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ld(1)                 GNU Development Tools                 ld(1)

NAME
       ld - the GNU linker

SYNOPSIS
       ld     [-o output] objfile...
              [-Aarchitecture] [-b input-format] [-Bstatic]
              [-Bgroup] [-Bdynamic] [-Bsymbolic] [-c commandfile]
              [--cref] [-d|-dc|-dp]
              [-defsym symbol=expression] [--demangle]
              [--no-demangle] [-e entry] [-embedded-relocs] [-E]
              [-export-dynamic] [-f name] [--auxiliary name]
              [-F name] [--filter name] [-format input-format]
              [-g] [-G size] [-h name] [-soname name] [--help]
              [-i] [-lar] [-Lsearchdir] [-M] [-Map mapfile] [-m
              emulation] [-n|-N] [-noinhibit-exec]
              [-no-keep-memory] [-no-warn-mismatch] [-Olevel]
              [--oformat output-format] [-R filename] [-relax]
              [-r|-Ur] [-rpath directory] [-rpath-link directory]
              [-S] [-s] [-shared] [-sort-common]
              [-split-by-reloc count] [-split-by-file]
              [-T commandfile]
              [--section-start sectionname=sectionorg]
              [-Ttext textorg] [-Tdata dataorg] [-Tbss bssorg]
              [-t] [-u sym] [-V] [-v] [--verbose] [--version]
              [-warn-common] [-warn-constructors]
              [-warn-multiple-gp] [-warn-once]
              [-warn-section-align] [--whole-archive]
              [--no-whole-archive] [--wrap symbol] [-X] [-x] [-Z]

DESCRIPTION
       ld  combines  a  number of object and archive files, relo-
       cates their data and ties up symbol references. Often  the
       last  step  in building a new compiled program to run is a
       call to ld.

       ld accepts Linker Command Language files  to  provide  ex-
       plicit  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  as-
       pects of the GNU linker.

       This  version of ld uses the general purpose BFD libraries
       to operate on object files. This allows ld to  read,  com-
       bine,  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.  You can use `objdump -i' to get a list  of  formats
       supported on various architectures; see objdump(1).

       Aside from its flexibility, the GNU linker is more helpful
       than other linkers in  providing  diagnostic  information.
       Many linkers abandon execution immediately upon encounter-

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ld(1)                 GNU Development Tools                 ld(1)

       ing 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 situ-
       ations,  and  to  be  as compatible as possible with other
       linkers.  As a result, you have many  choices  to  control
       its  behavior  through the command line, and through envi-
       ronment variables.

OPTIONS
       The plethora of command-line options may  seem  intimidat-
       ing,  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, support-
       ed Unix system.  On such a system, to link a file hello.o:

       $ ld -o output /lib/crt0.o hello.o -lc

       This  tells  ld to produce a file called output as the re-
       sult of linking the file /lib/crt0.o with hello.o and  the
       library  libc.a  which  will come from the standard search
       directories.

       The command-line options to ld may be specified in any or-
       der,  and may be repeated at will.  For the most part, re-
       peating an option with a different  argument  will  either
       have  no  further  effect,  or  override prior occurrences
       (those further to the left on the command line) of an  op-
       tion.

       The  exceptions--which  may meaningfully be used more than
       once--are -A, -b (or its synonym -format), -defsym, --sec-
       tion-start, -L, -l, -R, and -u.

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

       Usually the linker is invoked with  at  least  one  object
       file,  but  other  forms of binary input files can also be
       specified with -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'.

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

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       -Aarchitecture
              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 is
              one  of the two-letter names identifying members of
              the 960 family; the option  specifies  the  desired
              output  target,  and  warns of any incompatible in-
              structions in the input files.   It  also  modifies
              the linker's search strategy for archive libraries,
              to support the use of libraries  specific  to  each
              particular architecture, by including in the search
              loop names suffixed with the string identifying the
              architecture.

              For  example,  if  your  ld  command  line included
              `-ACA' as well as `-ltry', the  linker  would  look
              (in its built-in search paths, and in any paths you
              specify with -L) for a library with the names

              try
              libtry.a
              tryca
              libtryca.a

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

              Future releases of ld may support similar function-
              ality for other architecture families.

