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LD
!!!LD
NAME
SYNOPSIS
DESCRIPTION
OPTIONS
ENVIRONMENT
SEE ALSO
COPYRIGHT
----
!!NAME


ld - Using LD , the GNU linker
!!SYNOPSIS


ld [[__options__] ''objfile'' ...
!!DESCRIPTION


__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
__ld__.


__ld__ accepts Linker Command Language files written in a
superset of AT 's Link Editor Command
Language syntax, to provide explicit and total control over
the linking process.


This man page does not describe the command language; see
the __ld__ entry in info, or the manual ld: the
GNU linker, for full details on the command
language and on other aspects of the GNU
linker.


This version of __ld__ uses the general purpose
BFD libraries to operate on object files.
This allows __ld__ to read, combine, and write object
files in many different formats---for example,
COFF or a.out. Different formats may
be linked together to produce any available kind of object
file.


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, __ld__
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 __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.
!!OPTIONS


The linker supports a plethora of command-line options, but
in actual practice few of them are used in any particular
context. For instance, a frequent use of __ld__ is to
link standard Unix object files on a standard, supported
Unix system. On such a system, to link a file
hello.o:


        ld -o I
This tells __ld__ to produce a file called ''output'' as the result of linking the file /lib/crt0.o with hello.o and the library libc.a, which will come from the standard search directories. (See the discussion of the __-l__ option below.)


Some of the command-line options to __ld__ may be
specified at any point in the command line. However, options
which refer to files, such as __-l__ or __-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.


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
__-l__, __-R__, and the script command language. If
''no'' binary input files at all are specified, the
linker does not produce any output, and issues the message
__No input files__.


If the linker can not recognize the format of an object
file, it will assume that it is a linker script. A script
specified in this way augments the main linker script used
for the link (either the default linker script or the one
specified by using __-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 INPUT or GROUP to load
other objects. Note that specifying a script in this way
merely augments the main linker script; use the __-T__
option to replace the default linker script
entirely.


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,
__-trace-symbol__ and __--trace-symbol__ are
equivalent. Note - there is one exception to this rule.
Multiple letter options that start with a lower case 'o' can
only be preceeded by two dashes. This is to reduce confusion
with the __-o__ option. So for example __-omagic__
sets the output file name to __magic__ whereas
__--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, __--trace-symbol foo__
and __--trace-symbol=foo__ are equivalent. Unique
abbreviations of the names of multiple-letter options are
accepted.


Note - if the linker is being invoked indirectly, via a
compiler driver (eg __gcc__) then all the linker command
line options should be prefixed by __-Wl,__ (or whatever
is appropriate for the particular compiler driver) like
this:


          gcc -Wl,--startgroup foo.o bar.o -Wl,--endgroup
This is important, because otherwise the compiler driver program may silently drop the linker options, resulting in a bad link.


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


__-a__''keyword''


This option is supported for HP/UX
compatibility. The ''keyword'' argument must be one of
the strings __archive__, __shared__, or
__default__. __-aarchive__ is functionally equivalent
to __-Bstatic__, and the other two keywords are
functionally equivalent to __-Bdynamic__. This option may
be used any number of times.


__-A__''architecture''


__--architecture=__''architecture''


In the current release of __ld__, this option is useful
only for the Intel 960 family of architectures. In that
__ld__ configuration, the ''architecture'' argument
identifies the particular architecture in the 960 family,
enabling some safeguards and modifying the archive-library
search path.


Future releases of __ld__ may support similar
functionality for other architecture families.


__-b__ ''input-format''


__--format=__''input-format''


__ld__ may be configured to support more than one kind of
object file. If your __ld__ is configured this way, you
can use the __-b__ option to specify the binary format
for input object files that follow this option on the
command line. Even when __ld__ is configured to support
alternative object formats, you don't usually need to
specify this, as __ld__ should be configured to expect as
a default input format the most usual format on each
machine. ''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
__objdump -i__.)


You may want to use this option if you are linking files
with an unusual binary format. You can also use __-b__ to
switch formats explicitly (when linking object files of
different formats), by including __-b__
''input-format'' before each group of object files in a
particular format.


The default format is taken from the environment variable
GNUTARGET.


You can also define the input format from a script, using
the command TARGET;


__-c__ ''MRI-commandfile''


__--mri-script=__''MRI-commandfile''


For compatibility with linkers produced by
MRI , __ld__ accepts script files written
in an alternate, restricted command language, described in
the MRI Compatible Script Files section of
GNU ld documentation. Introduce
MRI script files with the option __-c__;
use the __-T__ option to run linker scripts written in
the general-purpose __ld__ scripting language. If
''MRI-cmdfile'' does not exist, __ld__ looks for it in
the directories specified by any __-L__
options.


__-d__


__-dc__


__-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 __-r__). The script command
FORCE_COMMON_ALLOCATION has the same
effect.


__-e__ ''entry''


__--entry=__''entry''


Use ''entry'' as the explicit symbol for beginning
execution of your program, rather than the default entry
point. If there is no symbol named ''entry'', the linker
will try to parse ''entry'' as a number, and use that as
the entry address (the number will be interpreted in base
10; you may use a leading __0x__ for base 16, or a
leading __0__ for base 8).


__-E__


__--export-dynamic__


When creating a dynamically linked executable, add all
symbols to the dynamic symbol table. The dynamic symbol
table is the set of symbols which are visible from dynamic
objects at run time.


If you do not use this option, the dynamic symbol table will
normally contain only those symbols which are referenced by
some dynamic object mentioned in the link.


