872 lines
18 KiB
Groff
872 lines
18 KiB
Groff
.\" Copyright (c) 1991, 1992 Free Software Foundation
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.\" See section COPYING for conditions for redistribution
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.TH ld 1 "17 August 1992" "cygnus support" "GNU Development Tools"
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.de BP
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.sp
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.ti \-.2i
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\(**
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..
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.SH NAME
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ld \- the GNU linker
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.SH SYNOPSIS
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.hy 0
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.na
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.TP
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.B ld
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.RB "[\|" \-o "
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.I output\c
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\&\|] \c
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.I objfile\c
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\&.\|.\|.
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.br
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.RB "[\|" \-A\c
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.I architecture\c
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\&\|]
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.RB "[\|" "\-b\ "\c
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.I input-format\c
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\&\|]
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.RB "[\|" \-Bstatic "\|]"
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.RB "[\|" "\-c\ "\c
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.I commandfile\c
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\&\|]
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.RB "[\|" \-d | \-dc | \-dp\c
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\|]
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.br
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.RB "[\|" "\-defsym\ "\c
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.I symbol\c
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\& = \c
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.I expression\c
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\&\|]
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.RB "[\|" "\-e\ "\c
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.I entry\c
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\&\|]
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.RB "[\|" \-F "\|]"
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.RB "[\|" "\-F\ "\c
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.I format\c
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\&\|]
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.RB "[\|" "\-format\ "\c
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.I input-format\c
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\&\|]
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.RB "[\|" \-g "\|]"
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.RB "[\|" \-G\c
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.I size\c
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\&\|]
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.RB "[\|" \-\-help "\|]"
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.RB "[\|" \-i "\|]"
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.RB "[\|" \-l\c
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.I ar\c
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\&\|]
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.RB "[\|" \-L\c
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.I searchdir\c
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\&\|]
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.RB "[\|" \-M "\|]"
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.RB "[\|" \-Map\c
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.I mapfile\c
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\&\|]
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.RB "[\|" \-m\c
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.I emulation\c
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\&\|]
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.RB "[\|" \-n | \-N "\|]"
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.RB "[\|" \-noinhibit-exec "\|]"
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.RB "[\|" "\-oformat\ "\c
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.I output-format\c
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\&\|]
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.RB "[\|" "\-R\ "\c
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.I filename\c
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\&\|]
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.RB "[\|" \-relax "\|]"
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.RB "[\|" \-r | \-Ur "\|]"
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.RB "[\|" \-S "\|]"
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.RB "[\|" \-s "\|]"
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.RB "[\|" \-sort\-common "\|]"
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.RB "[\|" "\-T\ "\c
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.I commandfile\c
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\&\|]
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.RB "[\|" "\-Ttext\ "\c
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.I textorg\c
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\&\|]
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.RB "[\|" "\-Tdata\ "\c
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.I dataorg\c
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\&\|]
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.RB "[\|" "\-Tbss\ "\c
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.I bssorg\c
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\&\|]
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.RB "[\|" \-t "\|]"
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.RB "[\|" "\-u\ "\c
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.I sym\c
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\&]
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.RB "[\|" \-V "\|]"
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.RB "[\|" \-v "\|]"
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.RB "[\|" \-\-version "\|]"
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.RB "[\|" \-warn\-common "\|]"
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.RB "[\|" \-X "\|]"
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.RB "[\|" \-x "\|]"
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.ad b
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.hy 1
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.SH DESCRIPTION
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\c
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.B ld\c
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\& combines a number of object and archive files, relocates
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their data and ties up symbol references. Often the last step in
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building a new compiled program to run is a call to \c
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.B ld\c
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\&.
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\c
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.B ld\c
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\& accepts Linker Command Language files
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to provide explicit and total control over the linking process.
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This man page does not describe the command language; see the `\|\c
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.B ld\c
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\|' entry in `\|\c
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.B info\c
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\|', or the manual
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.I
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ld: the GNU linker
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\&, for full details on the command language and on other aspects of
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the GNU linker.
