ld



LD(1)                        GNU Development Tools                       LD(1)




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&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 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 exe-
       cution  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 stan-
       dard, supported 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 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 descrip-
       tions below.

       Non-option arguments are object files  or  archives  which  are  to  be
       linked  together.   They  may follow, precede, or be mixed in with com-
       mand-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 speci-
       fied, the linker does not produce any output, and issues the message No
       input files.

       If  the  linker  cannot recognize the format of an object file, it will
       assume that it is a linker script.  A script specified in this way aug-
       ments  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 imme-
       diately  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
       (e.g.  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:

       -akeyword
           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.

       -Aarchitecture
       --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  "GNUTAR-
           GET".

           You  can also define the input format from a script, using the com-
           mand "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 doc-
           umentation.  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  sym-
           bol  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).

       --exclude-libs lib,lib,...
           Specifies a list of archive libraries from which symbols should not
           be  automatically  exported.  The library names may be delimited by
           commas or colons.  Specifying "--exclude-libs ALL" excludes symbols
           in  all  archive  libraries  from automatic export.  This option is
           available only for the i386 PE targeted port of the linker and  for
           ELF  targeted  ports.   For i386 PE, symbols explicitly listed in a
           .def file are still exported, regardless of this option.   For  ELF
           targeted  ports, symbols affected by this option will be treated as
           hidden.

       -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  nor-
           mally  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 for-
           mat.

       -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  auxil-
           iary 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 debug-
           ging 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  pro-
           vided by the object name.

           Some  older  linkers  used  the  -F option throughout a compilation
           toolchain for specifying object-file format for both input and out-
           put  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.

       -Gvalue
       --gpsize=value
           Set the maximum size of objects to be optimized using the GP regis-
           ter  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.

       -hname
       -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.

       -larchive
       --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 sym-
           bol  which  was  undefined in some object which appeared before the
           archive on the command line, the linker will include the  appropri-
           ate  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.   How-
           ever,  if  you  are using ld on AIX, note that it is different from
           the behaviour of the AIX linker.

       -Lsearchdir
       --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 speci-
           fied on the command line are searched before the  default  directo-
           ries.   All  -L  options apply to all -l options, regardless of the
           order in which the options appear.

           If searchdir begins with "=", then the "=" will be replaced by  the
           sysroot prefix, a path specified when the linker is configured.

           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.

       -memulation
           Emulate the emulation linker.  You can list  the  available  emula-
           tions 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, and disable linking against
           shared libraries.  If the output format supports Unix  style  magic
           numbers,  mark  the  output  as "OMAGIC". Note: Although a writable
           text section is allowed for PE-COFF targets, it does not conform to
           the format specification published by Microsoft.

       --no-omagic
           This  option negates most of the effects of the -N option.  It sets
           the text section to be read-only, and forces the data segment to be
           page-aligned.   Note  - this option does not enable linking against
           shared libraries.  Use -Bdynamic for this.

       -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 proba-
           bly should only be enabled for the final binary.

       -q
       --emit-relocs
           Leave relocation sections and contents in fully  linked  exececuta-
           bles.   Post  link  analysis  and  optimization tools may need this
           information in order to perform correct modifications  of  executa-
           bles.  This results in larger executables.

           This option is currently only supported on ELF platforms.

       -r
       --relocatable
           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  fol-
           lowed  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  sym-
           bol.   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:

           combreloc
               Combines multiple reloc sections and sorts them to make dynamic
               symbol lookup caching possible.

           defs
               Disallows undefined symbols in object files.  Undefined symbols
               in shared libraries are still allowed.

           initfirst
               This option is only meaningful when building a  shared  object.
               It  marks  the  object  so that its runtime initialization will
               occur before the runtime initialization of  any  other  objects
               brought  into the process at the same time.  Similarly the run-
               time finalization of the object will occur  after  the  runtime
               finalization of 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 filters be processed immediately  at
               runtime.

           muldefs
               Allows multiple definitions.

           nocombreloc
               Disables multiple reloc sections combining.

           nocopyreloc
               Disables production of copy relocs.

           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 When generating an executable or shared  library,  mark  it  to
               tell the dynamic linker to resolve all symbols when the program
               is started, or when the  shared  library  is  linked  to  using
               dlopen,  instead  of  deferring function call resolution to the
               point when the function is first called.

           origin
               Marks the object may contain $ORIGIN.

           Other keywords are ignored for Solaris compatibility.

       -( 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 unde-
           fined 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  sym-
           bol  referred  to  by an object in an archive that appears later on
           the command line, the linker would not be able to resolve that ref-
           erence.   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.