If you use 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 version script to control what symbols
should be added to the dynamic symbol table if the output
format supports it. See the description of
__--version-script__ in @ref{
VERSION }.


__-EB__


Link big-endian objects. This affects the default output
format.


__-EL__


Link little-endian objects. This affects the default output
format.


__-f__


__--auxiliary__ ''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
''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
''name''. If there is one, it will be used instead of the
definition in the filter object. The shared object
''name'' need not exist. Thus the shared object
''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.


__-F__ ''name''


__--filter__ ''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
''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 ''name''. Thus the
filter object can be used to select a subset of the symbols
provided by the object ''name''.


Some older linkers used the __-F__ option throughout a
compilation toolchain for specifying object-file format for
both input and output object files. The GNU
linker uses other mechanisms for this purpose: the
__-b__, __--format__, __--oformat__ options, the
TARGET command in linker scripts, and the
GNUTARGET environment variable. The
GNU linker will ignore the __-F__ option
when not creating an ELF shared
object.


__-fini__ ''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
_fini as the function to call.


__-g__


Ignored. Provided for compatibility with other
tools.


__-G__''value''


__--gpsize=__''value''


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


__-h__''name''


__-soname=__''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.


__-i__


Perform an incremental link (same as option
__-r__).


__-init__ ''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
_init as the function to call.


__-l__''archive''


__--library=__''archive''


Add archive file ''archive'' to the list of files to
link. This option may be used any number of times. __ld__
will search its path-list for occurrences of
libarchive.a for every ''archive''
specified.


On systems which support shared libraries, __ld__ may
also search for libraries with extensions other than
.a. Specifically, on ELF and SunOS
systems, __ld__ will search a directory for a library
with an extension of .so before searching for one
with an extension of .a. By convention, a
.so extension indicates a shared
library.


The linker will search an archive only once, at the location
where it is specified on the command line. If the archive
defines a symbol which was undefined in some object which
appeared before the archive on the command line, the linker
will include the appropriate file(s) from the archive.
However, an undefined symbol in an object appearing later on
the command line will not cause the linker to search the
archive again.


See the __-(__ 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.


This type of archive searching is standard for Unix linkers.
However, if you are using __ld__ on AIX ,
note that it is different from the behaviour of the
AIX linker.


__-L__''searchdir''


__--library-path=__''searchdir''


Add path ''searchdir'' to the list of paths that
__ld__ will search for archive libraries and __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 __-L__ options apply to all
__-l__ options, regardless of the order in which the
options appear.


The default set of paths searched (without being specified
with __-L__) depends on which emulation mode __ld__ is
using, and in some cases also on how it was
configured.


The paths can also be specified in a link script with the
SEARCH_DIR command. Directories specified this way
are searched at the point in which the linker script appears
in the command line.


__-m__''emulation''


Emulate the ''emulation'' linker. You can list the
available emulations with the __--verbose__ or __-V__
options.


If the __-m__ option is not used, the emulation is taken
from the LDEMULATION environment variable, if that
is defined.


Otherwise, the default emulation depends upon how the linker
was configured.


__-M__


__--print-map__


Print a link map to the standard output. A link map provides
information about the link, including the
following:


Where object files and symbols are mapped into
memory.


How common symbols are allocated.


All archive members included in the link, with a mention of
the symbol which caused the archive member to be brought
in.


__-n__


__--nmagic__


Turn off page alignment of sections, and mark the output as
NMAGIC if possible.


__-N__


__--omagic__


Set the text and data sections to be readable and writable.
Also, do not page-align the data segment. If the output
format supports Unix style magic numbers, mark the output as
OMAGIC.


__-o__ ''output''


__--output=__''output''


Use ''output'' as the name for the program produced by
__ld__; if this option is not specified, the name
''a.out'' is used by default. The script command
OUTPUT can also specify the output file
name.


__-O__ ''level''


If ''level'' is a numeric values greater than zero
__ld__ optimizes the output. This might take
significantly longer and therefore probably should only be
enabled for the final binary.


__-q__


__--emit-relocs__


Leave relocation sections and contents in fully linked
exececutables. Post link analysis and optimization tools may
need this information in order to perform correct
modifications of executables. This results in larger
executables.


This option is currently only supported on
ELF platforms.


__-r__


__--relocateable__


Generate relocatable output---i.e., generate an output file
that can in turn serve as input to __ld__. This is often
called ''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
OMAGIC. If this option is not specified, an
absolute file is produced. When linking C ++
programs, this option ''will not'' resolve references to
constructors; to do that, use __-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
a.out-based formats do not support partial linking
with input files in other formats at all.


This option does the same thing as __-i__.


__-R__ ''filename''


__--just-symbols=__''filename''


Read symbol names and their addresses from ''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 __-R__ option is followed by a directory name, rather
than a file name, it is treated as the __-rpath__
option.


__-s__


__--strip-all__


Omit all symbol information from the output
file.


__-S__


__--strip-debug__


Omit debugger symbol information (but not all symbols) from
the output file.


__-t__


__--trace__


Print the names of the input files as __ld__ processes
them.


__-T__ ''scriptfile''


__--script=__''scriptfile''


Use ''scriptfile'' as the linker script. This script
replaces __ld__'s default linker script (rather than
adding to it), so ''commandfile'' must specify everything
necessary to describe the output file. If ''scriptfile''
does not exist in the current directory, ld looks
for it in the directories specified by any preceding
__-L__ options. Multiple __-T__ options
accumulate.


