
+@node Overlays
+@subsection Overlays
+@kindex OVERLAY
+@cindex overlays
+
+The @code{OVERLAY} command provides an easy way to describe sections
+which are to be loaded as part of a single memory image but are to be
+run at the same memory address. At run time, some sort of overlay
+manager will copy the overlaid sections in and out of the runtime memory
+address as required, perhaps by simply manipulating addressing bits.
+This approach can be useful, for example, when a certain region of
+memory is faster than another.
+
+The @code{OVERLAY} command is used within a @code{SECTIONS} command. It
+appears as follows:
+@smallexample
+@group
+ OVERLAY @var{start} : [ NOCROSSREFS ] AT ( @var{ldaddr} )
+ @{
+ @var{secname1} @{ @var{contents} @} :@var{phdr} =@var{fill}
+ @var{secname2} @{ @var{contents} @} :@var{phdr} =@var{fill}
+ @dots{}
+ @} >@var{region} :@var{phdr} =@var{fill}
+@end group
+@end smallexample
+
+Everything is optional except @code{OVERLAY} (a keyword), and each
+section must have a name (@var{secname1} and @var{secname2} above). The
+section definitions within the @code{OVERLAY} construct are identical to
+those within the general @code{SECTIONS} contruct (@pxref{SECTIONS}),
+except that no addresses and no memory regions may be defined for
+sections within an @code{OVERLAY}.
+
+The sections are all defined with the same starting address. The load
+addresses of the sections are arranged such that they are consecutive in
+memory starting at the load address used for the @code{OVERLAY} as a
+whole (as with normal section definitions, the load address is optional,
+and defaults to the start address; the start address is also optional,
+and defaults to @code{.}).
+
+If the @code{NOCROSSREFS} keyword is used, and there any references
+among the sections, the linker will report an error. Since the sections
+all run at the same address, it normally does not make sense for one
+section to refer directly to another. @xref{Option Commands,
+NOCROSSREFS}.
+
+For each section within the @code{OVERLAY}, the linker automatically
+defines two symbols. The symbol @code{__load_start_@var{secname}} is
+defined as the starting load address of the section. The symbol
+@code{__load_stop_@var{secname}} is defined as the final load address of
+the section. Any characters within @var{secname} which are not legal
+within C identifiers are removed. C (or assembler) code may use these
+symbols to move the overlaid sections around as necessary.
+
+At the end of the overlay, the value of @code{.} is set to the start
+address of the overlay plus the size of the largest section.
+
+Here is an example. Remember that this would appear inside a
+@code{SECTIONS} construct.
+
+@smallexample
+@group
+ OVERLAY 0x1000 : AT (0x4000)
+ @{
+ .text0 @{ o1/*.o(.text) @}
+ .text1 @{ o2/*.o(.text) @}
+ @}
+@end group
+@end smallexample
+
+This will define both @code{.text0} and @code{.text1} to start at
+address 0x1000. @code{.text0} will be loaded at address 0x4000, and
+@code{.text1} will be loaded immediately after @code{.text0}. The
+following symbols will be defined: @code{__load_start_text0},
+@code{__load_stop_text0}, @code{__load_start_text1},
+@code{__load_stop_text1}.
+
+C code to copy overlay @code{.text1} into the overlay area might look
+like the following.
+
+@smallexample
+@group
+ extern char __load_start_text1, __load_stop_text1;
+ memcpy ((char *) 0x1000, &__load_start_text1,
+ &__load_stop_text1 - &__load_start_text1);
+@end group
+@end smallexample
+
+Note that the @code{OVERLAY} command is just syntactic sugar, since
+everything it does can be done using the more basic commands. The above
+example could have been written identically as follows.