       --accept-unknown-input-arch
       --no-accept-unknown-input-arch
           Tells the linker to accept input files whose architecture cannot be
           recognised.   The  assumption  is that the user knows what they are
           doing and deliberately wants to link in these unknown input  files.
           This  was the default behaviour of the linker, before release 2.14.
           The default behaviour from release 2.14 onwards is to  reject  such
           input files, and so the --accept-unknown-input-arch option has been
           added to restore the old behaviour.

       --as-needed
       --no-as-needed
           This option affects ELF DT_NEEDED tags for dynamic  libraries  men-
           tioned on the command line after the --as-needed option.  Normally,
           the linker will add a DT_NEEDED tag for each dynamic  library  men-
           tioned  on  the  command line, regardless of whether the library is
           actually needed. --as-needed causes DT_NEEDED tags to only be emit-
           ted for libraries that satisfy some reference from regular objects.
           --no-as-needed restores the default behaviour.

       --add-needed
       --no-add-needed
           This option affects the treatment of  dynamic  libraries  from  ELF
           DT_NEEDED  tags  in dynamic libraries mentioned on the command line
           after the --no-add-needed option.  Normally, the linker will add  a
           DT_NEEDED  tag  for  each  dynamic  library  from  DT_NEEDED  tags.
           --no-add-needed causes DT_NEEDED tags will  never  be  emitted  for
           those  libraries  from  DT_NEEDED  tags.  --add-needed restores the
           default behaviour.

       -assert keyword
           This option is ignored for SunOS compatibility.

       -Bdynamic
       -dy
       -call_shared
           Link against dynamic libraries.  This is only meaningful  on  plat-
           forms  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.
           --unresolved-symbols=report-all 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.  This
           option also implies --unresolved-symbols=report-all.

       -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  over-
           ride 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 gen-
           erated, the cross reference table is printed to the map file.  Oth-
           erwise, 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, con-
           sider 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.   Dif-
           ferent  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.

       --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. 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 out-
           put 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
           Report unresolved symbol  references  from  regular  object  files.
           This  is  done even if the linker is creating a non-symbolic shared
           library.   The  switch  --[no-]allow-shlib-undefined  controls  the
           behaviour  for  reporting  unresolved  references  found  in shared
           libraries being linked in.

       --allow-multiple-definition
       -z muldefs
           Normally when a symbol is defined multiple times, the  linker  will
           report  a fatal error. These options allow multiple definitions and
           the first definition will be used.

       --allow-shlib-undefined
       --no-allow-shlib-undefined
           Allows (the default)  or  disallows  undefined  symbols  in  shared
           libraries.  This switch is similar to --no-undefined except that it
           determines the behaviour when the undefined symbols are in a shared
           library  rather than a regular object file.  It does not affect how
           undefined symbols in regular object files are handled.

           The reason that --allow-shlib-undefined is the default is that  the
           shared  library being specified at link time may not be the same as
           the one that is available at load time, so the symbols might  actu-
           ally  be resolvable at load time.  Plus there are some systems, (eg
           BeOS) where undefined symbols in shared libraries is normal.   (The
           kernel  patches  them at load time to select which function is most
           appropriate for the current architecture.  This is used for example
           to  dynamically select an appropriate memset function).  Apparently
           it is also normal for HPPA shared libraries to have undefined  sym-
           bols.

       --no-undefined-version
           Normally  when  a  symbol has an undefined version, the linker will
           ignore it. This option disallows symbols with undefined version and
           a fatal error will be issued instead.

       --default-symver
           Create  and  use  a  default symbol version (the soname) for unver-
           sioned exported symbols.

       --default-imported-symver
           Create and use a default symbol version  (the  soname)  for  unver-
           sioned imported 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 endi-
           annesses.  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 encoun-
           ters 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.

       -pie
       --pic-executable
           Create a position independent executable.  This is  currently  only
           supported  on  ELF platforms.  Position independent executables are
           similar to shared libraries in  that  they  are  relocated  by  the
           dynamic  linker  to  the  virtual  address  the OS chooses for them
           (which can vary  between  invocations).   Like  normal  dynamically
           linked  executables they can be executed and symbols defined in the
           executable cannot be overridden by shared libraries.

       -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 sup-
           ported 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 gradu-
           ally, to conserve run-time memory.

           --retain-symbols-file does not discard undefined symbols,  or  sym-
           bols 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 fol-
           lowed 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  run-
               time,  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  direc-
               tories 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.

       --sort-section name
           This  option will apply "SORT_BY_NAME" to all wildcard section pat-
           terns in the linker script.