__-u__ ''symbol''


__--undefined=__''symbol''


Force ''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.
__-u__ may be repeated with different option arguments to
enter additional undefined symbols. This option is
equivalent to the EXTERN linker script
command.


__-Ur__


For anything other than C ++ programs, this
option is equivalent to __-r__: it generates relocatable
output---i.e., an output file that can in turn serve as
input to __ld__. When linking C ++
programs, __-Ur__ ''does'' resolve references to
constructors, unlike __-r__. It does not work to use
__-Ur__ on files that were themselves linked with
__-Ur__; once the constructor table has been built, it
cannot be added to. Use __-Ur__ only for the last partial
link, and __-r__ for the others.


__--unique[[=__ ''SECTION''
__]__


Creates a separate output section for every input section
matching ''SECTION'' , or if the optional
wildcard ''SECTION'' argument is missing,
for every orphan input section. An orphan section is one not
specifically mentioned in a linker script. You may use this
option multiple times on the command line; It prevents the
normal merging of input sections with the same name,
overriding output section assignments in a linker
script.


__-v__


__--version__


__-V__


Display the version number for __ld__. The __-V__
option also lists the supported emulations.


__-x__


__--discard-all__


Delete all local symbols.


__-X__


__--discard-locals__


Delete all temporary local symbols. For most targets, this
is all local symbols whose names begin with
__L__.


__-y__ ''symbol''


__--trace-symbol=__''symbol''


Print the name of each linked file in which ''symbol''
appears. This option may be given any number of times. On
many systems it is necessary to prepend an
underscore.


This option is useful when you have an undefined symbol in
your link but don't know where the reference is coming
from.


__-Y__ ''path''


Add ''path'' to the default library search path. This
option exists for Solaris compatibility.


__-z__ ''keyword''


The recognized keywords are initfirst,
interpose, loadfltr,
nodefaultlib, nodelete, nodlopen,
nodump, now, origin,
combreloc, nocombreloc and
nocopyreloc. The other keywords are ignored for
Solaris compatibility. initfirst marks the object
to be initialized first at runtime before any other objects.
interpose marks the object that its symbol table
interposes before all symbols but the primary executable.
loadfltr marks the object that its filtees be
processed immediately at runtime. nodefaultlib
marks the object that the search for dependencies of this
object will ignore any default library search paths.
nodelete marks the object shouldn't be unloaded at
runtime. nodlopen marks the object not available to
dlopen. nodump marks the object can not be
dumped by dldump. now marks the object
with the non-lazy runtime binding. origin marks the
object may contain $ORIGIN. defs disallows
undefined symbols. combreloc combines multiple
reloc sections and sorts them to make dynamic symbol lookup
caching possible. nocombreloc disables multiple
reloc sections combining. nocopyreloc disables
production of copy relocs.


__-(__ ''archives'' __-)__


__--start-group__ ''archives''
__--end-group__


The ''archives'' should be a list of archive files. They
may be either explicit file names, or __-l__
options.


The specified archives are searched repeatedly until no new
undefined references are created. Normally, an archive is
searched only once in the order that it is specified on the
command line. If a symbol in that archive is needed to
resolve an undefined symbol referred to by an object in an
archive that appears later on the command line, the linker
would not be able to resolve that reference. By grouping the
archives, they all be searched repeatedly until all possible
references are resolved.


Using this option has a significant performance cost. It is
best to use it only when there are unavoidable circular
references between two or more archives.


__-assert__ ''keyword''


This option is ignored for SunOS compatibility.


__-Bdynamic__


__-dy__


__-call_shared__


Link against dynamic libraries. This is only meaningful on
platforms for which shared libraries are supported. This
option is normally the default on such platforms. The
different variants of this option are for compatibility with
various systems. You may use this option multiple times on
the command line: it affects library searching for __-l__
options which follow it.


__-Bgroup__


Set the DF_1_GROUP flag in the DT_FLAGS_1
entry in the dynamic section. This causes the runtime linker
to handle lookups in this object and its dependencies to be
performed only inside the group. __--no-undefined__ is
implied. This option is only meaningful on
ELF platforms which support shared
libraries.


__-Bstatic__


__-dn__


__-non_shared__


__-static__


Do not link against shared libraries. This is only
meaningful on platforms for which shared libraries are
supported. The different variants of this option are for
compatibility with various systems. You may use this option
multiple times on the command line: it affects library
searching for __-l__ options which follow
it.


__-Bsymbolic__


When creating a shared library, bind references to global
symbols to the definition within the shared library, if any.
Normally, it is possible for a program linked against a
shared library to override the definition within the shared
library. This option is only meaningful on
ELF platforms which support shared
libraries.


__--check-sections__


__--no-check-sections__


Asks the linker ''not'' to check section addresses after
they have been assigned to see if there any overlaps.
Normally the linker will perform this check, and if it finds
any overlaps it will produce suitable error messages. The
linker does know about, and does make allowances for
sections in overlays. The default behaviour can be restored
by using the command line switch
__--check-sections__.


__--cref__


Output a cross reference table. If a linker map file is
being generated, the cross reference table is printed to the
map file. Otherwise, it is printed on the standard
output.


The format of the table is intentionally simple, so that it
may be easily processed by a script if necessary. The
symbols are printed out, sorted by name. For each symbol, a
list of file names is given. If the symbol is defined, the
first file listed is the location of the definition. The
remaining files contain references to the
symbol.


__--no-define-common__


This option inhibits the assignment of addresses to common
symbols. The script command
INHIBIT_COMMON_ALLOCATION has the same
effect.


