\input texinfo
@setfilename ld.info
+@c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
+@c 2001 Free Software Foundation, Inc.
@syncodeindex ky cp
@include configdoc.texi
@c (configdoc.texi is generated by the Makefile)
+@include ldver.texi
@c @smallbook
@ifinfo
@format
START-INFO-DIR-ENTRY
-* Ld:: The GNU linker.
+* Ld: (ld). The GNU linker.
END-INFO-DIR-ENTRY
@end format
@end ifinfo
@ifinfo
-This file documents the GNU linker LD.
+This file documents the @sc{gnu} linker LD version @value{VERSION}.
-Copyright (C) 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
+Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000 Free Software Foundation, Inc.
-Permission is granted to make and distribute verbatim copies of
-this manual provided the copyright notice and this permission notice
-are preserved on all copies.
-
-Permission is granted to copy and distribute modified versions of this
-manual under the conditions for verbatim copying, provided also that
-the entire resulting derived work is distributed under the terms of a
-permission notice identical to this one.
+@ignore
-Permission is granted to copy and distribute translations of this manual
-into another language, under the above conditions for modified versions.
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.1
+or any later version published by the Free Software Foundation;
+with no Invariant Sections, with no Front-Cover Texts, and with no
+Back-Cover Texts. A copy of the license is included in the
+section entitled "GNU Free Documentation License".
-@ignore
Permission is granted to process this file through Tex and print the
results, provided the printed document carries copying permission
notice identical to this one except for the removal of this paragraph
@subtitle The GNU linker
@sp 1
@subtitle @code{ld} version 2
-@subtitle January 1994
-@author Steve Chamberlain and Roland Pesch
-@author Cygnus Support
+@subtitle Version @value{VERSION}
+@author Steve Chamberlain
+@author Ian Lance Taylor
@page
@tex
{\parskip=0pt
-\hfill Cygnus Support\par
-\hfill steve\@cygnus.com, pesch\@cygnus.com\par
+\hfill Red Hat Inc\par
+\hfill nickc\@credhat.com, doc\@redhat.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.
-
-Permission is granted to make and distribute verbatim copies of
-this manual provided the copyright notice and this permission notice
-are preserved on all copies.
+Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000 Free Software Foundation, Inc.
-Permission is granted to copy and distribute modified versions of this
-manual under the conditions for verbatim copying, provided also that
-the entire resulting derived work is distributed under the terms of a
-permission notice identical to this one.
+ Permission is granted to copy, distribute and/or modify this document
+ under the terms of the GNU Free Documentation License, Version 1.1
+ or any later version published by the Free Software Foundation;
+ with no Invariant Sections, with no Front-Cover Texts, and with no
+ Back-Cover Texts. A copy of the license is included in the
+ section entitled "GNU Free Documentation License".
-Permission is granted to copy and distribute translations of this manual
-into another language, under the above conditions for modified versions.
@end titlepage
@end iftex
@c FIXME: Talk about importance of *order* of args, cmds to linker!
@ifinfo
@node Top
@top Using ld
-This file documents the GNU linker ld.
+This file documents the @sc{gnu} linker ld version @value{VERSION}.
+
+This document is distributed under the terms of the GNU Free
+Documentation License. A copy of the license is included in the
+section entitled "GNU Free Documentation License".
@menu
* Overview:: Overview
* Invocation:: Invocation
-* Commands:: Command Language
+* Scripts:: Linker Scripts
@ifset GENERIC
* Machine Dependent:: Machine Dependent Features
@end ifset
@ifset H8300
* H8/300:: ld and the H8/300
@end ifset
+@ifset Hitachi
+* Hitachi:: ld and other Hitachi micros
+@end ifset
@ifset I960
* i960:: ld and the Intel 960 family
@end ifset
+@ifset TICOFF
+* TI COFF:: ld and the TI COFF
+@end ifset
@end ifclear
@ifclear SingleFormat
* BFD:: BFD
@end ifclear
@c Following blank line required for remaining bug in makeinfo conds/menus
+* Reporting Bugs:: Reporting Bugs
* MRI:: MRI Compatible Script Files
+* GNU Free Documentation License:: GNU Free Documentation License
* Index:: Index
@end menu
@end ifinfo
@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 ]
- [ -c @var{MRI-commandfile} ] [ -d | -dc | -dp ]
- [ -defsym @var{symbol}=@var{expression} ]
- [ -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 ] [ -oformat @var{output-format} ]
- [ -R @var{filename} ] [ -relax ] [ -retain-symbols-file @var{filename} ]
- [ -r | -Ur ] [ -S ] [ -s ] [ -sort-common ] [ -stats ]
- [ -T @var{commandfile} ]
- [ -Ttext @var{org} ] [ -Tdata @var{org} ]
- [ -Tbss @var{org} ] [ -t ] [ -u @var{symbol}] [-V] [-v] [ -version ]
- [ -warn-common ] [ -y @var{symbol} ] [ -X ] [-x ]
-@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
the library @code{libc.a}, which will come from the standard search
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
+Some of the command-line options to @code{ld} may be specified at any
+point in the command line. However, options which refer to files, such
+as @samp{-l} or @samp{-T}, cause the file to be read at the point at
+which the option appears in the command line, relative to the object
+files and other file options. Repeating non-file 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}, and @samp{-u}.
-@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}, and @samp{-u}.
-@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 object files or archives 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},
are specified, the linker does not produce any output, and issues the
message @samp{No input files}.
+If the linker can not recognize the format of an object file, it will
+assume that it is a linker script. A script specified in this way
+augments the main linker script used for the link (either the default
+linker script or the one specified by using @samp{-T}). This feature
+permits the linker to link against a file which appears to be an object
+or an archive, but actually merely defines some symbol values, or uses
+@code{INPUT} or @code{GROUP} to load other objects. Note that
+specifying a script in this way 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{Scripts}.
+
For options whose names are a single letter,
option arguments must either follow the option letter without intervening
whitespace, or be given as separate arguments immediately following the
option that requires them.
For options whose names are multiple letters, either one dash or two can
-precede the option name; for example, @samp{--oformat} and
-@samp{-oformat} are equivalent. Arguments to multiple-letter options
-must either be separated from the option name by an equals sign, or be
-given as separate arguments immediately following the option that
-requires them. For example, @samp{--oformat srec} and
-@samp{--oformat=srec} are equivalent. Unique abbreviations of the names
-of multiple-letter options are accepted.
+precede the option name; for example, @samp{-trace-symbol} and
+@samp{--trace-symbol} are equivalent. Note - there is one exception to
+this rule. Multiple letter options that start with a lower case 'o' can
+only be preceeded by two dashes. This is to reduce confusion with the
+@samp{-o} option. So for example @samp{-omagic} sets the output file
+name to @samp{magic} whereas @samp{--omagic} sets the NMAGIC flag on the
+output.
+
+Arguments to multiple-letter options must either be separated from the
+option name by an equals sign, or be given as separate arguments
+immediately following the option that requires them. For example,
+@samp{--trace-symbol foo} and @samp{--trace-symbol=foo} are equivalent.
+Unique abbreviations of the names of multiple-letter options are
+accepted.
+
+Note - if the linker is being invoked indirectly, via a compiler driver
+(eg @samp{gcc}) then all the linker command line options should be
+prefixed by @samp{-Wl,} (or whatever is appropriate for the particular
+compiler driver) like this:
+
+@smallexample
+ gcc -Wl,--startgroup foo.o bar.o -Wl,--endgroup
+@end smallexample
+
+This is important, because otherwise the compiler driver program may
+silently drop the linker options, resulting in a bad link.
+
+Here is a table of the generic command line switches accepted by the GNU
+linker:
@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
binary format. You can also use @samp{-b} to switch formats explicitly (when
linking object files of different formats), by including
@samp{-b @var{input-format}} before each group of object files in a
-particular format.
+particular format.
The default format is taken from the environment variable
@code{GNUTARGET}.
@ifset UsesEnvVars
@xref{Environment}.
@end ifset
-You can also define the input
-format from a script, using the command @code{TARGET}; see @ref{Option
-Commands}.
+You can also define the input format from a script, using the command
+@code{TARGET}; see @ref{Format Commands}.
@end ifclear
-@kindex -Bstatic
-@item -Bstatic
-Ignored. This option is accepted for command-line compatibility with
-the SunOS linker.
-
@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
-assign space to common symbols even if a relocatable output file is
-specified (with @samp{-r}). The script command
-@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}.
+compatibility with other linkers. They assign space to common symbols
+even if a relocatable output file is specified (with @samp{-r}). The
+script command @code{FORCE_COMMON_ALLOCATION} has the same effect.
+@xref{Miscellaneous Commands}.
@cindex entry point, from command line
@kindex -e @var{entry}
-@item -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.
+program, rather than the default entry point. If there is no symbol
+named @var{entry}, the linker will try to parse @var{entry} as a number,
+and use that as the entry address (the number will be interpreted in
+base 10; you may use a leading @samp{0x} for base 16, or a leading
+@samp{0} for base 8). @xref{Entry Point}, for a discussion of defaults
+and other ways of specifying the entry point.
+
+@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. The dynamic symbol table is the set of symbols
+which are visible from dynamic objects at run time.
+
+If you do not use this option, the dynamic symbol table will normally
+contain only those symbols which are referenced by some dynamic object
+mentioned in the link.
+
+If you use @code{dlopen} to load a dynamic object which needs to refer
+back to the symbols defined by the program, rather than some other
+dynamic object, then you will probably need to use this option when
+linking the program itself.
+
+@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.
+
+@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.
+
+This option may be specified more than once. The DT_AUXILIARY entries
+will be created in the order in which they appear on the command line.
-@ifclear SingleFormat
@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.
+
+@cindex finalization function
+@kindex -fini
+@item -fini @var{name}
+When creating an ELF executable or shared object, call NAME when the
+executable or shared object is unloaded, by setting DT_FINI to the
+address of the function. By default, the linker uses @code{_fini} as
+the function to call.
@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.
-
-@cindex help
-@cindex usage
-@kindex -help
-@item -help
-Print a summary of the command-line options on the standard output and exit.
+@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 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
@item -i
Perform an incremental link (same as option @samp{-r}).
+@cindex initialization function
+@kindex -init
+@item -init @var{name}
+When creating an ELF executable or shared object, call NAME when the
+executable or shared object is loaded, by setting DT_INIT to the address
+of the function. By default, the linker uses @code{_init} as the
+function to call.
+
@cindex archive files, from cmd line
@kindex -l@var{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}
-@item -L@var{searchdir}
-@itemx -L @var{searchdir}
+@kindex --library-path=@var{dir}
+@item -L@var{searchdir}
+@itemx --library-path=@var{searchdir}
Add path @var{searchdir} to the list of paths that @code{ld} will search
for archive libraries and @code{ld} control scripts. You may use this
-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{-V} option. The
-default depends on how your @code{ld} was configured.
+emulations with the @samp{--verbose} or @samp{-V} options.
+
+If the @samp{-m} option is not used, the emulation is taken from the
+@code{LDEMULATION} environment variable, if that is defined.
+
+Otherwise, the default emulation depends upon how the linker was
+configured.
+
+@cindex link map
+@kindex -M
+@kindex --print-map
+@item -M
+@itemx --print-map
+Print a link map to the standard output. A link map provides
+information about the link, including the following:
+
+@itemize @bullet
+@item
+Where object files and symbols are mapped into memory.
+@item
+How common symbols are allocated.
+@item
+All archive members included in the link, with a mention of the symbol
+which caused the archive member to be brought in.
+@end itemize
+
+@kindex -n
+@cindex read-only text
+@cindex NMAGIC
+@kindex --nmagic
+@item -n
+@itemx --nmagic
+Turn off page alignment of sections, and mark the output as
+@code{NMAGIC} if possible.
@kindex -N
+@kindex --omagic
@cindex read/write from cmd line
-@kindex OMAGIC
-@item -N
+@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.
+
+@kindex -O @var{level}
+@cindex generating optimized output
+@item -O @var{level}
+If @var{level} is a numeric values greater than zero @code{ld} optimizes
+the output. This might take significantly longer and therefore probably
+should only be enabled for the final binary.
+
+@kindex -q
+@kindex --emit-relocs
+@cindex retain relocations in final executable
+@item -q
+@itemx --emit-relocs
+Leave relocation sections and contents in fully linked exececutables.
+Post link analysis and optimization tools may need this information in
+order to perform correct modifications of executables. This results
+in larger executables.
+
+@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{scriptfile}
+@itemx --script=@var{scriptfile}
+Use @var{scriptfile} as the linker script. This script replaces
+@code{ld}'s default linker script (rather than adding to it), so
+@var{commandfile} must specify everything necessary to describe the
+output file. You must use this option if you want to use a command
+which can only appear once in a linker script, such as the
+@code{SECTIONS} or @code{MEMORY} command. @xref{Scripts}. If
+@var{scriptfile} does not exist in the current directory, @code{ld}
+looks for it in the directories specified by any preceding @samp{-L}
+options. Multiple @samp{-T} options accumulate.
+
+@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. This
+option is equivalent to the @code{EXTERN} linker script command.
+
+@kindex -Ur
+@cindex constructors
+@item -Ur
+For anything other than C++ programs, this option is equivalent to
+@samp{-r}: it generates relocatable output---i.e., an output file that can in
+turn serve as input to @code{ld}. When linking C++ programs, @samp{-Ur}
+@emph{does} resolve references to constructors, unlike @samp{-r}.
+It does not work to use @samp{-Ur} on files that were themselves linked
+with @samp{-Ur}; once the constructor table has been built, it cannot
+be added to. Use @samp{-Ur} only for the last partial link, and
+@samp{-r} for the others.
+
+@kindex --unique[=@var{SECTION}]
+@item --unique[=@var{SECTION}]
+Creates a separate output section for every input section matching
+@var{SECTION}, or if the optional wildcard @var{SECTION} argument is
+missing, for every orphan input section. An orphan section is one not
+specifically mentioned in a linker script. You may use this option
+multiple times on the command line; It prevents the normal merging of
+input sections with the same name, overriding output section assignments
+in a linker script.
+
+@kindex -v
+@kindex -V
+@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}
+The recognized keywords are @code{initfirst}, @code{interpose},
+@code{loadfltr}, @code{nodefaultlib}, @code{nodelete}, @code{nodlopen},
+@code{nodump}, @code{now} and @code{origin}. The other keywords are
+ignored for Solaris compatibility. @code{initfirst} marks the object
+to be initialized first at runtime before any other objects.
+@code{interpose} marks the object that its symbol table interposes
+before all symbols but the primary executable. @code{loadfltr} marks
+the object that its filtees be processed immediately at runtime.
+@code{nodefaultlib} marks the object that the search for dependencies
+of this object will ignore any default library search paths.
+@code{nodelete} marks the object shouldn't be unloaded at runtime.
+@code{nodlopen} marks the object not available to @code{dlopen}.
+@code{nodump} marks the object can not be dumped by @code{dldump}.
+@code{now} marks the object with the non-lazy runtime binding.
+@code{origin} marks the object may contain $ORIGIN.
+@code{defs} disallows undefined symbols.
+
+@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 -Bgroup
+@item -Bgroup
+Set the @code{DF_1_GROUP} flag in the @code{DT_FLAGS_1} entry in the dynamic
+section. This causes the runtime linker to handle lookups in this
+object and its dependencies to be performed only inside the group.
+@code{--no-undefined} is implied. This option is only meaningful on ELF
+platforms which support shared libraries.
+
+@kindex -Bstatic
+@kindex -dn
+@kindex -non_shared
+@kindex -static
+@item -Bstatic
+@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.
+
+@kindex --check-sections
+@kindex --no-check-sections
+@item --check-sections
+@itemx --no-check-sections
+Asks the linker @emph{not} to check section addresses after they have
+been assigned to see if there any overlaps. Normally the linker will
+perform this check, and if it finds any overlaps it will produce
+suitable error messages. The linker does know about, and does make
+allowances for sections in overlays. The default behaviour can be
+restored by using the command line switch @samp{--check-sections}.
+
+@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{Assignments,,
+Assignment: Symbol Definitions}). @emph{Note:} there should be no white
+space between @var{symbol}, the equals sign (``@key{=}''), and
+@var{expression}.
+
+@cindex demangling, from command line
+@kindex --demangle[=@var{style}]
+@kindex --no-demangle
+@item --demangle[=@var{style}]
+@itemx --no-demangle
+These options control whether to demangle symbol names in error messages
+and other output. When the linker is told to demangle, it tries to
+present symbol names in a readable fashion: it strips leading
+underscores if they are used by the object file format, and converts C++
+mangled symbol names into user readable names. Different compilers have
+different mangling styles. The optional demangling style argument can be used
+to choose an appropriate demangling style for your compiler. The linker will
+demangle by default unless the environment variable @samp{COLLECT_NO_DEMANGLE}
+is set. These options may be used to override the default.
+
+@cindex dynamic linker, from command line
+@kindex --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 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.
+
+@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 --gc-sections
+@kindex --no-gc-sections
+@cindex garbage collection
+@item --no-gc-sections
+@itemx --gc-sections
+Enable garbage collection of unused input sections. It is ignored on
+targets that do not support this option. This option is not compatible
+with @samp{-r}, nor should it be used with dynamic linking. The default
+behaviour (of not performing this garbage collection) can be restored by
+specifying @samp{--no-gc-sections} on the command line.
+
+@cindex help
+@cindex usage
+@kindex --help
+@item --help
+Print a summary of the command-line options on the standard output and exit.
+
+@kindex --target-help
+@item --target-help
+Print a summary of all target specific options on the standard output and exit.
+
+@kindex -Map
+@item -Map @var{mapfile}
+Print a link map to the file @var{mapfile}. See the description of the
+@samp{-M} option, above.
+
+@cindex memory usage
+@kindex --no-keep-memory
+@item --no-keep-memory
+@code{ld} normally optimizes for speed over memory usage by caching the
+symbol tables of input files in memory. This option tells @code{ld} to
+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.
+
+@kindex --no-undefined
+@kindex -z defs
+@item --no-undefined
+@itemx -z defs
+Normally when creating a non-symbolic shared library, undefined symbols
+are allowed and left to be resolved by the runtime loader. These options
+disallows such undefined symbols.
+
+@kindex --allow-shlib-undefined
+@item --allow-shlib-undefined
+Allow undefined symbols in shared objects even when --no-undefined is
+set. The net result will be that undefined symbols in regular objects
+will still trigger an error, but undefined symbols in shared objects
+will be ignored. The implementation of no_undefined makes the
+assumption that the runtime linker will choke on undefined symbols.
+However there is at least one system (BeOS) where undefined symbols in
+shared libraries is normal since the kernel patches them at load time to
+select which function is most appropriate for the current architecture.
+I.E. dynamically select an appropriate memset function. Apparently it
+is also normal for HPPA shared libraries to have undefined symbols.
+
+@kindex --no-warn-mismatch
+@item --no-warn-mismatch
+Normally @code{ld} will give an error if you try to link together input
+files that are mismatched for some reason, perhaps because they have
+been compiled for different processors or for different endiannesses.
+This option tells @code{ld} that it should silently permit such possible
+errors. This option should only be used with care, in cases when you
+have taken some special action that ensures that the linker errors are
+inappropriate.