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

       -b input-format
              Specify  the  binary  format for input object files
              that follow this option on the command  line.   You
              don't  usually  need to specify this, as ld is con-
              figured 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 sup-
              ported  by the BFD libraries.  -format input-format
              has the same effect, as  does  the  script  command
              TARGET.

              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

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              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.

       -Bstatic
              Do not link against shared libraries.  This is only
              meaningful  on platforms for which shared libraries
              are supported.

       -Bdynamic
              Link against dynamic libraries.  This is only mean-
              ingful  on platforms for which shared libraries are
              supported.  This option is normally the default  on
              such platforms.

       -Bgroup
              Set  the DF_1_GROUP flag in the DT_FLAGS_1 entry in
              the dynamic section.  This causes the runtime link-
              er  to handle lookups in this object and its depen-
              dencies to be performed only inside the group.   No
              undefined symbols are allowed.  This option is only
              meaningful on ELF platforms  which  support  shared
              libraries.

       -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 op-
              tion is only meaningful on ELF platforms which sup-
              port shared libraries.

       -c commandfile
              Directs ld to read link commands from the file com-
              mandfile.  These commands will completely  override
              ld's  default  link  format  (rather than adding to
              it); commandfile must specify everything  necessary
              to describe the target format.

              You  may also include a script of link commands di-
              rectly in the command line by bracketing it between
              `{' and `}' characters.

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       --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.

       -d

       -dc

       -dp    These three options are equivalent; multiple  forms
              are supported for compatibility with other linkers.
              Use any of them to make ld assign space  to  common
              symbols even if a relocatable output file is speci-
              fied (-r).  The script command FORCE_COMMON_ALLOCA-
              TION has the same effect.

       -defsym symbol=expression
              Create a global symbol in the output file, contain-
              ing 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 ex-
              pression in this context: you may give a  hexadeci-
              mal  constant or the name of an existing symbol, or
              use + and - to add  or  subtract  hexadecimal  con-
              stants  or symbols.  If you need more elaborate ex-
              pressions, consider using the linker  command  lan-
              guage from a script.

       --demangle

       --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 lead-
              ing underscores if they are used by the object file
              format, and converts C++ mangled symbol names  into
              user  readable  names.  The linker will demangle by
              default  unless  the  environment   variable   COL-
              LECT_NO_DEMANGLE is set.  These options may be used
              to override the default.

       -e entry
               Use entry as the explicit symbol for beginning ex-
              ecution  of  your  program, rather than the default
              entry point.  See the `ld' entry in  `info'  for  a
              discussion of defaults and other ways of specifying
              the entry point.

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       -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 caus-
              es  the  linker to create a table which may be used
              at runtime to relocate any data which was statical-
              ly  initialized to pointer values.  See the code in
              testsuite/ld-empic for details.

       -E

       -export-dynamic
              When creating an ELF file, add all symbols  to  the
              dynamic symbol table.  Normally, the dynamic symbol
              table contains only symbols which are used by a dy-
              namic  object.  This option is needed for some uses
              of dlopen.

       -f name

       --auxiliary name
              When creating an ELF shared object, set the  inter-
              nal 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.

       -F name

       --filter name
              When  creating an ELF shared object, set the inter-
              nal DT_FILTER field to the  specified  name.   This
              tells  the  dynamic linker that the symbol table of
              the shared object should be used as a filter on the
              symbol table of the shared object name.

       -format input-format
              Synonym for -b input-format.

       -g     Accepted,  but  ignored; provided for compatibility
              with other tools.

       -G size
              Set the maximum size of objects to be optimized us-
              ing  the GP register to size under MIPS ECOFF.  Ig-
              nored for other object file formats.

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ld(1)                 GNU Development Tools                 ld(1)

       -h name

       -soname name
              When creating an ELF shared object, set the  inter-
              nal 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.

       --help Print a summary of the command-line options on  the
              standard  output  and exit.  This option and --ver-
              sion begin with two dashes instead of one for  com-
              patibility  with other GNU programs.  The other op-
              tions start with only one  dash  for  compatibility
              with other linkers.

       -i     Perform an incremental link (same as option -r).

       -lar     Add  an  archive  file ar 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
              libar.a for every ar specified.

       -Lsearchdir
              This command adds path searchdir  to  the  list  of
              paths  that  ld  will search for archive libraries.
              You may use this option any number of times.

              The default set of paths  searched  (without  being
              specified  with  -L) depends on what 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.