The __--no-define-common__ option allows decoupling the
decision to assign addresses to Common symbols from the
choice of the output file type; otherwise a non-Relocatable
output type forces assigning addresses to Common symbols.
Using __--no-define-common__ allows Common symbols that
are referenced from a shared library to be assigned
addresses only in the main program. This eliminates the
unused duplicate space in the shared library, and also
prevents any possible confusion over resolving to the wrong
duplicate when there are many dynamic modules with
specialized search paths for runtime symbol
resolution.


__--defsym__
''symbol''__=__''expression''


Create a global symbol in the output file, containing the
absolute address given by ''expression''. You may use
this option as many times as necessary to define multiple
symbols in the command line. A limited form of arithmetic is
supported for the ''expression'' in this context: you may
give a hexadecimal constant or the name of an existing
symbol, or use + and - to add or subtract
hexadecimal constants or symbols. If you need more elaborate
expressions, consider using the linker command language from
a script. ''Note:'' there should be no white space
between ''symbol'', the equals sign (``__=__''), and
''expression''.


__--demangle[[=__''style''__]__


__--no-demangle__


These options control whether to demangle symbol names in
error messages and other output. When the linker is told to
demangle, it tries to present symbol names in a readable
fashion: it strips leading underscores if they are used by
the object file format, and converts C ++
mangled symbol names into user readable names. Different
compilers have different mangling styles. The optional
demangling style argument can be used to choose an
appropriate demangling style for your compiler. The linker
will demangle by default unless the environment variable
__COLLECT_NO_DEMANGLE__ is set. These
options may be used to override the default.


__--dynamic-linker__ ''file''


Set the name of the dynamic linker. This is only meaningful
when generating dynamically linked ELF
executables. The default dynamic linker is normally correct;
don't use this unless you know what you are
doing.


__--embedded-relocs__


This option is only meaningful when linking
MIPS embedded PIC code,
generated by the -membedded-pic option to the
GNU compiler and assembler. It causes the
linker to create a table which may be used at runtime to
relocate any data which was statically initialized to
pointer values. See the code in testsuite/ld-empic for
details.


__--fatal-warnings__


Treat all warnings as errors.


__--force-exe-suffix__


Make sure that an output file has a .exe
suffix.


If a successfully built fully linked output file does not
have a .exe or .dll suffix, this option
forces the linker to copy the output file to one of the same
name with a .exe suffix. This option is useful when
using unmodified Unix makefiles on a Microsoft Windows host,
since some versions of Windows won't run an image unless it
ends in a .exe suffix.


__--no-gc-sections__


__--gc-sections__


Enable garbage collection of unused input sections. It is
ignored on targets that do not support this option. This
option is not compatible with __-r__, nor should it be
used with dynamic linking. The default behaviour (of not
performing this garbage collection) can be restored by
specifying __--no-gc-sections__ on the command
line.


__--help__


Print a summary of the command-line options on the standard
output and exit.


__--target-help__


Print a summary of all target specific options on the
standard output and exit.


__-Map__ ''mapfile''


Print a link map to the file ''mapfile''. See the
description of the __-M__ option, above.


__--no-keep-memory__


__ld__ normally optimizes for speed over memory usage by
caching the symbol tables of input files in memory. This
option tells __ld__ to instead optimize for memory usage,
by rereading the symbol tables as necessary. This may be
required if __ld__ runs out of memory space while linking
a large executable.


__--no-undefined__


__-z defs__


Normally when creating a non-symbolic shared library,
undefined symbols are allowed and left to be resolved by the
runtime loader. These options disallows such undefined
symbols.


__--allow-shlib-undefined__


Allow undefined symbols in shared objects even when
--no-undefined is set. The net result will be that undefined
symbols in regular objects will still trigger an error, but
undefined symbols in shared objects will be ignored. The
implementation of no_undefined makes the assumption that the
runtime linker will choke on undefined symbols. However
there is at least one system (BeOS) where undefined symbols
in shared libraries is normal since the kernel patches them
at load time to select which function is most appropriate
for the current architecture. I.E. dynamically select an
appropriate memset function. Apparently it is also normal
for HPPA shared libraries to have undefined
symbols.


__--no-warn-mismatch__


Normally __ld__ will give an error if you try to link
together input files that are mismatched for some reason,
perhaps because they have been compiled for different
processors or for different endiannesses. This option tells
__ld__ that it should silently permit such possible
errors. This option should only be used with care, in cases
when you have taken some special action that ensures that
the linker errors are inappropriate.


__--no-whole-archive__


Turn off the effect of the __--whole-archive__ option for
subsequent archive files.


__--noinhibit-exec__


Retain the executable output file whenever it is still
usable. Normally, the linker will not produce an output file
if it encounters errors during the link process; it exits
without writing an output file when it issues any error
whatsoever.


__-nostdlib__


Only search library directories explicitly specified on the
command line. Library directories specified in linker
scripts (including linker scripts specified on the command
line) are ignored.


__--oformat__ ''output-format''


__ld__ may be configured to support more than one kind of
object file. If your __ld__ is configured this way, you
can use the __--oformat__ option to specify the binary
format for the output object file. Even when __ld__ is
configured to support alternative object formats, you don't
usually need to specify this, as __ld__ should be
configured to produce as a default output format the most
usual format on each machine. ''output-format'' is a text
string, the name of a particular format supported by the
BFD libraries. (You can list the available
binary formats with __objdump -i__.) The script command
OUTPUT_FORMAT can also specify the output format,
but this option overrides it.