+
+@smallexample
+@group
+ .text0 0x1000 : AT (0x4000) @{ o1/*.o(.text) @}
+ __load_start_text0 = LOADADDR (.text0);
+ __load_stop_text0 = LOADADDR (.text0) + SIZEOF (.text0);
+ .text1 0x1000 : AT (0x4000 + SIZEOF (.text0)) @{ o2/*.o(.text) @}
+ __load_start_text1 = LOADADDR (.text1);
+ __load_stop_text1 = LOADADDR (.text1) + SIZEOF (.text1);
+ . = 0x1000 + MAX (SIZEOF (.text0), SIZEOF (.text1));
+@end group
+@end smallexample
+
+@node PHDRS
+@section ELF Program Headers
+@kindex PHDRS
+@cindex program headers
+@cindex ELF program headers
+
+The ELF object file format uses @dfn{program headers}, which are read by
+the system loader and describe how the program should be loaded into
+memory. These program headers must be set correctly in order to run the
+program on a native ELF system. The linker will create reasonable
+program headers by default. However, in some cases, it is desirable to
+specify the program headers more precisely; the @code{PHDRS} command may
+be used for this purpose. When the @code{PHDRS} command is used, the
+linker will not generate any program headers itself.
+
+The @code{PHDRS} command is only meaningful when generating an ELF
+output file. It is ignored in other cases. This manual does not
+describe the details of how the system loader interprets program
+headers; for more information, see the ELF ABI. The program headers of
+an ELF file may be displayed using the @samp{-p} option of the
+@code{objdump} command.
+
+This is the syntax of the @code{PHDRS} command. The words @code{PHDRS},
+@code{FILEHDR}, @code{AT}, and @code{FLAGS} are keywords.
+
+@smallexample
+@group
+PHDRS
+@{
+ @var{name} @var{type} [ FILEHDR ] [ PHDRS ] [ AT ( @var{address} ) ]
+ [ FLAGS ( @var{flags} ) ] ;
+@}
+@end group
+@end smallexample
+
+The @var{name} is used only for reference in the @code{SECTIONS} command
+of the linker script. It does not get put into the output file.
+
+Certain program header types describe segments of memory which are
+loaded from the file by the system loader. In the linker script, the
+contents of these segments are specified by directing allocated output
+sections to be placed in the segment. To do this, the command
+describing the output section in the @code{SECTIONS} command should use
+@samp{:@var{name}}, where @var{name} is the name of the program header
+as it appears in the @code{PHDRS} command. @xref{Section Options}.
+
+It is normal for certain sections to appear in more than one segment.
+This merely implies that one segment of memory contains another. This
+is specified by repeating @samp{:@var{name}}, using it once for each
+program header in which the section is to appear.
+
+If a section is placed in one or more segments using @samp{:@var{name}},
+then all subsequent allocated sections which do not specify
+@samp{:@var{name}} are placed in the same segments. This is for
+convenience, since generally a whole set of contiguous sections will be
+placed in a single segment. To prevent a section from being assigned to
+a segment when it would normally default to one, use @code{:NONE}.
+
+The @code{FILEHDR} and @code{PHDRS} keywords which may appear after the
+program header type also indicate contents of the segment of memory.
+The @code{FILEHDR} keyword means that the segment should include the ELF
+file header. The @code{PHDRS} keyword means that the segment should
+include the ELF program headers themselves.
+
+The @var{type} may be one of the following. The numbers indicate the
+value of the keyword.
+
+@table @asis
+@item @code{PT_NULL} (0)
+Indicates an unused program header.
+
+@item @code{PT_LOAD} (1)
+Indicates that this program header describes a segment to be loaded from
+the file.
+
+@item @code{PT_DYNAMIC} (2)
+Indicates a segment where dynamic linking information can be found.
+
+@item @code{PT_INTERP} (3)
+Indicates a segment where the name of the program interpreter may be
+found.
+
+@item @code{PT_NOTE} (4)
+Indicates a segment holding note information.
+
+@item @code{PT_SHLIB} (5)
+A reserved program header type, defined but not specified by the ELF
+ABI.
+
+@item @code{PT_PHDR} (6)
+Indicates a segment where the program headers may be found.
+
+@item @var{expression}
+An expression giving the numeric type of the program header. This may
+be used for types not defined above.
+@end table
+
+It is possible to specify that a segment should be loaded at a
+particular address in memory. This is done using an @code{AT}
+expression. This is identical to the @code{AT} command used in the
+@code{SECTIONS} command (@pxref{Section Options}). Using the @code{AT}
+command for a program header overrides any information in the
+@code{SECTIONS} command.
+
+Normally the segment flags are set based on the sections. The
+@code{FLAGS} keyword may be used to explicitly specify the segment
+flags. The value of @var{flags} must be an integer. It is used to
+set the @code{p_flags} field of the program header.
