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ld_classic(1)                                                    ld_classic(1)




NAME

       ld_classic - The old Mach object file link editor


SYNOPSIS

       ld_classic [ option ...  ] [ file ...  ]


DESCRIPTION

       The ld_classic command combines several Mach-O (Mach object) files into
       one by combining like sections in like segments  from  all  the  object
       files,  resolving external references, and searching libraries.  In the
       simplest case several object files are given, and  ld_classic  combines
       them,  producing  an object file which can either be executed or become
       the input for a further ld_classic run.  (In the latter  case,  the  -r
       option  must  be given to preserve the relocation information.)  Unless
       an output file is specified, ld_classic produces a  file  named  a.out.
       This file is made executable only if no errors occurred during the link
       editing and there are no undefined symbols.


UNIVERSAL FILE SUPPORT

       The link editor  accepts  ``universal''  (multiple-architecture)  input
       files,  but  always  creates a ``thin'' (single-architecture), standard
       Mach-O output file.  The architecture is specified  using  the  -arch
       arch_type  option.   If this option is not used, ld_classic(1) attempts
       to determine the output architecture by examining the first object file
       encountered  on the command line.  If it is a ``thin'' file, its archi-
       tecture determines that of the output file.  If the first input file is
       a  ``universal''  file, the ``best'' architecture for the host is used.
       (See the explanation of the -arch option, below.)

       The compiler driver cc(1) handles  creating  universal  executables  by
       calling  ld_classic(1)  multiple  times  and  using lipo(1) to create a
       ``universal'' file from the results of the ld_classic(1) executions.


OUTPUT FILE LAYOUT

       The object files are loaded in the order in which they are specified on
       the command line.  The segments and the sections in those segments will
       appear in the output file in the order  they  are  encountered  in  the
       object  files  being  linked.  All zero fill sections will appear after
       all non-zero fill sections in their segments.

       Sections created from files with the -sectcreate option will appear  in
       the  output  file  last.  Section names for sections created from files
       are not allowed to overlap with a section name in the same segment as a
       section coming from an object file.  Sections created from files may be
       in a segment which has sections from object files and  if  so  will  be
       loaded at the end of the non-zero fill sections for that segment.

       If  the option -seglinkedit is specified, the segment it creates is the
       last segment in the output file.

       The address of each segment can be specified with -segaddr, which takes
       the  segment's  name  as an argument.  The address of the first segment
       can alternatively be specified using -seg1addr, in which case a segment
       name  is  not used.  Segments that do not have a specified address will
       be assigned addresses in the order in which they appear in  the  output
       file.  A segment's address will be assigned based on the ending address
       of the previous segment.  If the address of the first segment  has  not
       been specified by name, its assigned address will be the specified (via
       -seg1addr) or default first segment address.  If neither flag  is  used
       to specify the first segment's address, its default address is zero for
       all formats except the demand-paged executable format (MH_EXECUTE),  in
       which case the default first address is the value of the segment align-
       ment.

       For demand-paged executable format (MH_EXECUTE) output files,  if  none
       of the segments' addresses covers address zero through the value of the
       segment alignment, a segment with no access protection will be  created
       to  cover those addresses.  This segment, named ``__PAGEZERO'', is cre-
       ated so that any attempt to dereference a NULL  pointer  will  cause  a
       memory exception.

       The  entry  point of the output file is the beginning of the first sec-
       tion in the first segment (unless the -e option is specified).


STATIC ARCHIVE LIBRARIES

       ld_classic supports two types of libraries:  static  archive  libraries
       and  dynamic shared libraries.  Searching for undefined symbols is per-
       formed differently for dynamic shared libraries than it is  for  static
       archive  libraries.   The  searching  of  dynamic  shared  libraries is
       described later.

       When a static archive library is specified as an argument  to  ld_clas-
       sic, it is searched exactly once, at the point it is encountered in the
       argument list.  Only those members defining an unresolved external ref-
       erence,  as  defined by the static archive library's table of contents,
       are loaded.  To produce the  table  of  contents,  all  static  archive
       libraries must be processed by ranlib(1).

       Generally, a static archive library does not have multiple members that
       define the same symbol.  For these types of libraries, the order of the
       members  is  not  important, so the table of contents can be sorted for
       faster link editing using the -s option to ranlib(1).  The first member
       of  the  static archive library is named ``__.SYMDEF SORTED'', which is
       understood to be a sorted table of contents.

       If the static archive library does have multiple  members  that  define
       the same symbol, the table of contents that ranlib(1) produces can't be
       sorted.  Instead, it follows the order in which the members  appear  in
       the static archive library.  The link editor searches the table of con-
       tents iteratively, loading members until no further references are sat-
       isfied.   In  the unsorted case, the first member of the static archive
       library is named ``__.SYMDEF'', which is understood to be  a  table  of
       contents in the order of the archive members.

