ld.1

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.\" Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
.\" 2001 Free Software Foundation, Inc.
.\" See section COPYING for conditions for redistribution
.TH ld 1 "" "Free Software Foundation" "GNU Development Tools"
.de BP
.sp
.ti \-.2i
\(**
..

.SH NAME
ld \- the GNU linker

.SH SYNOPSIS
.hy 0
.na
.TP
.B ld 
.RB "[\|" \-o "
.I output\c
\&\|] \c
.I objfile\c
\&.\|.\|.
.br
.RB "[\|" \-A\c
.I architecture\c
\&\|] 
.RB "[\|" "\-b\ "\c
.I input-format\c
\&\|] 
.RB "[\|" \-Bstatic "\|]"  
.RB "[\|" \-Bgroup "\|]"  
.RB "[\|" \-Bdynamic "\|]"  
.RB "[\|" \-Bsymbolic "\|]"  
.RB "[\|" "\-c\ "\c
.I commandfile\c
\&\|] 
.RB "[\|" \-\-cref "\|]"
.RB "[\|" \-d | \-dc | \-dp\c
\|]
.br
.RB "[\|" "\-defsym\ "\c
.I symbol\c
\&=\c
.I expression\c
\&\|]
.RB "[\|" \-\-demangle "\|]"
.RB "[\|" \-\-no\-demangle "\|]"
.RB "[\|" "\-e\ "\c
.I entry\c
\&\|] 
.RB "[\|" \-embedded\-relocs "\|]"
.RB "[\|" \-E "\|]" 
.RB "[\|" \-export\-dynamic "\|]"
.RB "[\|" "\-f\ "\c
.I name\c
\&\|]
.RB "[\|" "\-\-auxiliary\ "\c
.I name\c
\&\|]
.RB "[\|" "\-F\ "\c
.I name\c
\&\|]
.RB "[\|" "\-\-filter\ "\c
.I name\c
\&\|]
.RB "[\|" "\-format\ "\c
.I input-format\c
\&\|] 
.RB "[\|" \-g "\|]" 
.RB "[\|" \-G
.I size\c
\&\|]
.RB "[\|" "\-h\ "\c
.I name\c
\&\|]
.RB "[\|" "\-soname\ "\c
.I name\c
\&\|]
.RB "[\|" \-\-help "\|]"
.RB "[\|" \-i "\|]"
.RB "[\|" \-l\c
.I ar\c
\&\|] 
.RB "[\|" \-L\c
.I searchdir\c
\&\|] 
.RB "[\|" \-M "\|]" 
.RB "[\|" \-Map
.I mapfile\c
\&\|] 
.RB "[\|" \-m
.I emulation\c
\&\|] 
.RB "[\|" \-n | \-N "\|]" 
.RB "[\|" \-noinhibit-exec "\|]" 
.RB "[\|" \-no\-keep\-memory "\|]" 
.RB "[\|" \-no\-warn\-mismatch "\|]" 
.RB "[\|" \-O\c
.I level\c
\&\|]
.RB "[\|" "\--oformat\ "\c
.I output-format\c
\&\|] 
.RB "[\|" "\-R\ "\c
.I filename\c
\&\|]
.RB "[\|" \-relax "\|]"
.RB "[\|" \-r | \-Ur "\|]" 
.RB "[\|" "\-rpath\ "\c
.I directory\c
\&\|]
.RB "[\|" "\-rpath\-link\ "\c
.I directory\c
\&\|]
.RB "[\|" \-S "\|]" 
.RB "[\|" \-s "\|]" 
.RB "[\|" \-shared "\|]" 
.RB "[\|" \-sort\-common "\|]" 
.RB "[\|" "\-split\-by\-reloc\ "\c
.I count\c
\&\|]
.RB "[\|" \-split\-by\-file "\|]" 
.RB "[\|" "\-T\ "\c
.I commandfile\c
\&\|]  
.RB "[\|" "\-\-section\-start\ "\c
.I sectionname\c
\&=\c
.I sectionorg\c
\&\|]
.RB "[\|" "\-Ttext\ "\c
.I textorg\c
\&\|] 
.RB "[\|" "\-Tdata\ "\c
.I dataorg\c
\&\|] 
.RB "[\|" "\-Tbss\ "\c
.I bssorg\c
\&\|]
.RB "[\|" \-t "\|]" 
.RB "[\|" "\-u\ "\c
.I sym\c
\&]
.RB "[\|" \-V "\|]"
.RB "[\|" \-v "\|]"
.RB "[\|" \-\-verbose "\|]"
.RB "[\|" \-\-version "\|]"
.RB "[\|" \-warn\-common "\|]" 
.RB "[\|" \-warn\-constructors "\|]" 
.RB "[\|" \-warn\-multiple\-gp "\|]" 
.RB "[\|" \-warn\-once "\|]" 
.RB "[\|" \-warn\-section\-align "\|]" 
.RB "[\|" \-\-whole\-archive "\|]" 
.RB "[\|" \-\-no\-whole\-archive "\|]" 
.RB "[\|" "\-\-wrap\ "\c
.I symbol\c
\&\|]
.RB "[\|" \-X "\|]" 
.RB "[\|" \-x "\|]" 
.ad b
.hy 1
.SH DESCRIPTION
\c
.B ld\c
\& combines a number of object and archive files, relocates
their data and ties up symbol references. Often the last step in
building a new compiled program to run is a call to \c
.B ld\c
\&.

