MAN page from RedHat 8.X binutils-


Section: GNU Development Tools (1)
Updated: 2003-02-07


ld - Using LD, the GNU linker 


ld [options] objfile ... 


ld combines a number of object and archive files, relocatestheir data and ties up symbol references. Usually the last step incompiling a program is to run ld.

ld accepts Linker Command Language files written ina superset of AT&T'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 manualld: 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 librariesto operate on object files. This allows ld to read, combine, andwrite object files in many different formats---for example, COFF or"a.out". Different formats may be linked together to produce anyavailable kind of object file.

Aside from its flexibility, the GNU linker is more helpful than otherlinkers in providing diagnostic information. Many linkers abandonexecution 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. 


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

        ld -o <output> /lib/crt0.o hello.o -lc

This tells ld to produce a file called output as theresult of linking the file "/lib/crt0.o" with "hello.o" andthe library "libc.a", which will come from the standard searchdirectories. (See the discussion of the -l option below.)

Some of the command-line options to ld may be specified at anypoint in the command line. However, options which refer to files, suchas -l or -T, cause the file to be read at the point atwhich the option appears in the command line, relative to the objectfiles and other file options. Repeating non-file options with adifferent argument will either have no further effect, or override prioroccurrences (those further to the left on the command line) of thatoption. Options which may be meaningfully specified more than once arenoted in the descriptions below.

Non-option arguments are object files or archives which are to be linkedtogether. They may follow, precede, or be mixed in with command-lineoptions, except that an object file argument may not be placed betweenan option and its argument.

Usually the linker is invoked with at least one object file, but you canspecify other forms of binary input files using -l, -R,and the script command language. If no binary input files at allare specified, the linker does not produce any output, and issues themessage No input files.

If the linker can not recognize the format of an object file, it willassume that it is a linker script. A script specified in this wayaugments the main linker script used for the link (either the defaultlinker script or the one specified by using -T). This featurepermits the linker to link against a file which appears to be an objector an archive, but actually merely defines some symbol values, or uses"INPUT" or "GROUP" to load other objects. Note thatspecifying 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 interveningwhitespace, or be given as separate arguments immediately following theoption that requires them.

For options whose names are multiple letters, either one dash or two canprecede the option name; for example, -trace-symbol and--trace-symbol are equivalent. Note - there is one exception tothis rule. Multiple letter options that start with a lower case 'o' canonly be preceeded by two dashes. This is to reduce confusion with the-o option. So for example -omagic sets the output filename to magic whereas --omagic sets the NMAGIC flag on theoutput.

Arguments to multiple-letter options must either be separated from theoption name by an equals sign, or be given as separate argumentsimmediately 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 areaccepted.

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

          gcc -Wl,--startgroup foo.o bar.o -Wl,--endgroup

This is important, because otherwise the compiler driver program maysilently drop the linker options, resulting in a bad link.

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

This option is supported for HP/UX compatibility. The keywordargument must be one of the strings archive, shared, ordefault. -aarchive is functionally equivalent to-Bstatic, and the other two keywords are functionally equivalentto -Bdynamic. This option may be used any number of times.
In the current release of ld, this option is useful only for theIntel 960 family of architectures. In that ld configuration, thearchitecture argument identifies the particular architecture inthe 960 family, enabling some safeguards and modifying thearchive-library search path.

Future releases of ld may support similar functionality forother architecture families.

-b input-format
ld may be configured to support more than one kind of objectfile. If your ld is configured this way, you can use the-b option to specify the binary format for input object filesthat follow this option on the command line. Even when ld isconfigured to support alternative object formats, you don't usually needto specify this, as ld should be configured to expect as adefault input format the most usual format on each machine.input-format is a text string, the name of a particular formatsupported by the BFD libraries. (You can list the available binaryformats with objdump -i.)