__-qmagic__


This option is ignored for Linux compatibility.


__-Qy__


This option is ignored for SVR4
compatibility.


__--relax__


An option with machine dependent effects. This option is
only supported on a few targets.


On some platforms, the __--relax__ option performs global
optimizations that become possible when the linker resolves
addressing in the program, such as relaxing address modes
and synthesizing new instructions in the output object
file.


On some platforms these link time global optimizations may
make symbolic debugging of the resulting executable
impossible. This is known to be the case for the Matsushita
MN10200 and MN10300 family of
processors.


On platforms where this is not supported, __--relax__ is
accepted, but ignored.


__--retain-symbols-file__ ''filename''


Retain ''only'' the symbols listed in the file
''filename'', discarding all others. ''filename'' is
simply a flat file, with one symbol name per line. This
option is especially useful in environments (such as
!VxWorks) where a large global symbol table is accumulated
gradually, to conserve run-time memory.


__--retain-symbols-file__ does ''not'' discard
undefined symbols, or symbols needed for
relocations.


You may only specify __--retain-symbols-file__ once in
the command line. It overrides __-s__ and
__-S__.


__-rpath__ ''dir''


Add a directory to the runtime library search path. This is
used when linking an ELF executable with
shared objects. All __-rpath__ arguments are concatenated
and passed to the runtime linker, which uses them to locate
shared objects at runtime. The __-rpath__ option is also
used when locating shared objects which are needed by shared
objects explicitly included in the link; see the description
of the __-rpath-link__ option. If __-rpath__ is not
used when linking an ELF executable, the
contents of the environment variable LD_RUN_PATH
will be used if it is defined.


The __-rpath__ option may also be used on SunOS. By
default, on SunOS, the linker will form a runtime search
patch out of all the __-L__ options it is given. If a
__-rpath__ option is used, the runtime search path will
be formed exclusively using the __-rpath__ options,
ignoring the __-L__ options. This can be useful when
using gcc, which adds many __-L__ options which may be on
NFS mounted filesystems.


For compatibility with other ELF linkers, if
the __-R__ option is followed by a directory name, rather
than a file name, it is treated as the __-rpath__
option.


__-rpath-link__ ''DIR''


When using ELF or SunOS, one shared library
may require another. This happens when an ld
-shared link includes a shared library as one of the
input files.


When the linker encounters such a dependency when doing a
non-shared, non-relocatable link, it will automatically try
to locate the required shared library and include it in the
link, if it is not included explicitly. In such a case, the
__-rpath-link__ option specifies the first set of
directories to search. The __-rpath-link__ option may
specify a sequence of directory names either by specifying a
list of names separated by colons, or by appearing multiple
times.


This option should be used with caution as it overrides the
search path that may have been hard compiled into a shared
library. In such a case it is possible to use
unintentionally a different search path than the runtime
linker would do.


The linker uses the following search paths to locate
required shared libraries.


1.


Any directories specified by __-rpath-link__
options.


2.


Any directories specified by __-rpath__ options. The
difference between __-rpath__ and __-rpath-link__ is
that directories specified by __-rpath__ options are
included in the executable and used at runtime, whereas the
__-rpath-link__ option is only effective at link time. It
is for the native linker only.


3.


On an ELF system, if the __-rpath__ and
rpath-link options were not used, search the
contents of the environment variable LD_RUN_PATH.
It is for the native linker only.


4.


On SunOS, if the __-rpath__ option was not used, search
any directories specified using __-L__
options.


5.


For a native linker, the contents of the environment
variable LD_LIBRARY_PATH.


6.


For a native ELF linker, the directories in
DT_RUNPATH or DT_RPATH of a shared library
are searched for shared libraries needed by it. The
DT_RPATH entries are ignored if DT_RUNPATH
entries exist.


7.


The default directories, normally ''/lib'' and
''/usr/lib''.


8.


For a native linker on an ELF system, if the
file ''/etc/ld.so.conf'' exists, the list of directories
found in that file.


If the required shared library is not found, the linker will
issue a warning and continue with the link.


__-shared__


__-Bshareable__


Create a shared library. This is currently only supported on
ELF , XCOFF and SunOS
platforms. On SunOS, the linker will automatically create a
shared library if the __-e__ option is not used and there
are undefined symbols in the link.


__--sort-common__


This option tells __ld__ to sort the common symbols by
size when it places them in the appropriate output sections.
First come all the one byte symbols, then all the two byte,
then all the four byte, and then everything else. This is to
prevent gaps between symbols due to alignment
constraints.


__--split-by-file [[__''size''__]__


Similar to __--split-by-reloc__ but creates a new output
section for each input file when ''size'' is reached.
''size'' defaults to a size of 1 if not
given.


__--split-by-reloc [[__''count''__]__


Tries to creates extra sections in the output file so that
no single output section in the file contains more than
''count'' relocations. This is useful when generating
huge relocatable files for downloading into certain real
time kernels with the COFF object file
format; since COFF cannot represent more than
65535 relocations in a single section. Note that this will
fail to work with object file formats which do not support
arbitrary sections. The linker will not split up individual
input sections for redistribution, so if a single input
section contains more than ''count'' relocations one
output section will contain that many relocations.
''count'' defaults to a value of 32768.


__--stats__


Compute and display statistics about the operation of the
linker, such as execution time and memory
usage.


__--traditional-format__


For some targets, the output of __ld__ is different in
some ways from the output of some existing linker. This
switch requests __ld__ to use the traditional format
instead.