       Static  archive  library  members can also be loaded in response to the
       -ObjC and -all_load flags. See their descriptions below.



DYNAMIC SHARED LIBRARIES

       When a dynamic shared library or an object file that was linked against
       a  dynamic  shared  library  is specified as an argument to ld_classic,
       that library is placed in the dynamic shared library search  list.  The
       order  of  the  search list is always the same order the libraries were
       encountered on the command  line.  When  linking  -flat_namespace,  all
       dynamic  libraries  that  the  dynamic libraries are dependent upon are
       added to the end of the search list.

       Once the search list is constructed, the static link editor checks  for
       undefined  symbols by simulating the way the dynamic linker will search
       for undefined symbols at runtime. For each undefined symbol, the static
       link  editor  searches each library in the search list until it finds a
       module that defines the symbol.  With each undefined symbol, the search
       starts  with the first library in the list.  This is different than for
       static archive libraries, where each library is searched  exactly  once
       for all undefined symbols.

       The  static  link  editor simulates dynamic linking as if all the unde-
       fined symbols are to be bound  at  program  launch  time.  The  dynamic
       linker  actually binds undefined symbols as they are encountered during
       execution instead of at program launch. However, the static link editor
       always  produces the same linking as the dynamic linker as long as none
       of the dynamic shared libraries define the same symbol. Different link-
       ing  can  occur only when there is more than one definition of a symbol
       and the library modules that contain the definitions for that symbol do
       not  define and reference exactly the same symbols.  In this case, even
       different executions of the same program can produce different  linking
       because  the  dynamic  linker  binds  undefined  functions  as they are
       called, and this affects the  order  in  which  undefined  symbols  are
       bound.  Because it can produce different dynamic linking, using dynamic
       shared libraries that define the same symbols in the  same  program  is
       strongly discouraged.

       If  a  static archive library appears after a dynamic shared library on
       the command line, the static library is placed in the  dynamic  library
       search  list and is searched as a dynamic library.  In this way, when a
       dynamic library has undefined symbols, it will  cause  the  appropriate
       members  of the static libraries to be loaded into the output.  Search-
       ing static libraries as dynamic libraries can  cause  problems  if  the
       dynamic  library  later  changes  to  reference symbols from the static
       library that it did not previously reference. In  this  case  when  the
       program runs, the dynamic linker will report these symbols as undefined
       because the members for these symbols were not loaded into the  output.



TWO-LEVEL AND FLAT NAMESPACES

       Two-level  and  flat  namespaces  refer to how references to symbols in
       dynamic libraries are resolved to  a  definition  in  specific  dynamic
       library.   For  two-level  namespace  that resolution is done at static
       link time when each image  (program,  bundle  and  shared  library)  is
       built.   When  a program is using images built with two-level namespace
       there may be different global symbols with the same name being used  by
       different images in the program (this is now the default).  When a pro-
       gram is using all flat namespace images then only one global symbol for
       each  global symbol name is used by all images of the program (this was
       the default in MacOS X 10.0).

       When creating an output file with the static  link  editor  that  links
       against dynamic libraries, the references to symbols in those libraries
       can be recorded at static link time to bind to a specific library defi-
       nition  (two-level  namespace) or left to be bound at execution time to
       the first library in the search order of the program (flat  namespace).
       A  program,  its  dynamic  libraries and its bundles may each be either
       two-level or flat namespace images.  The dynamic linker will bind  each
       image according to how it was built.

       When  creating  an  output  file  with  the  static  link  editor  when
       -twolevel_namespace is in effect (now the default) all undefined refer-
       ences  must be satisfied at static link time.  The flags to allow unde-
       fined references, -Usymbol_name, -undefined warning and -undefined sup-
       press  can't  be  used.   When  the environment variable MACOSX_DEPLOY-
       MENT_TARGET is set to 10.3 or higher then -undefined dynamic_lookup can
       also be used.  The specific library definition recorded for each refer-
       ence is the first library that has a definition as listed on  the  link
       line.  Listing an umbrella framework implies all of its sub-frameworks,
       sub-umbrellas and sub-libraries.  For any  reference  to  a  definition
       found  in  an  umbrella framework's sub-framework, sub-umbrella or sub-
       library will be recorded as coming from the umbrella  framework.   Then
       at  execution  time the dynamic linker will search that umbrella frame-
       work's sub-frameworks, sub-umbrellas and sub-libraries for those refer-
       ences.   Also  when  two-level namespace is in effect only those frame-
       works listed on the link line (and  sub-frameworks,  sub-umbrellas  and
       sub-libraries  of  umbrella  frameworks) are searched.  Other dependent
       libraries which are not sub-frameworks, sub-umbrellas or  sub-libraries
       of umbrella frameworks are not searched.