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This version of \c
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.B ld\c
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\& uses the general purpose BFD libraries
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to operate on object files. This allows \c
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.B ld\c
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\& to read, combine, and
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write object files in many different formats\(em\&for example, COFF or
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\c
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.B a.out\c
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\&. Different formats may be linked together to produce any
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available kind of object file. You can use `\|\c
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.B objdump \-i\c
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\|' to get a list of formats supported on various architectures; see
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.BR objdump ( 1 ).
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Aside from its flexibility, the GNU linker is more helpful than other
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linkers in providing diagnostic information. Many linkers abandon
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execution immediately upon encountering an error; whenever possible,
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\c
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.B ld\c
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\& continues executing, allowing you to identify other errors
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(or, in some cases, to get an output file in spite of the error).
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The GNU linker \c
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.B ld\c
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\& is meant to cover a broad range of situations,
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and to be as compatible as possible with other linkers. As a result,
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you have many choices to control its behavior through the command line,
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and through environment variables.
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.SH OPTIONS
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The plethora of command-line options may seem intimidating, but in
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actual practice few of them are used in any particular context.
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For instance, a frequent use of \c
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.B ld\c
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\& is to link standard Unix
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object files on a standard, supported Unix system. On such a system, to
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link a file \c
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.B hello.o\c
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\&:
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.sp
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.br
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$\ ld\ \-o\ output\ /lib/crt0.o\ hello.o\ \-lc
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.br
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.sp
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This tells \c
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.B ld\c
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\& to produce a file called \c
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.B output\c
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\& as the
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result of linking the file \c
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.B /lib/crt0.o\c
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\& with \c
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.B hello.o\c
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\& and
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the library \c
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.B libc.a\c
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\& which will come from the standard search
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directories.
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The command-line options to \c
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.B ld\c
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\& may be specified in any order, and
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may be repeated at will. For the most part, repeating an option with a
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different argument will either have no further effect, or override prior
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occurrences (those further to the left on the command line) of an
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option.
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The exceptions\(em\&which may meaningfully be used more than once\(em\&are
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\c
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.B \-A\c
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\&, \c
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.B \-b\c
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\& (or its synonym \c
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.B \-format\c
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\&), \c
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.B \-defsym\c
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\&,
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\c
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.B \-L\c
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\&, \c
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.B \-l\c
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\&, \c
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.B \-R\c
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\&, and \c
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.B \-u\c
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\&.
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The list of object files to be linked together, shown as \c
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.I objfile\c
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\&,
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may follow, precede, or be mixed in with command-line options; save that
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an \c
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.I objfile\c
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\& argument may not be placed between an option flag and
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its argument.
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Usually the linker is invoked with at least one object file, but other
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forms of binary input files can also be specified with \c
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.B \-l\c
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\&,
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\c
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.B \-R\c
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\&, and the script command language. If \c
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.I no\c
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\& binary input
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files at all are specified, the linker does not produce any output, and
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issues the message `\|\c
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.B No input files\c
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\|'.
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Option arguments must either follow the option letter without intervening
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whitespace, or be given as separate arguments immediately following the
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option that requires them.
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.TP
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.BI "-A" "architecture"\c
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\&
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In the current release of \c
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.B ld\c
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\&, this option is useful only for the
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Intel 960 family of architectures. In that \c
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.B ld\c
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\& configuration, the
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\c
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.I architecture\c
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\& argument is one of the two-letter names identifying
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members of the 960 family; the option specifies the desired output
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target, and warns of any incompatible instructions in the input files.
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It also modifies the linker's search strategy for archive libraries, to
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support the use of libraries specific to each particular
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architecture, by including in the search loop names suffixed with the
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string identifying the architecture.