You may want to use this option if you are linking files with an unusualbinary format. You can also use -b to switch formats explicitly (whenlinking object files of different formats), by including-b input-format before each group of object files in aparticular 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
For compatibility with linkers produced by MRI, ld accepts scriptfiles written in an alternate, restricted command language, described inthe MRI Compatible Script Files section of GNU ld documentation.Introduce MRI script files withthe option -c; use the -T option to run linkerscripts written in the general-purpose ld scripting language.If MRI-cmdfile does not exist, ld looks for it in the directoriesspecified by any -L options.
These three options are equivalent; multiple forms are supported forcompatibility with other linkers. They assign space to common symbolseven if a relocatable output file is specified (with -r). Thescript command "FORCE_COMMON_ALLOCATION" has the same effect.
-e entry
Use entry as the explicit symbol for beginning execution of yourprogram, rather than the default entry point. If there is no symbolnamed entry, the linker will try to parse entry as a number,and use that as the entry address (the number will be interpreted inbase 10; you may use a leading 0x for base 16, or a leading0 for base 8).
When creating a dynamically linked executable, add all symbols to thedynamic symbol table. The dynamic symbol table is the set of symbolswhich are visible from dynamic objects at run time.

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

If you use "dlopen" to load a dynamic object which needs to referback to the symbols defined by the program, rather than some otherdynamic object, then you will probably need to use this option whenlinking the program itself.

You can also use the version script to control what symbols shouldbe added to the dynamic symbol table if the output format supports it.See the description of --version-script in @ref{VERSION}.

Link big-endian objects. This affects the default output format.
Link little-endian objects. This affects the default output format.
--auxiliary name
When creating an ELF shared object, set the internal DT_AUXILIARY fieldto the specified name. This tells the dynamic linker that the symboltable of the shared object should be used as an auxiliary filter on thesymbol table of the shared object name.

If you later link a program against this filter object, then, when yourun the program, the dynamic linker will see the DT_AUXILIARY field. Ifthe dynamic linker resolves any symbols from the filter object, it willfirst check whether there is a definition in the shared objectname. If there is one, it will be used instead of the definitionin the filter object. The shared object name need not exist.Thus the shared object name may be used to provide an alternativeimplementation of certain functions, perhaps for debugging or formachine specific performance.

This option may be specified more than once. The DT_AUXILIARY entrieswill 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 tothe specified name. This tells the dynamic linker that the symbol tableof the shared object which is being created should be used as a filteron the symbol table of the shared object name.

If you later link a program against this filter object, then, when yourun the program, the dynamic linker will see the DT_FILTER field. Thedynamic linker will resolve symbols according to the symbol table of thefilter object as usual, but it will actually link to the definitionsfound in the shared object name. Thus the filter object can beused to select a subset of the symbols provided by the objectname.

Some older linkers used the -F option throughout a compilationtoolchain for specifying object-file format for both input and outputobject files. The GNU linker uses other mechanisms for thispurpose: the -b, --format, --oformat options, the"TARGET" command in linker scripts, and the "GNUTARGET"environment variable. The GNU linker will ignore the -Foption when not creating an ELF shared object.

-fini name
When creating an ELF executable or shared object, call NAME when theexecutable or shared object is unloaded, by setting DT_FINI to theaddress of the function. By default, the linker uses "_fini" asthe function to call.
Ignored. Provided for compatibility with other tools.
Set the maximum size of objects to be optimized using the GP register tosize. This is only meaningful for object file formats such asMIPS ECOFF which supports putting large and small objects into differentsections. This is ignored for other object file formats.
When creating an ELF shared object, set the internal DT_SONAME field tothe specified name. When an executable is linked with a shared objectwhich has a DT_SONAME field, then when the executable is run the dynamiclinker will attempt to load the shared object specified by the DT_SONAMEfield rather than the using the file name given to the linker.
Perform an incremental link (same as option -r).
-init name
When creating an ELF executable or shared object, call NAME when theexecutable or shared object is loaded, by setting DT_INIT to the addressof the function. By default, the linker uses "_init" as thefunction to call.
Add archive file archive to the list of files to link. Thisoption may be used any number of times. ld will search itspath-list for occurrences of "libarchive.a" for everyarchive specified.