       -M     Print (to the standard output file) a link map--di-
              agnostic information about where symbols are mapped
              by ld, and information on global common storage al-
              location.

       -Map mapfile
              Print  to  the  file mapfile a link map--diagnostic
              information about where symbols are mapped  by  ld,
              and  information  on  global common storage alloca-
              tion.

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       -m emulation
              Emulate the emulation linker.   You  can  list  the
              available  emulations  with the --verbose or -V op-
              tions.  This option overrides the  compiled-in  de-
              fault, which is the system for which you configured
              ld.

       -N     specifies readable and writable text and data  sec-
              tions.  If  the  output  format supports Unix style
              magic numbers, the output is marked as OMAGIC.

              When you use the `-N' option, the linker  does  not
              page-align the data segment.

       -n     sets  the  text segment to be read only, and NMAGIC
              is written if possible.

       -noinhibit-exec
              Normally, the linker will  not  produce  an  output
              file  if  it encounters errors during the link pro-
              cess.  With this flag, you  can  specify  that  you
              wish  the output file retained even after non-fatal
              errors.

       -no-keep-memory
              The linker normally optimizes for speed over memory
              usage  by  caching the symbol tables of input files
              in memory.  This option tells the linker to instead
              optimize  for memory usage, by rereading the symbol
              tables as necessary.  This may be required  if  the
              linker  runs  out  of  memory space while linking a
              large executable.

       -no-warn-mismatch
              Normally the linker 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 the linker 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.

       -o output
              output is a 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 al-

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              so specify the output file name.

       -Olevel
              Generate  optimized  output  files.  This might use
              significantly  more  time  and  therefore  probably
              should be enabled only for generating the final bi-
              nary.  level is supposed to  be  a  numeric  value.
              Any  value  greater than zero enables the optimiza-
              tions.

       --oformat output-format
              Specify the binary format  for  the  output  object
              file.   You  don't usually need to specify this, as
              ld is configured to produce  as  a  default  output
              format the most usual format on each machine.  out-
              put-format is a text string, the name of a particu-
              lar  format  supported  by  the BFD libraries.  The
              script command OUTPUT_FORMAT can also  specify  the
              output format, but this option overrides it.

       -R filename
              Read  symbol  names  and their addresses from file-
              name, but do not relocate it or include it  in  the
              output.  This allows your output file to refer sym-
              bolically to absolute locations of  memory  defined
              in other programs.

       -relax An option with machine dependent effects.  Current-
              ly this option is only supported on the H8/300.

              On some platforms, use this option to perform glob-
              al  optimizations  that  become  possible  when the
              linker resolves addressing in your program, such as
              relaxing  address  modes  and  synthesizing new in-
              structions in the output object file.

              On platforms where this is not supported,  `-relax'
              is accepted, but has no effect.

       -r     Generates  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; -Ur is an alternative.

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              This option does the same as -i.

       -rpath directory
              Add a directory to the runtime library search path.
              This  is  used  when linking an ELF executable with
              shared objects.  All -rpath arguments are  concate-
              nated  and passed to the runtime linker, which uses
              them to locate  shared  objects  at  runtime.   The
              -rpath option is also used when locating shared ob-
              jects 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 en-
              vironment 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  path 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 op-
              tions, ignoring the -L options.  This can be useful
              when  using  gcc,  which adds many -L options which
              may be on NFS mounted filesystems.

       -rpath-link directory
              When using ELF or SunOS, one shared library may re-
              quire  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-relocateable link, it  will
              automatically try to locate the required shared li-
              brary and include it in the link, if it is not  in-
              cluded explicitly.  In such a case, the -rpath-link
              option specifies the first set  of  directories  to
              search.   The  -rpath-link option may specify a se-
              quence of directory names either  by  specifying  a
              list  of names separated by colons, or by appearing
              multiple times.

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

       -S     Omits debugger symbol information (but not all sym-
              bols) from the output file.

       -s     Omits  all symbol information from the output file.

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       -shared
              Create a shared library.  This  is  currently  only
              supported  on  ELF and SunOS platforms (on SunOS it
              is not required, as the linker  will  automatically
              create  a  shared  library when there are undefined
              symbols and the -e option is not used).