       --sort-section alignment
           This option will apply "SORT_BY_ALIGNMENT" to all wildcard  section
           patterns in the linker script.

       --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 sin-
           gle output section in the file contains  more  than  count  reloca-
           tions.   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 reloca-
           tions 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  redistribu-
           tion, so if a single input section contains more than count reloca-
           tions 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
           Same  as  --section-start,  with  ".bss", ".data" or ".text" as the
           sectionname.

       --unresolved-symbols=method
           Determine how to handle unresolved symbols.  There are four  possi-
           ble values for method:

           ignore-all
               Do not report any unresolved symbols.

           report-all
               Report all unresolved symbols.  This is the default.

           ignore-in-object-files
               Report   unresolved   symbols  that  are  contained  in  shared
               libraries, but ignore them if they  come  from  regular  object
               files.

           ignore-in-shared-libs
               Report  unresolved symbols that come from regular object files,
               but ignore them if they come from shared libraries.   This  can
               be  useful  when creating a dynamic binary and it is known that
               all the shared libraries that  it  should  be  referencing  are
               included on the linker’s command line.

           The  behaviour  for  shared libraries on their own can also be con-
           trolled by the --[no-]allow-shlib-undefined option.

           Normally the  linker  will  generate  an  error  message  for  each
           reported unresolved symbol but the option --warn-unresolved-symbols
           can change this to a warning.

       --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  typi-
           cally  used  when  creating  shared libraries to specify additional
           information about the version hierarchy for the library being  cre-
           ated.   This  option is only meaningful on ELF platforms which sup-
           port 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
           practise, 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 practise, 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  sym-
               bols  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 differ-
               ent sizes, it picks the largest size.  The linker turns a  com-
               mon  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.

                       <file>(<section>): warning: common of ‘<symbol>’
                          overridden by definition
                       <file>(<section>): warning: defined here

           2.  Turning a common symbol into a reference, because a later defi-
               nition for the 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

           3.  Merging a common symbol with a previous same-sized common  sym-
               bol.

                       <file>(<section>): warning: multiple common
                          of ‘<symbol>’
                       <file>(<section>): warning: previous common is here

           4.  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

           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.

                       <file>(<section>): warning: common of ‘<symbol>’
                          overriding smaller common
                       <file>(<section>): warning: smaller common is here

       --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 multi-
           ple global pointer values in order to be able to address all possi-
           ble  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 mod-
           ule 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  sec-
           tion.  The address will only be changed if it not explicitly speci-
           fied; that is, if the "SECTIONS" command does not specify  a  start
           address for the section.

       --warn-shared-textrel
           Warn if the linker adds a DT_TEXTREL to a shared object.

       --warn-unresolved-symbols
           If  the  linker  is  going  to report an unresolved symbol (see the
           option --unresolved-symbols) it will normally  generate  an  error.
           This option makes it generate a warning instead.

       --error-unresolved-symbols
           This  restores  the linker’s default behaviour of generating errors
           when it is reporting unresolved symbols.

       --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 sym-
           bol 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 (size_t c)
                   {
                     printf ("malloc called with %zu\n", c);
                     return __real_malloc (c);
                   }

           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 cre-
           ated. By default, the new dynamic tags are not created.  Note  that
           those options are only available for ELF systems.

           Set  the default size of the linker’s hash tables to a prime number
           close to number.  Increasing this value can reduce  the  length  of
           time  it  takes  the linker to perform its tasks, at the expense of
           increasing the linker’s memory  requirements.   Similarly  reducing
           this  value  can  reduce  the memory requirements at the expense of
           speed.

       --reduce-memory-overheads
           This option reduces memory  requirements  at  ld  runtime,  at  the
           expense of linking speed.  This was introduced to to select the old
           O(n^2) algorithm for link map file generation, rather than the  new
           O(n) algorithm which uses about 40% more memory for symbol storage.

           Another affect of the switch is to set the default hash table  size
           to  1021,  which  again saves memory at the cost of lengthening the
           linker’s run time.  This is not done  however  if  the  --hash-size
           switch has been used.

           The  --reduce-memory-overheads switch may be also be used to enable
           other tradeoffs in future versions of the linker.