For example, on SunOS, __ld__ combines duplicate entries
in the symbol string table. This can reduce the size of an
output file with full debugging information by over 30
percent. Unfortunately, the SunOS dbx program can
not read the resulting program (gdb has no
trouble). The __--traditional-format__ switch tells
__ld__ to not combine duplicate entries.


__--section-start__
''sectionname''__=__''org''


Locate a section in the output file at the absolute address
given by ''org''. You may use this option as many times
as necessary to locate multiple sections in the command
line. ''org'' must be a single hexadecimal integer; for
compatibility with other linkers, you may omit the leading
__0x__ usually associated with hexadecimal values.
''Note:'' there should be no white space between
''sectionname'', the equals sign (``__=__''), and
''org''.


__-Tbss__ ''org''


__-Tdata__ ''org''


__-Ttext__ ''org''


Use ''org'' as the starting address
for---respectively---the bss, data, or the
text segment of the output file. ''org'' must be
a single hexadecimal integer; for compatibility with other
linkers, you may omit the leading __0x__ usually
associated with hexadecimal values.


__--dll-verbose__


__--verbose__


Display the version number for __ld__ and list the linker
emulations supported. Display which input files can and
cannot be opened. Display the linker script being used by
the linker.


__--version-script=__''version-scriptfile''


Specify the name of a version script to the linker. This is
typically used when creating shared libraries to specify
additional information about the version heirarchy for the
library being created. This option is only meaningful on
ELF platforms which support shared
libraries.


__--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.
Unfortunately, some C libraries use this practice, so you
may get some warnings about symbols in the libraries as well
as in your programs.


There are three kinds of global symbols, illustrated here by
C examples:


__int i = 1;__


A definition, which goes in the initialized data section of
the output file.


__extern int i;__


An undefined reference, which does not allocate space. There
must be either a definition or a common symbol for the
variable somewhere.


__int i;__


A common symbol. If there are only (one or more) common
symbols for a variable, it goes in the uninitialized data
area of the output file. The linker merges multiple common
symbols for the same variable into a single symbol. If they
are of different sizes, it picks the largest size. The
linker turns a common symbol into a declaration, if there is
a definition of the same variable.


The __--warn-common__ option can produce five kinds of
warnings. Each warning consists of a pair of lines: the
first describes the symbol just encountered, and the second
describes the previous symbol encountered with the same
name. One or both of the two symbols will be a common
symbol.


1.


Turning a common symbol into a reference, because there is
already a definition for the symbol.


        I


2.


Turning a common symbol into a reference, because a later
definition for the symbol is encountered. This is the same
as the previous case, except that the symbols are
encountered in a different order.


        I


3.


Merging a common symbol with a previous same-sized common
symbol.


        I


4.


Merging a common symbol with a previous larger common
symbol.


        I


5.


Merging a common symbol with a previous smaller common
symbol. This is the same as the previous case, except that
the symbols are encountered in a different
order.


        I


__--warn-constructors__


Warn if any global constructors are used. This is only
useful for a few object file formats. For formats like
COFF or ELF , the linker can
not detect the use of global constructors.


__--warn-multiple-gp__


Warn if multiple global pointer values are required in the
output file. This is only meaningful for certain processors,
such as the Alpha. Specifically, some processors put
large-valued constants in a special section. A special
register (the global pointer) points into the middle of this
section, so that constants can be loaded efficiently via a
base-register relative addressing mode. Since the offset in
base-register relative mode is fixed and relatively small
(e.g., 16 bits), this limits the maximum size of the
constant pool. Thus, in large programs, it is often
necessary to use multiple global pointer values in order to
be able to address all possible constants. This option
causes a warning to be issued whenever this case
occurs.


__--warn-once__


Only warn once for each undefined symbol, rather than once
per module which refers to it.


__--warn-section-align__


Warn if the address of an output section is changed because
of alignment. Typically, the alignment will be set by an
input section. The address will only be changed if it not
explicitly specified; that is, if the SECTIONS
command does not specify a start address for the
section.


__--whole-archive__


For each archive mentioned on the command line after the
__--whole-archive__ option, include every object file in
the archive in the link, rather than searching the archive
for the required object files. This is normally used to turn
an archive file into a shared library, forcing every object
to be included in the resulting shared library. This option
may be used more than once.


Two notes when using this option from gcc: First, gcc
doesn't know about this option, so you have to use
__-Wl,-whole-archive__. Second, don't forget to use
__-Wl,-no-whole-archive__ after your list of archives,
because gcc will add its own list of archives to your link
and you may not want this flag to affect those as
well.


__--wrap__ ''symbol''


Use a wrapper function for ''symbol''. Any undefined
reference to ''symbol'' will be resolved to
__wrap_symbol. Any undefined reference to
__real_symbol will be resolved to
''symbol''.


This can be used to provide a wrapper for a system function.
The wrapper function should be called
__wrap_symbol. If it wishes to call the system
function, it should call
__real_symbol.


Here is a trivial example:


        void *
__wrap_malloc (int c)
{
printf (
If you link other code with this file using __--wrap malloc__, then all calls to malloc will call the function __wrap_malloc instead. The call to __real_malloc in __wrap_malloc will call the real malloc function.


You may wish to provide a __real_malloc function as
well, so that links without the __--wrap__ option will
succeed. If you do this, you should not put the definition
of __real_malloc in the same file as
__wrap_malloc; if you do, the assembler may resolve
the call before the linker has a chance to wrap it to
malloc.


