Subversion Repositories openrisc_2011-10-31

\input texinfo

@setfilename ld.info

@c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,

@c 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009

@c Free Software Foundation, Inc.

@syncodeindex ky cp

@c man begin INCLUDE

@include configdoc.texi

@c (configdoc.texi is generated by the Makefile)

@include bfdver.texi

@c man end

@c @smallbook

@macro gcctabopt{body}

@code{\body\}

@end macro

@c man begin NAME

@ifset man

@c Configure for the generation of man pages

@set UsesEnvVars

@set GENERIC

@set ARM

@set H8300

@set HPPA

@set I960

@set M68HC11

@set M68K

@set MMIX

@set MSP430

@set POWERPC

@set POWERPC64

@set Renesas

@set SPU

@set TICOFF

@set WIN32

@set XTENSA

@end ifset

@c man end

@ifinfo

@format

START-INFO-DIR-ENTRY

* Ld: (ld).                       The GNU linker.

END-INFO-DIR-ENTRY

@end format

@end ifinfo

@copying

This file documents the @sc{gnu} linker LD

@ifset VERSION_PACKAGE

@value{VERSION_PACKAGE}

@end ifset

version @value{VERSION}.

Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000,

2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document

under the terms of the GNU Free Documentation License, Version 1.3

or any later version published by the Free Software Foundation;

with no Invariant Sections, with no Front-Cover Texts, and with no

Back-Cover Texts.  A copy of the license is included in the

section entitled ``GNU Free Documentation License''.

@end copying

@iftex

@finalout

@setchapternewpage odd

@settitle The GNU linker

@titlepage

@title The GNU linker

@sp 1

@subtitle @code{ld}

@ifset VERSION_PACKAGE

@subtitle @value{VERSION_PACKAGE}

@end ifset

@subtitle Version @value{VERSION}

@author Steve Chamberlain

@author Ian Lance Taylor

@page

@tex

{\parskip=0pt

\hfill Red Hat Inc\par

\hfill nickc\@credhat.com, doc\@redhat.com\par

\hfill {\it The GNU linker}\par

\hfill Edited by Jeffrey Osier (jeffrey\@cygnus.com)\par

}

\global\parindent=0pt % Steve likes it this way.

@end tex

@vskip 0pt plus 1filll

@c man begin COPYRIGHT

Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001,

2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc.

Permission is granted to copy, distribute and/or modify this document

under the terms of the GNU Free Documentation License, Version 1.3

or any later version published by the Free Software Foundation;

with no Invariant Sections, with no Front-Cover Texts, and with no

Back-Cover Texts.  A copy of the license is included in the

section entitled ``GNU Free Documentation License''.

@c man end

@end titlepage

@end iftex

@contents

@c FIXME: Talk about importance of *order* of args, cmds to linker!

@ifnottex

@node Top

@top LD

This file documents the @sc{gnu} linker ld

@ifset VERSION_PACKAGE

@value{VERSION_PACKAGE}

@end ifset

version @value{VERSION}.

This document is distributed under the terms of the GNU Free

Documentation License version 1.3.  A copy of the license is included

in the section entitled ``GNU Free Documentation License''.

@menu

* Overview::                    Overview

* Invocation::                  Invocation

* Scripts::                     Linker Scripts

@ifset GENERIC

* Machine Dependent::           Machine Dependent Features

@end ifset

@ifclear GENERIC

@ifset H8300

* H8/300::                      ld and the H8/300

@end ifset

@ifset Renesas

* Renesas::                     ld and other Renesas micros

@end ifset

@ifset I960

* i960::                        ld and the Intel 960 family

@end ifset

@ifset ARM

* ARM::                         ld and the ARM family

@end ifset

@ifset HPPA

* HPPA ELF32::                  ld and HPPA 32-bit ELF

@end ifset

@ifset M68HC11

* M68HC11/68HC12::              ld and the Motorola 68HC11 and 68HC12 families

@end ifset

@ifset M68K

* M68K::                        ld and Motorola 68K family

@end ifset

@ifset POWERPC

* PowerPC ELF32::               ld and PowerPC 32-bit ELF Support

@end ifset

@ifset POWERPC64

* PowerPC64 ELF64::             ld and PowerPC64 64-bit ELF Support

@end ifset

@ifset SPU

* SPU ELF::                     ld and SPU ELF Support

@end ifset

@ifset TICOFF

* TI COFF::                     ld and the TI COFF

@end ifset

@ifset WIN32

* Win32::                       ld and WIN32 (cygwin/mingw)