              When  creating  bundles (MH_BUNDLE outputs) with the static link
              editor when two-level namespace is in effect (now  the  default)
              and  the bundle has references to symbols expected to be defined
              in the program loading the bundle, then the -bundle_loader  exe-
              cutable must be used.

              When  creating  an  output file with the static link editor when
              -flat_namespace is in effect (the  MacOS  X  10.0  default)  all
              undefined  references must be satisfied at static link time when
              -undefined error (the default) is used.  The static link  editor
              checks  the  undefined references by searching all the libraries
              listed on the link line then all dependent libraries.  The unde-
              fined symbols in the created output file are left to be resolved
              at execution time by the dynamic  link  editor  in  the  dynamic
              libraries in the search order of the program.



MULTIPLY DEFINED SYMBOLS

       If  there are multiply defined symbols in the object files being linked
       into the output file being created this always results  in  a  multiply
       defined symbol error.

       When  the  static  link  editor links symbols in from a dynamic library
       that result in multiply defined symbols the  handling  depends  on  the
       type  of  name space of output file being created and possibly the type
       of name space of the dynamic library.

       When the static link editor is creating a two-level namespace image and
       a  there  is  a  multiply defined symbol from dynamic library then that
       generates a multiply defined symbol warning  (by  default),  where  the
       treatment  of  this  warning  can be changed with the -multiply_defined
       flag.

       When the static link editor is creating a flat namespace  image  and  a
       there is a multiply defined symbol from dynamic library, if the library
       is a flat namespace image then that generates a multiply defined symbol
       error.   If the library is a two-level namespace image then that gener-
       ates a multiply defined symbol warning (by default), where  the  treat-
       ment of this warning can be changed with the -multiply_defined flag.



USING THE DYNAMIC LINK EDITOR AND DYNAMIC SHARED LIBRARIES

       The  option  -dynamic  must be specified in order to use dynamic shared
       libraries (and any of the features used to implement them)  and/or  the
       dynamic  link  editor.   To  make sure that the output is not using any
       features that would require the dynamic link editor, the  flag  -static
       can be specified.  Only one of these flags can be specified.



LINK EDITOR DEFINED SYMBOLS

       There  is  a  group  of link editor defined symbols for the MH_EXECUTE,
       MH_DYLIB  and  MH_PRELOAD  file  types  (see  the  header  file  <mach-
       o/ldsyms.h>).   Link  editor symbols are reserved; it is an error if an
       input object file defines such a symbol.  Only those link  editor  sym-
       bols that are referenced by the object file appear in the output file's
       symbol table.

       The  link  editor  defined  symbol   `__mh_execute_header'   (`_mh_exe-
       cute_header'  in  C) is reserved when the output file format is MH_EXE-
       CUTE.  This symbol is the address of the Mach header in a  Mach-O  exe-
       cutable  (a  file of type MH_EXECUTE).  It does not appear in any other
       Mach-O file type.  It can be used to get to the addresses and sizes  of
       all  the  segments and sections in the executable.  This can be done by
       parsing the headers and load commands (see Mach-O(5)).

       The link editor defined symbol `__mh_dylib_header'  (`_mh_dylib_header'
       in C) is reserved when the output file format is MH_DYLIB.  This symbol
       is the address of the Mach header in a Mach-O dynamic shared library (a
       file  of  type MH_DYLIB) and is a private external symbol.  It does not
       appear in any other Mach-O file type.  It can be used  to  get  to  the
       addresses  and  sizes  of  all  the  segments and sections in a dynamic
       shared  library.   The  addresses,  however,  must   have   the   value
       _dyld_get_image_vmaddr_slide(3) added to them.

       The MH_PRELOAD file type has link editor defined symbols for the begin-
       ning and ending of each segment, and for the beginning  and  ending  of
       each  section  within a segment.  These names are provided for use in a
       Mach-O preloaded file, since it does not have  its  headers  loaded  as
       part  of  the  first segment.  The names of the symbols for a segment's
       beginning and end have the form: __SEGNAME__begin  and  __SEGNAME__end,
       where __SEGNAME is the name of the segment.  Similarly, the symbols for
       a  section  have  the  form:  __SEGNAME__sectname__begin   and   __SEG-
       NAME__sectname__end, where __sectname is the name of the section in the
       segment __SEGNAME.  These symbols' types are those of the section  that
       the  names  refer  to.   (A  symbol that refers to the end of a section
       actually has, as its value, the beginning address of the next  section,
       but  the  symbol's  type  is still that of the section mentioned in the
       symbol's name.)