On systems which support shared libraries, ld may also search forlibraries with extensions other than ".a". Specifically, on ELFand SunOS systems, ld will search a directory for a library withan extension of ".so" before searching for one with an extension of".a". By convention, a ".so" extension indicates a sharedlibrary.

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

See the -( option for a way to force the linker to searcharchives 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 thebehaviour of the AIX linker.

Add path searchdir to the list of paths that ld will searchfor archive libraries and ld control scripts. You may use thisoption any number of times. The directories are searched in the orderin which they are specified on the command line. Directories specifiedon the command line are searched before the default directories. All-L options apply to all -l options, regardless of theorder 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 insome 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 searchedat the point in which the linker script appears in the command line.

Emulate the emulation linker. You can list the availableemulations 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 wasconfigured.

Print a link map to the standard output. A link map providesinformation 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 symbolwhich caused the archive member to be brought in.
Turn off page alignment of sections, and mark the output as"NMAGIC" if possible.
Set the text and data sections to be readable and writable. Also, donot page-align the data segment. If the output format supports Unixstyle magic numbers, mark the output as "OMAGIC".
-o output
Use output as the name for the program produced by ld; if thisoption is not specified, the name a.out is used by default. Thescript command "OUTPUT" can also specify the output file name.
-O level
If level is a numeric values greater than zero ld optimizesthe output. This might take significantly longer and therefore probablyshould only be enabled for the final binary.
Leave relocation sections and contents in fully linked exececutables.Post link analysis and optimization tools may need this information inorder to perform correct modifications of executables. This resultsin larger executables.

This option is currently only supported on ELF platforms.

Generate relocatable output---i.e., generate an output file that can inturn serve as input to ld. This is often called partiallinking. As a side effect, in environments that support standard Unixmagic numbers, this option also sets the output file's magic number to"OMAGIC".If this option is not specified, an absolute file is produced. Whenlinking C++ programs, this option will not resolve references toconstructors; 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 anyrelocations. Different output formats can have further restrictions; forexample some "a.out"-based formats do not support partial linkingwith input files in other formats at all.

This option does the same thing as -i.

-R filename
Read symbol names and their addresses from filename, but do notrelocate it or include it in the output. This allows your output fileto refer symbolically to absolute locations of memory defined in otherprograms. You may use this option more than once.

For compatibility with other ELF linkers, if the -R option isfollowed by a directory name, rather than a file name, it is treated asthe -rpath option.

Omit all symbol information from the output file.
Omit debugger symbol information (but not all symbols) from the output file.
Print the names of the input files as ld processes them.
-T scriptfile
Use scriptfile as the linker script. This script replacesld's default linker script (rather than adding to it), socommandfile must specify everything necessary to describe theoutput file. If scriptfile does not exist inthe current directory, "ld" looks for it in the directoriesspecified by any preceding -L options. Multiple -Toptions accumulate.
-u symbol
Force symbol to be entered in the output file as an undefinedsymbol. Doing this may, for example, trigger linking of additionalmodules from standard libraries. -u may be repeated withdifferent option arguments to enter additional undefined symbols. Thisoption is equivalent to the "EXTERN" linker script command.
For anything other than C++ programs, this option is equivalent to-r: it generates relocatable output---i.e., an output file that can inturn serve as input to ld. When linking C++ programs, -Urdoes resolve references to constructors, unlike -r.It does not work to use -Ur on files that were themselves linkedwith -Ur; once the constructor table has been built, it cannotbe added to. Use -Ur only for the last partial link, and-r for the others.
Creates a separate output section for every input section matchingSECTION, or if the optional wildcard SECTION argument ismissing, for every orphan input section. An orphan section is one notspecifically mentioned in a linker script. You may use this optionmultiple times on the command line; It prevents the normal merging ofinput sections with the same name, overriding output section assignmentsin a linker script.
Display the version number for ld. The -V option alsolists the supported emulations.
Delete all local symbols.
Delete all temporary local symbols. For most targets, this is all localsymbols whose names begin with L.
-y symbol
Print the name of each linked file in which symbol appears. Thisoption may be given any number of times. On many systems it is necessaryto prepend an underscore.