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For example, if your \c
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.B ld\c
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\& command line included `\|\c
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.B \-ACA\c
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\|' as
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well as `\|\c
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.B \-ltry\c
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\|', the linker would look (in its built-in search
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paths, and in any paths you specify with \c
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.B \-L\c
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\&) for a library with
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the names
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.sp
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.br
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try
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.br
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libtry.a
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.br
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tryca
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.br
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libtryca.a
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.br
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.sp
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The first two possibilities would be considered in any event; the last
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two are due to the use of `\|\c
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.B \-ACA\c
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\|'.
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Future releases of \c
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.B ld\c
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\& may support similar functionality for
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other architecture families.
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You can meaningfully use \c
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.B \-A\c
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\& more than once on a command line, if
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an architecture family allows combination of target architectures; each
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use will add another pair of name variants to search for when \c
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.B \-l\c
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\&
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specifies a library.
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.TP
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.BI "\-b " "input-format"\c
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\&
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Specify the binary format for input object files that follow this option
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on the command line. You don't usually need to specify this, as
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\c
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.B ld\c
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\& is configured to expect as a default input format the most
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usual format on each machine. \c
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.I input-format\c
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\& is a text string, the
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name of a particular format supported by the BFD libraries.
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\c
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.B \-format \c
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.I input-format\c
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\&\c
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\& has the same effect, as does the script command
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.BR TARGET .
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You may want to use this option if you are linking files with an unusual
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binary format. You can also use \c
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.B \-b\c
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\& to switch formats explicitly (when
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linking object files of different formats), by including
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\c
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.B \-b \c
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.I input-format\c
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\&\c
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\& before each group of object files in a
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particular format.
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The default format is taken from the environment variable
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.B GNUTARGET\c
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\&. You can also define the input
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format from a script, using the command \c
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.B TARGET\c
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\&.
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.TP
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.B \-Bstatic
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This flag is accepted for command-line compatibility with the SunOS linker,
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but has no effect on \c
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.B ld\c
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\&.
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.TP
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.BI "\-c " "commandfile"\c
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\&
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Directs \c
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.B ld\c
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\& to read link commands from the file
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\c
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.I commandfile\c
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\&. These commands will completely override \c
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.B ld\c
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\&'s
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default link format (rather than adding to it); \c
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.I commandfile\c
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\& must
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specify everything necessary to describe the target format.
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You may also include a script of link commands directly in the command
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line by bracketing it between `\|\c
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.B {\c
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\|' and `\|\c
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.B }\c
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\|' characters.
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.TP
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.B \-d
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.TP
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.B \-dc
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.TP
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.B \-dp
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These three options are equivalent; multiple forms are supported for
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compatibility with other linkers. Use any of them to make \c
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.B ld\c
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\&
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assign space to common symbols even if a relocatable output file is
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specified (\c
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.B \-r\c
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\&). The script command
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\c
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.B FORCE_COMMON_ALLOCATION\c
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\& has the same effect.
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.TP
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.BI "-defsym " "symbol"\c
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\& = \c
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.I expression\c
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\&
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Create a global symbol in the output file, containing the absolute
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address given by \c
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.I expression\c
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\&. You may use this option as many
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times as necessary to define multiple symbols in the command line. A
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limited form of arithmetic is supported for the \c
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.I expression\c
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\& in this
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context: you may give a hexadecimal constant or the name of an existing
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symbol, or use \c
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.B +\c
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\& and \c
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.B \-\c
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\& to add or subtract hexadecimal
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constants or symbols. If you need more elaborate expressions, consider
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using the linker command language from a script.
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.TP
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.BI "-e " "entry"\c
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\&
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Use \c
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.I entry\c
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\& as the explicit symbol for beginning execution of your
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program, rather than the default entry point. for a
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discussion of defaults and other ways of specifying the
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entry point.