OPTIONS

       Ld understands several options.  Filenames and options  that  refer  to
       libraries  (such  as -l and -framework), as well as options that create
       symbols (such as -u and -i), are position-dependent:  They  define  the
       load order and affect what gets loaded from libraries.  Some ld_classic
       options overlap with compiler options.  If the compiler driver cc(1) is
       used  to  invoke  ld_classic  , it maybe necessary to pass the ld_clas-
       sic(1) options to cc(1) using -Wl,-option,argument1,argument2.

       In this release of the static link editor, 64-bit code is processed  by
       a  the  new  link editor /usr/bin/ld.  And it is an error to pass -arch
       ppc64 or -arch x86_64 to ld_classic(1).

       The most common option is:

       -o name
              The output file is named name, instead of a.out.


       The following flags are related to architectures:

       -arch arch_type
              Specifies the architecture,  arch_type,  for  the  output  file.
              ``Universal''  input  files  that  do not contain this specified
              architecture are ignored.  Only one -arch arch_type can be spec-
              ified.   See  arch(3)  for  the currently known arch_types.  If
              arch_type specifies a certain implementation of an  architecture
              (such as -arch m68040 or -arch i486 ), the resulting object file
              has that specific CPU subtype, and it is an error if  any  input
              file  has a CPU subtype that will not combine to the CPU subtype
              for  arch_type.

              The default output file architecture is determined by the  first
              object file to be linked.  If it is a ``thin'' (standard Mach-O)
              file, or a ``universal'' file that contains only  one  architec-
              ture,  the  output file will have the same architecture.  Other-
              wise, if it is a ``universal'' file containing  an  architecture
              that  would  execute on the host, then the ``best'' architecture
              is used, as defined by what the  kernel  exec(2)  would  select.
              Otherwise,  it is an error, and a -arch arch_type must be speci-
              fied.  For family architectures (like ppc and i386) the CPU sub-
              type  of  the linked output is the ALL cpusubtype.  For specific
              CPU subtypes (ppc7400 vs. ppc970), the resulting CPU subtype  of
              the linked output is to 'combine' the CPU subtypes.  The combin-
              ing is CPU specific and generally results  in  the  minimum  CPU
              subtype needed to support all the combined CPU subtypes.

       -arch_multiple
              This  flag  is  used  by the cc(1) driver program when it is run
              with multiple -arch arch_type flags.  It instructs programs like
              ld_classic(1) to precede any displayed message with a line stat-
              ing the program name, in this case ld_classic, and the architec-
              ture  (from  the  -arch arch_type flag).  This helps distinguish
              which architecture the error messages refer to.

       -force_cpusubtype_ALL
              The -force_cpusubtype_ALL flag causes the CPU subtype to  remain
              the  ALL  CPU  subtype  and not to be combined or changed.  This
              flag has precedence over any -arch arch_type flag for a specific
              implementation.   This is the default for all x86 architectures.

       The following flags are related to using the dynamic link editor and/or
       dynamic  shared  libraries  (and  any of the features used to implement
       them):

       -dynamic
              Allows use of the features associated with dynamic link  editor.
              The default is -dynamic.

       -static
              Causes  those features associated with dynamic link editor to be
              treated as an error. (The description for the options that  will
              cause  an  error if you use them in conjunction with -static are
              marked with the statement "when -dynamic
               is used").

       -read_only_relocs treatment
              Specifies how relocation entries in read-only sections are to be
              treated  when  -dynamic is used.  To get the best possible shar-
              ing, the read-only  sections  should  not  have  any  relocation
              entries.   If they do, the dynamic linker will write on the sec-
              tion.  Having relocation entries appear in read-only sections is
              normally  avoided by compiling with the option -dynamic.  But in
              such cases non-converted assembly code or objects  not  compiled
              with  -dynamic  relocation entries will appear in read-only sec-
              tions.  The treatment  can  be:  error,  warning,  or  suppress.
              Which  cause  the  treatment  of relocation entries in read-only
              sections as either, errors, warnings,  or  suppressed  messages.
              The default is to treat these as errors.

       -sect_diff_relocs treatment
              Specifies  how  section  difference  relocation enries are to be
              treated when -dynamic and -execute are used.  To  get  the  best
              possible  code  generation the compiler should not generate code
              for executables (MH_EXECUTE format outputs) that have  any  sec-
              tion difference relocation entries.  The gcc(1) compiler has the
              -mdynamic-no-pic flag for generating code for executables.   The
              default treatment is suppress, where no message is printed.  The
              other treatments are error or warning.  This option can also  be
              specified     by     setting     the     environment    variable
              LD_SECT_DIFF_RELOCS to the treatment values.