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

-Y path
Add path to the default library search path. This option existsfor Solaris compatibility.
-z keyword
The recognized keywords are "initfirst", "interpose","loadfltr", "nodefaultlib", "nodelete", "nodlopen","nodump", "now", "origin", "combreloc", "nocombreloc" and "nocopyreloc".The other keywords areignored for Solaris compatibility. "initfirst" marks the objectto be initialized first at runtime before any other objects."interpose" marks the object that its symbol table interposesbefore all symbols but the primary executable. "loadfltr" marksthe object that its filtees be processed immediately at runtime."nodefaultlib" marks the object that the search for dependenciesof 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."muldefs" allows multiple definitions."combreloc" combines multiple reloc sections and sorts themto 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 beeither explicit file names, or -l options.

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

Using this option has a significant performance cost. It is best to useit only when there are unavoidable circular references between two ormore archives.

-assert keyword
This option is ignored for SunOS compatibility.
Link against dynamic libraries. This is only meaningful on platformsfor which shared libraries are supported. This option is normally thedefault on such platforms. The different variants of this option arefor compatibility with various systems. You may use this optionmultiple times on the command line: it affects library searching for-l options which follow it.
Set the "DF_1_GROUP" flag in the "DT_FLAGS_1" entry in the dynamicsection. This causes the runtime linker to handle lookups in thisobject and its dependencies to be performed only inside the group.--no-undefined is implied. This option is only meaningful on ELFplatforms which support shared libraries.
Do not link against shared libraries. This is only meaningful onplatforms for which shared libraries are supported. The differentvariants of this option are for compatibility with various systems. Youmay use this option multiple times on the command line: it affectslibrary searching for -l options which follow it.
When creating a shared library, bind references to global symbols to thedefinition within the shared library, if any. Normally, it is possiblefor a program linked against a shared library to override the definitionwithin the shared library. This option is only meaningful on ELFplatforms which support shared libraries.
Asks the linker not to check section addresses after they havebeen assigned to see if there any overlaps. Normally the linker willperform this check, and if it finds any overlaps it will producesuitable error messages. The linker does know about, and does makeallowances for sections in overlays. The default behaviour can berestored by using the command line switch --check-sections.
Output a cross reference table. If a linker map file is beinggenerated, 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 beeasily 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 thesymbol is defined, the first file listed is the location of thedefinition. The remaining files contain references to the symbol.

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 decouplingthe decision to assign addresses to Common symbols from the choiceof the output file type; otherwise a non-Relocatable output typeforces assigning addresses to Common symbols.Using --no-define-common allows Common symbols that are referencedfrom 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 wrongduplicate when there are many dynamic modules with specialized searchpaths for runtime symbol resolution.