+
+@kindex --no-whole-archive
+@item --no-whole-archive
+Turn off the effect of the @code{--whole-archive} option for subsequent
+archive files.
-@item -noinhibit-exec
@cindex output file after errors
-@kindex -noinhibit-exec
+@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.
-@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.
-
@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
-An option with machine dependent effects.
+@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.
+
+On some platforms these link time global optimizations may make symbolic
+debugging of the resulting executable impossible.
+@ifset GENERIC
+This is known to be
+the case for the Matsushita MN10200 and MN10300 family of processors.
+@end ifset
@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}.
-@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.
+@ifset GENERIC
+@item -rpath @var{dir}
+@cindex runtime library search path
+@kindex -rpath
+Add a directory to the runtime library search path. This is used when
+linking an ELF executable with shared objects. All @code{-rpath}
+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
-@kindex -s
-@cindex strip all symbols
-@item -s
-Omit all symbol information from the output file.
+@ifset GENERIC
+@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-relocatable link, it will automatically try to locate the required
+shared library and include it in the link, if it is not included
+explicitly. In such a case, the @code{-rpath-link} option
+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.
+
+This option should be used with caution as it overrides the search path
+that may have been hard compiled into a shared library. In such a case it
+is possible to use unintentionally a different search path than the
+runtime linker would do.
+
+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. It is for the native linker only.
+@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}. It is for the native linker only.
+@item
+On SunOS, if the @code{-rpath} option was not used, search any
+directories specified using @code{-L} options.
+@item
+For a native linker, the contents of the environment variable
+@code{LD_LIBRARY_PATH}.
+@item
+For a native ELF linker, the directories in @code{DT_RUNPATH} or
+@code{DT_RPATH} of a shared library are searched for shared
+libraries needed by it. The @code{DT_RPATH} entries are ignored if
+@code{DT_RUNPATH} entries exist.
+@item
+The default directories, normally @file{/lib} and @file{/usr/lib}.
+@item
+For a native linker on an ELF system, if the file @file{/etc/ld.so.conf}
+exists, the list of directories found in that file.
+@end enumerate
-@item -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.
+If the required shared library is not found, the linker will issue a
+warning and continue with the link.
+@end ifset
-@item -stats
-Compute and display statistics about the operation of the linker,
-such as execution time and memory usage.
+@kindex -shared
+@kindex -Bshareable
+@item -shared
+@itemx -Bshareable
+@cindex shared libraries
+Create a shared library. This is currently only supported on ELF, XCOFF
+and SunOS platforms. On SunOS, the linker will automatically create a
+shared library if the @code{-e} option is not used and there are
+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 [@var{size}]
+Similar to @code{--split-by-reloc} but creates a new output section for
+each input file when @var{size} is reached. @var{size} defaults to a
+size of 1 if not given.
+
+@kindex --split-by-reloc
+@item --split-by-reloc [@var{count}]
+Tries to creates extra sections in the output file so that no single
+output section in the file contains more than @var{count} relocations.
+This is useful when generating huge relocatable files for downloading into
+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. @var{count} defaults to a value of 32768.
+
+@kindex --stats
+@item --stats
+Compute and display statistics about the operation of the linker, such
+as execution time and memory usage.
+
+@kindex --traditional-format
+@cindex traditional format
+@item --traditional-format
+For some targets, the output of @code{ld} is different in some ways from
+the output of some existing linker. This switch requests @code{ld} to
+use the traditional format instead.
+
+@cindex dbx
+For example, on SunOS, @code{ld} combines duplicate entries in the
+symbol string table. This can reduce the size of an output file with
+full debugging information by over 30 percent. Unfortunately, the SunOS
+@code{dbx} program can not read the resulting program (@code{gdb} has no
+trouble). The @samp{--traditional-format} switch tells @code{ld} to not
+combine duplicate entries.
+
+@kindex --section-start @var{sectionname}=@var{org}
+@item --section-start @var{sectionname}=@var{org}
+Locate a section in the output file at the absolute
+address given by @var{org}. You may use this option as many
+times as necessary to locate multiple sections in the command
+line.
+@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. @emph{Note:} there
+should be no white space between @var{sectionname}, the equals
+sign (``@key{=}''), and @var{org}.
-@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
+@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.
-@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 -t
+@kindex --verbose
@cindex verbose
-@cindex input files, displaying
-@item -t
-Print the names of the input files as @code{ld} processes them.
-
-@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 -Ur
-@cindex constructors
-@item -Ur
-For anything other than C++ programs, this option is equivalent to
-@samp{-r}: it generates relocatable output---i.e., an output file that can in
-turn serve as input to @code{ld}. When linking C++ programs, @samp{-Ur}
-@emph{does} resolve references to constructors, unlike @samp{-r}.
-It does not work to use @samp{-Ur} on files that were themselves linked
-with @samp{-Ur}; once the constructor table has been built, it cannot
-be added to. Use @samp{-Ur} only for the last partial link, and
-@samp{-r} for the others.
-
-@kindex -V
-@cindex version
-@item -V
+@item --dll-verbose
+@itemx --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
-@cindex version
-@item -v
-Display the version number for @code{ld}.
-
-@item -version
-@kindex -version
-Display the version number for @code{ld} and exit.
-
-@item -warn-common
-@kindex -warn-comon
+supported. Display which input files can and cannot be opened. Display
+the linker script if using a default builtin script.
+
+@kindex --version-script=@var{version-scriptfile}
+@cindex version script, symbol versions
+@itemx --version-script=@var{version-scriptfile}
+Specify the name of a version script to the linker. This is typically
+used when creating shared libraries to specify additional information
+about the version heirarchy for the library being created. This option
+is only meaningful on ELF platforms which support shared libraries.
+@xref{VERSION}.
+
+@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 -X
-@cindex local symbols, deleting
-@cindex L, deleting symbols beginning
-@item -X
-If @samp{-s} or @samp{-S} is also specified, delete only local symbols
-beginning with @samp{L}.
+@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
+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
+@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.
+
+Two notes when using this option from gcc: First, gcc doesn't know
+about this option, so you have to use @code{-Wl,-whole-archive}.
+Second, don't forget to use @code{-Wl,-no-whole-archive} after your
+list of archives, because gcc will add its own list of archives to
+your link and you may not want this flag to affect those as well.
+
+@kindex --wrap
+@item --wrap @var{symbol}
+Use a wrapper function for @var{symbol}. Any undefined reference to
+@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:
-@kindex -x
-@cindex deleting local symbols
-@item -x
-If @samp{-s} or @samp{-S} is also specified, delete all local symbols,
-not just those beginning with @samp{L}.
+@smallexample
+void *
+__wrap_malloc (int c)
+@{
+ printf ("malloc called with %ld\n", c);
+ return __real_malloc (c);
+@}
+@end smallexample
-@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.
+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.
+
+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}.
+
+@kindex --enable-new-dtags
+@kindex --disable-new-dtags
+@item --enable-new-dtags
+@itemx --disable-new-dtags
+This linker can create the new dynamic tags in ELF. But the older ELF
+systems may not understand them. If you specify
+@code{--enable-new-dtags}, the dynamic tags will be created as needed.
+If you specify @code{--disable-new-dtags}, no new dynamic tags will be
+created. By default, the new dynamic tags are not created. Note that
+those options are only available for ELF systems.
+
+@end table
+
+@subsection Options specific to i386 PE targets
+
+The i386 PE linker supports the @code{-shared} option, which causes
+the output to be a dynamically linked library (DLL) instead of a
+normal executable. You should name the output @code{*.dll} when you
+use this option. In addition, the linker fully supports the standard
+@code{*.def} files, which may be specified on the linker command line
+like an object file (in fact, it should precede archives it exports
+symbols from, to ensure that they get linked in, just like a normal
+object file).
+
+In addition to the options common to all targets, the i386 PE linker
+support additional command line options that are specific to the i386
+PE target. Options that take values may be separated from their
+values by either a space or an equals sign.
+
+@table @code
+
+@kindex --add-stdcall-alias
+@item --add-stdcall-alias
+If given, symbols with a stdcall suffix (@@@var{nn}) will be exported
+as-is and also with the suffix stripped.
+
+@kindex --base-file
+@item --base-file @var{file}
+Use @var{file} as the name of a file in which to save the base
+addresses of all the relocations needed for generating DLLs with
+@file{dlltool}.
+
+@kindex --dll
+@item --dll
+Create a DLL instead of a regular executable. You may also use
+@code{-shared} or specify a @code{LIBRARY} in a given @code{.def}
+file.
+
+@kindex --enable-stdcall-fixup
+@kindex --disable-stdcall-fixup
+@item --enable-stdcall-fixup
+@itemx --disable-stdcall-fixup
+If the link finds a symbol that it cannot resolve, it will attempt to
+do "fuzzy linking" by looking for another defined symbol that differs
+only in the format of the symbol name (cdecl vs stdcall) and will
+resolve that symbol by linking to the match. For example, the
+undefined symbol @code{_foo} might be linked to the function
+@code{_foo@@12}, or the undefined symbol @code{_bar@@16} might be linked
+to the function @code{_bar}. When the linker does this, it prints a
+warning, since it normally should have failed to link, but sometimes
+import libraries generated from third-party dlls may need this feature
+to be usable. If you specify @code{--enable-stdcall-fixup}, this
+feature is fully enabled and warnings are not printed. If you specify
+@code{--disable-stdcall-fixup}, this feature is disabled and such
+mismatches are considered to be errors.
+
+@cindex DLLs, creating
+@kindex --export-all-symbols
+@item --export-all-symbols
+If given, all global symbols in the objects used to build a DLL will
+be exported by the DLL. Note that this is the default if there
+otherwise wouldn't be any exported symbols. When symbols are
+explicitly exported via DEF files or implicitly exported via function
+attributes, the default is to not export anything else unless this
+option is given. Note that the symbols @code{DllMain@@12},
+@code{DllEntryPoint@@0}, and @code{impure_ptr} will not be automatically
+exported.
+
+@kindex --exclude-symbols
+@item --exclude-symbols @var{symbol},@var{symbol},...
+Specifies a list of symbols which should not be automatically
+exported. The symbol names may be delimited by commas or colons.
+
+@kindex --file-alignment
+@item --file-alignment
+Specify the file alignment. Sections in the file will always begin at
+file offsets which are multiples of this number. This defaults to
+512.
+
+@cindex heap size
+@kindex --heap
+@item --heap @var{reserve}
+@itemx --heap @var{reserve},@var{commit}
+Specify the amount of memory to reserve (and optionally commit) to be
+used as heap for this program. The default is 1Mb reserved, 4K
+committed.
+
+@cindex image base
+@kindex --image-base
+@item --image-base @var{value}
+Use @var{value} as the base address of your program or dll. This is
+the lowest memory location that will be used when your program or dll
+is loaded. To reduce the need to relocate and improve performance of
+your dlls, each should have a unique base address and not overlap any
+other dlls. The default is 0x400000 for executables, and 0x10000000
+for dlls.
+
+@kindex --kill-at
+@item --kill-at
+If given, the stdcall suffixes (@@@var{nn}) will be stripped from
+symbols before they are exported.
+
+@kindex --major-image-version
+@item --major-image-version @var{value}
+Sets the major number of the "image version". Defaults to 1.
+
+@kindex --major-os-version
+@item --major-os-version @var{value}
+Sets the major number of the "os version". Defaults to 4.
+
+@kindex --major-subsystem-version
+@item --major-subsystem-version @var{value}
+Sets the major number of the "subsystem version". Defaults to 4.
+
+@kindex --minor-image-version
+@item --minor-image-version @var{value}
+Sets the minor number of the "image version". Defaults to 0.
+
+@kindex --minor-os-version
+@item --minor-os-version @var{value}
+Sets the minor number of the "os version". Defaults to 0.
+
+@kindex --minor-subsystem-version
+@item --minor-subsystem-version @var{value}
+Sets the minor number of the "subsystem version". Defaults to 0.
+
+@cindex DEF files, creating
+@cindex DLLs, creating
+@kindex --output-def
+@item --output-def @var{file}
+The linker will create the file @var{file} which will contain a DEF
+file corresponding to the DLL the linker is generating. This DEF file
+(which should be called @code{*.def}) may be used to create an import
+library with @code{dlltool} or may be used as a reference to
+automatically or implicitly exported symbols.
+
+@kindex --section-alignment
+@item --section-alignment
+Sets the section alignment. Sections in memory will always begin at
+addresses which are a multiple of this number. Defaults to 0x1000.
+
+@cindex stack size
+@kindex --stack
+@item --stack @var{reserve}
+@itemx --stack @var{reserve},@var{commit}
+Specify the amount of memory to reserve (and optionally commit) to be
+used as stack for this program. The default is 32Mb reserved, 4K
+committed.
+
+@kindex --subsystem
+@item --subsystem @var{which}
+@itemx --subsystem @var{which}:@var{major}
+@itemx --subsystem @var{which}:@var{major}.@var{minor}
+Specifies the subsystem under which your program will execute. The
+legal values for @var{which} are @code{native}, @code{windows},
+@code{console}, and @code{posix}. You may optionally set the
+subsystem version also.
-This option is useful when you have an undefined symbol in your link but
-don't know where the reference is coming from.
@end table
@ifset UsesEnvVars
@node Environment
@section Environment Variables
-You can change the behavior of @code{ld} with the environment
-variable @code{GNUTARGET}.
+You can change the behavior of @code{ld} with the environment variables
+@code{GNUTARGET}, @code{LDEMULATION}, and @code{COLLECT_NO_DEMANGLE}.
@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.
+
+@kindex LDEMULATION
+@cindex default emulation
+@cindex emulation, default
+@code{LDEMULATION} determines the default emulation if you don't use the
+@samp{-m} option. The emulation can affect various aspects of linker
+behaviour, particularly the default linker script. You can list the
+available emulations with the @samp{--verbose} or @samp{-V} options. If
+the @samp{-m} option is not used, and the @code{LDEMULATION} environment
+variable is not defined, the default emulation depends upon how the
+linker was configured.
@end ifset
-@node Commands
-@chapter Command Language
+@kindex COLLECT_NO_DEMANGLE
+@cindex demangling, default
+Normally, the linker will default to demangling symbols. However, if
+@code{COLLECT_NO_DEMANGLE} is set in the environment, then it will
+default to not demangling symbols. This environment variable is used in
+a similar fashion by the @code{gcc} linker wrapper program. The default
+may be overridden by the @samp{--demangle} and @samp{--no-demangle}
+options.
-@cindex command files
-The command language provides explicit control over the link process,
-allowing complete specification of the mapping between the linker's
-input files and its output. It controls:
-@itemize @bullet
-@item
-input files
-@item
-file formats
-@item
-output file layout
-@item
-addresses of sections
-@item
-placement of common blocks
-@end itemize
+@node Scripts
+@chapter Linker Scripts
-You may supply a command file (also known as a link 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.
+@cindex scripts
+@cindex linker scripts
+@cindex command files
+Every link is controlled by a @dfn{linker script}. This script is
+written in the linker command language.
+
+The main purpose of the linker script is to describe how the sections in
+the input files should be mapped into the output file, and to control
+the memory layout of the output file. Most linker scripts do nothing
+more than this. However, when necessary, the linker script can also
+direct the linker to perform many other operations, using the commands
+described below.
+
+The linker always uses a linker script. If you do not supply one
+yourself, the linker will use a default script that is compiled into the
+linker executable. You can use the @samp{--verbose} command line option
+to display the default linker script. Certain command line options,
+such as @samp{-r} or @samp{-N}, will affect the default linker script.
+
+You may supply your own linker script by using the @samp{-T} command
+line option. When you do this, your linker script will replace the
+default linker script.
+
+You may also use linker scripts implicitly by naming them as input files
+to the linker, as though they were files to be linked. @xref{Implicit
+Linker Scripts}.
@menu
-* Scripts:: Linker Scripts
-* Expressions:: Expressions
-* MEMORY:: MEMORY Command
-* SECTIONS:: SECTIONS Command
-* Entry Point:: The Entry Point
-* Option Commands:: Option Commands
+* Basic Script Concepts:: Basic Linker Script Concepts
+* Script Format:: Linker Script Format
+* Simple Example:: Simple Linker Script Example
+* Simple Commands:: Simple Linker Script Commands
+* Assignments:: Assigning Values to Symbols
+* SECTIONS:: SECTIONS Command
+* MEMORY:: MEMORY Command
+* PHDRS:: PHDRS Command
+* VERSION:: VERSION Command
+* Expressions:: Expressions in Linker Scripts
+* Implicit Linker Scripts:: Implicit Linker Scripts
@end menu
-@node Scripts
-@section Linker Scripts
-The @code{ld} command language is a collection of statements; some are
-simple keywords setting a particular option, some are used to select and
-group input files or name output files; and two statement
-types have a fundamental and pervasive impact on the linking process.
-
-@cindex fundamental script commands
-@cindex commands, fundamental
-@cindex output file layout
-@cindex layout of output file
-The most fundamental command of the @code{ld} command language is the
-@code{SECTIONS} command (@pxref{SECTIONS}). Every meaningful command
-script must have a @code{SECTIONS} command: it specifies a
-``picture'' of the output file's layout, in varying degrees of detail.
-No other command is required in all cases.
-
-The @code{MEMORY} command complements @code{SECTIONS} by describing the
-available memory in the target architecture. This command is optional;
-if you don't use a @code{MEMORY} command, @code{ld} assumes sufficient
-memory is available in a contiguous block for all output.
-@xref{MEMORY}.
-
-@cindex comments
-You may include comments in linker scripts just as in C: delimited
-by @samp{/*} and @samp{*/}. As in C, comments are syntactically
-equivalent to whitespace.
+@node Basic Script Concepts
+@section Basic Linker Script Concepts
+@cindex linker script concepts
+We need to define some basic concepts and vocabulary in order to
+describe the linker script language.
+
+The linker combines input files into a single output file. The output
+file and each input file are in a special data format known as an
+@dfn{object file format}. Each file is called an @dfn{object file}.
+The output file is often called an @dfn{executable}, but for our
+purposes we will also call it an object file. Each object file has,
+among other things, a list of @dfn{sections}. We sometimes refer to a
+section in an input file as an @dfn{input section}; similarly, a section
+in the output file is an @dfn{output section}.
+
+Each section in an object file has a name and a size. Most sections
+also have an associated block of data, known as the @dfn{section
+contents}. A section may be marked as @dfn{loadable}, which mean that
+the contents should be loaded into memory when the output file is run.
+A section with no contents may be @dfn{allocatable}, which means that an
+area in memory should be set aside, but nothing in particular should be
+loaded there (in some cases this memory must be zeroed out). A section
+which is neither loadable nor allocatable typically contains some sort
+of debugging information.
+
+Every loadable or allocatable output section has two addresses. The
+first is the @dfn{VMA}, or virtual memory address. This is the address
+the section will have when the output file is run. The second is the
+@dfn{LMA}, or load memory address. This is the address at which the
+section will be loaded. In most cases the two addresses will be the
+same. An example of when they might be different is when a data section
+is loaded into ROM, and then copied into RAM when the program starts up
+(this technique is often used to initialize global variables in a ROM
+based system). In this case the ROM address would be the LMA, and the
+RAM address would be the VMA.
