MirOS Manual: ld(1)


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 super-
     set of AT&T's Link Editor Command Language syntax, to pro-
     vide 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 exam-
     ple, COFF or "a.out".  Different formats may be linked
     together to produce any available kind of object file.

     Aside from its flexibility, the GNU linker is more helpful
     than other linkers in providing diagnostic information.
     Many linkers abandon execution immediately upon encountering
     an error; whenever possible, ld continues executing, allow-
     ing 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 situa-
     tions, and to be as compatible as possible with other link-
     ers.  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 stan-
     dard Unix object files on a standard, 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.)

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     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, rela-
     tive to the object files and other file options.  Repeating
     non-file options with a different argument will either have
     no further effect, or override prior occurrences (those
     further to the left on the command line) of that option.
     Options which may be meaningfully specified more than once
     are noted in the descriptions below.

     Non-option arguments are object files or archives which are
     to be linked together.  They may follow, precede, or be
     mixed in with command-line options, except that an object
     file argument may not be placed between an option and its
     argument.

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

     If the linker cannot recognize the format of an object file,
     it will assume that it is a linker script.  A script speci-
     fied in this way augments the main linker script used for
     the link (either the default linker script or the one speci-
     fied 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 speci-
     fying 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 argu-
     ments must either follow the option letter without interven-
     ing whitespace, or be given as separate arguments immedi-
     ately 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 pre-
     ceeded 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 out-
     put.

     Arguments to multiple-letter options must either be
     separated from the option name by an equals sign, or be

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     given as separate arguments immediately following the option
     that requires them.  For example, --trace-symbol foo and
     --trace-symbol=foo are equivalent. Unique abbreviations of
     the names of multiple-letter options are accepted.

     Note---if the linker is being invoked indirectly, via a com-
     piler driver (e.g. gcc) then all the linker command line
     options should be prefixed by -Wl, (or whatever is appropri-
     ate 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.)

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         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 vari-
         able "GNUTARGET".

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

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

     -d
     -dc
     -dp These three options are equivalent; multiple forms are
         supported for compatibility with other linkers.  They
         assign space to common symbols even if a relocatable
         output file is specified (with -r).  The script command
         "FORCE_COMMON_ALLOCATION" has the same effect.

     -e entry
     --entry=entry
         Use entry as the explicit symbol for beginning execution
         of your program, rather than the default entry point.
         If there is no symbol named entry, the linker will try
         to parse entry as a number, and use that as the entry
         address (the number will be interpreted in base 10; you
         may use a leading 0x for base 16, or a leading 0 for
         base 8).

     --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 avail-
         able only for the i386 PE targeted port of the linker
         and for ELF targeted ports.  For i386 PE, symbols expli-
         citly listed in a .def file are still exported, regard-
         less of this option.  For ELF targeted ports, symbols

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         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 normally contain only those symbols which are
         referenced by some dynamic object mentioned in the link.

         If you use "dlopen" to load a dynamic object which needs
         to refer back to the symbols defined by the program,
         rather than some other dynamic object, then you will
         probably need to use this option when linking the pro-
         gram itself.

         You can also use the version script to control what sym-
         bols 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 out-
         put format.

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

     -f
     --auxiliary name
         When creating an ELF shared object, set the internal
         DT_AUXILIARY field to the specified name.  This tells
         the dynamic linker that the symbol table of the shared
         object should be used as an auxiliary filter on the sym-
         bol table of the shared object name.

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

         This option may be specified more than once.  The
         DT_AUXILIARY entries will be created in the order in

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         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 sym-
         bols provided by the object name.

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

     -fini name
         When creating an ELF executable or shared object, call
         NAME when the executable or shared object is unloaded,
         by setting DT_FINI to the address of the function.  By
         default, the linker uses "_fini" as the function to
         call.

     -g  Ignored.  Provided for compatibility with other tools.

     -Gvalue
     --gpsize=value
         Set the maximum size of objects to be optimized using
         the GP register to size.  This is only meaningful for
         object file formats such as MIPS ECOFF which supports
         putting large and small objects into different sections.
         This is ignored for other object file formats.

     -hname
     -soname=name
         When creating an ELF shared object, set the internal
         DT_SONAME field to the specified name.  When an execut-
         able 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

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         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 symbol which was undefined in some
         object which appeared before the archive on the command
         line, the linker will include the appropriate file(s)
         from the archive.  However, an undefined symbol in an
         object appearing later on the command line will not
         cause the linker to search the archive again.