--defsym symbol=expression
Create a global symbol in the output file, containing the absoluteaddress given by expression. You may use this option as manytimes as necessary to define multiple symbols in the command line. Alimited form of arithmetic is supported for the expression in thiscontext: you may give a hexadecimal constant or the name of an existingsymbol, or use "+" and "-" to add or subtract hexadecimalconstants or symbols. If you need more elaborate expressions, considerusing the linker command language from a script. Note: there should be no whitespace between symbol, the equals sign (``=''), andexpression.
These options control whether to demangle symbol names in error messagesand other output. When the linker is told to demangle, it tries topresent symbol names in a readable fashion: it strips leadingunderscores if they are used by the object file format, and converts C++mangled symbol names into user readable names. Different compilers havedifferent mangling styles. The optional demangling style argument can be usedto choose an appropriate demangling style for your compiler. The linker willdemangle by default unless the environment variable COLLECT_NO_DEMANGLEis set. These options may be used to override the default.
--dynamic-linker file
Set the name of the dynamic linker. This is only meaningful whengenerating dynamically linked ELF executables. The default dynamiclinker is normally correct; don't use this unless you know what you aredoing.
This option is only meaningful when linking MIPS embedded PIC code,generated by the -membedded-pic option to the GNU compiler andassembler. It causes the linker to create a table which may be used atruntime to relocate any data which was statically initialized to pointervalues. See the code in testsuite/ld-empic for details.
Treat all warnings as errors.
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 copythe output file to one of the same name with a ".exe" suffix. Thisoption is useful when using unmodified Unix makefiles on a MicrosoftWindows host, since some versions of Windows won't run an image unlessit ends in a ".exe" suffix.

Enable garbage collection of unused input sections. It is ignored ontargets that do not support this option. This option is not compatiblewith -r, nor should it be used with dynamic linking. The defaultbehaviour (of not performing this garbage collection) can be restored byspecifying --no-gc-sections on the command line.
Print a summary of the command-line options on the standard output and exit.
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.
ld normally optimizes for speed over memory usage by caching thesymbol tables of input files in memory. This option tells ld toinstead optimize for memory usage, by rereading the symbol tables asnecessary. This may be required if ld runs out of memory spacewhile linking a large executable.
-z defs
Normally when creating a non-symbolic shared library, undefined symbolsare allowed and left to be resolved by the runtime loader. These optionsdisallows such undefined symbols.
-z muldefs
Normally when a symbol is defined multiple times, the linker willreport a fatal error. These options allow multiple definitions and thefirst definition will be used.
Allow undefined symbols in shared objects even when --no-undefined isset. The net result will be that undefined symbols in regular objectswill still trigger an error, but undefined symbols in shared objectswill be ignored. The implementation of no_undefined makes theassumption that the runtime linker will choke on undefined symbols.However there is at least one system (BeOS) where undefined symbols inshared libraries is normal since the kernel patches them at load time toselect which function is most appropriate for the current architecture.I.E. dynamically select an appropriate memset function. Apparently itis also normal for HPPA shared libraries to have undefined symbols.
Normally when a symbol has an undefined version, the linker will ignoreit. This option disallows symbols with undefined version and a fatal errorwill be issued instead.
Normally ld will give an error if you try to link together inputfiles that are mismatched for some reason, perhaps because they havebeen compiled for different processors or for different endiannesses.This option tells ld that it should silently permit such possibleerrors. This option should only be used with care, in cases when youhave taken some special action that ensures that the linker errors areinappropriate.
Turn off the effect of the --whole-archive option for subsequentarchive files.
Retain the executable output file whenever it is still usable.Normally, the linker will not produce an output file if it encounterserrors during the link process; it exits without writing an output filewhen it issues any error whatsoever.
Only search library directories explicitly specified on thecommand 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 objectfile. If your ld is configured this way, you can use the--oformat option to specify the binary format for the outputobject file. Even when ld is configured to support alternativeobject formats, you don't usually need to specify this, as ldshould be configured to produce as a default output format the mostusual format on each machine. output-format is a text string, thename of a particular format supported by the BFD libraries. (You canlist the available binary formats with objdump -i.) The scriptcommand "OUTPUT_FORMAT" can also specify the output format, butthis option overrides it.
This option is ignored for Linux compatibility.
This option is ignored for SVR4 compatibility.
An option with machine dependent effects.This option is only supported on a few targets.

On some platforms, the --relax option performs globaloptimizations that become possible when the linker resolves addressingin the program, such as relaxing address modes and synthesizing newinstructions in the output object file.