+
+Here is an example of the use of @code{PHDRS}. This shows a typical set
+of program headers used on a native ELF system.
+
+@example
+@group
+PHDRS
+@{
+ headers PT_PHDR PHDRS ;
+ interp PT_INTERP ;
+ text PT_LOAD FILEHDR PHDRS ;
+ data PT_LOAD ;
+ dynamic PT_DYNAMIC ;
+@}
+
+SECTIONS
+@{
+ . = SIZEOF_HEADERS;
+ .interp : @{ *(.interp) @} :text :interp
+ .text : @{ *(.text) @} :text
+ .rodata : @{ *(.rodata) @} /* defaults to :text */
+ @dots{}
+ . = . + 0x1000; /* move to a new page in memory */
+ .data : @{ *(.data) @} :data
+ .dynamic : @{ *(.dynamic) @} :data :dynamic
+ @dots{}
+@}
+@end group
+@end example
+
@node Entry Point
@section The Entry Point
@kindex ENTRY(@var{symbol})
The linker command language includes a command specifically for
defining the first executable instruction in an output file (its
@dfn{entry point}). Its argument is a symbol name:
-@example
+@smallexample
ENTRY(@var{symbol})
-@end example
+@end smallexample
Like symbol assignments, the @code{ENTRY} command may be placed either
as an independent command in the command file, or among the section
@item
the value of the symbol @code{start}, if present;
@item
-the value of the symbol @code{_main}, if present;
-@item
the address of the first byte of the @code{.text} section, if present;
@item
The address @code{0}.
input files, you can simply define it, assigning it an appropriate
value---
-@example
+@smallexample
start = 0x2020;
-@end example
+@end smallexample
@noindent
The example shows an absolute address, but you can use any expression.
convention for the entry point, you can just assign the value of
whatever symbol contains the start address to @code{start}:
-@example
+@smallexample
start = other_symbol ;
-@end example
+@end smallexample
@node Option Commands
@section Option Commands
@cindex C++ constructors, arranging in link
@cindex constructors, arranging in link
@item CONSTRUCTORS
-This command ties up C++ style constructor and destructor records. The
-details of the constructor representation vary from one object format to
-another, but usually lists of constructors and destructors appear as
-special sections. The @code{CONSTRUCTORS} command specifies where the
-linker is to place the data from these sections, relative to the rest of
-the linked output. Constructor data is marked by the symbol
-@w{@code{__CTOR_LIST__}} at the start, and @w{@code{__CTOR_LIST_END}} at
-the end; destructor data is bracketed similarly, between
-@w{@code{__DTOR_LIST__}} and @w{@code{__DTOR_LIST_END}}. (The compiler
-must arrange to actually run this code; GNU C++ calls constructors from
-a subroutine @code{__main}, which it inserts automatically into the
-startup code for @code{main}, and destructors from @code{_exit}.)
+When linking using the @code{a.out} object file format, the linker uses
+an unusual set construct to support C++ global constructors and
+destructors. When linking object file formats which do not support
+arbitrary sections, such as @code{ECOFF} and @code{XCOFF}, the linker
+will automatically recognize C++ global constructors and destructors by
+name. For these object file formats, the @code{CONSTRUCTORS} command
+tells the linker where this information should be placed. The
+@code{CONSTRUCTORS} command is ignored for other object file formats.
+
+The symbol @w{@code{__CTOR_LIST__}} marks the start of the global
+constructors, and the symbol @w{@code{__DTOR_LIST}} marks the end. The
+first word in the list is the number of entries, followed by the address
+of each constructor or destructor, followed by a zero word. The
+compiler must arrange to actually run the code. For these object file
+formats @sc{gnu} C++ calls constructors from a subroutine @code{__main};
+a call to @code{__main} is automatically inserted into the startup code
+for @code{main}. @sc{gnu} C++ runs destructors either by using
+@code{atexit}, or directly from the function @code{exit}.
+
+For object file formats such as @code{COFF} or @code{ELF} which support
+multiple sections, @sc{gnu} C++ will normally arrange to put the
+addresses of global constructors and destructors into the @code{.ctors}
+and @code{.dtors} sections. Placing the following sequence into your
+linker script will build the sort of table which the @sc{gnu} C++
+runtime code expects to see.