+
+You can see the sections in an object file by using the @code{objdump}
+program with the @samp{-h} option.
+
+Every object file also has a list of @dfn{symbols}, known as the
+@dfn{symbol table}. A symbol may be defined or undefined. Each symbol
+has a name, and each defined symbol has an address, among other
+information. If you compile a C or C++ program into an object file, you
+will get a defined symbol for every defined function and global or
+static variable. Every undefined function or global variable which is
+referenced in the input file will become an undefined symbol.
+
+You can see the symbols in an object file by using the @code{nm}
+program, or by using the @code{objdump} program with the @samp{-t}
+option.
+
+@node Script Format
+@section Linker Script Format
+@cindex linker script format
+Linker scripts are text files.
+
+You write a linker script as a series of commands. Each command is
+either a keyword, possibly followed by arguments, or an assignment to a
+symbol. You may separate commands using semicolons. Whitespace is
+generally ignored.
+
+Strings such as file or format names can normally be entered directly.
+If the file name contains a character such as a comma which would
+otherwise serve to separate file names, you may put the file name in
+double quotes. There is no way to use a double quote character in a
+file name.
+
+You may include comments in linker scripts just as in C, delimited by
+@samp{/*} and @samp{*/}. As in C, comments are syntactically equivalent
+to whitespace.
+
+@node Simple Example
+@section Simple Linker Script Example
+@cindex linker script example
+@cindex example of linker script
+Many linker scripts are fairly simple.
+
+The simplest possible linker script has just one command:
+@samp{SECTIONS}. You use the @samp{SECTIONS} command to describe the
+memory layout of the output file.
+
+The @samp{SECTIONS} command is a powerful command. Here we will
+describe a simple use of it. Let's assume your program consists only of
+code, initialized data, and uninitialized data. These will be in the
+@samp{.text}, @samp{.data}, and @samp{.bss} sections, respectively.
+Let's assume further that these are the only sections which appear in
+your input files.
+
+For this example, let's say that the code should be loaded at address
+0x10000, and that the data should start at address 0x8000000. Here is a
+linker script which will do that:
+@smallexample
+SECTIONS
+@{
+ . = 0x10000;
+ .text : @{ *(.text) @}
+ . = 0x8000000;
+ .data : @{ *(.data) @}
+ .bss : @{ *(.bss) @}
+@}
+@end smallexample
-@node Expressions
-@section Expressions
-@cindex expression syntax
-@cindex arithmetic
-Many useful commands involve arithmetic expressions. The syntax for
-expressions in the command language is identical to that of C
-expressions, with the following features:
-@itemize @bullet
-@item
-All expressions evaluated as integers and
-are of ``long'' or ``unsigned long'' type.
-@item
-All constants are integers.
-@item
-All of the C arithmetic operators are provided.
-@item
-You may reference, define, and create global variables.
-@item
-You may call special purpose built-in functions.
-@end itemize
+You write the @samp{SECTIONS} command as the keyword @samp{SECTIONS},
+followed by a series of symbol assignments and output section
+descriptions enclosed in curly braces.
+
+The first line inside the @samp{SECTIONS} command of the above example
+sets the value of the special symbol @samp{.}, which is the location
+counter. If you do not specify the address of an output section in some
+other way (other ways are described later), the address is set from the
+current value of the location counter. The location counter is then
+incremented by the size of the output section. At the start of the
+@samp{SECTIONS} command, the location counter has the value @samp{0}.
+
+The second line defines an output section, @samp{.text}. The colon is
+required syntax which may be ignored for now. Within the curly braces
+after the output section name, you list the names of the input sections
+which should be placed into this output section. The @samp{*} is a
+wildcard which matches any file name. The expression @samp{*(.text)}
+means all @samp{.text} input sections in all input files.
+
+Since the location counter is @samp{0x10000} when the output section
+@samp{.text} is defined, the linker will set the address of the
+@samp{.text} section in the output file to be @samp{0x10000}.
+
+The remaining lines define the @samp{.data} and @samp{.bss} sections in
+the output file. The linker will place the @samp{.data} output section
+at address @samp{0x8000000}. After the linker places the @samp{.data}
+output section, the value of the location counter will be
+@samp{0x8000000} plus the size of the @samp{.data} output section. The
+effect is that the linker will place the @samp{.bss} output section
+immediately after the @samp{.data} output section in memory
+
+The linker will ensure that each output section has the required
+alignment, by increasing the location counter if necessary. In this
+example, the specified addresses for the @samp{.text} and @samp{.data}
+sections will probably satisfy any alignment constraints, but the linker
+may have to create a small gap between the @samp{.data} and @samp{.bss}
+sections.
+
+That's it! That's a simple and complete linker script.
+
+@node Simple Commands
+@section Simple Linker Script Commands
+@cindex linker script simple commands
+In this section we describe the simple linker script commands.
@menu
-* Integers:: Integers
-* Symbols:: Symbol Names
-* Location Counter:: The Location Counter
-* Operators:: Operators
-* Evaluation:: Evaluation
-* Assignment:: Assignment: Defining Symbols
-* Arithmetic Functions:: Built-In Functions
+* Entry Point:: Setting the entry point
+* File Commands:: Commands dealing with files
+@ifclear SingleFormat
+* Format Commands:: Commands dealing with object file formats
+@end ifclear
+
+* Miscellaneous Commands:: Other linker script commands
@end menu
-@node Integers
-@subsection Integers
-@cindex integer notation
-@cindex octal integers
-An octal integer is @samp{0} followed by zero or more of the octal
-digits (@samp{01234567}).
-@example
-_as_octal = 0157255;
-@end example
+@node Entry Point
+@subsection Setting the entry point
+@kindex ENTRY(@var{symbol})
+@cindex start of execution
+@cindex first instruction
+@cindex entry point
+The first instruction to execute in a program is called the @dfn{entry
+point}. You can use the @code{ENTRY} linker script command to set the
+entry point. The argument is a symbol name:
+@smallexample
+ENTRY(@var{symbol})
+@end smallexample
-@cindex decimal integers
-A decimal integer starts with a non-zero digit followed by zero or
-more digits (@samp{0123456789}).
-@example
-_as_decimal = 57005;
-@end example
+There are several ways to set the entry point. The linker will set the
+entry point by trying each of the following methods in order, and
+stopping when one of them succeeds:
+@itemize @bullet
+@item
+the @samp{-e} @var{entry} command-line option;
+@item
+the @code{ENTRY(@var{symbol})} command in a linker script;
+@item
+the value of the symbol @code{start}, if defined;
+@item
+the address of the first byte of the @samp{.text} section, if present;
+@item
+The address @code{0}.
+@end itemize
-@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
-_as_hex = 0xdead;
-@end example
+@node File Commands
+@subsection Commands dealing with files
+@cindex linker script file commands
+Several linker script commands deal with files.
-@cindex negative integers
-To write a negative integer, use
-the prefix operator @samp{-}; @pxref{Operators}.
-@example
-_as_neg = -57005;
-@end example
+@table @code
+@item INCLUDE @var{filename}
+@kindex INCLUDE @var{filename}
+@cindex including a linker script
+Include the linker script @var{filename} at this point. The file will
+be searched for in the current directory, and in any directory specified
+with the @code{-L} option. You can nest calls to @code{INCLUDE} up to
+10 levels deep.
+
+@item INPUT(@var{file}, @var{file}, @dots{})
+@itemx INPUT(@var{file} @var{file} @dots{})
+@kindex INPUT(@var{files})
+@cindex input files in linker scripts
+@cindex input object files in linker scripts
+@cindex linker script input object files
+The @code{INPUT} command directs the linker to include the named files
+in the link, as though they were named on the command line.
+
+For example, if you always want to include @file{subr.o} any time you do
+a link, but you can't be bothered to put it on every link command line,
+then you can put @samp{INPUT (subr.o)} in your linker script.
+
+In fact, if you like, you can list all of your input files in the linker
+script, and then invoke the linker with nothing but a @samp{-T} option.
+
+The linker will first try to open the file in the current directory. If
+it is not found, the linker will search through the archive library
+search path. See the description of @samp{-L} in @ref{Options,,Command
+Line Options}.
+
+If you use @samp{INPUT (-l@var{file})}, @code{ld} will transform the
+name to @code{lib@var{file}.a}, as with the command line argument
+@samp{-l}.
+
+When you use the @code{INPUT} command in an implicit linker script, the
+files will be included in the link at the point at which the linker
+script file is included. This can affect archive searching.
+
+@item GROUP(@var{file}, @var{file}, @dots{})
+@itemx GROUP(@var{file} @var{file} @dots{})
+@kindex GROUP(@var{files})
+@cindex grouping input files
+The @code{GROUP} command is like @code{INPUT}, except that the named
+files should all be archives, and they are searched repeatedly until no
+new undefined references are created. See the description of @samp{-(}
+in @ref{Options,,Command Line Options}.
+
+@item OUTPUT(@var{filename})
+@kindex OUTPUT(@var{filename})
+@cindex output file name in linker scripot
+The @code{OUTPUT} command names the output file. Using
+@code{OUTPUT(@var{filename})} in the linker script is exactly like using
+@samp{-o @var{filename}} on the command line (@pxref{Options,,Command
+Line Options}). If both are used, the command line option takes
+precedence.
+
+You can use the @code{OUTPUT} command to define a default name for the
+output file other than the usual default of @file{a.out}.
+
+@item SEARCH_DIR(@var{path})
+@kindex SEARCH_DIR(@var{path})
+@cindex library search path in linker script
+@cindex archive search path in linker script
+@cindex search path in linker script
+The @code{SEARCH_DIR} command adds @var{path} to the list of paths where
+@code{ld} looks for archive libraries. Using
+@code{SEARCH_DIR(@var{path})} is exactly like using @samp{-L @var{path}}
+on the command line (@pxref{Options,,Command Line Options}). If both
+are used, then the linker will search both paths. Paths specified using
+the command line option are searched first.
+
+@item STARTUP(@var{filename})
+@kindex STARTUP(@var{filename})
+@cindex first input file
+The @code{STARTUP} command is just like the @code{INPUT} command, except
+that @var{filename} will become the first input file to be linked, as
+though it were specified first on the command line. This may be useful
+when using a system in which the entry point is always the start of the
+first file.
+@end table
-@cindex scaled integers
-@cindex K and M integer suffixes
-@cindex M and K integer suffixes
-@cindex suffixes for integers
-@cindex integer suffixes
-Additionally the suffixes @code{K} and @code{M} may be used to scale a
-constant by
-@c TEXI2ROFF-KILL
-@ifinfo
-@c END TEXI2ROFF-KILL
-@code{1024} or @code{1024*1024}
-@c TEXI2ROFF-KILL
-@end ifinfo
-@tex
-${\rm 1024}$ or ${\rm 1024}^2$
-@end tex
-@c END TEXI2ROFF-KILL
-respectively. For example, the following all refer to the same quantity:
+@ifclear SingleFormat
+@node Format Commands
+@subsection Commands dealing with object file formats
+A couple of linker script commands deal with object file formats.
-@example
- _fourk_1 = 4K;
- _fourk_2 = 4096;
- _fourk_3 = 0x1000;
-@end example
+@table @code
+@item OUTPUT_FORMAT(@var{bfdname})
+@itemx OUTPUT_FORMAT(@var{default}, @var{big}, @var{little})
+@kindex OUTPUT_FORMAT(@var{bfdname})
+@cindex output file format in linker script
+The @code{OUTPUT_FORMAT} command names the BFD format to use for the
+output file (@pxref{BFD}). Using @code{OUTPUT_FORMAT(@var{bfdname})} is
+exactly like using @samp{-oformat @var{bfdname}} on the command line
+(@pxref{Options,,Command Line Options}). If both are used, the command
+line option takes precedence.
+
+You can use @code{OUTPUT_FORMAT} with three arguments to use different
+formats based on the @samp{-EB} and @samp{-EL} command line options.
+This permits the linker script to set the output format based on the
+desired endianness.
+
+If neither @samp{-EB} nor @samp{-EL} are used, then the output format
+will be the first argument, @var{default}. If @samp{-EB} is used, the
+output format will be the second argument, @var{big}. If @samp{-EL} is
+used, the output format will be the third argument, @var{little}.
+
+For example, the default linker script for the MIPS ELF target uses this
+command:
+@smallexample
+OUTPUT_FORMAT(elf32-bigmips, elf32-bigmips, elf32-littlemips)
+@end smallexample
+This says that the default format for the output file is
+@samp{elf32-bigmips}, but if the user uses the @samp{-EL} command line
+option, the output file will be created in the @samp{elf32-littlemips}
+format.
+
+@item TARGET(@var{bfdname})
+@kindex TARGET(@var{bfdname})
+@cindex input file format in linker script
+The @code{TARGET} command names the BFD format to use when reading input
+files. It affects subsequent @code{INPUT} and @code{GROUP} commands.
+This command is like using @samp{-b @var{bfdname}} on the command line
+(@pxref{Options,,Command Line Options}). If the @code{TARGET} command
+is used but @code{OUTPUT_FORMAT} is not, then the last @code{TARGET}
+command is also used to set the format for the output file. @xref{BFD}.
+@end table
+@end ifclear
-@node Symbols
-@subsection Symbol Names
-@cindex symbol names
-@cindex names
-@cindex quoted symbol names
-@kindex "
-Unless quoted, symbol names start with a letter, underscore, or point
-and may include any letters, underscores, digits, points,
-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
- "SECTION" = 9;
- "with a space" = "also with a space" + 10;
-@end example
+@node Miscellaneous Commands
+@subsection Other linker script commands
+There are a few other linker scripts commands.
-Since symbols can contain many non-alphabetic characters, it is safest
-to delimit symbols with spaces. For example, @samp{A-B} is one symbol,
-whereas @samp{A - B} is an expression involving subtraction.
+@table @code
+@item ASSERT(@var{exp}, @var{message})
+@kindex ASSERT
+@cindex assertion in linker script
+Ensure that @var{exp} is non-zero. If it is zero, then exit the linker
+with an error code, and print @var{message}.
+
+@item EXTERN(@var{symbol} @var{symbol} @dots{})
+@kindex EXTERN
+@cindex undefined symbol in linker script
+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. You may list several @var{symbol}s for
+each @code{EXTERN}, and you may use @code{EXTERN} multiple times. This
+command has the same effect as the @samp{-u} command-line option.
-@node Location Counter
-@subsection The Location Counter
-@kindex .
-@cindex dot
-@cindex location counter
-@cindex current output location
-The special linker variable @dfn{dot} @samp{.} always contains the
-current output location counter. Since the @code{.} always refers to
-a location in an output section, it must always appear in an
-expression within a @code{SECTIONS} command. The @code{.} symbol
-may appear anywhere that an ordinary symbol is allowed in an
-expression, but its assignments have a side effect. Assigning a value
-to the @code{.} symbol will cause the location counter to be moved.
-@cindex holes
-This may be used to create holes in the output section. The location
-counter may never be moved backwards.
-@example
-SECTIONS
-@{
- output :
- @{
- file1(.text)
- . = . + 1000;
- file2(.text)
- . += 1000;
- file3(.text)
- @} = 0x1234;
-@}
-@end example
-@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}
-appears, also with a 1000 byte gap following before @code{file3} is
-loaded. The notation @samp{= 0x1234} specifies what data to write in
-the gaps (@pxref{Section Options}).
+@item FORCE_COMMON_ALLOCATION
+@kindex FORCE_COMMON_ALLOCATION
+@cindex common allocation in linker script
+This command has the same effect as the @samp{-d} command-line option:
+to make @code{ld} assign space to common symbols even if a relocatable
+output file is specified (@samp{-r}).
-@iftex
-@vfill
-@end iftex
+@item NOCROSSREFS(@var{section} @var{section} @dots{})
+@kindex NOCROSSREFS(@var{sections})
+@cindex cross references
+This command may be used to tell @code{ld} to issue an error about any
+references among certain output sections.
-@need 5000
-@node Operators
-@subsection Operators
-@cindex Operators for arithmetic
-@cindex arithmetic operators
-@cindex precedence in expressions
-The linker recognizes the standard C set of arithmetic operators, with
-the standard bindings and precedence levels:
-@c TEXI2ROFF-KILL
-@ifinfo
-@c END TEXI2ROFF-KILL
-@example
-precedence associativity Operators Notes
-(highest)
-1 left ! - ~ (1)
-2 left * / %
-3 left + -
-4 left >> <<
-5 left == != > < <= >=
-6 left &
-7 left |
-8 left &&
-9 left ||
-10 right ? :
-11 right &= += -= *= /= (2)
-(lowest)
-@end example
-Notes:
-(1) Prefix operators
-(2) @xref{Assignment}
-@c TEXI2ROFF-KILL
-@end ifinfo
-@tex
-\vskip \baselineskip
-%"lispnarrowing" is the extra indent used generally for @example
-\hskip\lispnarrowing\vbox{\offinterlineskip
-\hrule
-\halign
-{\vrule#&\strut\hfil\ #\ \hfil&\vrule#&\strut\hfil\ #\ \hfil&\vrule#&\strut\hfil\ {\tt #}\ \hfil&\vrule#\cr
-height2pt&\omit&&\omit&&\omit&\cr
-&Precedence&& Associativity &&{\rm Operators}&\cr
-height2pt&\omit&&\omit&&\omit&\cr
-\noalign{\hrule}
-height2pt&\omit&&\omit&&\omit&\cr
-&highest&&&&&\cr
-% '176 is tilde, '~' in tt font
-&1&&left&&\qquad- \char'176\ !\qquad\dag&\cr
-&2&&left&&* / \%&\cr
-&3&&left&&+ -&\cr
-&4&&left&&>> <<&\cr
-&5&&left&&== != > < <= >=&\cr
-&6&&left&&\&&\cr
-&7&&left&&|&\cr
-&8&&left&&{\&\&}&\cr
-&9&&left&&||&\cr
-&10&&right&&? :&\cr
-&11&&right&&\qquad\&= += -= *= /=\qquad\ddag&\cr
-&lowest&&&&&\cr
-height2pt&\omit&&\omit&&\omit&\cr}
-\hrule}
-@end tex
-@iftex
-{
-@obeylines@parskip=0pt@parindent=0pt
-@dag@quad Prefix operators.
-@ddag@quad @xref{Assignment}.
-}
-@end iftex
-@c END TEXI2ROFF-KILL
+In certain types of programs, particularly on embedded systems when
+using overlays, 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.
-@node Evaluation
-@subsection Evaluation
+The @code{NOCROSSREFS} command takes a list of output section names. If
+@code{ld} detects any cross references between the sections, it reports
+an error and returns a non-zero exit status. Note that the
+@code{NOCROSSREFS} command uses output section names, not input section
+names.
-@cindex lazy evaluation
-@cindex expression evaluation order
-The linker uses ``lazy evaluation'' for expressions; it only calculates
-an expression when absolutely necessary. The linker needs the value of
-the start address, and the lengths of memory regions, in order to do any
-linking at all; these values are computed as soon as possible when the
-linker reads in the command file. However, other values (such as symbol
-values) are not known or needed until after storage allocation. Such
-values are evaluated later, when other information (such as the sizes of
-output sections) is available for use in the symbol assignment
-expression.