On some platforms these link time global optimizations may make symbolicdebugging of the resulting executable impossible.This is known to bethe 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 onesymbol name per line. This option is especially useful in environments(such as VxWorks)where a large global symbol table is accumulated gradually, to conserverun-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 commandline. It overrides -s and -S.

-rpath dir
Add a directory to the runtime library search path. This is used whenlinking an ELF executable with shared objects. All -rpatharguments are concatenated and passed to the runtime linker, which usesthem to locate shared objects at runtime. The -rpath option isalso used when locating shared objects which are needed by sharedobjects explicitly included in the link; see the description of the-rpath-link option. If -rpath is not used when linking anELF 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, onSunOS, the linker will form a runtime search patch out of all the-L options it is given. If a -rpath option is used, theruntime search path will be formed exclusively using the -rpathoptions, ignoring the -L options. This can be useful when usinggcc, which adds many -L options which may be on NFS mountedfilesystems.

For compatibility with other ELF linkers, if the -R option isfollowed by a directory name, rather than a file name, it is treated asthe -rpath option.

-rpath-link DIR
When using ELF or SunOS, one shared library may require another. Thishappens when an "ld -shared" link includes a shared library as oneof 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 requiredshared library and include it in the link, if it is not includedexplicitly. In such a case, the -rpath-link optionspecifies the first set of directories to search. The-rpath-link option may specify a sequence of directory nameseither by specifying a list of names separated by colons, or byappearing multiple times.

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

The linker uses the following search paths to locate required sharedlibraries.

Any directories specified by -rpath-link options.
Any directories specified by -rpath options. The differencebetween -rpath and -rpath-link is that directoriesspecified by -rpath options are included in the executable andused at runtime, whereas the -rpath-link option is only effectiveat link time. It is for the native linker only.
On an ELF system, if the -rpath and "rpath-link" optionswere not used, search the contents of the environment variable"LD_RUN_PATH". It is for the native linker only.
On SunOS, if the -rpath option was not used, search anydirectories specified using -L options.
For a native linker, the contents of the environment variable"LD_LIBRARY_PATH".
For a native ELF linker, the directories in "DT_RUNPATH" or"DT_RPATH" of a shared library are searched for sharedlibraries needed by it. The "DT_RPATH" entries are ignored if"DT_RUNPATH" entries exist.
The default directories, normally /lib and /usr/lib.
For a native linker on an ELF system, if the file /etc/, the list of directories found in that file.

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

Create a shared library. This is currently only supported on ELF, XCOFFand SunOS platforms. On SunOS, the linker will automatically create ashared library if the -e option is not used and there areundefined symbols in the link.
This option tells ld to sort the common symbols by size when itplaces them in the appropriate output sections. First come all the onebyte symbols, then all the two byte, then all the four byte, and theneverything else. This is to prevent gaps between symbols due toalignment constraints.
--split-by-file [size]
Similar to --split-by-reloc but creates a new output section foreach input file when size is reached. size defaults to asize of 1 if not given.
--split-by-reloc [count]
Tries to creates extra sections in the output file so that no singleoutput section in the file contains more than count relocations.This is useful when generating huge relocatable files for downloading intocertain real time kernels with the COFF object file format; since COFFcannot represent more than 65535 relocations in a single section. Notethat this will fail to work with object file formats which do notsupport arbitrary sections. The linker will not split up individualinput sections for redistribution, so if a single input section containsmore than count relocations one output section will contain thatmany relocations. count defaults to a value of 32768.
Compute and display statistics about the operation of the linker, suchas execution time and memory usage.
For some targets, the output of ld is different in some ways fromthe output of some existing linker. This switch requests ld touse the traditional format instead.

For example, on SunOS, ld combines duplicate entries in thesymbol string table. This can reduce the size of an output file withfull debugging information by over 30 percent. Unfortunately, the SunOS"dbx" program can not read the resulting program ("gdb" has notrouble). The --traditional-format switch tells ld to notcombine duplicate entries.