       The i386 PE linker supports the -shared option, which causes the output
       to  be  a  dynamically  linked  library  (DLL) instead of a normal exe-
       cutable.  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.  [This option is specific  to
           the i386 PE targeted port of the linker]

       --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.
           [This is an i386 PE specific option]

       --dll
           Create  a  DLL  instead  of a regular executable.  You may also use
           -shared or specify a "LIBRARY"  in  a  given  ".def"  file.   [This
           option is specific to the i386 PE targeted port of the linker]

       --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 --dis-
           able-stdcall-fixup, this feature is disabled  and  such  mismatches
           are  considered to be errors.  [This option is specific to the i386
           PE targeted port of the linker]

       --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 func-
           tion attributes, the default is to not export anything else  unless
           this  option is given.  Note that the symbols "DllMain@12", "DllEn-
           tryPoint@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-pri-
           vate 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_noncyg-
           win_dll_entry@12",  "_fmode",  "_impure_ptr",  "cygwin_attach_dll",
           "cygwin_premain0",  "cygwin_premain1",   "cygwin_premain2",   "cyg-
           win_premain3", and "environ".  [This option is specific to the i386
           PE targeted port of the linker]

       --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.
           [This option is specific to  the  i386  PE  targeted  port  of  the
           linker]

       --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.   [This option is specific to the i386 PE targeted port of
           the linker]

       --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.  [This option is specific to the i386 PE  targeted  port
           of the linker]

       --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  over-
           lap  any  other dlls.  The default is 0x400000 for executables, and
           0x10000000 for dlls.  [This option is specific to the i386 PE  tar-
           geted port of the linker]

       --kill-at
           If  given, the stdcall suffixes (@nn) will be stripped from symbols
           before they are exported.  [This option is specific to the i386  PE
           targeted port of the linker]

       --large-address-aware
           If  given,  the  appropriate bit in the ‘‘Charateristics’’ field of
           the COFF header is set to indicate that  this  executable  supports
           virtual addresses greater than 2 gigabytes.  This should be used in
           conjuction with the /3GB or /USERVA=value megabytes switch  in  the
           ‘‘[operating  systems]’’  section of the BOOT.INI.  Otherwise, this
           bit has no effect.  [This option is specific to PE  targeted  ports
           of the linker]

       --major-image-version value
           Sets  the  major  number  of the ‘‘image version’’.  Defaults to 1.
           [This option is specific to  the  i386  PE  targeted  port  of  the
           linker]

       --major-os-version value
           Sets the major number of the ‘‘os version’’.  Defaults to 4.  [This
           option is specific to the i386 PE targeted port of the linker]

       --major-subsystem-version value
           Sets the major number of the ‘‘subsystem version’’.  Defaults to 4.
           [This  option  is  specific  to  the  i386  PE targeted port of the
           linker]

       --minor-image-version value
           Sets the minor number of the ‘‘image  version’’.   Defaults  to  0.
           [This  option  is  specific  to  the  i386  PE targeted port of the
           linker]

       --minor-os-version value
           Sets the minor number of the ‘‘os version’’.  Defaults to 0.  [This
           option is specific to the i386 PE targeted port of the linker]

       --minor-subsystem-version value
           Sets the minor number of the ‘‘subsystem version’’.  Defaults to 0.
           [This option is specific to  the  i386  PE  targeted  port  of  the
           linker]

       --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  automati-
           cally  or implicitly exported symbols.  [This option is specific to
           the i386 PE targeted port of the linker]

       --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 behaviour makes it possible
           to skip a separate "dlltool" import library creation  step.   [This
           option is specific to the i386 PE targeted port of the linker]

       --enable-auto-image-base
           Automatically  choose the image base for DLLs, unless one is speci-
           fied using the "--image-base" argument.  By using a hash  generated
           from the dllname to create unique image bases for each DLL, in-mem-
           ory collisions and relocations which can  delay  program  execution
           are avoided.  [This option is specific to the i386 PE targeted port
           of the linker]

       --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.  [This option is specific to the i386 PE targeted port  of
           the linker]

       --dll-search-prefix string
           When linking dynamically to a dll without an import library, search
           for "<string><basename>.dll" in preference to  "lib<basename>.dll".
           This  behaviour  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".
           [This option is specific to  the  i386  PE  targeted  port  of  the
           linker]

       --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 import libraries with those DATA exports. Note: Use of
           the ’auto-import’ extension will cause  the  text  section  of  the
           image  file  to  be made writable. This does not conform to the PE-
           COFF format specification published by Microsoft.

           Using ’auto-import’ generally will ’just work’ -- but sometimes you
           may see this message:

           "variable  ’<var>’ can’t be auto-imported. Please read the documen-
           tation for ld’s "--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 way is to use --enable-runtime-pseudo-reloc switch. This leaves
           the task of adjusting references in your client  code  for  runtime
           environment,  so  this  method  works only when runtime environment
           supports this feature.