__--enable-new-dtags__


__--disable-new-dtags__


This linker can create the new dynamic tags in
ELF . But the older ELF
systems may not understand them. If you specify
__--enable-new-dtags__, the dynamic tags will be created
as needed. If you specify __--disable-new-dtags__, no new
dynamic tags will be created. By default, the new dynamic
tags are not created. Note that those options are only
available for ELF systems.


The i386 PE linker supports the
__-shared__ option, which causes the output to be a
dynamically linked library ( DLL ) instead of
a normal executable. You should name the output
*.dll when you use this option. In addition, the
linker fully supports the standard *.def files,
which may be specified on the linker command line like an
object file (in fact, it should precede archives it exports
symbols from, to ensure that they get linked in, just like a
normal object file).


In addition to the options common to all targets, the i386
PE linker support additional command line
options that are specific to the i386 PE
target. Options that take values may be separated from their
values by either a space or an equals sign.


__--add-stdcall-alias__


If given, symbols with a stdcall suffix (@''nn'') will be
exported as-is and also with the suffix
stripped.


__--base-file__ ''file''


Use ''file'' as the name of a file in which to save the
base addresses of all the relocations needed for generating
DLLs with ''dlltool''.


__--dll__


Create a DLL instead of a regular executable.
You may also use __-shared__ or specify a
LIBRARY in a given .def file.


__--enable-stdcall-fixup__


__--disable-stdcall-fixup__


If the link finds a symbol that it cannot resolve, it will
attempt to do ``fuzzy linking'' by looking for another
defined symbol that differs only in the format of the symbol
name (cdecl vs stdcall) and will resolve that symbol by
linking to the match. For example, the undefined symbol
_foo might be linked to the function
_foo@12, or the undefined symbol _bar@16
might be linked to the function _bar. When the
linker does this, it prints a warning, since it normally
should have failed to link, but sometimes import libraries
generated from third-party dlls may need this feature to be
usable. If you specify __--enable-stdcall-fixup__, this
feature is fully enabled and warnings are not printed. If
you specify __--disable-stdcall-fixup__, this feature is
disabled and such mismatches are considered to be
errors.


__--export-all-symbols__


If given, all global symbols in the objects used to build a
DLL will be exported by the
DLL . Note that this is the default if there
otherwise wouldn't be any exported symbols. When symbols are
explicitly exported via DEF files or
implicitly exported via function attributes, the default is
to not export anything else unless this option is given.
Note that the symbols !DllMain@12,
!DllEntryPoint@0, DllMainCRTStartup@12, and
impure_ptr will not be automatically exported.
Also, symbols imported from other DLLs will not be
re-exported, nor will symbols specifying the
DLL 's internal layout such as those
beginning with _head_ or ending with
_iname. In addition, no symbols from
libgcc, libstd++, libmingw32, or
crtX.o will be exported. Symbols whose names begin
with __rtti_ or __builtin_ will not be
exported, to help with C ++ DLLs. Finally,
there is an extensive list of cygwin-private symbols that
are not exported (obviously, this applies on when building
DLLs for cygwin targets). These cygwin-excludes are:
_cygwin_dll_entry@12,
_cygwin_crt0_common@8,
_cygwin_noncygwin_dll_entry@12, _fmode,
_impure_ptr, cygwin_attach_dll,
cygwin_premain0, cygwin_premain1,
cygwin_premain2, cygwin_premain3, and
environ.


__--exclude-symbols__
''symbol''__,__''symbol''__,...__


Specifies a list of symbols which should not be
automatically exported. The symbol names may be delimited by
commas or colons.


__--file-alignment__


Specify the file alignment. Sections in the file will always
begin at file offsets which are multiples of this number.
This defaults to 512.


__--heap__ ''reserve''


__--heap__
''reserve''__,__''commit''


Specify the amount of memory to reserve (and optionally
commit) to be used as heap for this program. The default is
1Mb reserved, 4K committed.


__--image-base__ ''value''


Use ''value'' as the base address of your program or dll.
This is the lowest memory location that will be used when
your program or dll is loaded. To reduce the need to
relocate and improve performance of your dlls, each should
have a unique base address and not overlap any other dlls.
The default is 0x400000 for executables, and 0x10000000 for
dlls.


__--kill-at__


If given, the stdcall suffixes (@''nn'') will be stripped
from symbols before they are exported.


__--major-image-version__ ''value''


Sets the major number of the ``image version''. Defaults to
1.


__--major-os-version__ ''value''


Sets the major number of the ``os version''. Defaults to
4.


__--major-subsystem-version__ ''value''


Sets the major number of the ``subsystem version''. Defaults
to 4.


__--minor-image-version__ ''value''


Sets the minor number of the ``image version''. Defaults to
0.


__--minor-os-version__ ''value''


Sets the minor number of the ``os version''. Defaults to
0.


__--minor-subsystem-version__ ''value''


Sets the minor number of the ``subsystem version''. Defaults
to 0.


__--output-def__ ''file''


The linker will create the file ''file'' which will
contain a DEF file corresponding to the
DLL the linker is generating. This
DEF file (which should be called
*.def) may be used to create an import library with
dlltool or may be used as a reference to
automatically or implicitly exported symbols.


__--out-implib__ ''file''


The linker will create the file ''file'' which will
contain an import lib corresponding to the
DLL the linker is generating. This import lib
(which should be called *.dll.a or *.a may
be used to link clients against the generated
DLL ; this behavior makes it possible to skip
a separate dlltool import library creation
step.


__--enable-auto-image-base__


Automatically choose the image base for DLLs, unless one is
specified using the --image-base argument. By using
a hash generated from the dllname to create unique image
bases for each DLL , in-memory collisions and
relocations which can delay program execution are
avoided.