         See the -( option for a way to force the linker to
         search archives multiple times.

         You may list the same archive multiple times on the com-
         mand line.

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

     -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 direc-
         tories are searched in the order in which they are

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         specified on the command line.  Directories specified on
         the command line are searched before the default direc-
         tories.  All -L options apply to all -l options, regard-
         less 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 speci-
         fied 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 avail-
         able emulations with the --verbose or -V options.

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

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

     -M
     --print-map
         Print a link map to the standard output.  A link map
         provides information about the link, including the fol-
         lowing:

         *   Where object files 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.

         *   The values assigned to symbols.

             Note - symbols whose values are computed by an
             expression which involves a reference to a previous
             value of the same symbol may not have correct result
             displayed in the link map.  This is because the
             linker discards intermediate results and only
             retains the final value of an expression.  Under
             such circumstances the linker will display the final

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             value enclosed by square brackets.  Thus for example
             a linker script containing:

                        foo = 1
                        foo = foo * 4
                        foo = foo + 8

             will produce the following output in the link map if
             the -M option is used:

                        0x00000001                foo = 0x1
                        [0x0000000c]                foo = (foo * 0x4)
                        [0x0000000c]                foo = (foo + 0x8)

             See @ref{Expressions} for more information about
             expressions in linker scripts.

     -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 writ-
         able.  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 out-
         put 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 optim-
         izes the output.  This might take significantly longer
         and therefore probably should only be enabled for the
         final binary.

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

         This option is currently only supported on ELF plat-
         forms.

     -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 exam-
         ple 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 abso-
         lute locations of memory defined in other programs.  You
         may use this option more than once.

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

     -s
     --strip-all
         Omit all symbol information from the output file.

     -S
     --strip-debug
         Omit debugger symbol information (but not all symbols)
         from the output file.

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     -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.  Mul-
         tiple -T options accumulate.

     -u symbol
     --undefined=symbol
         Force symbol to be entered in the output file as an
         undefined symbol.  Doing this may, for example, trigger
         linking of additional modules from standard libraries.
         -u may be repeated with different option arguments to
         enter additional undefined symbols.  This option is
         equivalent to the "EXTERN" linker script command.

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

     --unique[=SECTION]
         Creates a separate output section for every input sec-
         tion matching SECTION, or if the optional wildcard SEC-
         TION argument is missing, for every orphan input sec-
         tion.  An orphan section is one not specifically men-
         tioned in a linker script.  You may use this option mul-
         tiple 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.

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     -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 under-
         score.

         This option is useful when you have an undefined symbol
         in your link but don't know where the reference is com-
         ing 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.  Unde-
             fined 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 run-
             time initialization will occur before the runtime
             initialization of any other objects brought into the
             process at the same time.  Similarly the runtime
             finalization of the object will occur after the run-
             time 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

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             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 undefined references are created.  Normally, an
         archive is searched only once in the order that it is
         specified on the command line.  If a symbol in that
         archive is needed to resolve an undefined symbol
         referred to by an object in an archive that appears
         later on the command line, the linker would not be able
         to resolve that reference.  By grouping the archives,
         they all be searched repeatedly until all possible
         references are resolved.

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

     --accept-unknown-input-arch

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     --no-accept-unknown-input-arch
         Tells the linker to accept input files whose architec-
         ture 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 mentioned on the command line after the
         --as-needed option.  Normally, the linker will add a
         DT_NEEDED tag for each dynamic library mentioned on the
         command line, regardless of whether the library is actu-
         ally needed.  --as-needed causes DT_NEEDED tags to only
         be emitted for libraries that satisfy some symbol refer-
         ence from regular objects which is undefined at the
         point that the library was linked. --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 platforms for which shared libraries are supported.
         This option is normally the default on such platforms.
         The different variants of this option are for compati-
         bility 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

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         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 glo-
         bal symbols to the definition within the shared library,
         if any.  Normally, it is possible for a program linked
         against a shared library to override the definition
         within the shared library.  This option is only meaning-
         ful 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 mes-
         sages.  The linker does know about, and does make
         allowances for sections in overlays.  The default
         behaviour can be restored by using the command line
         switch --check-sections.