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.TP
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.B \-F
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.TP
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.BI "-F" "format"\c
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\&
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Some older linkers used this option throughout a compilation toolchain
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for specifying object-file format for both input and output object
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files. \c
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.B ld\c
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\&'s mechanisms (the \c
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.B \-b\c
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\& or \c
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.B \-format\c
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\& options
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for input files, the \c
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.B TARGET\c
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\& command in linker scripts for output
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files, the \c
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.B GNUTARGET\c
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\& environment variable) are more flexible, but
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but it accepts (and ignores) the \c
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.B \-F\c
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\& option flag for compatibility
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with scripts written to call the old linker.
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.TP
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.BI "\-format " "input\-format"\c
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\&
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Synonym for \c
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.B \-b\c
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\& \c
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.I input\-format\c
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\&.
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.TP
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.B \-g
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Accepted, but ignored; provided for compatibility with other tools.
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|
|
.TP
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|
.BI "\-G " "size"\c
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Set the maximum size of objects to be optimized using the GP register
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to
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.I size
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under MIPS ECOFF. Ignored for other object file formats.
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.TP
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.B \-\-help
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Print a summary of the command-line options on the standard output and exit.
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This option and
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.B \-\-version
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begin with two dashes instead of one
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for compatibility with other GNU programs. The other options start with
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only one dash for compatibility with other linkers.
|
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|
.TP
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.B \-i
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Perform an incremental link (same as option \c
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.B \-r\c
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\&).
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.TP
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.BI "\-l" "ar"\c
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\&
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Add an archive file \c
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.I ar\c
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\& to the list of files to link. This
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option may be used any number of times. \c
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.B ld\c
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\& will search its
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path-list for occurrences of \c
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.B lib\c
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.I ar\c
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\&.a\c
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\& for every \c
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.I ar\c
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\&
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specified.
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.TP
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.BI "\-L" "searchdir"\c
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\&
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This command adds path \c
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.I searchdir\c
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\& to the list of paths that
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\c
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.B ld\c
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\& will search for archive libraries. You may use this option
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any number of times.
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The default set of paths searched (without being specified with
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\c
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.B \-L\c
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\&) depends on what emulation mode \c
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.B ld\c
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\& is using, and in
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some cases also on how it was configured. The
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paths can also be specified in a link script with the \c
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.B SEARCH_DIR\c
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\&
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command.
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.TP
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.B \-M
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Print (to the standard output file) a link map\(em\&diagnostic information
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about where symbols are mapped by \c
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.B ld\c
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\&, and information on global
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common storage allocation.
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.TP
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.BI "\-Map " "mapfile"\c
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Print to the file
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.I mapfile
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a link map\(em\&diagnostic information
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about where symbols are mapped by \c
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.B ld\c
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\&, and information on global
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common storage allocation.
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.TP
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.BI "\-m " "emulation"\c
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Emulate the
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.I emulation
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linker. You can list the available emulations with the
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.I \-V
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option. This option overrides the compiled-in default, which is the
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system for which you configured
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.BR ld .
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.TP
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.B \-N
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specifies readable and writable \c
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.B text\c
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\& and \c
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.B data\c
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\& sections. If
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the output format supports Unix style magic numbers, the output is
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marked as \c
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.B OMAGIC\c
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\&.
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When you use the `\|\c
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.B \-N\c
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|
\&\|' option, the linker does not page-align the
|
|
data segment.
|
|
|
|
.TP
|
|
.B \-n
|
|
sets the text segment to be read only, and \c
|
|
.B NMAGIC\c
|
|
\& is written
|
|
if possible.
|
|
|
|
.TP
|
|
.B \-noinhibit\-exec
|
|
Normally, the linker will not produce an output file if it encounters
|
|
errors during the link process. With this flag, you can specify that
|
|
you wish the output file retained even after non-fatal errors.
|
|
|
|
.TP
|
|
.BI "\-o " "output"\c
|
|
\&
|
|
.I output\c
|
|
\&
|
|
\c
|
|
.I output\c
|
|
\& is a name for the program produced by \c
|
|
.B ld\c
|
|
\&; if this
|
|
option is not specified, the name `\|\c
|
|
.B a.out\c
|
|
\|' is used by default. The
|
|
script command \c
|
|
.B OUTPUT\c
|
|
\& can also specify the output file name.