+
+@smallexample
+ __CTOR_LIST__ = .;
+ LONG((__CTOR_END__ - __CTOR_LIST__) / 4 - 2)
+ *(.ctors)
+ LONG(0)
+ __CTOR_END__ = .;
+ __DTOR_LIST__ = .;
+ LONG((__DTOR_END__ - __DTOR_LIST__) / 4 - 2)
+ *(.dtors)
+ LONG(0)
+ __DTOR_END__ = .;
+@end smallexample
+
+Normally the compiler and linker will handle these issues automatically,
+and you will not need to concern yourself with them. However, you may
+need to consider this if you are using C++ and writing your own linker
+scripts.
@need 1000
@kindex FLOAT
@ref{Options,,Command Line Options}.
@ignore
-@item MAP ( @var{name} )
@kindex MAP ( @var{name} )
+@item MAP ( @var{name} )
@c MAP(...) appears to look for an F in the arg, ignoring all other
@c chars; if it finds one, it sets "map_option_f" to true. But nothing
@c checks map_option_f. Apparently a stub for the future...
@end ignore
-@item OUTPUT ( @var{filename} )
@kindex OUTPUT ( @var{filename} )
@cindex naming the output file
+@item OUTPUT ( @var{filename} )
Use this command to name the link output file @var{filename}. The
effect of @code{OUTPUT(@var{filename})} is identical to the effect of
@w{@samp{-o @var{filename}}}, which overrides it. You can use this
command to supply a default output-file name other than @code{a.out}.
@ifclear SingleFormat
-@item OUTPUT_ARCH ( @var{bfdname} )
@kindex OUTPUT_ARCH ( @var{bfdname} )
@cindex machine architecture, output
+@item OUTPUT_ARCH ( @var{bfdname} )
Specify a particular output machine architecture, with one of the names
used by the BFD back-end routines (@pxref{BFD}). This command is often
unnecessary; the architecture is most often set implicitly by either the
system BFD configuration or as a side effect of the @code{OUTPUT_FORMAT}
command.
-@item OUTPUT_FORMAT ( @var{bfdname} )
@kindex OUTPUT_FORMAT ( @var{bfdname} )
@cindex format, output file
+@item OUTPUT_FORMAT ( @var{bfdname} )
When @code{ld} is configured to support multiple object code formats,
you can use this command to specify a particular output format.
@var{bfdname} is one of the names used by the BFD back-end routines
(@pxref{BFD}). The effect is identical to the effect of the
-@samp{-oformat} command-line option. This selection affects only
-the output file; the related command @code{TARGET} affects primarily
-input files.
+@samp{--oformat} command-line option. This selection affects only the
+output file; the related command @code{TARGET} affects primarily input
+files.
@end ifclear
-@item SEARCH_DIR ( @var{path} )
@kindex SEARCH_DIR ( @var{path} )
@cindex path for libraries
@cindex search path, libraries
+@item SEARCH_DIR ( @var{path} )
Add @var{path} to the list of paths where @code{ld} looks for
archive libraries. @code{SEARCH_DIR(@var{path})} has the same
effect as @samp{-L@var{path}} on the command line.
-@item STARTUP ( @var{filename} )
@kindex STARTUP ( @var{filename} )
@cindex first input file
+@item STARTUP ( @var{filename} )
Ensure that @var{filename} is the first input file used in the link
process.
@ifclear SingleFormat
-@item TARGET ( @var{format} )
@cindex input file format
@kindex TARGET ( @var{format} )
+@item TARGET ( @var{format} )
When @code{ld} is configured to support multiple object code formats,
you can use this command to change the input-file object code format
-(like the command-line option @samp{-b} or its synonym @samp{-format}).
+(like the command-line option @samp{-b} or its synonym @samp{--format}).
The argument @var{format} is one of the strings used by BFD to name
binary formats. If @code{TARGET} is specified but @code{OUTPUT_FORMAT}
is not, the last @code{TARGET} argument is also used as the default
output file format. If that variable is also absent, @code{ld} uses
the default format configured for your machine in the BFD libraries.