__--disable-auto-image-base__


Do not automatically generate a unique image base. If there
is no user-specified image base (--image-base) then
use the platform default.


__--dll-search-prefix__ ''string''


When linking dynamically to a dll without an import library,
i search for  in
preference to lib. This
behavior allows easy distinction between DLLs built for the
various ``subplatforms'': native, cygwin, uwin, pw, etc. For
instance, cygwin DLLs typically use
--dll-search-prefix=cyg.


__--enable-auto-import__


Do sophisticated linking of _symbol to
__imp__symbol for DATA imports from
DLLs, and create the necessary thunking symbols when
building the DLLs with those DATA exports.
This generally will 'just work' -- but sometimes you may see
this message:


--enable-auto-import for
details.


This message occurs when some (sub)expression accesses an
address ultimately given by the sum of two constants (Win32
import tables only allow one). Instances where this may
occur include accesses to member fields of struct variables
imported from a DLL , as well as using a
constant index into an array variable imported from a
DLL . Any multiword variable (arrays,
structs, long long, etc) may trigger this error condition.
However, regardless of the exact data type of the offending
exported variable, ld will always detect it, issue the
warning, and exit.


There are several ways to address this difficulty,
regardless of the data type of the exported
variable:


One solution is to force one of the 'constants' to be a
variable -- that is, unknown and un-optimizable at compile
time. For arrays, there are two possibilities: a) make the
indexee (the array's address) a variable, or b) make the
'constant' index a variable. Thus:


        extern type extern_array[[];
extern_array[[1] --
or


        extern type extern_array[[];
extern_array[[1] --
For structs (and most other multiword data types) the only option is to make the struct itself (or the long long, or the ...) variable:


        extern struct s extern_struct;
extern_struct.field --
or


        extern long long extern_ll;
extern_ll --
A second method of dealing with this difficulty is to abandon 'auto-import' for the offending symbol and mark it with __declspec(dllimport). However, in practice that requires using compile-time #defines to indicate whether you are building a DLL , building client code that will link to the DLL , or merely building/linking to a static library. In making the choice between the various methods of resolving the 'direct address with constant offset' problem, you should consider typical real-world usage:


Original:


        --foo.h
extern int arr[[];
--foo.c
#include
Solution 1:


        --foo.h
extern int arr[[];
--foo.c
#include
Solution 2:


        --foo.h
/* Note: auto-export is assumed (no __declspec(dllexport)) */
#if (defined(_WIN32)  defined(__CYGWIN__))
A third way to avoid this problem is to re-code your library to use a functional interface rather than a data interface for the offending variables (e.g. ''set_foo()'' and ''get_foo()'' accessor functions).


__--disable-auto-import__


Do not attempt to do sophisticalted linking of
_symbol to __imp__symbol for
DATA imports from DLLs.


__--enable-extra-pe-debug__


Show additional debug info related to auto-import symbol
thunking.


__--section-alignment__


Sets the section alignment. Sections in memory will always
begin at addresses which are a multiple of this number.
Defaults to 0x1000.


__--stack__ ''reserve''


__--stack__
''reserve''__,__''commit''


Specify the amount of memory to reserve (and optionally
commit) to be used as stack for this program. The default is
2Mb reserved, 4K committed.


__--subsystem__ ''which''


__--subsystem__
''which''__:__''major''


__--subsystem__
''which''__:__''major''__.__''minor''


Specifies the subsystem under which your program will
execute. The legal values for ''which'' are
native, windows, console, and
posix. You may optionally set the subsystem version
also.
!!ENVIRONMENT


You can change the behavior of __ld__ with the
environment variables GNUTARGET,
LDEMULATION, and
COLLECT_NO_DEMANGLE.


GNUTARGET determines the input-file object format
if you don't use __-b__ (or its synonym __--format__).
Its value should be one of the BFD names for
an input format. If there is no GNUTARGET in the
environment, __ld__ uses the natural format of the
target. If GNUTARGET is set to default
then BFD attempts to discover the input
format by examining binary input files; this method often
succeeds, but there are potential ambiguities, since there
is no method of ensuring that the magic number used to
specify object-file formats is unique. However, the
configuration procedure for BFD on each
system places the conventional format for that system first
in the search-list, so ambiguities are resolved in favor of
convention.


LDEMULATION determines the default emulation if you
don't use the __-m__ option. The emulation can affect
various aspects of linker behaviour, particularly the
default linker script. You can list the available emulations
with the __--verbose__ or __-V__ options. If the
__-m__ option is not used, and the LDEMULATION
environment variable is not defined, the default emulation
depends upon how the linker was configured.


Normally, the linker will default to demangling symbols.
However, if COLLECT_NO_DEMANGLE is set in the
environment, then it will default to not demangling symbols.
This environment variable is used in a similar fashion by
the gcc linker wrapper program. The default may be
overridden by the __--demangle__ and __--no-demangle__
options.
!!SEE ALSO


ar(1), nm(1), objcopy(1),
objdump(1), readelf(1) and the Info entries
for ''binutils'' and ''ld''.
!!COPYRIGHT


Copyright (c) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000,
2001 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 1.1 or any later version
published by the Free Software Foundation; with no Invariant
Sections, with no Front-Cover Texts, and with no Back-Cover
Texts. A copy of the license is included in the section
entitled `` GNU Free Documentation
License''.
----
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Last edited on Tuesday, June 4, 2002 12:22:14 am by "perry"
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