|
|
|
|
.TP
|
|
.BI "\-oformat " "output\-format"\c
|
|
\&
|
|
Specify the binary format for the output object file.
|
|
You don't usually need to specify this, as
|
|
\c
|
|
.B ld\c
|
|
\& is configured to produce as a default output format the most
|
|
usual format on each machine. \c
|
|
.I output-format\c
|
|
\& is a text string, the
|
|
name of a particular format supported by the BFD libraries.
|
|
The script command
|
|
.B OUTPUT_FORMAT
|
|
can also specify the output format, but this option overrides it.
|
|
|
|
.TP
|
|
.BI "\-R " "filename"\c
|
|
\&
|
|
.I file\c
|
|
\&
|
|
Read symbol names and their addresses from \c
|
|
.I filename\c
|
|
\&, 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.
|
|
|
|
.TP
|
|
.B \-relax
|
|
An option with machine dependent effects. Currently this option is only
|
|
supported on the H8/300.
|
|
|
|
On some platforms, use this option to perform global optimizations that
|
|
become possible when the linker resolves addressing in your program, such
|
|
as relaxing address modes and synthesizing new instructions in the
|
|
output object file.
|
|
|
|
On platforms where this is not supported, `\|\c
|
|
.B \-relax\c
|
|
\&\|' is accepted, but has no effect.
|
|
|
|
.TP
|
|
.B \-r
|
|
Generates relocatable output\(em\&i.e., generate an output file that can in
|
|
turn serve as input to \c
|
|
.B ld\c
|
|
\&. This is often called \c
|
|
.I partial
|
|
linking\c
|
|
\&. As a side effect, in environments that support standard Unix
|
|
magic numbers, this option also sets the output file's magic number to
|
|
\c
|
|
.B OMAGIC\c
|
|
\&.
|
|
If this option is not specified, an absolute file is produced. When
|
|
linking C++ programs, this option \c
|
|
.I will not\c
|
|
\& resolve references to
|
|
constructors; \c
|
|
.B \-Ur\c
|
|
\& is an alternative.
|
|
|
|
This option does the same as \c
|
|
.B \-i\c
|
|
\&.
|
|
|
|
.TP
|
|
.B \-S
|
|
Omits debugger symbol information (but not all symbols) from the output file.
|
|
|
|
.TP
|
|
.B \-s
|
|
Omits all symbol information from the output file.
|
|
|
|
.TP
|
|
.B \-sort\-common
|
|
Normally, when
|
|
.B 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 option disables that sorting.
|
|
|
|
.TP
|
|
.BI "\-Tbss " "org"\c
|
|
.TP
|
|
.BI "\-Tdata " "org"\c
|
|
.TP
|
|
.BI "\-Ttext " "org"\c
|
|
Use \c
|
|
.I org\c
|
|
\& as the starting address for\(em\&respectively\(em\&the
|
|
\c
|
|
.B bss\c
|
|
\&, \c
|
|
.B data\c
|
|
\&, or the \c
|
|
.B text\c
|
|
\& segment of the output file.
|
|
\c
|
|
.I textorg\c
|
|
\& must be a hexadecimal integer.
|
|
|
|
.TP
|
|
.BI "\-T " "commandfile"\c
|
|
\&
|
|
.TP
|
|
.BI "\-T" "commandfile"\c
|
|
Equivalent to \c
|
|
.B \-c \c
|
|
.I commandfile\c
|
|
\&\c
|
|
\&; supported for compatibility with
|
|
other tools.
|
|
|
|
.TP
|
|
.B \-t
|
|
Prints names of input files as \c
|
|
.B ld\c
|
|
\& processes them.
|
|
|
|
.TP
|
|
.BI "\-u " "sym"
|
|
Forces \c
|
|
.I sym\c
|
|
\& to be entered in the output file as an undefined symbol.
