freebsd-dev/gnu/usr.bin/ld/ld.1

.\"
.\" Copyright (c) 1993 Paul Kranenburg
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.\"    must display the following acknowledgement:
.\"      This product includes software developed by Paul Kranenburg.
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.\"	$Id: ld.1,v 1.19 1997/08/23 21:59:41 steve Exp $
.\"
.Dd October 14, 1993
.Dt LD 1
.Os FreeBSD
.Sh NAME
.Nm ld
.Nd link editor
.Sh SYNOPSIS
.Nm ld
.Op Fl fMNnrSstXxz
.Bk -words
.Op Fl A Ar symbol-file
.Op Fl assert Ar keyword
.Op Fl B Ns Ar linkmode
.Op Fl D Ar datasize
.Op Fl d Ar c
.Op Fl d Ar p
.Op Fl e Ar entry
.Op Fl l Ns Ar library-specifier
.Op Fl L Ns Ar library-search-path
.Op Fl nostdlib
.Op Fl O Ar filename
.Op Fl o Ar filename
.Op Fl R Ns Ar record-library-search-path
.Op Fl T Ar address
.Op Fl u Ar symbol
.Op Fl V Ar shlib-version
.Op Fl y Ar symbol
.Ek
.Sh DESCRIPTION
.Nm
combines the object and archive files given on the command line into a new
object file. The output object file is either an executable program, a
shared object suitable for loading at run-time, or an object file that can
once again be processed by
.Nm ld.
Object files and archives are processed in the order given on the command line.
.Pp
The options are as follows:
.Pp
.Bl -tag -width indent
.It Fl A Ar symbol-file
The the symbol-file is taken as a base for link-editing the object files
on the command line.
.It Fl assert Ar keyword
This option is here mainly for compatibility with SunOS
.Nm ld .
Most conditions which would cause a Sun assertion to fail will
currently always cause error or warning messages from
.Nm ld .
The only keyword implemented by
.Nm ld
is
.Nm pure-text ,
which generates a warning if a position independent object is being
created and some of the files being linked are not position
independent.
.It Fl B Ns Ar dynamic
Specifies that linking against dynamic libraries can take place. If a library
specifier of the form -lx appears on the command line,
.Nm ld
searches for a library of the from libx.so.n.m
.Po see the \&
.Fl l
option
.Pc
according to the search rules in effect. If such a file can not be
found a traditional archive is looked for.
This options can appear anywhere on the command line and is complementary
to
.Fl B Ns Ar static.
.It Fl B Ns Ar forcedynamic
This is similar to
.Fl B Ns Ar dynamic
except that if no dynamic libraries are linked against,
.Nm ld
will still produce a dynamic executable.  This is useful for programs
which are static but still need to load dynamic objects at runtime.
.It Fl B Ns Ar static
The counterpart of
.Fl B Ns Ar dynamic .
This option turns off dynamic linking for
all library specifiers until a
.Fl B Ns Ar dynamic
is once again given. Any explicitly
mentioned shared object encountered on the command line while this option is
in effect is flagged as an error.
.It Fl B Ns Ar shareable
Instructs the linker to build a shared object from the object files rather
than a normal executable image.
.It Fl B Ns Ar symbolic
This option causes all symbolic references in the output to be resolved in
this link-edit session. The only remaining run-time relocation requirements are
.Em base-relative
relocations, ie. translation with respect to the load address. Failure to
resolve any symbolic reference causes an error to be reported.
.It Fl B Ns Ar forcearchive
Force all members of archives to be loaded, whether or not such members
contribute a definition to any plain object files. Useful for making a
shared library from an archive of PIC objects without having to unpack
the archive.
.It Fl B Ns Ar silly
Search for
.Em \.sa
silly archive companions of shared objects. Useful for compatibility with
version 3 shared objects.
.It Fl D Ar data-size
Set the size of the data segment. For sanity's sake, this should be larger
than the cumulative data sizes of the input files.
.It Fl d Ar c
Force allocation of commons even producing relocatable output.