\c
.B ld\c
\& accepts Linker Command Language files 
to provide explicit and total control over the linking process.
This man page does not describe the command language; see the `\|\c
.B ld\c
\|' entry in `\|\c
.B info\c
\|', or the manual
.I
ld: the GNU linker
\&, for full details on the command language and on other aspects of
the GNU linker. 

This version of \c
.B ld\c
\& uses the general purpose BFD libraries
to operate on object files. This allows \c
.B ld\c
\& to read, combine, and
write object files in many different formats\(em\&for example, COFF or
\c
.B a.out\c
\&.  Different formats may be linked together to produce any
available kind of object file.  You can use `\|\c
.B objdump \-i\c
\|' to get a list of formats supported on various architectures; see 
.BR objdump ( 1 ).

Aside from its flexibility, the GNU linker is more helpful than other
linkers in providing diagnostic information.  Many linkers abandon
execution immediately upon encountering an error; whenever possible,
\c
.B ld\c
\& continues executing, allowing you to identify other errors
(or, in some cases, to get an output file in spite of the error).

The GNU linker \c
.B ld\c
\& 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 through the command line,
and through environment variables.

.SH OPTIONS
The plethora of command-line options may seem intimidating, but in
actual practice few of them are used in any particular context.
For instance, a frequent use of \c
.B ld\c
\& is to link standard Unix
object files on a standard, supported Unix system.  On such a system, to
link a file \c
.B hello.o\c
\&:
.sp
.br
$\ ld\ \-o\ output\ /lib/crt0.o\ hello.o\ \-lc
.br
.sp
This tells \c
.B ld\c
\& to produce a file called \c
.B output\c
\& as the
result of linking the file \c
.B /lib/crt0.o\c
\& with \c
.B hello.o\c
\& and
the library \c
.B libc.a\c
\& which will come from the standard search
directories.

The command-line options to \c
.B ld\c
\& may be specified in any order, and
may be repeated at will.  For the most part, repeating an option with a
different argument will either have no further effect, or override prior
occurrences (those further to the left on the command line) of an
option.  

The exceptions\(em\&which may meaningfully be used more than once\(em\&are
\c
.B \-A\c
\&, \c
.B \-b\c
\& (or its synonym \c
.B \-format\c
\&), \c
.B \-defsym\c
\&, \c
.B \-\-section\-start\c
\&, \c
.B \-L\c
\&, \c
.B \-l\c
\&, \c
.B \-R\c
\&, and \c
.B \-u\c
\&.

The list of object files to be linked together, shown as \c
.I objfile\c
\&,
may follow, precede, or be mixed in with command-line options; save that
an \c
.I objfile\c
\& argument may not be placed between an option flag and
its argument.

Usually the linker is invoked with at least one object file, but other
forms of binary input files can also be specified with \c
.B \-l\c
\&,
\c
.B \-R\c
\&, and the script command language.  If \c
.I no\c
\& binary input
files at all are specified, the linker does not produce any output, and
issues the message `\|\c
.B No input files\c
\|'.

Option arguments must either follow the option letter without intervening
whitespace, or be given as separate arguments immediately following the
option that requires them.

.TP
.BI "-A" "architecture"
In the current release of \c
.B ld\c
\&, this option is useful only for the
Intel 960 family of architectures.  In that \c
.B ld\c
\& configuration, the
\c
.I architecture\c
\& argument is one of the two-letter names identifying
members of the 960 family; the option specifies the desired output
target, and warns of any incompatible instructions in the input files.
It also modifies the linker's search strategy for archive libraries, to
support the use of libraries specific to each particular
architecture, by including in the search loop names suffixed with the
string identifying the architecture.

For example, if your \c
.B ld\c
\& command line included `\|\c
.B \-ACA\c
\|' as
well as `\|\c
.B \-ltry\c
\|', the linker would look (in its built-in search
paths, and in any paths you specify with \c
.B \-L\c
\&) for a library with
the names
.sp
.br
try
.br
libtry.a
.br
tryca
.br
libtryca.a
.br
.sp

The first two possibilities would be considered in any event; the last
two are due to the use of `\|\c
.B \-ACA\c
\|'.

Future releases of \c
.B ld\c
\& may support similar functionality for
other architecture families.

You can meaningfully use \c
.B \-A\c
\& more than once on a command line, if
an architecture family allows combination of target architectures; each
use will add another pair of name variants to search for when \c
.B \-l
specifies a library.

.TP
.BI "\-b " "input-format"
Specify the binary format for input object files that follow this option
on the command line.  You don't usually need to specify this, as
\c
.B ld\c
\& is configured to expect as a default input format the most
usual format on each machine.  \c
.I input-format\c
\& is a text string, the
name of a particular format supported by the BFD libraries.  
\c
.B \-format \c
.I input-format\c
\&\c
\& has the same effect, as does the script command
.BR TARGET .