-
-@node Assignment
-@subsection Assignment: Defining Symbols
+@ifclear SingleFormat
+@item OUTPUT_ARCH(@var{bfdarch})
+@kindex OUTPUT_ARCH(@var{bfdarch})
+@cindex machine architecture
+@cindex architecture
+Specify a particular output machine architecture. The argument is one
+of the names used by the BFD library (@pxref{BFD}). You can see the
+architecture of an object file by using the @code{objdump} program with
+the @samp{-f} option.
+@end ifclear
+@end table
+
+@node Assignments
+@section Assigning Values to Symbols
@cindex assignment in scripts
@cindex symbol definition, scripts
@cindex variables, defining
-You may create global symbols, and assign values (addresses) to global
-symbols, using any of the C assignment operators:
+You may assign a value to a symbol in a linker script. This will define
+the symbol as a global symbol.
+
+@menu
+* Simple Assignments:: Simple Assignments
+* PROVIDE:: PROVIDE
+@end menu
+
+@node Simple Assignments
+@subsection Simple Assignments
+
+You may assign to a symbol using any of the C assignment operators:
@table @code
-@item @var{symbol} = @var{expression} ;
-@itemx @var{symbol} &= @var{expression} ;
+@item @var{symbol} = @var{expression} ;
@itemx @var{symbol} += @var{expression} ;
@itemx @var{symbol} -= @var{expression} ;
@itemx @var{symbol} *= @var{expression} ;
@itemx @var{symbol} /= @var{expression} ;
+@itemx @var{symbol} <<= @var{expression} ;
+@itemx @var{symbol} >>= @var{expression} ;
+@itemx @var{symbol} &= @var{expression} ;
+@itemx @var{symbol} |= @var{expression} ;
@end table
-Two things distinguish assignment from other operators in @code{ld}
-expressions.
-@itemize @bullet
-@item
-Assignment may only be used at the root of an expression;
-@samp{a=b+3;} is allowed, but @samp{a+b=3;} is an error.
-
-@kindex ;
-@cindex semicolon
-@item
-You must place a trailing semicolon (``@key{;}'') at the end of an
-assignment statement.
-@end itemize
+The first case will define @var{symbol} to the value of
+@var{expression}. In the other cases, @var{symbol} must already be
+defined, and the value will be adjusted accordingly.
-Assignment statements may appear:
-@itemize @bullet
-@item
-as commands in their own right in an @code{ld} script; or
-@item
-as independent statements within a @code{SECTIONS} command; or
-@item
-as part of the contents of a section definition in a
-@code{SECTIONS} command.
-@end itemize
+The special symbol name @samp{.} indicates the location counter. You
+may only use this within a @code{SECTIONS} command.
-The first two cases are equivalent in effect---both define a symbol with
-an absolute address. The last case defines a symbol whose address is
-relative to a particular section (@pxref{SECTIONS}).
+The semicolon after @var{expression} is required.
-@cindex absolute and relocatable symbols
-@cindex relocatable and absolute symbols
-@cindex symbols, relocatable and absolute
-When a linker expression is evaluated and assigned to a variable, it is
-given either an absolute or a relocatable type. An absolute expression
-type is one in which the symbol contains the value that it will have in
-the output file; a relocatable expression type is one in which the
-value is expressed as a fixed offset from the base of a section.
-
-The type of the expression is controlled by its position in the script
-file. A symbol assigned within a section definition is created relative
-to the base of the section; a symbol assigned in any other place is
-created as an absolute symbol. Since a symbol created within a
-section definition is relative to the base of the section, it
-will remain relocatable if relocatable output is requested. A symbol
-may be created with an absolute value even when assigned to within a
-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
-SECTIONS@{ @dots{}
- .data :
- @{
- *(.data)
- _edata = ABSOLUTE(.) ;
- @}
-@dots{} @}
-@end example
+Expressions are defined below; see @ref{Expressions}.
-The linker tries to put off the evaluation of an assignment until all
-the terms in the source expression are known (@pxref{Evaluation}). For
-instance, the sizes of sections cannot be known until after allocation,
-so assignments dependent upon these are not performed until after
-allocation. Some expressions, such as those depending upon the location
-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
-SECTIONS @{ @dots{}
- text 9+this_isnt_constant :
- @{ @dots{}
+You may write symbol assignments as commands in their own right, or as
+statements within a @code{SECTIONS} command, or as part of an output
+section description in a @code{SECTIONS} command.
+
+The section of the symbol will be set from the section of the
+expression; for more information, see @ref{Expression Section}.
+
+Here is an example showing the three different places that symbol
+assignments may be used:
+
+@smallexample
+floating_point = 0;
+SECTIONS
+@{
+ .text :
+ @{
+ *(.text)
+ _etext = .;
@}
-@dots{} @}
-@end example
-@kindex Non constant expression
+ _bdata = (. + 3) & ~ 4;
+ .data : @{ *(.data) @}
+@}
+@end smallexample
@noindent
-will cause the error message ``@code{Non constant expression for initial
-address}''.
-
-@node Arithmetic Functions
-@subsection Arithmetic Functions
-@cindex functions in expression language
-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
-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
-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
-SECTIONS@{ @dots{}
- .output1 :
- @{
- start_of_output_1 = ABSOLUTE(.);
- @dots{}
- @}
- .output :
+In this example, the symbol @samp{floating_point} will be defined as
+zero. The symbol @samp{_etext} will be defined as the address following
+the last @samp{.text} input section. The symbol @samp{_bdata} will be
+defined as the address following the @samp{.text} output section aligned
+upward to a 4 byte boundary.
+
+@node PROVIDE
+@subsection PROVIDE
+@cindex PROVIDE
+In some cases, it is desirable for a linker script to define a symbol
+only if it is referenced and is not defined by any object included in
+the link. For example, traditional linkers defined the symbol
+@samp{etext}. However, ANSI C requires that the user be able to use
+@samp{etext} as a function name without encountering an error. The
+@code{PROVIDE} keyword may be used to define a symbol, such as
+@samp{etext}, only if it is referenced but not defined. The syntax is
+@code{PROVIDE(@var{symbol} = @var{expression})}.
+
+Here is an example of using @code{PROVIDE} to define @samp{etext}:
+@smallexample
+SECTIONS
+@{
+ .text :
@{
- symbol_1 = ADDR(.output1);
- symbol_2 = start_of_output_1;
+ *(.text)
+ _etext = .;
+ PROVIDE(etext = .);
@}
-@dots{} @}
-@end example
-
-@item ALIGN(@var{exp})
-@kindex ALIGN(@var{exp})
-@cindex rounding up location counter
-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
-(. + @var{exp} - 1) & ~(@var{exp} - 1)
-@end example
-
-@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
-SECTIONS@{ @dots{}
- .data ALIGN(0x2000): @{
- *(.data)
- variable = ALIGN(0x8000);
- @}
-@dots{} @}
-@end example
-@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
-section definition (@pxref{Section Options}). The second use simply
-defines the value of a variable.
+@}
+@end smallexample
-The built-in @code{NEXT} is closely related to @code{ALIGN}.
+In this example, if the program defines @samp{_etext} (with a leading
+underscore), the linker will give a multiple definition error. If, on
+the other hand, the program defines @samp{etext} (with no leading
+underscore), the linker will silently use the definition in the program.
+If the program references @samp{etext} but does not define it, the
+linker will use the definition in the linker script.
-@item DEFINED(@var{symbol})
-@kindex DEFINED(@var{symbol})
-@cindex symbol defaults
-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
-to set a global symbol @code{begin} to the first location in the
-@code{.text} section---but if a symbol called @code{begin} already
-existed, its value is preserved:
+@node SECTIONS
+@section SECTIONS command
+@kindex SECTIONS
+The @code{SECTIONS} command tells the linker how to map input sections
+into output sections, and how to place the output sections in memory.
+The format of the @code{SECTIONS} command is:
@smallexample
-SECTIONS@{ @dots{}
- .text : @{
- begin = DEFINED(begin) ? begin : . ;
- @dots{}
- @}
-@dots{} @}
+SECTIONS
+@{
+ @var{sections-command}
+ @var{sections-command}
+ @dots{}
+@}
@end smallexample
-@item NEXT(@var{exp})
-@kindex NEXT(@var{exp})
-@cindex unallocated address, next
-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.
+Each @var{sections-command} may of be one of the following:
-@item SIZEOF(@var{section})
-@kindex SIZEOF(@var{section})
-@cindex section size
-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
-SECTIONS@{ @dots{}
- .output @{
- .start = . ;
- @dots{}
- .end = . ;
- @}
- symbol_1 = .end - .start ;
- symbol_2 = SIZEOF(.output);
-@dots{} @}
+@itemize @bullet
+@item
+an @code{ENTRY} command (@pxref{Entry Point,,Entry command})
+@item
+a symbol assignment (@pxref{Assignments})
+@item
+an output section description
+@item
+an overlay description
+@end itemize
-@end example
+The @code{ENTRY} command and symbol assignments are permitted inside the
+@code{SECTIONS} command for convenience in using the location counter in
+those commands. This can also make the linker script easier to
+understand because you can use those commands at meaningful points in
+the layout of the output file.
-@item SIZEOF_HEADERS
-@kindex SIZEOF_HEADERS
-@cindex header size
-@itemx sizeof_headers
-@kindex 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.
+Output section descriptions and overlay descriptions are described
+below.
-@end table
+If you do not use a @code{SECTIONS} command in your linker script, the
+linker will place each input section into an identically named output
+section in the order that the sections are first encountered in the
+input files. If all input sections are present in the first file, for
+example, the order of sections in the output file will match the order
+in the first input file. The first section will be at address zero.
-@node MEMORY
-@section Memory Layout
-@kindex MEMORY
-@cindex regions of memory
-@cindex discontinuous memory
-@cindex allocating memory
-The linker's default configuration permits allocation of all available memory.
-You can override this configuration by using the @code{MEMORY} command. The
-@code{MEMORY} command describes the location and size of blocks of
-memory in the target. By using it carefully, you can describe which
-memory regions may be used by the linker, and which memory regions it
-must avoid. The linker does not shuffle sections to fit into the
-available regions, but does move the requested sections into the correct
-regions and issue errors when the regions become too full.
-
-A command file may contain at most one use of the @code{MEMORY}
-command; however, you can define as many blocks of memory within it as
-you wish. The syntax is:
-
-@example
-MEMORY
+@menu
+* Output Section Description:: Output section description
+* Output Section Name:: Output section name
+* Output Section Address:: Output section address
+* Input Section:: Input section description
+* Output Section Data:: Output section data
+* Output Section Keywords:: Output section keywords
+* Output Section Discarding:: Output section discarding
+* Output Section Attributes:: Output section attributes
+* Overlay Description:: Overlay description
+@end menu
+
+@node Output Section Description
+@subsection Output section description
+The full description of an output section looks like this:
+@smallexample
+@group
+@var{section} [@var{address}] [(@var{type})] : [AT(@var{lma})]
@{
- @var{name} (@var{attr}) : ORIGIN = @var{origin}, LENGTH = @var{len}
+ @var{output-section-command}
+ @var{output-section-command}
@dots{}
- @}
-@end example
-@table @code
-@cindex naming memory regions
-@item @var{name}
-is a name used internally by the linker to refer to the region. Any
-symbol name may be used. The region names are stored in a separate
-name space, and will not conflict with symbols, file names or section
-names. Use distinct names to specify multiple regions.
+ @} [>@var{region}] [AT>@var{lma_region}] [:@var{phdr} :@var{phdr} @dots{}] [=@var{fillexp}]
+@end group
+@end smallexample
-@cindex memory region attributes
-@item (@var{attr})
-is an optional list of attributes, permitted for compatibility with the
-AT&T linker but not used by @code{ld} beyond checking that the
-attribute list is valid. Valid attribute lists must be made up of the
-characters ``@code{LIRWX}''. If you omit the attribute list, you may
-omit the parentheses around it as well.
+Most output sections do not use most of the optional section attributes.
-@kindex ORIGIN =
-@kindex o =
-@kindex org =
-@item @var{origin}
-is the start address of the region in physical memory. It is
-an expression that must evaluate to a constant before
-memory allocation is performed. The keyword @code{ORIGIN} may be
-abbreviated to @code{org} or @code{o} (but not, for example, @samp{ORG}).
+The whitespace around @var{section} is required, so that the section
+name is unambiguous. The colon and the curly braces are also required.
+The line breaks and other white space are optional.
-@kindex LENGTH =
-@kindex len =
-@kindex l =
-@item @var{len}
-is the size in bytes of the region (an expression).
-The keyword @code{LENGTH} may be abbreviated to @code{len} or @code{l}.
-@end table
+Each @var{output-section-command} may be one of the following:
-For example, to specify that memory has two regions available for
-allocation---one starting at 0 for 256 kilobytes, and the other
-starting at @code{0x40000000} for four megabytes:
+@itemize @bullet
+@item
+a symbol assignment (@pxref{Assignments})
+@item
+an input section description (@pxref{Input Section})
+@item
+data values to include directly (@pxref{Output Section Data})
+@item
+a special output section keyword (@pxref{Output Section Keywords})
+@end itemize
-@example
-MEMORY
- @{
- rom : ORIGIN = 0, LENGTH = 256K
- ram : org = 0x40000000, l = 4M
- @}
-@end example
+@node Output Section Name
+@subsection Output section name
+@cindex name, section
+@cindex section name
+The name of the output section is @var{section}. @var{section} must
+meet the constraints of your output format. In formats which only
+support a limited number of sections, such as @code{a.out}, the name
+must be one of the names supported by the format (@code{a.out}, for
+example, allows only @samp{.text}, @samp{.data} or @samp{.bss}). If the
+output format supports any number of sections, but with numbers and not
+names (as is the case for Oasys), the name should be supplied as a
+quoted numeric string. A section name may consist of any sequence of
+characters, but a name which contains any unusual characters such as
+commas must be quoted.
+
+The output section name @samp{/DISCARD/} is special; @ref{Output Section
+Discarding}.
+
+@node Output Section Address
+@subsection Output section address
+@cindex address, section
+@cindex section address
+The @var{address} is an expression for the VMA (the virtual memory
+address) of the output section. If you do not provide @var{address},
+the linker will set it based on @var{region} if present, or otherwise
+based on the current value of the location counter.
+
+If you provide @var{address}, the address of the output section will be
+set to precisely that. If you provide neither @var{address} nor
+@var{region}, then the address of the output section will be set to the
+current value of the location counter aligned to the alignment
+requirements of the output section. The alignment requirement of the
+output section is the strictest alignment of any input section contained
+within the output section.
+
+For example,
+@smallexample
+.text . : @{ *(.text) @}
+@end smallexample
+@noindent
+and
+@smallexample
+.text : @{ *(.text) @}
+@end smallexample
+@noindent
+are subtly different. The first will set the address of the
+@samp{.text} output section to the current value of the location
+counter. The second will set it to the current value of the location
+counter aligned to the strictest alignment of a @samp{.text} input
+section.
+
+The @var{address} may be an arbitrary expression; @ref{Expressions}.
+For example, if you want to align the section on a 0x10 byte boundary,
+so that the lowest four bits of the section address are zero, you could
+do something like this:
+@smallexample
+.text ALIGN(0x10) : @{ *(.text) @}
+@end smallexample
+@noindent
+This works because @code{ALIGN} returns the current location counter
+aligned upward to the specified value.
-Once you have defined a region of memory named @var{mem}, you can direct
-specific output sections there by using a command ending in
-@samp{>@var{mem}} within the @code{SECTIONS} command (@pxref{Section
-Options}). If the combined output sections directed to a region are too
-big for the region, the linker will issue an error message.
+Specifying @var{address} for a section will change the value of the
+location counter.
-@node SECTIONS
-@section Specifying Output Sections
+@node Input Section
+@subsection Input section description
+@cindex input sections
+@cindex mapping input sections to output sections
+The most common output section command is an input section description.
-@kindex SECTIONS
-The @code{SECTIONS} command controls exactly where input sections are
-placed into output sections, their order in the output file, and to
-which output sections they are allocated.
+The input section description is the most basic linker script operation.
+You use output sections to tell the linker how to lay out your program
+in memory. You use input section descriptions to tell the linker how to
+map the input files into your memory layout.
-You may use at most one @code{SECTIONS} command in a script file,
-but you can have as many statements within it as you wish. Statements
-within the @code{SECTIONS} command can do one of three things:
+@menu
+* Input Section Basics:: Input section basics
+* Input Section Wildcards:: Input section wildcard patterns
+* Input Section Common:: Input section for common symbols
+* Input Section Keep:: Input section and garbage collection
+* Input Section Example:: Input section example
+@end menu
-@itemize @bullet
-@item
-define the entry point;
+@node Input Section Basics
+@subsubsection Input section basics
+@cindex input section basics
+An input section description consists of a file name optionally followed
+by a list of section names in parentheses.
-@item
-assign a value to a symbol;
+The file name and the section name may be wildcard patterns, which we
+describe further below (@pxref{Input Section Wildcards}).
-@item
-describe the placement of a named output section, and which input
-sections go into it.
-@end itemize
+The most common input section description is to include all input
+sections with a particular name in the output section. For example, to
+include all input @samp{.text} sections, you would write:
+@smallexample
+*(.text)
+@end smallexample
+@noindent
+Here the @samp{*} is a wildcard which matches any file name. To exclude a list
+of files from matching the file name wildcard, EXCLUDE_FILE may be used to
+match all files except the ones specified in the EXCLUDE_FILE list. For
+example:
+@smallexample
+(*(EXCLUDE_FILE (*crtend.o *otherfile.o) .ctors))
+@end smallexample
+will cause all .ctors sections from all files except @file{crtend.o} and
+@file{otherfile.o} to be included.
-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
-your convenience in reading the script, so that symbols and the entry
-point can be defined at meaningful points in your output-file layout.
+There are two ways to include more than one section:
+@smallexample
+*(.text .rdata)
+*(.text) *(.rdata)
+@end smallexample
+@noindent
+The difference between these is the order in which the @samp{.text} and
+@samp{.rdata} input sections will appear in the output section. In the
+first example, they will be intermingled. In the second example, all
+@samp{.text} input sections will appear first, followed by all
+@samp{.rdata} input sections.
+
+You can specify a file name to include sections from a particular file.
+You would do this if one or more of your files contain special data that
+needs to be at a particular location in memory. For example:
+@smallexample
+data.o(.data)
+@end smallexample
-If you do not use a @code{SECTIONS} command, the linker places each input
-section into an identically named output section in the order that the
-sections are first encountered in the input files. If all input sections
-are present in the first file, for example, the order of sections in the
-output file will match the order in the first input file.
+If you use a file name without a list of sections, then all sections in
+the input file will be included in the output section. This is not
+commonly done, but it may by useful on occasion. For example:
+@smallexample
+data.o
+@end smallexample
-@menu
-* Section Definition:: Section Definitions
-* Section Placement:: Section Placement
-* Section Data Expressions:: Section Data Expressions
-* Section Options:: Optional Section Attributes
-@end menu
+When you use a file name which does not contain any wild card
+characters, the linker will first see if you also specified the file
+name on the linker command line or in an @code{INPUT} command. If you
+did not, the linker will attempt to open the file as an input file, as
+though it appeared on the command line. Note that this differs from an
+@code{INPUT} command, because the linker will not search for the file in
+the archive search path.