@end ifset

@ifset XTENSA

* Xtensa::                      ld and Xtensa Processors

@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

* LD Index::                       LD Index

@end menu

@end ifnottex

@node Overview

@chapter Overview

@cindex @sc{gnu} linker

@cindex what is this?

@ifset man

@c man begin SYNOPSIS

ld [@b{options}] @var{objfile} @dots{}

@c man end

@c man begin SEEALSO

ar(1), nm(1), objcopy(1), objdump(1), readelf(1) and

the Info entries for @file{binutils} and

@file{ld}.

@c man end

@end ifset

@c man begin DESCRIPTION

@command{ld} combines a number of object and archive files, relocates

their data and ties up symbol references. Usually the last step in

compiling a program is to run @command{ld}.

@command{ld} accepts Linker Command Language files written in

a superset of AT&T's Link Editor Command Language syntax,

to provide explicit and total control over the linking process.

@ifset man

@c For the man only

This man page does not describe the command language; see the

@command{ld} entry in @code{info} for full details on the command

language and on other aspects of the GNU linker.

@end ifset

@ifclear SingleFormat

This version of @command{ld} uses the general purpose BFD libraries

to operate on object files. This allows @command{ld} to read, combine, and

write object files in many different formats---for example, COFF or

@code{a.out}.  Different formats may be linked together to produce any

available kind of object file.  @xref{BFD}, for more information.

@end ifclear

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,

@command{ld} continues executing, allowing you to identify other errors

(or, in some cases, to get an output file in spite of the error).

@c man end

@node Invocation

@chapter Invocation

@c man begin DESCRIPTION

The @sc{gnu} linker @command{ld} is meant to cover a broad range of situations,

and to be as compatible as possible with other linkers.  As a result,

you have many choices to control its behavior.

@c man end

@ifset UsesEnvVars

@menu

* Options::                     Command Line Options

* Environment::                 Environment Variables

@end menu

@node Options

@section Command Line Options

@end ifset

@cindex command line

@cindex options

@c man begin OPTIONS

The linker supports a plethora of command-line options, but in actual

practice few of them are used in any particular context.

@cindex standard Unix system

For instance, a frequent use of @command{ld} is to link standard Unix

object files on a standard, supported Unix system.  On such a system, to

link a file @code{hello.o}:

@smallexample

ld -o @var{output} /lib/crt0.o hello.o -lc

@end smallexample

This tells @command{ld} to produce a file called @var{output} as the

result of linking the file @code{/lib/crt0.o} with @code{hello.o} and

the library @code{libc.a}, which will come from the standard search

directories.  (See the discussion of the @samp{-l} option below.)

Some of the command-line options to @command{ld} may be specified at any

point in the command line.  However, options which refer to files, such

as @samp{-l} or @samp{-T}, cause the file to be read at the point at

which the option appears in the command line, relative to the object

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.  Options which may be meaningfully specified more than once are

noted in the descriptions below.

@cindex object files

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},

and the script command language.  If @emph{no} binary input files at all

are specified, the linker does not produce any output, and issues the

message @samp{No input files}.

If the linker cannot 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.  Specifying a

script in this way merely augments the main linker script, with the

extra commands placed after the main script; use the @samp{-T} option

to replace the default linker script entirely, but note the effect of

the @code{INSERT} command.  @xref{Scripts}.