       -weak_reference_mismatches treatment
              Specifies how to treat mismatches of symbol  references  in  the
              the  object  files  being linked. Normally the all the undefined
              symbol references of the object files  being  linked  should  be
              consistent  for  each  undefined  symbol.  That is all undefined
              symbols should  either  be  weak  or  non-weak  references.  The
              default  treatment  is error, where the link fails with an error
              message.  The other treatments are weak or non-weak, which makes
              mismatched  undefined  symbol references either weak or non-weak
              in the output, respectively.  Care must be taken when using  the
              treatment  weak  as the use of the non-weak symbol references in
              an object file may cause the program to crash when the symbol is
              not present at execution time.

       -prebind
              Have  the  static linker, ld_classic(1), prebind an executable's
              or dynamic shared library's undefined symbols to  the  addresses
              of  the  dynamic  libraries it is being linked with.  This opti-
              mization can only be done if the libraries don't overlap and  no
              symbols  are  overridden.  When the resulting program is run and
              the same libraries are used to run the program as when the  pro-
              gram  was  linked,  the  dynamic  linker  can  use  the prebound
              addresses.  If not, the dynamic linker undoes the prebinding and
              binds  normally.   This  option can also be specified by setting
              the environment variable LD_PREBIND.  If the  environment  vari-
              able LD_FORCE_NO_PREBIND is set both the option -prebind LD_PRE-
              BIND environment variable are ignore and the output is not  pre-
              bound.   Or if the environment variable MACOSX_DEPLOYMENT_TARGET
              is set to 10.4 or greater and  the  output  is  not  a  split  a
              dynamic library the output is not prebound.

       -noprebind
              Do  not  have the static linker, ld_classic(1), prebind the out-
              put.  If this is specified the environment  variable  LD_PREBIND
              is ignored.

       -prebind_allow_overlap
              Have  the  static linker, ld_classic(1), prebind the output even
              if the addresses of the dynamic libraries it uses overlap.   The
              resulting  output  can then have redo_prebinding(1) run on it to
              fix up the prebinding after the  overlapping  dynamic  libraries
              have been rebuilt.  This option can also be specified by setting
              the environment variable LD_PREBIND_ALLOW_OVERLAP.

       -prebind_all_twolevel_modules
              Have the static linker, ld_classic(1),  mark  all  modules  from
              prebound  two-level  namespace  dynamic libraries as used by the
              program even if they are not statically  referenced.   This  can
              provide  improved launch time for programs like Objective-C pro-
              grams that use symbols indirectly through NIB files. This option
              can  also  be  specified  by  setting  the  environment variable
              LD_PREBIND_ALL_TWOLEVEL_MODULES.

       -noprebind_all_twolevel_modules
              Don't have the static linker, ld_classic(1),  mark  all  modules
              from  prebound  two-level namespace dynamic libraries as used by
              the program.  This flag overrides the setting of the environment
              variable LD_PREBIND_ALL_TWOLEVEL_MODULES.

       -nofixprebinding
              Have  the  static  linker, ld_classic(1), mark the executable so
              that the dynamic linker will never notify the  prebinding  agent
              if  this  launched  and  its prebinding is out of date.  This is
              used when building the prebinding agent itself.

       The following flags are related to libraries:

       -lx    This option is an abbreviation for the  library  name  `libx.a',
              where  x is a string.  If -dynamic is specified the abbreviation
              for the library name is first search as  `libx.dylib'  and  then
              `libx.a'  is  searched  for.   ld_classic searches for libraries
              first in any directories specified with -L options, then in  any
              directories specified in the colon separated set of paths in the
              environment variable LD_LIBRARY_PATH, then the standard directo-
              ries  /lib, /usr/lib, and /usr/local/lib.  A library is searched
              when its name is encountered, so the placement of the -l flag is
              significant.   If string x is of the form x.o, then that file is
              searched for in the same places, but without prepending `lib' or
              appending `.a' or `.dylib' to the filename.

       -weak-lx
              This  is the same as the -lx but forces the library and all ref-
              erences to it to be marked as weak imports.  Care must be  taken
              when  using this as the use of the non-weak symbol references in
              an object file may cause the program to crash when the symbol or
              library is not present at execution time.

       -weak_library file_name_path_to_library
              This is the same as listing a file name path to a library on the
              link line except that it forces the library and  all  references
              to  it  to  be  marked as weak imports.  Care must be taken when
              using this as the use of the non-weak symbol  references  in  an
              object  file  may  cause the program to crash when the symbol or
              library is not present at execution time.

       -Ldir  Add dir to the list  of  directories  in  which  to  search  for
              libraries.   Directories  specified  with -L are searched before
              the standard directories.

       -Z     Do not  search  the  standard  directories  when  searching  for
              libraries.

       -syslibroot rootdir
              Prepend  rootdir  to the standard directories when searching for
              libraries or frameworks.