--section-start sectionname=org
Locate a section in the output file at the absoluteaddress given by org. You may use this option as manytimes as necessary to locate multiple sections in the must be a single hexadecimal integer;for compatibility with other linkers, you may omit the leading0x usually associated with hexadecimal values. Note: thereshould be no white space between sectionname, the equalssign (``=''), 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 must be a single hexadecimal integer;for compatibility with other linkers, you may omit the leading0x usually associated with hexadecimal values.
Display the version number for ld and list the linker emulationssupported. Display which input files can and cannot be opened. Displaythe linker script being used by the linker.
Specify the name of a version script to the linker. This is typicallyused when creating shared libraries to specify additional informationabout the version heirarchy for the library being created. This optionis only meaningful on ELF platforms which support shared libraries.
Warn when a common symbol is combined with another common symbol or witha symbol definition. Unix linkers allow this somewhat sloppy practice,but linkers on some other operating systems do not. This option allowsyou to find potential problems from combining global symbols.Unfortunately, some C libraries use this practice, so you may get somewarnings 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 outputfile.
extern int i;
An undefined reference, which does not allocate space.There must be either a definition or a common symbol for thevariable somewhere.
int i;
A common symbol. If there are only (one or more) common symbols for avariable, it goes in the uninitialized data area of the output file.The linker merges multiple common symbols for the same variable into asingle symbol. If they are of different sizes, it picks the largestsize. The linker turns a common symbol into a declaration, if there isa 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 symboljust encountered, and the second describes the previous symbolencountered with the same name. One or both of the two symbols will bea common symbol.

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

        <file>(<section>): warning: common of `<symbol>'           overridden by definition        <file>(<section>): warning: defined here
Turning a common symbol into a reference, because a later definition forthe symbol is encountered. This is the same as the previous case,except that the symbols are encountered in a different order.

        <file>(<section>): warning: definition of `<symbol>'           overriding common        <file>(<section>): warning: common is here
Merging a common symbol with a previous same-sized common symbol.

        <file>(<section>): warning: multiple common           of `<symbol>'        <file>(<section>): warning: previous common is here
Merging a common symbol with a previous larger common symbol.

        <file>(<section>): warning: common of `<symbol>'           overridden by larger common        <file>(<section>): warning: larger common is here
Merging a common symbol with a previous smaller common symbol. This isthe same as the previous case, except that the symbols areencountered in a different order.

        <file>(<section>): warning: common of `<symbol>'           overriding smaller common        <file>(<section>): warning: smaller common is here
Warn if any global constructors are used. This is only useful for a fewobject file formats. For formats like COFF or ELF, the linker can notdetect the use of global constructors.
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 specialsection. A special register (the global pointer) points into the middleof this section, so that constants can be loaded efficiently via abase-register relative addressing mode. Since the offset inbase-register relative mode is fixed and relatively small (e.g., 16bits), this limits the maximum size of the constant pool. Thus, inlarge programs, it is often necessary to use multiple global pointervalues in order to be able to address all possible constants. Thisoption causes a warning to be issued whenever this case occurs.
Only warn once for each undefined symbol, rather than once per modulewhich refers to it.
Warn if the address of an output section is changed because ofalignment. Typically, the alignment will be set by an input section.The address will only be changed if it not explicitly specified; thatis, if the "SECTIONS" command does not specify a start address forthe section.
For each archive mentioned on the command line after the--whole-archive option, include every object file in the archivein the link, rather than searching the archive for the required objectfiles. This is normally used to turn an archive file into a sharedlibrary, forcing every object to be included in the resulting sharedlibrary. This option may be used more than once.

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

--wrap symbol
Use a wrapper function for symbol. Any undefined reference tosymbol will be resolved to "__wrap_symbol". Anyundefined reference to "__real_symbol" will be resolved tosymbol.