For options whose names are a single letter,

option arguments must either follow the option letter without intervening

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{-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 preceded 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

(e.g. @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,--start-group foo.o bar.o -Wl,--end-group

@end smallexample

This is important, because otherwise the compiler driver program may

silently drop the linker options, resulting in a bad link.  Confusion

may also arise when passing options that require values through a

driver, as the use of a space between option and argument acts as

a separator, and causes the driver to pass only the option to the linker

and the argument to the compiler.  In this case, it is simplest to use

the joined forms of both single- and multiple-letter options, such as:

@smallexample

  gcc foo.o bar.o -Wl,-eENTRY -Wl,-Map=a.map

@end smallexample

Here is a table of the generic command line switches accepted by the GNU

linker:

@table @gcctabopt

@include at-file.texi

@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 @command{ld}, this option is useful only for the

Intel 960 family of architectures.  In that @command{ld} configuration, the

@var{architecture} argument identifies the particular architecture in

the 960 family, enabling some safeguards and modifying the

archive-library search path.  @xref{i960,,@command{ld} and the Intel 960

family}, for details.

Future releases of @command{ld} may support similar functionality for

other architecture families.

@end ifset

@ifclear SingleFormat

@cindex binary input format

@kindex -b @var{format}

@kindex --format=@var{format}

@cindex input format

@cindex input format

@item -b @var{input-format}

@itemx --format=@var{input-format}

@command{ld} may be configured to support more than one kind of object

file.  If your @command{ld} is configured this way, you can use the

@samp{-b} option to specify the binary format for input object files

that follow this option on the command line.  Even when @command{ld} is

configured to support alternative object formats, you don't usually need

to specify this, as @command{ld} should be configured to expect as a

default input format the most usual format on each machine.

@var{input-format} is a text string, the name of a particular format

supported by the BFD libraries.  (You can list the available binary

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.

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};

@ifclear man

see @ref{Format Commands}.

@end ifclear

@end ifclear

@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, @command{ld} accepts script

files written in an alternate, restricted command language, described in

@ifclear man

@ref{MRI,,MRI Compatible Script Files}.

@end ifclear

@ifset man

the MRI Compatible Script Files section of GNU ld documentation.

@end ifset

Introduce MRI script files with

the option @samp{-c}; use the @samp{-T} option to run linker

scripts written in the general-purpose @command{ld} scripting language.

If @var{MRI-cmdfile} does not exist, @command{ld} looks for it in the directories

specified by any @samp{-L} options.

@cindex common allocation

@kindex -d

@kindex -dc

@kindex -dp

@item -d

@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{Miscellaneous Commands}.

@cindex entry point, from command line

@kindex -e @var{entry}

@kindex --entry=@var{entry}

@item -e @var{entry}

@itemx --entry=@var{entry}

Use @var{entry} as the explicit symbol for beginning execution of your

program, rather than the default entry point.  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.

@kindex --exclude-libs

@item --exclude-libs @var{lib},@var{lib},...

Specifies a list of archive libraries from which symbols should not be automatically

exported.  The library names may be delimited by commas or colons.  Specifying

@code{--exclude-libs ALL} excludes symbols in all archive libraries from

automatic export.  This option is available only for the i386 PE targeted

port of the linker and for ELF targeted ports.  For i386 PE, symbols

explicitly listed in a .def file are still exported, regardless of this

option.  For ELF targeted ports, symbols affected by this option will

be treated as hidden.

@kindex --exclude-modules-for-implib

@item --exclude-modules-for-implib @var{module},@var{module},...

Specifies a list of object files or archive members, from which symbols

should not be automatically exported, but which should be copied wholesale

into the import library being generated during the link.  The module names

may be delimited by commas or colons, and must match exactly the filenames

used by @command{ld} to open the files; for archive members, this is simply

the member name, but for object files the name listed must include and

match precisely any path used to specify the input file on the linker's

command-line.  This option is available only for the i386 PE targeted port

of the linker.  Symbols explicitly listed in a .def file are still exported,

regardless of this option.

@cindex dynamic symbol table

@kindex -E

@kindex --export-dynamic

@kindex --no-export-dynamic

@item -E

@itemx --export-dynamic

@itemx --no-export-dynamic

When creating a dynamically linked executable, using the @option{-E}

option or the @option{--export-dynamic} option causes the linker to 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 either of these options (or use the

@option{--no-export-dynamic} option to restore the default behavior), 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.

You can also use the dynamic list to control what symbols should

be added to the dynamic symbol table if the output format supports it.