-@node Section Definition
-@subsection Section Definitions
-@cindex section definition
-The most frequently used statement in the @code{SECTIONS} command is
-the @dfn{section definition}, which specifies the
-properties of an output section: its location, alignment, contents,
-fill pattern, and target memory region. Most of
-these specifications are optional; the simplest form of a section
-definition is
-@example
-SECTIONS @{ @dots{}
- @var{secname} : @{
- @var{contents}
- @}
-@dots{} @}
-@end example
-@cindex naming output sections
-@noindent
-@var{secname} is the name of the output section, and @var{contents} a
-specification of what goes there---for example, a list of input files or
-sections of input files (@pxref{Section Placement}). As you might
-assume, the whitespace shown is optional. You do need the colon
-@samp{:} and the braces @samp{@{@}}, however.
-
-@var{secname} must meet the constraints of your output format. In
-formats which only support a limited number of sections, such as
-@code{a.out}, the name must be one of the names supported by the format
-(@code{a.out}, for example, allows only @code{.text}, @code{.data} or
-@code{.bss}). If the output format supports any number of sections, but
-with numbers and not names (as is the case for Oasys), the name should be
-supplied as a quoted numeric string. A section name may consist of any
-sequence of characters, but any name which does not conform to the standard
-@code{ld} symbol name syntax must be quoted.
-@xref{Symbols, , Symbol Names}.
-
-@node Section Placement
-@subsection Section Placement
-
-@cindex contents of a section
-In a section definition, you can specify the contents of an output
-section by listing particular input files, by listing particular
-input-file sections, or by a combination of the two. You can also place
-arbitrary data in the section, and define symbols relative to the
-beginning of the section.
-
-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.
+@node Input Section Wildcards
+@subsubsection Input section wildcard patterns
+@cindex input section wildcards
+@cindex wildcard file name patterns
+@cindex file name wildcard patterns
+@cindex section name wildcard patterns
+In an input section description, either the file name or the section
+name or both may be wildcard patterns.
-@table @code
-@kindex @var{filename}
-@cindex input files, section defn
-@cindex files, including in output sections
-@item @var{filename}
-You may simply name a particular input file to be placed in the current
-output section; @emph{all} sections from that file are placed in the
-current section definition. If the file name has already been mentioned
-in another section definition, with an explicit section name list, then
-only those sections which have not yet been allocated are used.
-
-To specify a list of particular files by name:
-@example
-.data : @{ afile.o bfile.o cfile.o @}
-@end example
-@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
-statement.
-
-@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{} )
-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
-of input-file sections inside the parentheses, you may separate the
-section names by either commas or whitespace.
-
-@cindex input sections to output section
-@kindex *(@var{section})
-@item * (@var{section})
-@itemx * (@var{section}, @var{section}, @dots{})
-@itemx * (@var{section} @var{section} @dots{})
-Instead of explicitly naming particular input files in a link control
-script, you can refer to @emph{all} files from the @code{ld} command
-line: use @samp{*} instead of a particular file name before the
-parenthesized input-file section list.
-
-If you have already explicitly included some files by name, @samp{*}
-refers to all @emph{remaining} files---those whose places in the output
-file have not yet been defined.
-
-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
-SECTIONS @{
- .text :@{
- *("1" "2" "3" "4")
- @}
-
- .data :@{
- *("13" "14")
- @}
-@}
-@end example
+The file name of @samp{*} seen in many examples is a simple wildcard
+pattern for the file name.
-@cindex @code{[@var{section}@dots{}]}, not supported
-@samp{[ @var{section} @dots{} ]} used to be accepted as an alternate way
-to specify named sections from all unallocated input files. Because
-some operating systems (VMS) allow brackets in file names, that notation
-is no longer supported.
-
-@cindex uninitialized data
-@cindex commons in output
-@kindex *( COMMON )
-@item @var{filename}@code{( COMMON )}
-@itemx *( COMMON )
-Specify where in your output file to place uninitialized data
-with this notation. @code{*(COMMON)} by itself refers to all
-uninitialized data from all input files (so far as it is not yet
-allocated); @var{filename}@code{(COMMON)} refers to uninitialized data
-from a particular file. Both are special cases of the general
-mechanisms for specifying where to place input-file sections:
-@code{ld} permits you to refer to uninitialized data as if it
-were in an input-file section named @code{COMMON}, regardless of the
-input file's format.
+The wildcard patterns are like those used by the Unix shell.
+
+@table @samp
+@item *
+matches any number of characters
+@item ?
+matches any single character
+@item [@var{chars}]
+matches 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
+@item \
+quotes the following character
@end table
-For example, the following 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:
+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, whether it contains a
+@samp{/} or not. In a section name, the wildcard characters will match
+a @samp{/} character.
+
+File name wildcard patterns only match files which are explicitly
+specified on the command line or in an @code{INPUT} command. The linker
+does not search directories to expand wildcards.
+
+If a file name matches more than one wildcard pattern, or if a file name
+appears explicitly and is also matched by a wildcard pattern, the linker
+will use the first match in the linker script. For example, this
+sequence of input section descriptions is probably in error, because the
+@file{data.o} rule will not be used:
+@smallexample
+.data : @{ *(.data) @}
+.data1 : @{ data.o(.data) @}
+@end smallexample
-@example
-SECTIONS @{
+@cindex SORT
+Normally, the linker will place files and sections matched by wildcards
+in the order in which they are seen during the link. You can change
+this by using the @code{SORT} keyword, which appears before a wildcard
+pattern in parentheses (e.g., @code{SORT(.text*)}). When the
+@code{SORT} keyword is used, the linker will sort the files or sections
+into ascending order by name before placing them in the output file.
+
+If you ever get confused about where input sections are going, use the
+@samp{-M} linker option to generate a map file. The map file shows
+precisely how input sections are mapped to output sections.
+
+This example shows how wildcard patterns might be used to partition
+files. This linker script directs the linker to place all @samp{.text}
+sections in @samp{.text} and all @samp{.bss} sections in @samp{.bss}.
+The linker will place the @samp{.data} section from all files beginning
+with an upper case character in @samp{.DATA}; for all other files, the
+linker will place the @samp{.data} section in @samp{.data}.
+@smallexample
+@group
+SECTIONS @{
.text : @{ *(.text) @}
- .data : @{ *(.data) @}
- .bss : @{ *(.bss) *(COMMON) @}
-@}
-@end example
+ .DATA : @{ [A-Z]*(.data) @}
+ .data : @{ *(.data) @}
+ .bss : @{ *(.bss) @}
+@}
+@end group
+@end smallexample
+
+@node Input Section Common
+@subsubsection Input section for common symbols
+@cindex common symbol placement
+@cindex uninitialized data placement
+A special notation is needed for common symbols, because in many object
+file formats common symbols do not have a particular input section. The
+linker treats common symbols as though they are in an input section
+named @samp{COMMON}.
+
+You may use file names with the @samp{COMMON} section just as with any
+other input sections. You can use this to place common symbols from a
+particular input file in one section while common symbols from other
+input files are placed in another section.
+
+In most cases, common symbols in input files will be placed in the
+@samp{.bss} section in the output file. For example:
+@smallexample
+.bss @{ *(.bss) *(COMMON) @}
+@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
-starts at location @code{0x10000}. All of section @code{.input1} from
-file @code{foo.o} follows immediately, in the same output section. All
-of section @code{.input2} from @code{foo.o} goes into output section
-@code{outputb}, followed by section @code{.input1} from @code{foo1.o}.
-All of the remaining @code{.input1} and @code{.input2} sections from any
-files are written to output section @code{outputc}.
+@cindex scommon section
+@cindex small common symbols
+Some object file formats have more than one type of common symbol. For
+example, the MIPS ELF object file format distinguishes standard common
+symbols and small common symbols. In this case, the linker will use a
+different special section name for other types of common symbols. In
+the case of MIPS ELF, the linker uses @samp{COMMON} for standard common
+symbols and @samp{.scommon} for small common symbols. This permits you
+to map the different types of common symbols into memory at different
+locations.
+
+@cindex [COMMON]
+You will sometimes see @samp{[COMMON]} in old linker scripts. This
+notation is now considered obsolete. It is equivalent to
+@samp{*(COMMON)}.
+
+@node Input Section Keep
+@subsubsection Input section and garbage collection
+@cindex KEEP
+@cindex garbage collection
+When link-time garbage collection is in use (@samp{--gc-sections}),
+it is often useful to mark sections that should not be eliminated.
+This is accomplished by surrounding an input section's wildcard entry
+with @code{KEEP()}, as in @code{KEEP(*(.init))} or
+@code{KEEP(SORT(*)(.ctors))}.
+
+@node Input Section Example
+@subsubsection Input section example
+The following example is a complete linker script. It tells the linker
+to read all of the sections from file @file{all.o} and place them at the
+start of output section @samp{outputa} which starts at location
+@samp{0x10000}. All of section @samp{.input1} from file @file{foo.o}
+follows immediately, in the same output section. All of section
+@samp{.input2} from @file{foo.o} goes into output section
+@samp{outputb}, followed by section @samp{.input1} from @file{foo1.o}.
+All of the remaining @samp{.input1} and @samp{.input2} sections from any
+files are written to output section @samp{outputc}.
-@example
+@smallexample
+@group
SECTIONS @{
outputa 0x10000 :
@{
*(.input2)
@}
@}
-@end example
+@end group
+@end smallexample
-@node Section Data Expressions
-@subsection Section Data Expressions
+@node Output Section Data
+@subsection Output section data
+@cindex data
+@cindex section data
+@cindex output section data
+@kindex BYTE(@var{expression})
+@kindex SHORT(@var{expression})
+@kindex LONG(@var{expression})
+@kindex QUAD(@var{expression})
+@kindex SQUAD(@var{expression})
+You can include explicit bytes of data in an output section by using
+@code{BYTE}, @code{SHORT}, @code{LONG}, @code{QUAD}, or @code{SQUAD} as
+an output section command. Each keyword is followed by an expression in
+parentheses providing the value to store (@pxref{Expressions}). The
+value of the expression is stored at the current value of the location
+counter.
+
+The @code{BYTE}, @code{SHORT}, @code{LONG}, and @code{QUAD} commands
+store one, two, four, and eight bytes (respectively). After storing the
+bytes, the location counter is incremented by the number of bytes
+stored.
+
+For example, this will store the byte 1 followed by the four byte value
+of the symbol @samp{addr}:
+@smallexample
+BYTE(1)
+LONG(addr)
+@end smallexample
+
+When using a 64 bit host or target, @code{QUAD} and @code{SQUAD} are the
+same; they both store an 8 byte, or 64 bit, value. When both host and
+target are 32 bits, an expression is computed as 32 bits. In this case
+@code{QUAD} stores a 32 bit value zero extended to 64 bits, and
+@code{SQUAD} stores a 32 bit value sign extended to 64 bits.
+
+If the object file format of the output file has an explicit endianness,
+which is the normal case, the value will be stored in that endianness.
+When the object file format does not have an explicit endianness, as is
+true of, for example, S-records, the value will be stored in the
+endianness of the first input object file.
+
+Note - these commands only work inside a section description and not
+between them, so the following will produce an error from the linker:
+@smallexample
+SECTIONS @{@ .text : @{@ *(.text) @}@ LONG(1) .data : @{@ *(.data) @}@ @}@
+@end smallexample
+whereas this will work:
+@smallexample
+SECTIONS @{@ .text : @{@ *(.text) ; LONG(1) @}@ .data : @{@ *(.data) @}@ @}@
+@end smallexample
+
+@kindex FILL(@var{expression})
+@cindex holes, filling
+@cindex unspecified memory
+You may use the @code{FILL} command to set the fill pattern for the
+current section. It is followed by an expression in parentheses. Any
+otherwise unspecified regions of memory within the section (for example,
+gaps left due to the required alignment of input sections) are filled
+with the two least significant bytes of the expression, repeated as
+necessary. A @code{FILL} statement covers memory locations after the
+point at which it occurs in the section definition; by including more
+than one @code{FILL} statement, you can have different fill patterns in
+different parts of an output section.
+
+This example shows how to fill unspecified regions of memory with the
+value @samp{0x9090}:
+@smallexample
+FILL(0x9090)
+@end smallexample
+
+The @code{FILL} command is similar to the @samp{=@var{fillexp}} output
+section attribute (@pxref{Output Section Fill}), but it only affects the
+part of the section following the @code{FILL} command, rather than the
+entire section. If both are used, the @code{FILL} command takes
+precedence.
-@cindex expressions in a section
-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 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
-just described.
+@node Output Section Keywords
+@subsection Output section keywords
+There are a couple of keywords which can appear as output section
+commands.
@table @code
+@kindex CREATE_OBJECT_SYMBOLS
@cindex input filename symbols
@cindex filename symbols
-@kindex CREATE_OBJECT_SYMBOLS
@item CREATE_OBJECT_SYMBOLS
-Create a symbol for each input file
-in the current section, set to the address of the first byte of
-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
-SECTIONS @{
- .text 0x2020 :
- @{
- CREATE_OBJECT_SYMBOLS
- *(.text)
- _etext = ALIGN(0x2000);
- @}
- @dots{}
-@}
-@end example
+The command tells the linker to create a symbol for each input file.
+The name of each symbol will be the name of the corresponding input
+file. The section of each symbol will be the output section in which
+the @code{CREATE_OBJECT_SYMBOLS} command appears.
-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
-/* a.c */
+This is conventional for the a.out object file format. It is not
+normally used for any other object file format.
-afunction() @{ @}
-int adata=1;
-int abss;
-@end example
+@kindex CONSTRUCTORS
+@cindex C++ constructors, arranging in link
+@cindex constructors, arranging in link
+@item CONSTRUCTORS
+When linking using the 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 ECOFF and 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 to place constructor information in the output section where the
+@code{CONSTRUCTORS} command appears. 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++ normally 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++ normally 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
+arbitrary section names, @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
+
+If you are using the @sc{gnu} C++ support for initialization priority,
+which provides some control over the order in which global constructors
+are run, you must sort the constructors at link time to ensure that they
+are executed in the correct order. When using the @code{CONSTRUCTORS}
+command, use @samp{SORT(CONSTRUCTORS)} instead. When using the
+@code{.ctors} and @code{.dtors} sections, use @samp{*(SORT(.ctors))} and
+@samp{*(SORT(.dtors))} instead of just @samp{*(.ctors)} and
+@samp{*(.dtors)}.
+
+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.
+
+@end table
+@node Output Section Discarding
+@subsection Output section discarding
+@cindex discarding sections
+@cindex sections, discarding
+@cindex removing sections
+The linker will not create output section which do not have any
+contents. This is for convenience when referring to input sections that
+may or may not be present in any of the input files. For example:
+@smallexample
+.foo @{ *(.foo) @}
+@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
-00000000 A __DYNAMIC
-00004020 B _abss
-00004000 D _adata
-00002020 T _afunction
-00004024 B _bbss
-00004008 D _bdata
-00002038 T _bfunction
-00004028 B _cbss
-00004010 D _cdata
-00002050 T _cfunction
-0000402c B _dbss
-00004018 D _ddata
-00002068 T _dfunction
-00004020 D _edata
-00004030 B _end
-00004000 T _etext
-00002020 t a.o
-00002038 t b.o
-00002050 t c.o
-00002068 t d.o
-@end example
+will only create a @samp{.foo} section in the output file if there is a
+@samp{.foo} section in at least one input file.
+
+If you use anything other than an input section description as an output
+section command, such as a symbol assignment, then the output section
+will always be created, even if there are no matching input sections.
+
+@cindex /DISCARD/
+The special output section name @samp{/DISCARD/} may be used to discard
+input sections. Any input sections which are assigned to an output
+section named @samp{/DISCARD/} are not included in the output file.
+
+@node Output Section Attributes
+@subsection Output section attributes
+@cindex output section attributes
+We showed above that the full description of an output section looked
+like this:
+@smallexample
+@group
+@var{section} [@var{address}] [(@var{type})] : [AT(@var{lma})]
+ @{
+ @var{output-section-command}
+ @var{output-section-command}
+ @dots{}
+ @} [>@var{region}] [AT>@var{lma_region}] [:@var{phdr} :@var{phdr} @dots{}] [=@var{fillexp}]
+@end group
+@end smallexample
+We've already described @var{section}, @var{address}, and
+@var{output-section-command}. In this section we will describe the
+remaining section attributes.
-@kindex @var{symbol} = @var{expression} ;
-@kindex @var{symbol} @var{f}= @var{expression} ;
-@item @var{symbol} = @var{expression} ;
-@itemx @var{symbol} @var{f}= @var{expression} ;
-@var{symbol} is any symbol name (@pxref{Symbols}). ``@var{f}=''
-refers to any of the operators @code{&= += -= *= /=} which combine
-arithmetic and assignment.
+@menu
+* Output Section Type:: Output section type
+* Output Section LMA:: Output section LMA
+* Output Section Region:: Output section region
+* Output Section Phdr:: Output section phdr
+* Output Section Fill:: Output section fill
+@end menu
-@cindex assignment, in section defn
-When you assign a value to a symbol within a particular section
-definition, the value is relative to the beginning of the section
-(@pxref{Assignment}). If you write
+@node Output Section Type
+@subsubsection Output section type
+Each output section may have a type. The type is a keyword in
+parentheses. The following types are defined:
-@example
+@table @code
+@item NOLOAD
+The section should be marked as not loadable, so that it will not be
+loaded into memory when the program is run.
+@item DSECT
+@itemx COPY
+@itemx INFO
+@itemx OVERLAY
+These type names are supported for backward compatibility, and are
+rarely used. They all have the same effect: the section should be
+marked as not allocatable, so that no memory is allocated for the
+section when the program is run.
+@end table
+
+@kindex NOLOAD
+@cindex prevent unnecessary loading
+@cindex loading, preventing
+The linker normally sets the attributes of an output section based on
+the input sections which map into it. You can override this by using
+the section type. For example, in the script sample below, the
+@samp{ROM} section is addressed at memory location @samp{0} and does not
+need to be loaded when the program is run. The contents of the
+@samp{ROM} section will appear in the linker output file as usual.
+@smallexample
+@group
SECTIONS @{
- abs = 14 ;
- @dots{}
- .data : @{ @dots{} rel = 14 ; @dots{} @}
- abs2 = 14 + ADDR(.data);
+ ROM 0 (NOLOAD) : @{ @dots{} @}
@dots{}
@}
-@end example
+@end group
+@end smallexample
-@c FIXME: Try above example!
-@noindent
-@code{abs} and @code{rel} do not have the same value; @code{rel} has the
-same value as @code{abs2}.
+@node Output Section LMA
+@subsubsection Output section LMA
+@kindex AT>@var{lma_region}
+@kindex AT(@var{lma})
+@cindex load address
+@cindex section load address
+Every section has a virtual address (VMA) and a load address (LMA); see
+@ref{Basic Script Concepts}. The address expression which may appear in
+an output section description sets the VMA (@pxref{Output Section
+Address}).