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

Here is a trivial example:

        void *        __wrap_malloc (int c)        {          printf ("malloc called with %ld\n", c);          return __real_malloc (c);        }

If you link other code with this file using --wrap malloc, thenall calls to "malloc" will call the function "__wrap_malloc"instead. The call to "__real_malloc" in "__wrap_malloc" willcall the real "malloc" function.

You may wish to provide a "__real_malloc" function as well, so thatlinks without the --wrap option will succeed. If you do this,you should not put the definition of "__real_malloc" in the samefile as "__wrap_malloc"; if you do, the assembler may resolve thecall before the linker has a chance to wrap it to "malloc".

This linker can create the new dynamic tags in ELF. But the older ELFsystems 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 becreated. By default, the new dynamic tags are not created. Note thatthose options are only available for ELF systems.

The i386 PE linker supports the -shared option, which causesthe output to be a dynamically linked library (DLL) instead of anormal executable. You should name the output "*.dll" when youuse this option. In addition, the linker fully supports the standard"*.def" files, which may be specified on the linker command linelike an object file (in fact, it should precede archives it exportssymbols from, to ensure that they get linked in, just like a normalobject file).

In addition to the options common to all targets, the i386 PE linkersupport additional command line options that are specific to the i386PE target. Options that take values may be separated from theirvalues by either a space or an equals sign.

If given, symbols with a stdcall suffix (@nn) will be exportedas-is and also with the suffix stripped.
--base-file file
Use file as the name of a file in which to save the baseaddresses of all the relocations needed for generating DLLs withdlltool.
Create a DLL instead of a regular executable. You may also use-shared or specify a "LIBRARY" in a given ".def"file.
If the link finds a symbol that it cannot resolve, it will attempt todo ``fuzzy linking'' by looking for another defined symbol that differsonly in the format of the symbol name (cdecl vs stdcall) and willresolve that symbol by linking to the match. For example, theundefined symbol "_foo" might be linked to the function"_foo@12", or the undefined symbol "_bar@16" might be linkedto the function "_bar". When the linker does this, it prints awarning, since it normally should have failed to link, but sometimesimport libraries generated from third-party dlls may need this featureto be usable. If you specify --enable-stdcall-fixup, thisfeature is fully enabled and warnings are not printed. If you specify--disable-stdcall-fixup, this feature is disabled and suchmismatches are considered to be errors.
If given, all global symbols in the objects used to build a DLL willbe exported by the DLL. Note that this is the default if thereotherwise wouldn't be any exported symbols. When symbols areexplicitly exported via DEF files or implicitly exported via functionattributes, the default is to not export anything else unless thisoption is given. Note that the symbols "DllMain@12","DllEntryPoint@0", "DllMainCRTStartup@12", and "impure_ptr" will not be automaticallyexported. 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_" willnot be exported, to help with C++ DLLs. Finally, there is anextensive 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 automaticallyexported. The symbol names may be delimited by commas or colons.
--exclude-libs lib,lib,...
Specifies a list of archive libraries from which symbols should not be automaticallyexported. The library names may be delimited by commas or colons. Specifying"--exclude-libs ALL" excludes symbols in all archive libraries fromautomatic export. Symbols explicitly listed in a .def file are still exported,regardless of this option.
Specify the file alignment. Sections in the file will always begin atfile offsets which are multiples of this number. This defaults to512.
--heap reserve
--heap reserve,commit
Specify the amount of memory to reserve (and optionally commit) to beused as heap for this program. The default is 1Mb reserved, 4Kcommitted.
--image-base value
Use value as the base address of your program or dll. This isthe lowest memory location that will be used when your program or dllis loaded. To reduce the need to relocate and improve performance ofyour dlls, each should have a unique base address and not overlap anyother dlls. The default is 0x400000 for executables, and 0x10000000for dlls.
If given, the stdcall suffixes (@nn) will be stripped fromsymbols 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.