|
|
This may, for example, trigger linking of additional modules from
|
|
standard libraries. \c
|
|
.B \-u\c
|
|
\& may be repeated with different option
|
|
arguments to enter additional undefined symbols.
|
|
|
|
.TP
|
|
.B \-Ur
|
|
For anything other than C++ programs, this option is equivalent to
|
|
\c
|
|
.B \-r\c
|
|
\&: it generates relocatable output\(em\&i.e., an output file that can in
|
|
turn serve as input to \c
|
|
.B ld\c
|
|
\&. When linking C++ programs, \c
|
|
.B \-Ur\c
|
|
\&
|
|
\c
|
|
.I will\c
|
|
\& resolve references to constructors, unlike \c
|
|
.B \-r\c
|
|
\&.
|
|
|
|
.TP
|
|
.B \-V
|
|
Display the version number for \c
|
|
.B ld
|
|
and list the supported emulations.
|
|
Display which input files can and can not be opened.
|
|
|
|
.TP
|
|
.B \-v
|
|
Display the version number for \c
|
|
.B ld\c
|
|
\&.
|
|
|
|
.TP
|
|
.B \-\-version
|
|
Display the version number for \c
|
|
.B ld
|
|
and exit.
|
|
|
|
.TP
|
|
.B \-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
|
|
you to find potential problems from combining global symbols.
|
|
|
|
.TP
|
|
.B \-X
|
|
If \c
|
|
.B \-s\c
|
|
\& or \c
|
|
.B \-S\c
|
|
\& is also specified, delete only local symbols
|
|
beginning with `\|\c
|
|
.B L\c
|
|
\|'.
|
|
|
|
.TP
|
|
.B \-x
|
|
If \c
|
|
.B \-s\c
|
|
\& or \c
|
|
.B \-S\c
|
|
\& is also specified, delete all local symbols,
|
|
not just those beginning with `\|\c
|
|
.B L\c
|
|
\|'.
|
|
|
|
.PP
|
|
|
|
.SH ENVIRONMENT
|
|
\c
|
|
You can change the behavior of
|
|
.B ld\c
|
|
\& with the environment variable \c
|
|
.B GNUTARGET\c
|
|
\&.
|
|
|
|
\c
|
|
.B GNUTARGET\c
|
|
\& determines the input-file object format if you don't
|
|
use \c
|
|
.B \-b\c
|
|
\& (or its synonym \c
|
|
.B \-format\c
|
|
\&). Its value should be one
|
|
of the BFD names for an input format. If there is no
|
|
\c
|
|
.B GNUTARGET\c
|
|
\& in the environment, \c
|
|
.B ld\c
|
|
\& uses the natural format
|
|
of the host. If \c
|
|
.B GNUTARGET\c
|
|
\& is set to \c
|
|
.B default\c
|
|
\& 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 flag 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.
|
|
|
|
.PP
|
|
|
|
.SH "SEE ALSO"
|
|
|
|
.BR objdump ( 1 )
|
|
.br
|
|
.br
|
|
.RB "`\|" ld "\|' and `\|" binutils "\|'"
|
|
entries in
|
|
.B info\c
|
|
.br
|
|
.I
|
|
ld: the GNU linker\c
|
|
, Steve Chamberlain and Roland Pesch;
|
|
.I
|
|
The GNU Binary Utilities\c
|
|
, Roland H. Pesch.
|
|
|
|
.SH COPYING
|
|
Copyright (c) 1991, 1992 Free Software Foundation, Inc.
|
|
.PP
|
|
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.
|
|
.PP
|
|
Permission is granted to copy and distribute modified versions of this
|
|
manual under the conditions for verbatim copying, provided that the
|
|
entire resulting derived work is distributed under the terms of a
|
|
permission notice identical to this one.
|
|
.PP
|
|
Permission is granted to copy and distribute translations of this
|
|
manual into another language, under the above conditions for modified
|
|
versions, except that this permission notice may be included in
|
|
translations approved by the Free Software Foundation instead of in
|
|
the original English.
|