       -search_paths_first
              By default when the -dynamic flag is  in  effect,  the  -lx  and
              -weak-lx   options   first   search  for  a  file  of  the  form
              `libx.dylib' in each directory in the library search path,  then
              a  file  of  the  form  `libx.a'  is searched for in the library
              search paths.  This option changes  it  so  that  in  each  path
              `libx.dylib'  is searched for then `libx.a' before the next path
              in the library search path is searched.

       -framework name[,suffix]
              Specifies a framework to link against.  Frameworks  are  dynamic
              shared  libraries,  but  they are stored in different locations,
              and therefore must be searched for differently. When this option
              is  specified,  ld_classic  searches  for framework `name.frame-
              work/name' first  in  any  directories  specified  with  the  -F
              option,    then    in   the   standard   framework   directories
              /Library/Frameworks,  /Network/Library/Frameworks,   and   /Sys-
              tem/Library/Frameworks.   The placement of the -framework option
              is significant, as it determines when and how the  framework  is
              searched.   If the optional suffix is specified the framework is
              first searched for the name with the suffix and then without.

       -weak_framework name[,suffix]
              This is the same as the -framework name[,suffix] but forces  the
              framework and all references to it to be marked as weak imports.
              Care must be taken when using this as the use  of  the  non-weak
              symbol  references  in  an  object file may cause the program to
              crash when the symbol or framework is not present  at  execution
              time.

       -Fdir  Add dir to the list of directories in which to search for frame-
              works.  Directories specified with -F are  searched  before  the
              standard framework directories.

       -ObjC  Loads  all  members  of  static archive libraries that define an
              Objective C class or a category. This option does not  apply  to
              dynamic shared libraries.

       -all_load
              Loads all members of static archive libraries.  This option does
              not apply to dynamic shared libraries.

       -dylib_file install_name:file_name
              Specifies that a dynamic shared library is in a different  loca-
              tion  than  its standard location. Use this option when you link
              with a library that is dependent on a dynamic library,  and  the
              dynamic  library  is  in a location other than its default loca-
              tion.  install_name specifies the path where  the  library  nor-
              mally  resides.  file_name specifies the path of the library you
              want to use instead.  For example, if you link to a library that
              depends  upon  the  dynamic  library  libsys and you have libsys
              installed in a nondefault location, you would use  this  option:
              -dylib_file /lib/libsys_s.A.dylib:/me/lib/libsys_s.A.dylib.

       -executable_path path_name
              Specifies that path_name is used to replace @executable_path for
              dependent libraries.


       The following options specify the output file format (the file type):

       -execute
              Produce a Mach-O demand-paged executable format file.  The head-
              ers are placed in the first segment, and all segments are padded
              to the segment alignment.  This has a file type  of  MH_EXECUTE.
              This  is  the  default.   If  no segment address is specified at
              address zero, a segment with no protection (no read,  write,  or
              execute  permission)  is created at address zero.  This segment,
              whose  size  is  that  of  the  segment  alignment,   is   named
              ``__PAGEZERO''.   This  option was previously named -Mach, which
              will continue to be recognized.

       -object
              Produce a Mach-O file in the relocatable object file format that
              is  intended  for  execution.   This  differs  from using the -r
              option in that it defines common symbols, does not  allow  unde-
              fined  symbols  and  does not preserve relocation entries.  This
              has a file type of MH_OBJECT.  In this format all  sections  are
              placed in one unnamed segment with all protections (read, write,
              execute)  allowed  on  that  segment.   This  is  intended   for
              extremely  small  programs  that would otherwise be large due to
              segment padding.  In this format, and  all  non-MH_EXECUTE  for-
              mats,  the link editor defined symbol ``__mh_execute_header'' is
              not defined since the headers are not part of the segment.  This
              format file can't be used with the dynamic linker.

       -preload
              Produce  a Mach-O preloaded executable format file.  The headers
              are not placed in any segment.  All sections are placed in their
              proper  segments  and  they are padded to the segment alignment.
              This has a file type of MH_PRELOAD.  This option was  previously
              -p, which will continue to be recognized.

       -dylib Produce  a Mach-O dynamically linked shared library format file.
              The headers are placed in the first segment.  All  sections  are
              placed  in their proper segments and they are padded to the seg-
              ment alignment.  This has a file type of MH_DYLIB.  This  option
              is used by libtool(1) when its -dynamic option is specified.

       -bundle
              Produce  a Mach-O bundle format file.  The headers are placed in
              the first segment.  All sections are placed in their proper seg-
              ments  and they are padded to the segment alignment.  This has a
              file type of MH_BUNDLE.

       -dylinker
              Produces a Mach-O dynamic link editor format file.  The  headers
              are  placed  in  the  first segment.  All sections are placed in
              their proper segments, and they are padded to the segment align-
              ment.  This has a file type of MH_DYLINKER.