@end ifclear
+
+@cindex cross references
+@kindex NOCROSSREFS ( @var{sections} )
+@item NOCROSSREFS ( @var{section} @var{section} @dots{} )
+This command may be used to tell @code{ld} to issue an error about any
+references among certain sections.
+
+In certain types of programs, particularly on embedded systems, when one
+section is loaded into memory, another section will not be. Any direct
+references between the two sections would be errors. For example, it
+would be an error if code in one section called a function defined in
+the other section.
+
+The @code{NOCROSSREFS} command takes a list of section names. If
+@code{ld} detects any cross references between the sections, it reports
+an error and returns a non-zero exit status. The @code{NOCROSSREFS}
+command uses output section names, defined in the @code{SECTIONS}
+command. It does not use the names of input sections.
@end table
@ifset GENERIC
@cindex H8/300 support
For the H8/300, @code{ld} can perform these global optimizations when
-you specify the @samp{-relax} command-line option.
+you specify the @samp{--relax} command-line option.
@table @emph
-@item relaxing address modes
@cindex relaxing on H8/300
+@item relaxing address modes
@code{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.
-@item synthesizing instructions
@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
sixteen-bit absolute address form, but refer to the top
paths, and in any paths you specify with @samp{-L}) for a library with
the names
-@example
+@smallexample
+@group
try
libtry.a
tryca
libtryca.a
-@end example
+@end group
+@end smallexample
@noindent
The first two possibilities would be considered in any event; the last
use will add another pair of name variants to search for when @w{@samp{-l}}
specifies a library.
-@cindex @code{-relax} on i960
+@cindex @code{--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 @code{calx}
-instructions whose targets are within 24 bits, and turns them into
-24-bit program-counter relative @code{bal} and @code{cal}
+@code{ld} supports the @samp{--relax} option for the i960 family. If
+you specify @samp{--relax}, @code{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 into @code{bal} instructions when it determines that the
target subroutine is a leaf routine (that is, the target subroutine does
@include bfdsumm.texi
@end ifclear
+@node Reporting Bugs
+@chapter Reporting Bugs
+@cindex bugs in @code{ld}
+@cindex reporting bugs in @code{ld}
+
+Your bug reports play an essential role in making @code{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}
+work better. Bug reports are your contribution to the maintenance of
+@code{ld}.
+
+In order for a bug report to serve its purpose, you must include the
+information that enables us to fix the bug.
+
+@menu
+* Bug Criteria:: Have you found a bug?
+* Bug Reporting:: How to report bugs
+@end menu
+
+@node Bug Criteria
+@section Have you found a bug?
+@cindex bug criteria
+
+If you are not sure whether you have found a bug, here are some guidelines:
+
+@itemize @bullet
+@cindex fatal signal
+@cindex linker crash
+@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.
+
+@cindex error on valid input
+@item
+If @code{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
+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.
+@end itemize
+
+@node Bug Reporting
+@section How to report bugs
+@cindex bug reports
+@cindex @code{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
+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.
+
+In any event, we also recommend that you send bug reports for @code{ld}
+to @samp{bug-gnu-utils@@prep.ai.mit.edu}.
+
+The fundamental principle of reporting bugs usefully is this:
+@strong{report all the facts}. If you are not sure whether to state a
+fact or leave it out, state it!
+
+Often people omit facts because they think they know what causes the
+problem and assume that some details do not matter. Thus, you might
+assume that the name of a symbol you use in an example does not matter.
+Well, probably it does not, but one cannot be sure. Perhaps the bug is
+a stray memory reference which happens to fetch from the location where
+that name is stored in memory; perhaps, if the name were different, the
+contents of that location would fool the linker into doing the right
+thing despite the bug. Play it safe and give a specific, complete
+example. That is the easiest thing for you to do, and the most helpful.
+
+Keep in mind that the purpose of a bug report is to enable us to fix the bug if
+it is new to us. Therefore, always write your bug reports on the assumption
+that the bug has not been reported previously.
+
+Sometimes people give a few sketchy facts and ask, ``Does this ring a
+bell?'' Those bug reports are useless, and we urge everyone to
+@emph{refuse to respond to them} except to chide the sender to report
+bugs properly.