           A second solution is to force one of the ’constants’ to be a  vari-
           able  --  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] -->
                      { volatile type *t=extern_array; t[1] }

           or

                   extern type extern_array[];
                   extern_array[1] -->
                      { volatile int t=1; extern_array[t] }

           For structs (and most other multiword data types) the  only  option
           is  to  make the struct itself (or the long long, or the ...) vari-
           able:

                   extern struct s extern_struct;
                   extern_struct.field -->
                      { volatile struct s *t=&extern_struct; t->field }

           or

                   extern long long extern_ll;
                   extern_ll -->
                     { volatile long long * local_ll=&extern_ll; *local_ll }

           A third method of  dealing  with  this  difficulty  is  to  abandon
           ’auto-import’   for   the   offending   symbol  and  mark  it  with
           "__declspec(dllimport)".  However, in practise 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  build-
           ing/linking to a static library.   In making the choice between the
           various methods of resolving the ’direct address with constant off-
           set’ problem, you should consider typical real-world usage:

           Original:

                   --foo.h
                   extern int arr[];
                   --foo.c
                   #include "foo.h"
                   void main(int argc, char **argv){
                     printf("%d\n",arr[1]);
                   }

           Solution 1:

                   --foo.h
                   extern int arr[];
                   --foo.c
                   #include "foo.h"
                   void main(int argc, char **argv){
                     /* This workaround is for win32 and cygwin; do not "optimize" */
                     volatile int *parr = arr;
                     printf("%d\n",parr[1]);
                   }

           Solution 2:

                   --foo.h
                   /* Note: auto-export is assumed (no __declspec(dllexport)) */
                   #if (defined(_WIN32) ││ defined(__CYGWIN__)) && \
                     !(defined(FOO_BUILD_DLL) ││ defined(FOO_STATIC))
                   #define FOO_IMPORT __declspec(dllimport)
                   #else
                   #define FOO_IMPORT
                   #endif
                   extern FOO_IMPORT int arr[];
                   --foo.c
                   #include "foo.h"
                   void main(int argc, char **argv){
                     printf("%d\n",arr[1]);
                   }

           A  fourth  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 func-
           tions).  [This option is specific to the i386 PE targeted  port  of
           the linker]

       --disable-auto-import
           Do  not  attempt  to  do  sophisticated  linking  of  "_symbol"  to
           "__imp__symbol" for DATA imports from DLLs.  [This option  is  spe-
           cific to the i386 PE targeted port of the linker]

       --enable-runtime-pseudo-reloc
           If your code contains expressions described in --enable-auto-import
           section, that is, DATA imports from DLL with non-zero offset,  this
           switch  will  create a vector of ’runtime pseudo relocations’ which
           can be used by runtime environment to  adjust  references  to  such
           data  in your client code.  [This option is specific to the i386 PE
           targeted port of the linker]

       --disable-runtime-pseudo-reloc
           Do not create pseudo relocations for non-zero offset  DATA  imports
           from  DLLs.   This is the default.  [This option is specific to the
           i386 PE targeted port of the linker]

       --enable-extra-pe-debug
           Show additional debug info related to auto-import symbol  thunking.
           [This  option  is  specific  to  the  i386  PE targeted port of the
           linker]

       --section-alignment
           Sets the section alignment.  Sections in memory will  always  begin
           at  addresses  which  are  a  multiple of this number.  Defaults to
           0x1000.  [This option is specific to the i386 PE targeted  port  of
           the linker]

       --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.   [This  option is specific to the i386 PE targeted port
           of the linker]

       --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", "posix",
           and "xbox".  You may optionally set  the  subsystem  version  also.
           Numeric  values  are also accepted for which.  [This option is spe-
           cific to the i386 PE targeted port of the linker]

       The 68HC11 and 68HC12 linkers support specific options to  control  the
       memory bank switching mapping and trampoline code generation.

       --no-trampoline
           This  option  disables  the  generation of trampoline. By default a
           trampoline is generated for each far function which is called using
           a  "jsr" instruction (this happens when a pointer to a far function
           is taken).

       --bank-window name
           This option indicates to the linker the name of the  memory  region
           in  the MEMORY specification that describes the memory bank window.
           The definition of such region is then used by the linker to compute
           paging and addresses within the memory window.


ENVIRONMENT

       You can change the behaviour of ld with the environment variables "GNU-
       TARGET", "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 configura-
       tion 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 sim-
       ilar 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,  2002,
       2003, 2004 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’’.



binutils-2.15.94.0.2.2            2005-06-29                             LD(1)

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