       -fvmlib
              Produce a Mach-O fixed VM shared library format file.  The head-
              ers are placed in the first segment but  the  first  section  in
              that segment will be placed on the next segment alignment bound-
              ary in that segment.  All sections are placed  in  their  proper
              segments and they are padded to the segment alignment.  This has
              a file type of MH_FVMLIB.


       The following flags affect the contents of the output file:

       -r     Save the relocation information in the output file  so  that  it
              can  be  the  subject  of another ld_classic run.  The resulting
              file type is a Mach-O relocatable file (MH_OBJECT) if not other-
              wise  specified.  This flag also prevents final definitions from
              being given to common symbols,  and  suppresses  the  `undefined
              symbol' diagnostics.

       -d     Force  definition  of  common  storage  even if the -r option is
              present.  This option also forces link editor defined symbols to
              be defined.  This option is assumed when there is a dynamic link
              editor load command in the input and -r is not specified.


       The following flags support segment specifications:

       -segalign value
              Specifies the segment alignment.  value is a hexadecimal  number
              that  must be an integral power of 2.  The default is the target
              pagesize (currently 1000 hex for the PowerPC and i386).

       -seg1addr addr
              Specifies the starting address of the first segment in the  out-
              put  file.   addr is a hexadecimal number and must be a multiple
              of the segment alignment.  This option can also be specified  as
              -image_base.

       -segaddr name addr
              Specifies  the  starting address of the segment named name to be
              addr.  The address must be a hexadecimal number that is a multi-
              ple of the segment alignment.

       -segs_read_only_addr addr
              Specifies  the  starting  address of the read-only segments in a
              dynamic shared library.  When this option is  used  the  dynamic
              shared  library  is built such that the read-only and read-write
              segments are split into separate address ranges.  By default the
              read-write  segments are 256meg (0x10000000) after the read-only
              segments.  addr is a hexadecimal number and must be  a  multiple
              of the segment alignment.

       -segs_read_write_addr addr
              Specifies  the  starting address of the read-write segments in a
              dynamic  shared  library.   When  this  option   is   used   the
              -segs_read_only_addr  must  also be used (see above).  addr is a
              hexadecimal number and must be a multiple of the segment  align-
              ment.

       -seg_addr_table filename
              For  dynamic  shared  libraries  the  -seg1addr  or  the pair of
              -segs_read_only_addr and -segs_read_write_addr are specified  by
              an  entry  in the segment address table in filename that matches
              the install name of the library.  The entries in the  table  are
              lines containing either a single hex address and an install name
              or two hex addresses and an install name.  In the first form the
              single  hex  address  is  used as the -seg1addr .  In the second
              form the first  address  is  used  as  the  -segs_read_only_addr
              address    and    the    second   address   is   used   as   the
              -segs_read_write_addr address.  This option can also  be  speci-
              fied  by setting the environment variable LD_SEG_ADDR_TABLE.  If
              the  environment   variable   is   set   then   any   -seg1addr,
              -segs_read_only_addr,  -segs_read_write_addr and -seg_addr_table
              options are ignored and a warning is printed.

       -seg_addr_table_filename pathname
              Use pathname instead of the install  name  of  the  library  for
              matching an entry in the segment address table.

       -segprot name max init
              Specifies  the  maximum and initial virtual memory protection of
              the named segment, name, to be max and init ,respectively.   The
              values  for  max  and init are any combination of the characters
              `r' (for read), `w' (for write), `x' (for execute) and  '-'  (no
              access).   The  default  is `rwx' for the maximum protection for
              all segments for PowerPC architecures and `rw` for the all Intel
              architecures.   The  default  for the initial protection for all
              segments is `rw' unless the segment  contains  a  section  which
              contains  some  machine  instructions, in which case the default
              for the initial protection is `rwx' (and for Intel  architecures
              it also sets the maximum protection to `rwx' in this case).  The
              default for the initial protection for the ``__TEXT'' segment is
              `rx' (not writable).

       -seglinkedit
              Create  the link edit segment, named ``__LINKEDIT'' (this is the
              default).  This segment contains all the link  edit  information
              (relocation  information,  symbol  table, string table, etc.) in
              the object file.  If the segment protection for this segment  is
              not specified, the initial protection is not writable.  This can
              only be specified when the output file type is not MH_OBJECT and
              MH_PRELOAD  output  file  types.  To get at the contents of this
              section, the Mach header and load commands must be  parsed  from
              the  link editor defined symbols like `__mh_execute_header' (see
              Mach-O(5)).

       -noseglinkedit
              Do not create the link edit segment (see -seglinkedit above).

       -pagezero_size value
              Specifies the segment size of __PAGEZERO to be  of  size  value,
              where  value  is  a  hexadecimal  number  rounded to the segment
              alignment.  The default is the target pagesize (currently,  1000
              hexadecimal for the PowerPC and for i386).