See the description of @samp{--dynamic-list}.

Note that this option is specific to ELF targeted ports.  PE targets

support a similar function to export all symbols from a DLL or EXE; see

the description of @samp{--export-all-symbols} below.

@ifclear SingleFormat

@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.

@end ifclear

@kindex -f @var{name}

@kindex --auxiliary=@var{name}

@item -f @var{name}

@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.

@kindex -F @var{name}

@kindex --filter=@var{name}

@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 @option{-F} option throughout a compilation

toolchain for specifying object-file format for both input and output

object files.

@ifclear SingleFormat

The @sc{gnu} linker uses other mechanisms for this purpose: the

@option{-b}, @option{--format}, @option{--oformat} options, the

@code{TARGET} command in linker scripts, and the @code{GNUTARGET}

environment variable.

@end ifclear

The @sc{gnu} linker will ignore the @option{-F} option when not

creating an ELF shared object.

@cindex finalization function

@kindex -fini=@var{name}

@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 @var{value}

@kindex --gpsize=@var{value}

@cindex object size

@item -G @var{value}

@itemx --gpsize=@var{value}

Set the maximum size of objects to be optimized using the GP register to

@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=@var{name}

@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{namespec}

@kindex --library=@var{namespec}

@item -l @var{namespec}

@itemx --library=@var{namespec}

Add the archive or object file specified by @var{namespec} to the

list of files to link.  This option may be used any number of times.

If @var{namespec} is of the form @file{:@var{filename}}, @command{ld}

will search the library path for a file called @var{filename}, otherwise it

will search the library path for a file called @file{lib@var{namespec}.a}.

On systems which support shared libraries, @command{ld} may also search for

files other than @file{lib@var{namespec}.a}.  Specifically, on ELF

and SunOS systems, @command{ld} will search a directory for a library

called @file{lib@var{namespec}.so} before searching for one called

@file{lib@var{namespec}.a}.  (By convention, a @code{.so} extension

indicates a shared library.)  Note that this behavior does not apply

to @file{:@var{filename}}, which always specifies a file called

@var{filename}.

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 @option{-(} option for a way to force the linker to search

archives multiple times.

You may list the same archive multiple times on the command line.

@ifset GENERIC

This type of archive searching is standard for Unix linkers.  However,

if you are using @command{ld} on AIX, note that it is different from the

behaviour of the AIX linker.

@end ifset

@cindex search directory, from cmd line

@kindex -L @var{dir}

@kindex --library-path=@var{dir}

@item -L @var{searchdir}

@itemx --library-path=@var{searchdir}

Add path @var{searchdir} to the list of paths that @command{ld} will search

for archive libraries and @command{ld} control scripts.  You may use this

option any number of times.  The directories are searched in the order

in which they are specified on the command line.  Directories specified

on the command line are searched before the default directories.  All

@option{-L} options apply to all @option{-l} options, regardless of the

order in which the options appear.  @option{-L} options do not affect

how @command{ld} searches for a linker script unless @option{-T}

option is specified.

If @var{searchdir} begins with @code{=}, then the @code{=} will be replaced

by the @dfn{sysroot prefix}, a path specified when the linker is configured.

@ifset UsesEnvVars

The default set of paths searched (without being specified with

@samp{-L}) depends on which emulation mode @command{ld} is using, and in

some cases also on how it was configured.  @xref{Environment}.

@end ifset

The paths can also be specified in a link script with the

@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}

Emulate the @var{emulation} linker.  You can list the available

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 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.

@item

The values assigned to symbols.

Note - symbols whose values are computed by an expression which

involves a reference to a previous value of the same symbol may not

have correct result displayed in the link map.  This is because the

linker discards intermediate results and only retains the final value

of an expression.  Under such circumstances the linker will display

the final value enclosed by square brackets.  Thus for example a

linker script containing:

@smallexample

   foo = 1

   foo = foo * 4

   foo = foo + 8

@end smallexample

will produce the following output in the link map if the @option{-M}

option is used:

@smallexample

   0x00000001                foo = 0x1

   [0x0000000c]                foo = (foo * 0x4)

   [0x0000000c]                foo = (foo + 0x8)

@end smallexample

See @ref{Expressions} for more information about expressions in linker

scripts.