.It Fl d Ar p
Force alias definitions of procedure calls in non-PIC code. Useful to
obtain shareable code in the presence of run-time relocations as such
calls will be re-directed through the Procedure Linkage Table (see
.Xr link 5)
.It Fl e Ar entry-symbol
Specifies the entry symbol for an executable.
.It Fl f
List the resolved paths of all the object files and libraries on the
standard output, and exit.
.It Fl L Ns Ar path
Add
.Ar path
to the list of directories to search for libraries specified with the
.Fl l
option.
.It Fl l Ns Ar lib-spec
This option specifies a library to be considered for inclusion in the
output. If the
.Fl B Ns Ar dynamic
option is in effect, a shared library of the
form lib<spec>.so.m.n
.Po where \&
.Em m
is the major, and
.Em n
is the minor version number, respectively
.Pc is searched for first. The
library with the highest version found in the search path is selected.
If no shared library is found or the
.Fl B Ns Ar static
options is in effect, an archive of the form lib<spec>.a is looked for in
the library search path.
.It Fl M
Produce output about the mapping of segments of the input files and the
values assigned to
.Pq global
symbols in the output file.
.It Fl N
Produce a
.Dv OMAGIC
output file.
.It Fl n
Produce a
.Dv NMAGIC
output file.
.It Fl nostdlib
Do not search the built-in path
.Po
usually
.Dq /usr/lib
.Pc
for
.Fl l
specified libraries.
.It Fl O Ar filename
Specifies the name of the output file.
The file is created as
.Ar filename .tmp
and when output is complete renamed to
.Ar filename .
.It Fl o Ar filename
Specifies the name of the output file. Defaults to
.Dq a.out.
.It Fl Q
Produce a
.Dv QMAGIC
(FreeBSD/BSDi-i386) output file.  This is the default.
.It Fl r
Produce relocatable object file, suitable for another pass through
.Nm ld.
.It Fl R
Record the given path within the executable for run-time library search.
This only applies to dynamically linked executables.
.It Fl S
Strip all debugger symbols from the output.
.It Fl s
Strip all symbols from the output.
.It Fl T
Specifies the start address of the text segment, with respect to which
all input files will be relocated.
.It Fl t
Leave a trace of the input files as they are processed.
.It Fl u Ar symbol
Force
.Ar symbol
to be marked as undefined. Useful to force loading of an archive member
in the absence of any other references to that member.
.It Fl V Ar version
Put the given version number into the output shared library
.Pq if one is created .
Useful to make shared libraries compatible with other operating
systems. E.g., SunOS 4.x libraries use version number 3. Defaults to 8.
.It Fl X
Discard local symbols in the input files that start with the letter
.Dq L
.It Fl x
Discard all local symbols in the input files.
.It Fl y Ar symbol
Trace the manipulations inflicted on
.Ar symbol
.It Fl Z
Make a 386BSD
.Dv ZMAGIC
output file.
.It Fl z
Make a NetBSD
.Dv ZMAGIC
output file.
.Sh ENVIRONMENT
.Nm
utilizes the following environment variables:
.Bl -tag -width "LD_LIBRARY_PATH"
.It Ev LD_LIBRARY_PATH
This colon-separated list of directories is inserted into the search
path for libraries following any directories specified via
.Fl L
options and preceding the built-in path.
.\" .It Ev LD_NOSTD_PATH
.\" When set, do not search the built-in path for libraries.
.\" This is an alternative to the
.\" .Fl nostdlib
.\" command-line flag.
.El
.Sh FILES
.Sh SEE ALSO
.Xr ldd 1 ,
.Xr rtld 1 ,
.Xr link 5 ,
.Xr ldconfig 8
.Sh CAVEATS
An entry point must now explicitly be given if the output is intended to be
a normal executable program. This was not the case for the previous version of
.Nm ld .
.Sh BUGS
Shared objects are not properly checked for undefined symbols.
.Pp
Cascading of shared object defeats the
.Dq -Bstatic
option.
.Pp
All shared objects presented to
.Nm ld
are marked for run-time loading in the output file, even if no symbols
are needed from them.
.Sh HISTORY
A
.Nm
command appeared in
.At v1 .
The shared library model employed by
.Nm
appeared first in SunOS 4.0