       -sort-common
              Normally, when ld places the global common  symbols
              in  the  appropriate output sections, it sorts them
              by size.  First come all the one byte symbols, then
              all  the  two  bytes,  then all the four bytes, and
              then everything else.  This is to prevent gaps  be-
              tween  symbols  due to alignment constraints.  This
              option disables that sorting.

       -split-by-reloc count
              Trys to creates extra sections in the  output  file
              so  that  no single output section in the file con-
              tains more than count relocations.  This is  useful
              when  generating  huge  relocatable 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 link-
              er  will not split up individual input sections for
              redistribution, so if a single input  section  con-
              tains  more  than count relocations one output sec-
              tion will contain that many relocations.

       -split-by-file
              Similar to -split-by-reloc but creates a new output
              section for each input file.

       --section-start sectionname=org
              Locate a section in the output file at the absolute
              address given by org.  org must  be  a  hexadecimal
              integer.   You may use this option as many times as
              necessary to locate multiple sections in  the  com-
              mand line.  If you need more elaborate expressions,
              consider using the linker command language  from  a
              script.

       -Tbss org

       -Tdata org

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       -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 hexadecimal integer.

       -T commandfile
              Equivalent to -c commandfile; supported for compat-
              ibility with other tools.

       -t     Prints names of input files as ld processes them.

       -u sym Forces sym to be entered in the output file  as  an
              undefined  symbol.   This may, for example, trigger
              linking of additional  modules  from  standard  li-
              braries.   -u may be repeated with different option
              arguments to enter additional undefined symbols.

       -Ur    For anything other than C++ programs,  this  option
              is  equivalent to -r: it generates relocatable out-
              put--i.e., an output file that can in turn serve as
              input  to  ld.  When linking C++ programs, -Ur will
              resolve references to constructors, unlike -r.

       --verbose
              Display the version number for ld and list the sup-
              ported  emulations.   Display which input files can
              and can not be opened.

       -v, -V Display the version number for ld.  The  -V  option
              also lists the supported emulations.

       --version
              Display the version number for ld and exit.

       -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.

       -warn-constructors
              Warn if any global constructors are used.  This  is
              only  useful  for  a  few object file formats.  For

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ld(1)                 GNU Development Tools                 ld(1)

              formats like COFF or ELF, the linker can not detect
              the use of global constructors.

       -warn-multiple-gp
              Warn  if  the output file requires multiple global-
              pointer values.  This option is only meaningful for
              certain processors, such as the Alpha.

       -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 af-
              ter the --whole-archive option, include  every  ob-
              ject  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.

       --no-whole-archive
              Turn  off  the effect of the --whole-archive option
              for archives which  appear  later  on  the  command
              line.

       --wrap symbol
              Use  a  wrapper function for symbol.  Any undefined
              reference to symbol will be resolved to __wrap_sym-
              bol.  Any undefined reference to __real_symbol will
              be resolved to symbol.

       -X     Delete all temporary local symbols.  For most  tar-
              gets,  this  is all local symbols whose names begin
              with `L'.

       -x     Delete all local symbols.

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ld(1)                 GNU Development Tools                 ld(1)

       -Z     Produce 'Standard' executables,  disables  Writable
              XOR Executable features of resulting binaries.

ENVIRONMENT
       You  can  change  the  behavior of ld with the environment
       variable GNUTARGET.

       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 for-
       mat of the host. 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 po-
       tential  ambiguities, since there is no method of ensuring
       that the magic number used to flag object-file formats  is
       unique.   However,  the configuration procedure for BFD on
       each system places the conventional format for that system
       first  in  the search-list, so ambiguities are resolved in
       favor of convention.

SEE ALSO
       objdump(1)
       `ld' and `binutils' entries in info
       ld: the GNU linker, Steve Chamberlain  and  Roland  Pesch;
       The GNU Binary Utilities, Roland H. Pesch.

COPYING
       Copyright  (c)  1991,  92,  93, 94, 95, 96, 97, 1998, 2000
       Free Software Foundation, Inc.

       This document is distributed under the terms  of  the  GNU
       Free  Documentation License, version 1.1.  That license is
       described in the sources for this manual page, but  it  is
       not  displayed here in order to make this manual more con-
       sise.  Copies of this license can also be  obtained  from:
       http://www.gnu.org/copyleft/.

Free Software Foundation                                       14

ld(1)                 GNU Development Tools                 ld(1)

Free Software Foundation                                       15


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