+
+To enable us to fix the bug, you should include all these things:
+
+@itemize @bullet
+@item
+The version of @code{ld}. @code{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}.
+
+@item
+Any patches you may have applied to the @code{ld} source, including any
+patches made to the @code{BFD} library.
+
+@item
+The type of machine you are using, and the operating system name and
+version number.
+
+@item
+What compiler (and its version) was used to compile @code{ld}---e.g.
+``@code{gcc-2.7}''.
+
+@item
+The command arguments you gave the linker to link your example and
+observe the bug. To guarantee you will not omit something important,
+list them all. A copy of the Makefile (or the output from make) is
+sufficient.
+
+If we were to try to guess the arguments, we would probably guess wrong
+and then we might not encounter the bug.
+
+@item
+A complete input file, or set of input files, that will reproduce the
+bug. It is generally most helpful to send the actual object files,
+uuencoded if necessary to get them through the mail system. Making them
+available for anonymous FTP is not as good, but may be the only
+reasonable choice for large object files.
+
+If the source files were assembled using @code{gas} or compiled using
+@code{gcc}, then it may be OK to send the source files rather than the
+object files. In this case, be sure to say exactly what version of
+@code{gas} or @code{gcc} was used to produce the object files. Also say
+how @code{gas} or @code{gcc} were configured.
+
+@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
+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
+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
+you had not told us to expect a crash, then we would not be able to draw
+any conclusion from our observations.
+
+@item
+If you wish to suggest changes to the @code{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
+context, not by line number.
+
+The line numbers in our development sources will not match those in your
+sources. Your line numbers would convey no useful information to us.
+@end itemize
+
+Here are some things that are not necessary:
+
+@itemize @bullet
+@item
+A description of the envelope of the bug.
+
+Often people who encounter a bug spend a lot of time investigating
+which changes to the input file will make the bug go away and which
+changes will not affect it.
+
+This is often time consuming and not very useful, because the way we
+will find the bug is by running a single example under the debugger
+with breakpoints, not by pure deduction from a series of examples.
+We recommend that you save your time for something else.
+
+Of course, if you can find a simpler example to report @emph{instead}
+of the original one, that is a convenience for us. Errors in the
+output will be easier to spot, running under the debugger will take
+less time, and so on.
+
+However, simplification is not vital; if you do not want to do this,
+report the bug anyway and send us the entire test case you used.
+
+@item
+A patch for the bug.
+
+A patch for the bug does help us if it is a good one. But do not omit
+the necessary information, such as the test case, on the assumption that
+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
+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
+fixed.
+
+And if we cannot understand what bug you are trying to fix, or why your
+patch should be an improvement, we will not install it. A test case will
+help us to understand.
+
+@item
+A guess about what the bug is or what it depends on.
+
+Such guesses are usually wrong. Even we cannot guess right about such
+things without first using the debugger to find the facts.
+@end itemize
+
@node MRI
@appendix MRI Compatible Script Files
@cindex MRI compatibility
@table @code
@cindex @code{ABSOLUTE} (MRI)
@item ABSOLUTE @var{secname}
-@item ABSOLUTE @var{secname}, @var{secname}, @dots{} @var{secname}
+@itemx ABSOLUTE @var{secname}, @var{secname}, @dots{} @var{secname}
Normally, @code{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
@var{in-secname} may be an integer.
+@cindex @code{ALIGN} (MRI)
+@item ALIGN @var{secname} = @var{expression}
+Align the section called @var{secname} to @var{expression}. The
+@var{expression} should be a power of two.
+
@cindex @code{BASE} (MRI)
@item BASE @var{expression}
Use the value of @var{expression} as the lowest address (other than
@cindex @code{LOAD} (MRI)
@item LOAD @var{filename}
-@item LOAD @var{filename}, @var{filename}, @dots{} @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}
command line.
@var{secname}, only the @emph{first} sets the start address.
@end table
-
@node Index
@unnumbered Index
\centerline{{\sl\fontname\tensl\/}}
\centerline{are used for emphasis.}\vfill}
\page\colophon
-% Blame: pesch@cygnus.com, 28mar91.
+% Blame: doc@cygnus.com, 28mar91.
@end tex
projects / deliverable / binutils-gdb.git / blobdiff