+
+The linker will normally set the LMA equal to the VMA. You can change
+that by using the @code{AT} keyword. The expression @var{lma} that
+follows the @code{AT} keyword specifies the load address of the
+section. Alternatively, with @samp{AT>@var{lma_region}} expression,
+you may specify a memory region for the section's load address. @xref{MEMORY}.
+
+@cindex ROM initialized data
+@cindex initialized data in ROM
+This feature is designed to make it easy to build a ROM image. For
+example, the following linker script creates three output sections: one
+called @samp{.text}, which starts at @code{0x1000}, one called
+@samp{.mdata}, which is loaded at the end of the @samp{.text} section
+even though its VMA is @code{0x2000}, and one called @samp{.bss} to hold
+uninitialized data at address @code{0x3000}. The symbol @code{_data} is
+defined with the value @code{0x2000}, which shows that the location
+counter holds the VMA value, not the LMA value.
-@kindex BYTE(@var{expression})
-@kindex SHORT(@var{expression})
-@kindex LONG(@var{expression})
-@kindex QUAD(@var{expression})
-@cindex direct output
-@item BYTE(@var{expression})
-@itemx SHORT(@var{expression})
-@itemx LONG(@var{expression})
-@itemx QUAD(@var{expression})
-By including one of these four statements in a section definition, you
-can explicitly place one, two, four, or eight bytes (respectively) at
-the current address of that section. @code{QUAD} is only supported when
-using a 64 bit host or target.
+@smallexample
+@group
+SECTIONS
+ @{
+ .text 0x1000 : @{ *(.text) _etext = . ; @}
+ .mdata 0x2000 :
+ AT ( ADDR (.text) + SIZEOF (.text) )
+ @{ _data = . ; *(.data); _edata = . ; @}
+ .bss 0x3000 :
+ @{ _bstart = . ; *(.bss) *(COMMON) ; _bend = . ;@}
+@}
+@end group
+@end smallexample
-@ifclear SingleFormat
-Multiple-byte quantities are represented in whatever byte order is
-appropriate for the output file format (@pxref{BFD}).
-@end ifclear
+The run-time initialization code for use with a program generated with
+this linker script would include something like the following, to copy
+the initialized data from the ROM image to its runtime address. Notice
+how this code takes advantage of the symbols defined by the linker
+script.
-@item FILL(@var{expression})
-@kindex FILL(@var{expression})
-@cindex holes, filling
-@cindex unspecified memory
-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{.})
-are filled with the two least significant bytes from the
-@var{expression} argument. A @code{FILL} statement covers memory
-locations @emph{after} the point it occurs in the section definition; by
-including more than one @code{FILL} statement, you can have different
-fill patterns in different parts of an output section.
+@smallexample
+@group
+extern char _etext, _data, _edata, _bstart, _bend;
+char *src = &_etext;
+char *dst = &_data;
+
+/* ROM has data at end of text; copy it. */
+while (dst < &_edata) @{
+ *dst++ = *src++;
+@}
+
+/* Zero bss */
+for (dst = &_bstart; dst< &_bend; dst++)
+ *dst = 0;
+@end group
+@end smallexample
+
+@node Output Section Region
+@subsubsection Output section region
+@kindex >@var{region}
+@cindex section, assigning to memory region
+@cindex memory regions and sections
+You can assign a section to a previously defined region of memory by
+using @samp{>@var{region}}. @xref{MEMORY}.
+
+Here is a simple example:
+@smallexample
+@group
+MEMORY @{ rom : ORIGIN = 0x1000, LENGTH = 0x1000 @}
+SECTIONS @{ ROM : @{ *(.text) @} >rom @}
+@end group
+@end smallexample
+
+@node Output Section Phdr
+@subsubsection Output section phdr
+@kindex :@var{phdr}
+@cindex section, assigning to program header
+@cindex program headers and sections
+You can assign a section to a previously defined program segment by
+using @samp{:@var{phdr}}. @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. You can use @code{:NONE} to tell the
+linker to not put the section in any segment at all.
+
+Here is a simple example:
+@smallexample
+@group
+PHDRS @{ text PT_LOAD ; @}
+SECTIONS @{ .text : @{ *(.text) @} :text @}
+@end group
+@end smallexample
+
+@node Output Section Fill
+@subsubsection Output section fill
+@kindex =@var{fillexp}
+@cindex section fill pattern
+@cindex fill pattern, entire section
+You can set the fill pattern for an entire section by using
+@samp{=@var{fillexp}}. @var{fillexp} is an expression
+(@pxref{Expressions}). Any otherwise unspecified regions of memory
+within the output section (for example, gaps left due to the required
+alignment of input sections) will be filled with the two least
+significant bytes of the value, repeated as necessary.
+
+You can also change the fill value with a @code{FILL} command in the
+output section commands; see @ref{Output Section Data}.
+
+Here is a simple example:
+@smallexample
+@group
+SECTIONS @{ .text : @{ *(.text) @} =0x9090 @}
+@end group
+@end smallexample
+
+@node Overlay Description
+@subsection Overlay description
+@kindex OVERLAY
+@cindex overlays
+An overlay description 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.
+
+Overlays are described using the @code{OVERLAY} command. The
+@code{OVERLAY} command is used within a @code{SECTIONS} command, like an
+output section description. The full syntax of the @code{OVERLAY}
+command is as follows:
+@smallexample
+@group
+OVERLAY [@var{start}] : [NOCROSSREFS] [AT ( @var{ldaddr} )]
+ @{
+ @var{secname1}
+ @{
+ @var{output-section-command}
+ @var{output-section-command}
+ @dots{}
+ @} [:@var{phdr}@dots{}] [=@var{fill}]
+ @var{secname2}
+ @{
+ @var{output-section-command}
+ @var{output-section-command}
+ @dots{}
+ @} [:@var{phdr}@dots{}] [=@var{fill}]
+ @dots{}
+ @} [>@var{region}] [:@var{phdr}@dots{}] [=@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 the current value of the location counter).
+
+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{Miscellaneous 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 the location counter 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
+@noindent
+This will define both @samp{.text0} and @samp{.text1} to start at
+address 0x1000. @samp{.text0} will be loaded at address 0x4000, and
+@samp{.text1} will be loaded immediately after @samp{.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 MEMORY
+@section MEMORY command
+@kindex MEMORY
+@cindex memory regions
+@cindex regions of memory
+@cindex allocating memory
+@cindex discontinuous memory
+The linker's default configuration permits allocation of all available
+memory. You can override this by using the @code{MEMORY} command.
+
+The @code{MEMORY} command describes the location and size of blocks of
+memory in the target. You can use it to describe which memory regions
+may be used by the linker, and which memory regions it must avoid. You
+can then assign sections to particular memory regions. The linker will
+set section addresses based on the memory regions, and will warn about
+regions that become too full. The linker will not shuffle sections
+around to fit into the available regions.
+
+A linker script may contain at most one use of the @code{MEMORY}
+command. However, you can define as many blocks of memory within it as
+you wish. The syntax is:
+@smallexample
+@group
+MEMORY
+ @{
+ @var{name} [(@var{attr})] : ORIGIN = @var{origin}, LENGTH = @var{len}
+ @dots{}
+ @}
+@end group
+@end smallexample
+
+The @var{name} is a name used in the linker script to refer to the
+region. The region name has no meaning outside of the linker script.
+Region names are stored in a separate name space, and will not conflict
+with symbol names, file names, or section names. Each memory region
+must have a distinct name.
+
+@cindex memory region attributes
+The @var{attr} string is an optional list of attributes that specify
+whether to use a particular memory region for an input section which is
+not explicitly mapped in the linker script. As described in
+@ref{SECTIONS}, if you do not specify an output section for some input
+section, the linker will create an output section with the same name as
+the input section. If you define region attributes, the linker will use
+them to select the memory region for the output section that it creates.
+
+The @var{attr} string must consist only of the following characters:
+@table @samp
+@item R
+Read-only section
+@item W
+Read/write section
+@item X
+Executable section
+@item A
+Allocatable section
+@item I
+Initialized section
+@item L
+Same as @samp{I}
+@item !
+Invert the sense of any of the preceding attributes
@end table
-@node Section Options
-@subsection Optional Section Attributes
-@cindex section defn, full syntax
-Here is the full syntax of a section definition, including all the
-optional portions:
+If a unmapped section matches any of the listed attributes other than
+@samp{!}, it will be placed in the memory region. The @samp{!}
+attribute reverses this test, so that an unmapped section will be placed
+in the memory region only if it does not match any of the listed
+attributes.
+
+@kindex ORIGIN =
+@kindex o =
+@kindex org =
+The @var{origin} is an expression for the start address of the memory
+region. The expression must evaluate to a constant before memory
+allocation is performed, which means that you may not use any section
+relative symbols. The keyword @code{ORIGIN} may be abbreviated to
+@code{org} or @code{o} (but not, for example, @code{ORG}).
+
+@kindex LENGTH =
+@kindex len =
+@kindex l =
+The @var{len} is an expression for the size in bytes of the memory
+region. As with the @var{origin} expression, the expression must
+evaluate to a constant before memory allocation is performed. The
+keyword @code{LENGTH} may be abbreviated to @code{len} or @code{l}.
+
+In the following example, we specify that there are two memory regions
+available for allocation: one starting at @samp{0} for 256 kilobytes,
+and the other starting at @samp{0x40000000} for four megabytes. The
+linker will place into the @samp{rom} memory region every section which
+is not explicitly mapped into a memory region, and is either read-only
+or executable. The linker will place other sections which are not
+explicitly mapped into a memory region into the @samp{ram} memory
+region.
+
+@smallexample
+@group
+MEMORY
+ @{
+ rom (rx) : ORIGIN = 0, LENGTH = 256K
+ ram (!rx) : org = 0x40000000, l = 4M
+ @}
+@end group
+@end smallexample
+
+Once you define a memory region, you can direct the linker to place
+specific output sections into that memory region by using the
+@samp{>@var{region}} output section attribute. For example, if you have
+a memory region named @samp{mem}, you would use @samp{>mem} in the
+output section definition. @xref{Output Section Region}. If no address
+was specified for the output section, the linker will set the address to
+the next available address within the memory region. If the combined
+output sections directed to a memory region are too large for the
+region, the linker will issue an error message.
+
+@node PHDRS
+@section PHDRS Command
+@kindex PHDRS
+@cindex program headers
+@cindex ELF program headers
+@cindex program segments
+@cindex segments, ELF
+The ELF object file format uses @dfn{program headers}, also knows as
+@dfn{segments}. The program headers describe how the program should be
+loaded into memory. You can print them out by using the @code{objdump}
+program with the @samp{-p} option.
+
+When you run an ELF program on a native ELF system, the system loader
+reads the program headers in order to figure out how to load the
+program. This will only work if the program headers are set correctly.
+This manual does not describe the details of how the system loader
+interprets program headers; for more information, see the ELF ABI.
+
+The linker will create reasonable program headers by default. However,
+in some cases, you may need to specify the program headers more
+precisely. You may use the @code{PHDRS} command for this purpose. When
+the linker sees the @code{PHDRS} command in the linker script, it will
+not create any program headers other than the ones specified.
+
+The linker only pays attention to the @code{PHDRS} command when
+generating an ELF output file. In other cases, the linker will simply
+ignore @code{PHDRS}.
+
+This is the syntax of the @code{PHDRS} command. The words @code{PHDRS},
+@code{FILEHDR}, @code{AT}, and @code{FLAGS} are keywords.
@smallexample
-SECTIONS @{
-@dots{}
-@var{secname} @var{start} BLOCK(@var{align}) (NOLOAD) : AT ( @var{ldadr} )
- @{ @var{contents} @} =@var{fill} >@var{region}
-@dots{}
+@group
+PHDRS
+@{
+ @var{name} @var{type} [ FILEHDR ] [ PHDRS ] [ AT ( @var{address} ) ]
+ [ FLAGS ( @var{flags} ) ] ;
@}
+@end group
@end smallexample
-@var{secname} and @var{contents} are required. @xref{Section
-Definition}, and @pxref{Section Placement} for details on
-@var{contents}. The remaining elements---@var{start},
-@code{BLOCK(@var{align)}}, @code{(NOLOAD)}, @code{AT ( @var{ldadr} )},
-@code{=@var{fill}}, and @code{>@var{region}}---are all optional.
+The @var{name} is used only for reference in the @code{SECTIONS} command
+of the linker script. It is not put into the output file. Program
+header names are stored in a separate name space, and will not conflict
+with symbol names, file names, or section names. Each program header
+must have a distinct name.
+
+Certain program header types describe segments of memory which the
+system loader will load from the file. In the linker script, you
+specify the contents of these segments by placing allocatable output
+sections in the segments. You use the @samp{:@var{phdr}} output section
+attribute to place a section in a particular segment. @xref{Output
+Section Phdr}.
+
+It is normal to put certain sections in more than one segment. This
+merely implies that one segment of memory contains another. You may
+repeat @samp{:@var{phdr}}, using it once for each segment which should
+contain the section.
+
+If you place a section in one or more segments using @samp{:@var{phdr}},
+then the linker will place all subsequent allocatable sections which do
+not specify @samp{:@var{phdr}} in the same segments. This is for
+convenience, since generally a whole set of contiguous sections will be
+placed in a single segment. You can use @code{:NONE} to override the
+default segment and tell the linker to not put the section in any
+segment at all.
+
+@kindex FILEHDR
+@kindex PHDRS
+You may use the @code{FILEHDR} and @code{PHDRS} keywords appear after
+the program header type to further describe the contents of the segment.
+The @code{FILEHDR} keyword means that the segment should include the ELF
+file header. The @code{PHDRS} keyword means that the segment should
+include the ELF program headers themselves.
+
+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
-@table @code
-@cindex start address, section
-@cindex section start
-@cindex section address
-@item @var{start}
-You can force the output section to be loaded at a specified address by
-specifying @var{start} immediately following the section name.
-@var{start} can be represented as any expression. The following
-example generates section @var{output} at location
-@code{0x40000000}:
+You can specify that a segment should be loaded at a particular address
+in memory by using an @code{AT} expression. This is identical to the
+@code{AT} command used as an output section attribute (@pxref{Output
+Section LMA}). The @code{AT} command for a program header overrides the
+output section attribute.
+
+The linker will normally set the segment flags based on the sections
+which comprise the segment. You may use the @code{FLAGS} keyword 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 @code{PHDRS}. This shows a typical set of program
+headers used on a native ELF system.
@example
-SECTIONS @{
+@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{}
- output 0x40000000: @{
- @dots{}
- @}
+ . = . + 0x1000; /* move to a new page in memory */
+ .data : @{ *(.data) @} :data
+ .dynamic : @{ *(.dynamic) @} :data :dynamic
@dots{}
@}
+@end group
@end example
-@kindex BLOCK(@var{align})
-@cindex section alignment
-@cindex aligning sections
-@item BLOCK(@var{align})
-You can include @code{BLOCK()} specification to advance
-the location counter @code{.} prior to the beginning of the section, so
-that the section will begin at the specified alignment. @var{align} is
-an expression.
+@node VERSION
+@section VERSION Command
+@kindex VERSION @{script text@}
+@cindex symbol versions
+@cindex version script
+@cindex versions of symbols
+The linker supports symbol versions when using ELF. Symbol versions are
+only useful when using shared libraries. The dynamic linker can use
+symbol versions to select a specific version of a function when it runs
+a program that may have been linked against an earlier version of the
+shared library.
+
+You can include a version script directly in the main linker script, or
+you can supply the version script as an implicit linker script. You can
+also use the @samp{--version-script} linker option.
+
+The syntax of the @code{VERSION} command is simply
+@smallexample
+VERSION @{ version-script-commands @}
+@end smallexample
-@kindex NOLOAD
-@cindex prevent unnecessary loading
-@cindex loading, preventing
-@item (NOLOAD)
-Use @samp{(NOLOAD)} to prevent a section from being loaded into memory
-each time it is accessed. For example, in the script sample below, the
-@code{ROM} segment is addressed at memory location @samp{0} and does not
-need to be loaded into each object file:
+The format of the version script commands is identical to that used by
+Sun's linker in Solaris 2.5. The version script defines a tree of
+version nodes. You specify the node names and interdependencies in the
+version script. You can specify which symbols are bound to which
+version nodes, and you can reduce a specified set of symbols to local
+scope so that they are not globally visible outside of the shared
+library.
-@example
-SECTIONS @{
- ROM 0 (NOLOAD) : @{ @dots{} @}
- @dots{}
+The easiest way to demonstrate the version script language is with a few
+examples.
+
+@smallexample
+VERS_1.1 @{
+ global:
+ foo1;
+ local:
+ old*;
+ original*;
+ new*;
+@};
+
+VERS_1.2 @{
+ foo2;
+@} VERS_1.1;
+
+VERS_2.0 @{
+ bar1; bar2;
+@} VERS_1.2;
+@end smallexample
+
+This example version script defines three version nodes. The first
+version node defined is @samp{VERS_1.1}; it has no other dependencies.
+The script binds the symbol @samp{foo1} to @samp{VERS_1.1}. It reduces
+a number of symbols to local scope so that they are not visible outside
+of the shared library.
+
+Next, the version script defines node @samp{VERS_1.2}. This node
+depends upon @samp{VERS_1.1}. The script binds the symbol @samp{foo2}
+to the version node @samp{VERS_1.2}.
+
+Finally, the version script defines node @samp{VERS_2.0}. This node
+depends upon @samp{VERS_1.2}. The scripts binds the symbols @samp{bar1}
+and @samp{bar2} are bound to the version node @samp{VERS_2.0}.
+
+When the linker finds a symbol defined in a library which is not
+specifically bound to a version node, it will effectively bind it to an
+unspecified base version of the library. You can bind all otherwise
+unspecified symbols to a given version node by using @samp{global: *}
+somewhere in the version script.
+
+The names of the version nodes have no specific meaning other than what
+they might suggest to the person reading them. The @samp{2.0} version
+could just as well have appeared in between @samp{1.1} and @samp{1.2}.
+However, this would be a confusing way to write a version script.
+
+When you link an application against a shared library that has versioned
+symbols, the application itself knows which version of each symbol it
+requires, and it also knows which version nodes it needs from each
+shared library it is linked against. Thus at runtime, the dynamic
+loader can make a quick check to make sure that the libraries you have
+linked against do in fact supply all of the version nodes that the
+application will need to resolve all of the dynamic symbols. In this
+way it is possible for the dynamic linker to know with certainty that
+all external symbols that it needs will be resolvable without having to
+search for each symbol reference.
+
+The symbol versioning is in effect a much more sophisticated way of
+doing minor version checking that SunOS does. The fundamental problem
+that is being addressed here is that typically references to external
+functions are bound on an as-needed basis, and are not all bound when
+the application starts up. If a shared library is out of date, a
+required interface may be missing; when the application tries to use
+that interface, it may suddenly and unexpectedly fail. With symbol
+versioning, the user will get a warning when they start their program if
+the libraries being used with the application are too old.
+
+There are several GNU extensions to Sun's versioning approach. The
+first of these is the ability to bind a symbol to a version node in the
+source file where the symbol is defined instead of in the versioning
+script. This was done mainly to reduce the burden on the library
+maintainer. You can do this by putting something like:
+@smallexample
+__asm__(".symver original_foo,foo@@VERS_1.1");
+@end smallexample
+@noindent
+in the C source file. This renames the function @samp{original_foo} to
+be an alias for @samp{foo} bound to the version node @samp{VERS_1.1}.