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

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

     --no-define-common

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         This option inhibits the assignment of addresses to com-
         mon 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 elim-
         inates 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 multi-
         ple symbols in the command line.  A limited form of
         arithmetic is supported for the expression in this con-
         text: you may give a hexadecimal constant or the name of
         an existing symbol, or use "+" and "-" to add or sub-
         tract hexadecimal constants or symbols.  If you need
         more elaborate expressions, consider using the linker
         command language from a script.  Note: there should be
         no white space between symbol, the equals sign (``=''),
         and expression.

     --demangle[=style]
     --no-demangle
         These options control whether to demangle symbol names
         in error messages and other output.  When the linker is
         told to demangle, it tries to present symbol names in a
         readable fashion: it strips leading underscores if they
         are used by the object file format, and converts C++
         mangled symbol names into user readable names.  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 mean-
         ingful when generating dynamically linked ELF execut-
         ables.  The default dynamic linker is normally correct;
         don't use this unless you know what you are doing.

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     --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 stan-
         dard output and exit.

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

     -Map mapfile
         Print a link map to the file mapfile.  See the descrip-
         tion 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.

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     --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 han-
         dled.

         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 actually 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 func-
         tion 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
         unversioned exported symbols.

     --default-imported-symver
         Create and use a default symbol version (the soname) for
         unversioned imported symbols.

     --no-warn-mismatch
         Normally ld will give an error if you try to link
         together input files that are mismatched for some rea-
         son, perhaps because they have been compiled for dif-
         ferent processors or for different endiannesses. This
         option tells ld that it should silently permit such pos-
         sible errors.  This option should only be used with
         care, in cases when you have taken some special action

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         that ensures that the linker errors are inappropriate.

     --no-whole-archive
         Turn off the effect of the --whole-archive option for
         subsequent archive files.

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

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

     --oformat output-format
         ld may be configured to support more than one kind of
         object file.  If your ld is configured this way, you can
         use the --oformat option to specify the binary format
         for the output object file.  Even when ld is configured
         to support alternative object formats, you don't usually
         need to specify this, as ld should be configured to pro-
         duce 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 supported on a few targets.

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         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 espe-
         cially useful in environments (such as VxWorks) where a
         large global symbol table is accumulated gradually, to
         conserve run-time memory.

         --retain-symbols-file does not discard undefined sym-
         bols, or symbols needed for relocations.

         You may only specify --retain-symbols-file once in the
         command line.  It overrides -s and -S.

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

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

         For compatibility with other ELF linkers, if the -R
         option is followed by a directory name, rather than a

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         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 automati-
         cally try to locate the required shared library and
         include it in the link, if it is not included expli-
         citly.  In such a case, the -rpath-link option specifies
         the first set of directories to search.  The -rpath-link
         option may specify a sequence of directory names either
         by specifying a list of names separated by colons, or by
         appearing multiple times.

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

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

         1.  Any directories specified by -rpath-link options.

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

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

         4.  On SunOS, if the -rpath option was not used, search
             any directories specified using -L options.

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

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

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         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 sup-
         ported 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 patterns in the linker script.

     --sort-section alignment
         This option will apply "SORT_BY_ALIGNMENT" to all wild-
         card 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 single output section in the file contains more
         than count relocations. This is useful when generating
         huge relocatable files for downloading into certain real
         time kernels with the COFF object file format; since
         COFF cannot represent more than 65535 relocations in a
         single section.  Note that this will fail to work with
         object file formats which do not support arbitrary sec-
         tions.  The linker will not split up individual input
         sections for redistribution, so if a single input sec-
         tion contains more than count relocations one output
         section will contain that many relocations.  count
         defaults to a value of 32768.

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

     --sysroot=directory
         Use directory as the location of the sysroot, overriding
         the configure-time default.  This option is only sup-
         ported by linkers that were configured using
         --with-sysroot.

     --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 section-
         name, 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 possible 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

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             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 controlled 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 typically used when creating shared libraries to
         specify additional information about the version hierar-
         chy for the library being created.  This option is only
         meaningful on ELF platforms which support shared
         libraries.

     --warn-common
         Warn when a common symbol is combined with another com-
         mon 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 sym-
         bols. 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;

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

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

         The --warn-common option can produce five kinds of warn-
         ings. 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 definition 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 symbol.