@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

@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, and disable linking against shared

libraries.  If the output format supports Unix style magic numbers,

mark the output as @code{OMAGIC}. Note: Although a writable text section

is allowed for PE-COFF targets, it does not conform to the format

specification published by Microsoft.

@kindex --no-omagic

@cindex OMAGIC

@item --no-omagic

This option negates most of the effects of the @option{-N} option.  It

sets the text section to be read-only, and forces the data segment to

be page-aligned.  Note - this option does not enable linking against

shared libraries.  Use @option{-Bdynamic} for this.

@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 @command{ld}; if this

option is not specified, the name @file{a.out} is used by default.  The

script command @code{OUTPUT} can also specify the output file name.

@kindex -O @var{level}

@cindex generating optimized output

@item -O @var{level}

If @var{level} is a numeric values greater than zero @command{ld} optimizes

the output.  This might take significantly longer and therefore probably

should only be enabled for the final binary.  At the moment this

option only affects ELF shared library generation.  Future releases of

the linker may make more use of this option.  Also currently there is

no difference in the linker's behaviour for different non-zero values

of this option.  Again this may change with future releases.

@kindex -q

@kindex --emit-relocs

@cindex retain relocations in final executable

@item -q

@itemx --emit-relocs

Leave relocation sections and contents in fully linked executables.

Post link analysis and optimization tools may need this information in

order to perform correct modifications of executables.  This results

in larger executables.

This option is currently only supported on ELF platforms.

@kindex --force-dynamic

@cindex forcing the creation of dynamic sections

@item --force-dynamic

Force the output file to have dynamic sections.  This option is specific

to VxWorks targets.

@cindex partial link

@cindex relocatable output

@kindex -r

@kindex --relocatable

@item -r

@itemx --relocatable

Generate relocatable output---i.e., generate an output file that can in

turn serve as input to @command{ld}.  This is often called @dfn{partial

linking}.  As a side effect, in environments that support standard Unix

magic numbers, this option also sets the output file's magic number to

@code{OMAGIC}.

@c ; see @option{-N}.

If this option is not specified, an absolute file is produced.  When

linking C++ programs, this option @emph{will not} resolve references to

constructors; to do that, use @samp{-Ur}.

When an input file does not have the same format as the output file,

partial linking is only supported if that input file does not contain any

relocations.  Different output formats can have further restrictions; for

example some @code{a.out}-based formats do not support partial linking

with input files in other formats at all.

This option does the same thing as @samp{-i}.

@kindex -R @var{file}

@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 @option{-R} option is

followed by a directory name, rather than a file name, it is treated as

the @option{-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 @command{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

@command{ld}'s default linker script (rather than adding to it), so

@var{commandfile} must specify everything necessary to describe the

output file.  @xref{Scripts}.  If @var{scriptfile} does not exist in

the current directory, @code{ld} looks for it in the directories

specified by any preceding @samp{-L} options.  Multiple @samp{-T}

options accumulate.

@kindex -dT @var{script}

@kindex --default-script=@var{script}

@cindex script files

@item -dT @var{scriptfile}

@itemx --default-script=@var{scriptfile}

Use @var{scriptfile} as the default linker script.  @xref{Scripts}.

This option is similar to the @option{--script} option except that

processing of the script is delayed until after the rest of the

command line has been processed.  This allows options placed after the

@option{--default-script} option on the command line to affect the

behaviour of the linker script, which can be important when the linker

command line cannot be directly controlled by the user.  (eg because

the command line is being constructed by another tool, such as

@samp{gcc}).

@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 @command{ld}.  When linking C++ programs, @samp{-Ur}

@emph{does} resolve references to constructors, unlike @samp{-r}.

It does not work to use @samp{-Ur} on files that were themselves linked

with @samp{-Ur}; once the constructor table has been built, it cannot

be added to.  Use @samp{-Ur} only for the last partial link, and

@samp{-r} for the others.

@kindex --unique[=@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