+The @samp{local:} directive can be used to prevent the symbol
+@samp{original_foo} from being exported.
+
+The second GNU extension is to allow multiple versions of the same
+function to appear in a given shared library. In this way you can make
+an incompatible change to an interface without increasing the major
+version number of the shared library, while still allowing applications
+linked against the old interface to continue to function.
+
+To do this, you must use multiple @samp{.symver} directives in the
+source file. Here is an example:
+
+@smallexample
+__asm__(".symver original_foo,foo@@");
+__asm__(".symver old_foo,foo@@VERS_1.1");
+__asm__(".symver old_foo1,foo@@VERS_1.2");
+__asm__(".symver new_foo,foo@@@@VERS_2.0");
+@end smallexample
+
+In this example, @samp{foo@@} represents the symbol @samp{foo} bound to the
+unspecified base version of the symbol. The source file that contains this
+example would define 4 C functions: @samp{original_foo}, @samp{old_foo},
+@samp{old_foo1}, and @samp{new_foo}.
+
+When you have multiple definitions of a given symbol, there needs to be
+some way to specify a default version to which external references to
+this symbol will be bound. You can do this with the
+@samp{foo@@@@VERS_2.0} type of @samp{.symver} directive. You can only
+declare one version of a symbol as the default in this manner; otherwise
+you would effectively have multiple definitions of the same symbol.
+
+If you wish to bind a reference to a specific version of the symbol
+within the shared library, you can use the aliases of convenience
+(i.e. @samp{old_foo}), or you can use the @samp{.symver} directive to
+specifically bind to an external version of the function in question.
+
+@node Expressions
+@section Expressions in Linker Scripts
+@cindex expressions
+@cindex arithmetic
+The syntax for expressions in the linker script language is identical to
+that of C expressions. All expressions are evaluated as integers. All
+expressions are evaluated in the same size, which is 32 bits if both the
+host and target are 32 bits, and is otherwise 64 bits.
+
+You can use and set symbol values in expressions.
+
+The linker defines several special purpose builtin functions for use in
+expressions.
+
+@menu
+* Constants:: Constants
+* Symbols:: Symbol Names
+* Location Counter:: The Location Counter
+* Operators:: Operators
+* Evaluation:: Evaluation
+* Expression Section:: The Section of an Expression
+* Builtin Functions:: Builtin Functions
+@end menu
+
+@node Constants
+@subsection Constants
+@cindex integer notation
+@cindex constants in linker scripts
+All constants are integers.
+
+As in C, the linker considers an integer beginning with @samp{0} to be
+octal, and an integer beginning with @samp{0x} or @samp{0X} to be
+hexadecimal. The linker considers other integers to be decimal.
+
+@cindex scaled integers
+@cindex K and M integer suffixes
+@cindex M and K integer suffixes
+@cindex suffixes for integers
+@cindex integer suffixes
+In addition, you can use the suffixes @code{K} and @code{M} to scale a
+constant by
+@c TEXI2ROFF-KILL
+@ifinfo
+@c END TEXI2ROFF-KILL
+@code{1024} or @code{1024*1024}
+@c TEXI2ROFF-KILL
+@end ifinfo
+@tex
+${\rm 1024}$ or ${\rm 1024}^2$
+@end tex
+@c END TEXI2ROFF-KILL
+respectively. For example, the following all refer to the same quantity:
+@smallexample
+ _fourk_1 = 4K;
+ _fourk_2 = 4096;
+ _fourk_3 = 0x1000;
+@end smallexample
+
+@node Symbols
+@subsection Symbol Names
+@cindex symbol names
+@cindex names
+@cindex quoted symbol names
+@kindex "
+Unless quoted, symbol names start with a letter, underscore, or period
+and may include letters, digits, underscores, periods, 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:
+@smallexample
+ "SECTION" = 9;
+ "with a space" = "also with a space" + 10;
+@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,
+whereas @samp{A - B} is an expression involving subtraction.
+
+@node Location Counter
+@subsection The Location Counter
+@kindex .
+@cindex dot
+@cindex location counter
+@cindex current output location
+The special linker variable @dfn{dot} @samp{.} always contains the
+current output location counter. Since the @code{.} always refers to a
+location in an output section, it may only appear in an expression
+within a @code{SECTIONS} command. The @code{.} symbol may appear
+anywhere that an ordinary symbol is allowed in an expression.
+
+@cindex holes
+Assigning a value to @code{.} will cause the location counter to be
+moved. This may be used to create holes in the output section. The
+location counter may never be moved backwards.
+
+@smallexample
+SECTIONS
+@{
+ output :
+ @{
+ file1(.text)
+ . = . + 1000;
+ file2(.text)
+ . += 1000;
+ file3(.text)
+ @} = 0x1234;
@}
-@end example
+@end smallexample
+@noindent
+In the previous example, the @samp{.text} section from @file{file1} is
+located at the beginning of the output section @samp{output}. It is
+followed by a 1000 byte gap. Then the @samp{.text} section from
+@file{file2} appears, also with a 1000 byte gap following before the
+@samp{.text} section from @file{file3}. The notation @samp{= 0x1234}
+specifies what data to write in the gaps (@pxref{Output Section Fill}).
+
+@cindex dot inside sections
+Note: @code{.} actually refers to the byte offset from the start of the
+current containing object. Normally this is the @code{SECTIONS}
+statement, whoes start address is 0, hence @code{.} can be used as an
+absolute address. If @code{.} is used inside a section description
+however, it refers to the byte offset from the start of that section,
+not an absolute address. Thus in a script like this:
+
+@smallexample
+SECTIONS
+@{
+ . = 0x100
+ .text: @{
+ *(.text)
+ . = 0x200
+ @}
+ . = 0x500
+ .data: @{
+ *(.data)
+ . += 0x600
+ @}
+@}
+@end smallexample
+
+The @samp{.text} section will be assigned a starting address of 0x100
+and a size of exactly 0x200 bytes, even if there is not enough data in
+the @samp{.text} input sections to fill this area. (If there is too
+much data, an error will be produced because this would be an attempt to
+move @code{.} backwards). The @samp{.data} section will start at 0x500
+and it will have an extra 0x600 bytes worth of space after the end of
+the values from the @samp{.data} input sections and before the end of
+the @samp{.data} output section itself.
+
+@need 2000
+@node Operators
+@subsection Operators
+@cindex operators for arithmetic
+@cindex arithmetic operators
+@cindex precedence in expressions
+The linker recognizes the standard C set of arithmetic operators, with
+the standard bindings and precedence levels:
+@c TEXI2ROFF-KILL
+@ifinfo
+@c END TEXI2ROFF-KILL
+@smallexample
+precedence associativity Operators Notes
+(highest)
+1 left ! - ~ (1)
+2 left * / %
+3 left + -
+4 left >> <<
+5 left == != > < <= >=
+6 left &
+7 left |
+8 left &&
+9 left ||
+10 right ? :
+11 right &= += -= *= /= (2)
+(lowest)
+@end smallexample
+Notes:
+(1) Prefix operators
+(2) @xref{Assignments}.
+@c TEXI2ROFF-KILL
+@end ifinfo
+@tex
+\vskip \baselineskip
+%"lispnarrowing" is the extra indent used generally for smallexample
+\hskip\lispnarrowing\vbox{\offinterlineskip
+\hrule
+\halign
+{\vrule#&\strut\hfil\ #\ \hfil&\vrule#&\strut\hfil\ #\ \hfil&\vrule#&\strut\hfil\ {\tt #}\ \hfil&\vrule#\cr
+height2pt&\omit&&\omit&&\omit&\cr
+&Precedence&& Associativity &&{\rm Operators}&\cr
+height2pt&\omit&&\omit&&\omit&\cr
+\noalign{\hrule}
+height2pt&\omit&&\omit&&\omit&\cr
+&highest&&&&&\cr
+% '176 is tilde, '~' in tt font
+&1&&left&&\qquad- \char'176\ !\qquad\dag&\cr
+&2&&left&&* / \%&\cr
+&3&&left&&+ -&\cr
+&4&&left&&>> <<&\cr
+&5&&left&&== != > < <= >=&\cr
+&6&&left&&\&&\cr
+&7&&left&&|&\cr
+&8&&left&&{\&\&}&\cr
+&9&&left&&||&\cr
+&10&&right&&? :&\cr
+&11&&right&&\qquad\&= += -= *= /=\qquad\ddag&\cr
+&lowest&&&&&\cr
+height2pt&\omit&&\omit&&\omit&\cr}
+\hrule}
+@end tex
+@iftex
+{
+@obeylines@parskip=0pt@parindent=0pt
+@dag@quad Prefix operators.
+@ddag@quad @xref{Assignments}.
+}
+@end iftex
+@c END TEXI2ROFF-KILL
+
+@node Evaluation
+@subsection Evaluation
+@cindex lazy evaluation
+@cindex expression evaluation order
+The linker evaluates expressions lazily. It only computes the value of
+an expression when absolutely necessary.
+
+The linker needs some information, such as the value of the start
+address of the first section, and the origins and lengths of memory
+regions, in order to do any linking at all. These values are computed
+as soon as possible when the linker reads in the linker script.
+
+However, other values (such as symbol values) are not known or needed
+until after storage allocation. Such values are evaluated later, when
+other information (such as the sizes of output sections) is available
+for use in the symbol assignment expression.
+
+The sizes of sections cannot be known until after allocation, so
+assignments dependent upon these are not performed until after
+allocation.
-@kindex AT ( @var{ldadr} )
-@cindex specify load address
-@cindex load address, specifying
-@item AT ( @var{ldadr} )
-The expression @var{ldadr} that follows the @code{AT} keyword specifies
-the load address of the section. The default (if you do not use the
-@code{AT} keyword) is to make the load address the same as the
-relocation address. This feature is designed to make it easy to build a
-ROM image. For example, this @code{SECTIONS} definition creates two
-output sections: one called @samp{.text}, which starts at @code{0x1000},
-and one called @samp{.mdata}, which is loaded at the end of the
-@samp{.text} section even though its relocation address is
-@code{0x2000}. The symbol @code{_data} is defined with the value
-@code{0x2000}:
+Some expressions, such as those depending upon the location counter
+@samp{.}, must be evaluated during section 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
@smallexample
+@group
SECTIONS
@{
- .text 0x1000 : @{ *(.text) _etext = . ; @}
- .mdata 0x2000 :
- AT ( ADDR(.text) + SIZEOF ( .text ) )
- @{ _data = . ; *(.data); _edata = . ; @}
- .bss 0x3000 :
- @{ _bstart = . ; *(.bss) *(COMMON) ; _bend = . ;@}
-@}
+ .text 9+this_isnt_constant :
+ @{ *(.text) @}
+ @}
+@end group
@end smallexample
-
-The run-time initialization code (for C programs, usually @code{crt0})
-for use with a ROM generated this way has to include something like
-the following, to copy the initialized data from the ROM image to its runtime
-address:
-
+@noindent
+will cause the error message @samp{non constant expression for initial
+address}.
+
+@node Expression Section
+@subsection The Section of an Expression
+@cindex expression sections
+@cindex absolute expressions
+@cindex relative expressions
+@cindex absolute and relocatable symbols
+@cindex relocatable and absolute symbols
+@cindex symbols, relocatable and absolute
+When the linker evaluates an expression, the result is either absolute
+or relative to some section. A relative expression is expressed as a
+fixed offset from the base of a section.
+
+The position of the expression within the linker script determines
+whether it is absolute or relative. An expression which appears within
+an output section definition is relative to the base of the output
+section. An expression which appears elsewhere will be absolute.
+
+A symbol set to a relative expression will be relocatable if you request
+relocatable output using the @samp{-r} option. That means that a
+further link operation may change the value of the symbol. The symbol's
+section will be the section of the relative expression.
+
+A symbol set to an absolute expression will retain the same value
+through any further link operation. The symbol will be absolute, and
+will not have any particular associated section.
+
+You can use the builtin function @code{ABSOLUTE} to force an expression
+to be absolute when it would otherwise be relative. For example, to
+create an absolute symbol set to the address of the end of the output
+section @samp{.data}:
@smallexample
-char *src = _etext;
-char *dst = _data;
-
-/* ROM has data at end of text; copy it. */
-while (dst < _edata) @{
- *dst++ = *src++;
-@}
-
-/* Zero bss */
-for (dst = _bstart; dst< _bend; dst++)
- *dst = 0;
+SECTIONS
+ @{
+ .data : @{ *(.data) _edata = ABSOLUTE(.); @}
+ @}
@end smallexample
+@noindent
+If @samp{ABSOLUTE} were not used, @samp{_edata} would be relative to the
+@samp{.data} section.
-@kindex =@var{fill}
-@cindex section fill pattern
-@cindex fill pattern, entire section
-@item =@var{fill}
-Including @code{=@var{fill}} in a section definition specifies the
-initial fill value for that section. You may use any expression to
-specify @var{fill}. Any unallocated holes in the current output section
-when written to the output file will be filled with the two least
-significant bytes of the value, repeated as necessary. You can also
-change the fill value with a @code{FILL} statement in the @var{contents}
-of a section definition.
-
-@kindex >@var{region}
-@cindex section, assigning to memory region
-@cindex memory regions and sections
-@item >@var{region}
-Assign this section to a previously defined region of memory.
-@xref{MEMORY}.
-
-@end table
-
-@node Entry Point
-@section The Entry Point
-@kindex ENTRY(@var{symbol})
-@cindex start of execution
-@cindex first instruction
-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
-ENTRY(@var{symbol})
-@end example
-
-Like symbol assignments, the @code{ENTRY} command may be placed either
-as an independent command in the command file, or among the section
-definitions within the @code{SECTIONS} command---whatever makes the most
-sense for your layout.
+@node Builtin Functions
+@subsection Builtin Functions
+@cindex functions in expressions
+The linker script language includes a number of builtin functions for
+use in linker script expressions.
-@cindex entry point, defaults
-@code{ENTRY} is only one of several ways of choosing the entry point.
-You may indicate it in any of the following ways (shown in descending
-order of priority: methods higher in the list override methods lower down).
-@itemize @bullet
-@item
-the @samp{-e} @var{entry} command-line option;
-@item
-the @code{ENTRY(@var{symbol})} command in a linker control script;
-@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}.
-@end itemize
+@table @code
+@item ABSOLUTE(@var{exp})
+@kindex ABSOLUTE(@var{exp})
+@cindex expression, absolute
+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. @xref{Expression Section}.
-For example, you can use these rules to generate an entry point with an
-assignment statement: if no symbol @code{start} is defined within your
-input files, you can simply define it, assigning it an appropriate
-value---
+@item ADDR(@var{section})
+@kindex ADDR(@var{section})
+@cindex section address in expression
+Return the absolute address (the VMA) 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:
+@smallexample
+@group
+SECTIONS @{ @dots{}
+ .output1 :
+ @{
+ start_of_output_1 = ABSOLUTE(.);
+ @dots{}
+ @}
+ .output :
+ @{
+ symbol_1 = ADDR(.output1);
+ symbol_2 = start_of_output_1;
+ @}
+@dots{} @}
+@end group
+@end smallexample
-@example
-start = 0x2020;
-@end example
+@item ALIGN(@var{exp})
+@kindex ALIGN(@var{exp})
+@cindex round up location counter
+@cindex align location counter
+Return the 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
+@smallexample
+(. + @var{exp} - 1) & ~(@var{exp} - 1)
+@end smallexample
+@code{ALIGN} doesn't change the value of the location counter---it just
+does arithmetic on it. Here is an example which aligns the output
+@code{.data} section to the next @code{0x2000} byte boundary after the
+preceding section and sets a variable within the section to the next
+@code{0x8000} boundary after the input sections:
+@smallexample
+@group
+SECTIONS @{ @dots{}
+ .data ALIGN(0x2000): @{
+ *(.data)
+ variable = ALIGN(0x8000);
+ @}
+@dots{} @}
+@end group
+@end smallexample
@noindent
-The example shows an absolute address, but you can use any expression.
-For example, if your input object files use some other symbol-name
-convention for the entry point, you can just assign the value of
-whatever symbol contains the start address to @code{start}:
+The first use of @code{ALIGN} in this example specifies the location of
+a section because it is used as the optional @var{address} attribute of
+a section definition (@pxref{Output Section Address}). The second use
+of @code{ALIGN} is used to defines the value of a symbol.
-@example
-start = other_symbol ;
-@end example
+The builtin function @code{NEXT} is closely related to @code{ALIGN}.
-@node Option Commands
-@section Option Commands
-The command language includes a number of other commands that you can
-use for specialized purposes. They are similar in purpose to
-command-line options.
+@item BLOCK(@var{exp})
+@kindex BLOCK(@var{exp})
+This is a synonym for @code{ALIGN}, for compatibility with older linker
+scripts. It is most often seen when setting the address of an output
+section.
-@table @code
-@kindex CONSTRUCTORS
-@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}.)
-
-@need 1000
-@kindex FLOAT
-@kindex NOFLOAT
-@item FLOAT
-@itemx NOFLOAT
-These keywords were used in some older linkers to request a particular
-math subroutine library. @code{ld} doesn't use the keywords, assuming
-instead that any necessary subroutines are in libraries specified using
-the general mechanisms for linking to archives; but to permit the use of
-scripts that were written for the older linkers, the keywords
-@code{FLOAT} and @code{NOFLOAT} are accepted and ignored.
+@item DEFINED(@var{symbol})
+@kindex DEFINED(@var{symbol})
+@cindex symbol defaults
+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 script fragment
+shows how to set a global symbol @samp{begin} to the first location in
+the @samp{.text} section---but if a symbol called @samp{begin} already
+existed, its value is preserved:
-@kindex FORCE_COMMON_ALLOCATION
-@cindex common allocation
-@item FORCE_COMMON_ALLOCATION
-This command has the same effect as the @samp{-d} command-line option:
-to make @code{ld} assign space to common symbols even if a relocatable
-output file is specified (@samp{-r}).
+@smallexample
+@group
+SECTIONS @{ @dots{}
+ .text : @{
+ begin = DEFINED(begin) ? begin : . ;
+ @dots{}
+ @}
+ @dots{}
+@}
+@end group
+@end smallexample
-@kindex INPUT ( @var{files} )
-@cindex binary input files
-@item INPUT ( @var{file}, @var{file}, @dots{} )
-@itemx INPUT ( @var{file} @var{file} @dots{} )
-Use this command to include binary input files in the link, without
-including them in a particular section definition.
-Specify the full name for each @var{file}, including @samp{.a} if
-required.
+@item LOADADDR(@var{section})
+@kindex LOADADDR(@var{section})
+@cindex section load address in expression
+Return the absolute LMA of the named @var{section}. This is normally
+the same as @code{ADDR}, but it may be different if the @code{AT}
+attribute is used in the output section definition (@pxref{Output
+Section LMA}).
-@code{ld} searches for each @var{file} through the archive-library
-search path, just as for files you specify on the command line.
-See the description of @samp{-L} in @ref{Options,,Command Line
-Options}.