                     <file>(<section>): warning: multiple common
                        of `<symbol>'
                     <file>(<section>): warning: previous common is here

         4.  Merging a common symbol with a previous larger com-
             mon 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

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             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 pro-
         cessors 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 lim-
         its the maximum size of the constant pool.  Thus, in
         large programs, it is often necessary to use multiple
         global pointer values in order to be able to address all
         possible constants.  This option causes a warning to be
         issued whenever this case occurs.

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

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

     --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 warn-
         ing instead.

     --error-unresolved-symbols

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         This restores the linker's default behaviour of generat-
         ing 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 refer-
         ence to symbol will be resolved to "__wrap_symbol".  Any
         undefined reference to "__real_symbol" will be resolved
         to symbol.

         This can be used to provide a wrapper for a system func-
         tion.  The wrapper function should be called
         "__wrap_symbol".  If it wishes to call the system func-
         tion, 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 mal-
         loc, 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 defini-
         tion 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".

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

     --hash-size=number
         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 executable.  You should name the output "*.dll"
     when you use this option.  In addition, the linker fully
     supports the standard "*.def" files, which may be specified
     on the linker command line like an object file (in fact, it
     should precede archives it exports symbols from, to ensure
     that they get linked in, just like a normal object file).

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

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

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         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 --disable-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 function attri-
         butes, the default is to not export anything else unless
         this option is given.  Note that the symbols
         "DllMain@12", "DllEntryPoint@0", "DllMainCRTStartup@12",
         and "impure_ptr" will not be automatically exported.
         Also, symbols imported from other DLLs will not be
         re-exported, nor will symbols specifying the DLL's
         internal layout such as those beginning with "_head_" or
         ending with "_iname".  In addition, no symbols from
         "libgcc", "libstd++", "libmingw32", or "crtX.o" will be
         exported. Symbols whose names begin with "__rtti_" or
         "__builtin_" will not be exported, to help with C++
         DLLs.  Finally, there is an extensive list of cygwin-

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         private symbols that are not exported (obviously, this
         applies on when building DLLs for cygwin targets). These
         cygwin-excludes are: "_cygwin_dll_entry@12",
         "_cygwin_crt0_common@8",
         "_cygwin_noncygwin_dll_entry@12", "_fmode",
         "_impure_ptr", "cygwin_attach_dll", "cygwin_premain0",
         "cygwin_premain1", "cygwin_premain2", "cygwin_premain3",
         and "environ". [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 automat-
         ically 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 overlap any
         other dlls.  The default is 0x400000 for executables,
         and 0x10000000 for dlls. [This option is specific to the
         i386 PE targeted 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 ``[operat-
         ing systems]'' section of the BOOT.INI.  Otherwise, this
         bit has no effect. [This option is specific to PE

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         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 gen-
         erating.  This DEF file (which should be called "*.def")
         may be used to create an import library with "dlltool"
         or may be used as a reference to automatically or impli-
         citly 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

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         Automatically choose the image base for DLLs, unless one
         is specified using the "--image-base" argument.  By
         using a hash generated from the dllname to create unique
         image bases for each DLL, in-memory collisions and relo-
         cations 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 prefer-
         ence to "lib<basename>.dll". This behaviour allows easy
         distinction between DLLs built for the various "subplat-
         forms": 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 documentation 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.

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

                 extern type extern_array[];
                 extern_array[1] -->
                    { 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 ...) variable:

                 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 building/linking to
         a static library.   In making the choice between the
         various methods of resolving the 'direct address with
         constant offset' problem, you should consider typical
         real-world usage:

         Original:

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                 --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 functions). [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 specific 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

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         DLL with non-zero offset, this switch will create a vec-
         tor 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 tar-
         geted 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", "win-
         dows", "console", "posix", and "xbox".  You may option-
         ally set the subsystem version also.  Numeric values are
         also accepted for which. [This option is specific 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

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         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 "GNUTARGET", "LDEMULATION" and
     "COLLECT_NO_DEMANGLE".

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

     "LDEMULATION" determines the default emulation if you don't
     use the -m option.  The emulation can affect various aspects
     of linker behaviour, particularly the default linker script.
     You can list the available emulations with the --verbose or
     -V options.  If the -m option is not used, and the "LDEMULA-
     TION" environment variable is not defined, the default emu-
     lation depends upon how the linker was configured.

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

SEE ALSO

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

COPYRIGHT

     Copyright (c) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000,
     2001, 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

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     of the license is included in the section entitled ``GNU
     Free Documentation License''.

binutils-050707            2014-07-04                          37

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