+@kindex MAX
+@item MAX(@var{exp1}, @var{exp2})
+Returns the maximum of @var{exp1} and @var{exp2}.
-@ignore
-@item MAP ( @var{name} )
-@kindex 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
+@kindex MIN
+@item MIN(@var{exp1}, @var{exp2})
+Returns the minimum of @var{exp1} and @var{exp2}.
-@item OUTPUT ( @var{filename} )
-@kindex OUTPUT ( @var{filename} )
-@cindex naming the output file
-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}.
+@item NEXT(@var{exp})
+@kindex NEXT(@var{exp})
+@cindex unallocated address, next
+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.
-@ifclear SingleFormat
-@item OUTPUT_ARCH ( @var{bfdname} )
-@kindex OUTPUT_ARCH ( @var{bfdname} )
-@cindex machine architecture, output
-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
-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.
-@end ifclear
+@item SIZEOF(@var{section})
+@kindex SIZEOF(@var{section})
+@cindex section size
+Return the size in bytes of the named @var{section}, if that section has
+been allocated. If the section has not been allocated when this is
+evaluated, the linker will report an error. In the following example,
+@code{symbol_1} and @code{symbol_2} are assigned identical values:
+@smallexample
+@group
+SECTIONS@{ @dots{}
+ .output @{
+ .start = . ;
+ @dots{}
+ .end = . ;
+ @}
+ symbol_1 = .end - .start ;
+ symbol_2 = SIZEOF(.output);
+@dots{} @}
+@end group
+@end smallexample
+
+@item SIZEOF_HEADERS
+@itemx sizeof_headers
+@kindex SIZEOF_HEADERS
+@cindex header size
+Return the size in bytes of the output file's headers. This is
+information which appears at the start of the output file. You can use
+this number when setting the start address of the first section, if you
+choose, to facilitate paging.
+
+@cindex not enough room for program headers
+@cindex program headers, not enough room
+When producing an ELF output file, if the linker script uses the
+@code{SIZEOF_HEADERS} builtin function, the linker must compute the
+number of program headers before it has determined all the section
+addresses and sizes. If the linker later discovers that it needs
+additional program headers, it will report an error @samp{not enough
+room for program headers}. To avoid this error, you must avoid using
+the @code{SIZEOF_HEADERS} function, or you must rework your linker
+script to avoid forcing the linker to use additional program headers, or
+you must define the program headers yourself using the @code{PHDRS}
+command (@pxref{PHDRS}).
+@end table
-@item SEARCH_DIR ( @var{path} )
-@kindex SEARCH_DIR ( @var{path} )
-@cindex path for libraries
-@cindex search path, libraries
-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.
+@node Implicit Linker Scripts
+@section Implicit Linker Scripts
+@cindex implicit linker scripts
+If you specify a linker input file which the linker can not recognize as
+an object file or an archive file, it will try to read the file as a
+linker script. If the file can not be parsed as a linker script, the
+linker will report an error.
-@item STARTUP ( @var{filename} )
-@kindex STARTUP ( @var{filename} )
-@cindex first input file
-Ensure that @var{filename} is the first input file used in the link
-process.
+An implicit linker script will not replace the default linker script.
-@ifclear SingleFormat
-@item TARGET ( @var{format} )
-@cindex input file format
-@kindex 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}).
-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
-format for the @code{ld} output file. @xref{BFD}.
+Typically an implicit linker script would contain only symbol
+assignments, or the @code{INPUT}, @code{GROUP}, or @code{VERSION}
+commands.
-@kindex GNUTARGET
-If you don't use the @code{TARGET} command, @code{ld} uses the value of
-the environment variable @code{GNUTARGET}, if available, to select the
-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
-@end table
+Any input files read because of an implicit linker script will be read
+at the position in the command line where the implicit linker script was
+read. This can affect archive searching.
@ifset GENERIC
@node Machine Dependent
@menu
* H8/300:: @code{ld} and the H8/300
* i960:: @code{ld} and the Intel 960 family
+* ARM:: @code{ld} and the ARM family
+* HPPA ELF32:: @code{ld} and HPPA 32-bit ELF
+@ifset TICOFF
+* TI COFF:: @code{ld} and TI COFF
+@end ifset
@end menu
@end ifset
@ifclear GENERIC
@raisesections
@end ifclear
+
@node H8/300
@section @code{ld} and the H8/300
@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
@samp{mov.b @code{@@}@var{aa}:8} whenever the address @var{aa} is in the
top page of memory).
@end table
+
@ifclear GENERIC
@lowersections
@end ifclear
@end ifset
+@ifclear GENERIC
+@ifset Hitachi
+@c This stuff is pointless to say unless you're especially concerned
+@c with Hitachi chips; don't enable it for generic case, please.
+@node Hitachi
+@chapter @code{ld} and other Hitachi chips
+
+@code{ld} also supports the H8/300H, the H8/500, and the Hitachi SH. No
+special features, commands, or command-line options are required for
+these chips.
+@end ifset
+@end ifclear
+
@ifset I960
@ifclear GENERIC
@raisesections
@end ifclear
+
@node i960
@section @code{ld} and the Intel 960 family
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
@end ifclear
@end ifset
+@ifclear GENERIC
+@raisesections
+@end ifclear
+
+@node ARM
+@section @code{ld}'s support for interworking between ARM and Thumb code
+
+@cindex ARM interworking support
+@kindex --support-old-code
+For the ARM, @code{ld} will generate code stubs to allow functions calls
+betweem ARM and Thumb code. These stubs only work with code that has
+been compiled and assembled with the @samp{-mthumb-interwork} command
+line option. If it is necessary to link with old ARM object files or
+libraries, which have not been compiled with the -mthumb-interwork
+option then the @samp{--support-old-code} command line switch should be
+given to the linker. This will make it generate larger stub functions
+which will work with non-interworking aware ARM code. Note, however,
+the linker does not support generating stubs for function calls to
+non-interworking aware Thumb code.
+
+@cindex thumb entry point
+@cindex entry point, thumb
+@kindex --thumb-entry=@var{entry}
+The @samp{--thumb-entry} switch is a duplicate of the generic
+@samp{--entry} switch, in that it sets the program's starting address.
+But it also sets the bottom bit of the address, so that it can be
+branched to using a BX instruction, and the program will start
+executing in Thumb mode straight away.
+
+@node HPPA ELF32
+@section @code{ld} and HPPA 32-bit ELF support
+@cindex HPPA multiple sub-space stubs
+@kindex --multi-subspace
+When generating a shared library, @code{ld} will by default generate
+import stubs suitable for use with a single sub-space application.
+The @samp{--multi-subspace} switch causes @code{ld} to generate export
+stubs, and different (larger) import stubs suitable for use with
+multiple sub-spaces.
+
+@cindex HPPA stub grouping
+@kindex --stub-group-size=@var{N}
+Long branch stubs and import/export stubs are placed by @code{ld} in
+stub sections located between groups of input sections.
+@samp{--stub-group-size} specifies the maximum size of a group of input
+sections handled by one stub section. Since branch offsets are signed,
+a stub section may serve two groups of input sections, one group before
+the stub section, and one group after it. However, when using
+conditional branches that require stubs, it may be better (for branch
+prediction) that stub sections only serve one group of input sections.
+A negative value for @samp{N} chooses this scheme, ensuring that
+branches to stubs always use a negative offset. Two special values of
+@samp{N} are recognized, @samp{1} and @samp{-1}. These both instruct
+@code{ld} to automatically size input section groups for the branch types
+detected, with the same behaviour regarding stub placement as other
+positive or negative values of @samp{N} respectively.
+
+Note that @samp{--stub-group-size} does not split input sections. A
+single input section larger than the group size specified will of course
+create a larger group (of one section). If input sections are too
+large, it may not be possible for a branch to reach its stub.
+
+@ifset TICOFF
+@node TI COFF
+@section @code{ld}'s support for various TI COFF versions
+@cindex TI COFF versions
+@kindex --format=@var{version}
+The @samp{--format} switch allows selection of one of the various
+TI COFF versions. The latest of this writing is 2; versions 0 and 1 are
+also supported. The TI COFF versions also vary in header byte-order
+format; @code{ld} will read any version or byte order, but the output
+header format depends on the default specified by the specific target.
+@end ifset
+
+@ifclear GENERIC
+@lowersections
+@end ifclear
+
@ifclear SingleFormat
@node BFD
@chapter BFD
@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.
+
+Otherwise, send bug reports for @code{ld} to
+@samp{bug-binutils@@gnu.org}.
+
+The fundamental principle of reporting bugs usefully is this:
+@strong{report all the facts}. If you are not sure whether to state a
+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
To aid users making the transition to @sc{gnu} @code{ld} from the MRI
linker, @code{ld} can use MRI compatible linker scripts as an
alternative to the more general-purpose linker scripting language
-described in @ref{Commands,,Command Language}. MRI compatible linker
-scripts have a much simpler command set than the scripting language
-otherwise used with @code{ld}. @sc{gnu} @code{ld} supports the most
-commonly used MRI linker commands; these commands are described here.
+described in @ref{Scripts}. MRI compatible linker scripts have a much
+simpler command set than the scripting language otherwise used with
+@code{ld}. @sc{gnu} @code{ld} supports the most commonly used MRI
+linker commands; these commands are described here.
In general, MRI scripts aren't of much use with the @code{a.out} object
file format, since it only has three sections and MRI scripts lack some
@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{FORMAT} (MRI)
@item FORMAT @var{output-format}
Similar to the @code{OUTPUT_FORMAT} command in the more general linker
-language, but restricted to one of these output formats:
+language, but restricted to one of these output formats:
@enumerate
-@item
+@item
S-records, if @var{output-format} is @samp{S}
@item
@cindex @code{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 GNU Free Documentation License
+@appendix GNU Free Documentation License
+@cindex GNU Free Documentation License
+
+ GNU Free Documentation License
+
+ Version 1.1, March 2000
+
+ Copyright (C) 2000 Free Software Foundation, Inc.
+ 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+
+0. PREAMBLE
+
+The purpose of this License is to make a manual, textbook, or other
+written document "free" in the sense of freedom: to assure everyone
+the effective freedom to copy and redistribute it, with or without
+modifying it, either commercially or noncommercially. Secondarily,
+this License preserves for the author and publisher a way to get
+credit for their work, while not being considered responsible for
+modifications made by others.
+
+This License is a kind of "copyleft", which means that derivative
+works of the document must themselves be free in the same sense. It
+complements the GNU General Public License, which is a copyleft
+license designed for free software.
+
+We have designed this License in order to use it for manuals for free
+software, because free software needs free documentation: a free
+program should come with manuals providing the same freedoms that the
+software does. But this License is not limited to software manuals;
+it can be used for any textual work, regardless of subject matter or
+whether it is published as a printed book. We recommend this License
+principally for works whose purpose is instruction or reference.
+
+
+1. APPLICABILITY AND DEFINITIONS
+
+This License applies to any manual or other work that contains a
+notice placed by the copyright holder saying it can be distributed
+under the terms of this License. The "Document", below, refers to any
+such manual or work. Any member of the public is a licensee, and is
+addressed as "you".
+
+A "Modified Version" of the Document means any work containing the
+Document or a portion of it, either copied verbatim, or with
+modifications and/or translated into another language.
+
+A "Secondary Section" is a named appendix or a front-matter section of
+the Document that deals exclusively with the relationship of the
+publishers or authors of the Document to the Document's overall subject
+(or to related matters) and contains nothing that could fall directly
+within that overall subject. (For example, if the Document is in part a
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+mathematics.) The relationship could be a matter of historical
+connection with the subject or with related matters, or of legal,
+commercial, philosophical, ethical or political position regarding
+them.
+
+The "Invariant Sections" are certain Secondary Sections whose titles
+are designated, as being those of Invariant Sections, in the notice
+that says that the Document is released under this License.
+
+The "Cover Texts" are certain short passages of text that are listed,
+as Front-Cover Texts or Back-Cover Texts, in the notice that says that
+the Document is released under this License.
+
+A "Transparent" copy of the Document means a machine-readable copy,
+represented in a format whose specification is available to the
+general public, whose contents can be viewed and edited directly and
+straightforwardly with generic text editors or (for images composed of
+pixels) generic paint programs or (for drawings) some widely available
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+for automatic translation to a variety of formats suitable for input
+to text formatters. A copy made in an otherwise Transparent file
+format whose markup has been designed to thwart or discourage
+subsequent modification by readers is not Transparent. A copy that is
+not "Transparent" is called "Opaque".
+
+Examples of suitable formats for Transparent copies include plain
+ASCII without markup, Texinfo input format, LaTeX input format, SGML
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+HTML designed for human modification. Opaque formats include
+PostScript, PDF, proprietary formats that can be read and edited only
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+machine-generated HTML produced by some word processors for output
+purposes only.
+
+The "Title Page" means, for a printed book, the title page itself,
+plus such following pages as are needed to hold, legibly, the material
+this License requires to appear in the title page. For works in
+formats which do not have any title page as such, "Title Page" means
+the text near the most prominent appearance of the work's title,
+preceding the beginning of the body of the text.
+
+
+2. VERBATIM COPYING
+
+You may copy and distribute the Document in any medium, either
+commercially or noncommercially, provided that this License, the
+copyright notices, and the license notice saying this License applies
+to the Document are reproduced in all copies, and that you add no other
+conditions whatsoever to those of this License. You may not use
+technical measures to obstruct or control the reading or further
+copying of the copies you make or distribute. However, you may accept
+compensation in exchange for copies. If you distribute a large enough
+number of copies you must also follow the conditions in section 3.
+
+You may also lend copies, under the same conditions stated above, and
+you may publicly display copies.
+
+
+3. COPYING IN QUANTITY
+
+If you publish printed copies of the Document numbering more than 100,
+and the Document's license notice requires Cover Texts, you must enclose
+the copies in covers that carry, clearly and legibly, all these Cover
+Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
+the back cover. Both covers must also clearly and legibly identify
+you as the publisher of these copies. The front cover must present
+the full title with all words of the title equally prominent and
+visible. You may add other material on the covers in addition.
+Copying with changes limited to the covers, as long as they preserve
+the title of the Document and satisfy these conditions, can be treated
+as verbatim copying in other respects.
+
+If the required texts for either cover are too voluminous to fit
+legibly, you should put the first ones listed (as many as fit
+reasonably) on the actual cover, and continue the rest onto adjacent
+pages.
+
+If you publish or distribute Opaque copies of the Document numbering
+more than 100, you must either include a machine-readable Transparent
+copy along with each Opaque copy, or state in or with each Opaque copy
+a publicly-accessible computer-network location containing a complete
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+until at least one year after the last time you distribute an Opaque
+copy (directly or through your agents or retailers) of that edition to
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+
+It is requested, but not required, that you contact the authors of the
+Document well before redistributing any large number of copies, to give
+them a chance to provide you with an updated version of the Document.
+
+
+4. MODIFICATIONS
+
+You may copy and distribute a Modified Version of the Document under
+the conditions of sections 2 and 3 above, provided that you release
+the Modified Version under precisely this License, with the Modified
+Version filling the role of the Document, thus licensing distribution
+and modification of the Modified Version to whoever possesses a copy
+of it. In addition, you must do these things in the Modified Version:
+
+A. Use in the Title Page (and on the covers, if any) a title distinct
+ from that of the Document, and from those of previous versions
+ (which should, if there were any, be listed in the History section
+ of the Document). You may use the same title as a previous version
+ if the original publisher of that version gives permission.
+B. List on the Title Page, as authors, one or more persons or entities
+ responsible for authorship of the modifications in the Modified
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+ Document (all of its principal authors, if it has less than five).
+C. State on the Title page the name of the publisher of the
+ Modified Version, as the publisher.
+D. Preserve all the copyright notices of the Document.
+E. Add an appropriate copyright notice for your modifications
+ adjacent to the other copyright notices.
+F. Include, immediately after the copyright notices, a license notice
+ giving the public permission to use the Modified Version under the
+ terms of this License, in the form shown in the Addendum below.
+G. Preserve in that license notice the full lists of Invariant Sections
+ and required Cover Texts given in the Document's license notice.
+H. Include an unaltered copy of this License.
+I. Preserve the section entitled "History", and its title, and add to
+ it an item stating at least the title, year, new authors, and
+ publisher of the Modified Version as given on the Title Page. If
+ there is no section entitled "History" in the Document, create one
+ stating the title, year, authors, and publisher of the Document as
+ given on its Title Page, then add an item describing the Modified
+ Version as stated in the previous sentence.
+J. Preserve the network location, if any, given in the Document for
+ public access to a Transparent copy of the Document, and likewise
+ the network locations given in the Document for previous versions
+ it was based on. These may be placed in the "History" section.
+ You may omit a network location for a work that was published at
+ least four years before the Document itself, or if the original
+ publisher of the version it refers to gives permission.
+K. In any section entitled "Acknowledgements" or "Dedications",
+ preserve the section's title, and preserve in the section all the
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+N. Do not retitle any existing section as "Endorsements"
+ or to conflict in title with any Invariant Section.
+
+If the Modified Version includes new front-matter sections or
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+5. COMBINING DOCUMENTS
+
+You may combine the Document with other documents released under this
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+6. COLLECTIONS OF DOCUMENTS
+
+You may make a collection consisting of the Document and other documents
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+7. AGGREGATION WITH INDEPENDENT WORKS
+
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+If the Cover Text requirement of section 3 is applicable to these
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+8. TRANSLATION
+
+Translation is considered a kind of modification, so you may
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+
+9. TERMINATION
+
+You may not copy, modify, sublicense, or distribute the Document except
+as expressly provided for under this License. Any other attempt to
+copy, modify, sublicense or distribute the Document is void, and will
+automatically terminate your rights under this License. However,
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+License will not have their licenses terminated so long as such
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+
+
+10. FUTURE REVISIONS OF THIS LICENSE
+
+The Free Software Foundation may publish new, revised versions
+of the GNU Free Documentation License from time to time. Such new
+versions will be similar in spirit to the present version, but may
+differ in detail to address new problems or concerns. See
+http://www.gnu.org/copyleft/.
+
+Each version of the License is given a distinguishing version number.
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+
+
+ADDENDUM: How to use this License for your documents
+
+To use this License in a document you have written, include a copy of
+the License in the document and put the following copyright and
+license notices just after the title page:
+
+@smallexample
+ Copyright (c) YEAR YOUR NAME.
+ Permission is granted to copy, distribute and/or modify this document
+ under the terms of the GNU Free Documentation License, Version 1.1
+ or any later version published by the Free Software Foundation;
+ with the Invariant Sections being LIST THEIR TITLES, with the
+ Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
+ A copy of the license is included in the section entitled "GNU
+ Free Documentation License".
+@end smallexample
+
+If you have no Invariant Sections, write "with no Invariant Sections"
+instead of saying which ones are invariant. If you have no
+Front-Cover Texts, write "no Front-Cover Texts" instead of
+"Front-Cover Texts being LIST"; likewise for Back-Cover Texts.
+
+If your document contains nontrivial examples of program code, we
+recommend releasing these examples in parallel under your choice of
+free software license, such as the GNU General Public License,
+to permit their use in free software.
@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
@contents
@bye
-
-
projects / deliverable / binutils-gdb.git / blobdiff