       -stack_addr value
              Specifies  the initial address of the stack pointer value, where
              value is a hexadecimal number rounded to the segment  alignment.
              The default segment alignment is the target pagesize (currently,
              1000 hexadecimal for the PowerPC and for i386).  If  -stack_size
              is  specified  and  -stack_addr  is not, a default stack address
              specific for the architecture being linked will be used and  its
              value  printed  as  a  warning  message.  This creates a segment
              named __UNIXSTACK.  Note that the initial stack address will  be
              either  at the high address of the segment or the low address of
              the segment depending on which direction the stack grows for the
              architecture being linked.

       -stack_size value
              Specifies  the size of the stack segment value, where value is a
              hexadecimal  number  rounded  to  the  segment  alignment.   The
              default  segment  alignment  is  the target pagesize (currently,
              1000 hexadecimal for the PowerPC and for i386).  If  -stack_addr
              is  specified  and -stack_size is not, a default stack size spe-
              cific for the architecture being linked will  be  used  and  its
              value  printed  as  a  warning  message.  This creates a segment
              named __UNIXSTACK .

       -allow_stack_execute
              Marks executable so that all stacks in the task  will  be  given
              stack execution privilege.  This includes pthread stacks.


       The following flags support section specifications:

       -sectcreate segname sectname file
              The  section sectname in the segment segname is created from the
              contents of file.  The combination of segname and sectname  must
              be  unique; there cannot already be a section (segname,sectname)
              in any input object file.  This  option  was  previously  called
              -segcreate, which will continue to be recognized.

       -sectalign segname sectname value
              The  section named sectname in the segment segname will have its
              alignment set to value, where value is a hexadecimal number that
              must  be  an  integral  power of 2.  This can be used to set the
              alignment of a section created from a file, or to  increase  the
              alignment  of a section from an object file, or to set the maxi-
              mum alignment of the  (__DATA,__common)  section,  where  common
              symbols  are  defined by the link editor.  Setting the alignment
              of a literal  section  causes  the  individual  literals  to  be
              aligned on that boundary.  If the section alignment is not spec-
              ified by a section header in an object file or  on  the  command
              line, it defaults to 10 (hex), indicating 16-byte alignment.

       -sectorder segname sectname orderfile
              The  section  sectname in the segment segname of the input files
              will be broken up into blocks associated  with  symbols  in  the
              section.   The  output  section  will be created by ordering the
              blocks as specified by the lines in the orderfile.  These blocks
              are aligned to the output file's section alignment for this sec-
              tion.  Any section can be ordered in the output file except sym-
              bol pointer and symbol stub sections.

              For non-literal sections, each line of the orderfile contains an
              object name and a symbol  name,  separated  by  a  single  colon
              (':').   Lines that start with # are ignored and treated as com-
              ments.  If the object file is in an archive, the  archive  name,
              followed  by  a single colon, must precede the object file name.
              The object file names and archive names should  be  exactly  the
              names  as  seen  by the link editor, but if not, the link editor
              attempts to match up the names the best it can.  For non-literal
              sections,  the easiest way to generate an order file is with the
              ``-jonls +segname sectname'' options to nm(1).

              The format of the orderfile for literal sections is specific  to
              each  type  of  literal section.  For C string literal sections,
              each line of the order file contains one literal C string, which
              may include ANSI C escape sequences.  For four-byte literal sec-
              tions, the order file format is one 32-bit  hex  number  with  a
              leading 0x per line, with the rest of the line treated as a com-
              ment.  For eight-byte literal sections, the order file  has  two
              32-bit  hex  numbers per line; each number has a leading 0x, the
              two numbers are separated by white space, and the  rest  of  the
              line is treated as a comment.  For literal pointer sections, the
              lines in the order file represent pointers,  one  per  line.   A
              literal  pointer  is represented by the name of the segment that
              contains the literal being pointed to, followed by  the  section
              name, followed by the literal. These three strings are separated
              by colons with no extra white space.  For all the  literal  sec-
              tions,  each  line  in the the order file is simply entered into
              the literal section and will appear in the output  file  in  the
              same  order  as  in  the  order  file.  There is no check to see
              whether the literal is present in the loaded objects.  For  lit-
              eral sections, the easiest way to generate an order file is with
              the ``-X -v -s segname sectname'' options to otool(1).

       -sectorder_detail
              When using the -sectorder option,   any  pairs  of  object  file
              names and symbol names that are found in the loaded objects, but
              not specified in the orderfile, are placed last  in  the  output
              file's section.   These pairs are ordered by object file (as the
              filenames appear on the command line), with the  different  sym-
              bols from a given object file being ordered by increasing symbol
              address (that is, the order in which the symbols occurred in the
              object  file, not their order in the symbol table).  By default,
              the link editor displays a summary that simply shows the  number
              of  symbol  names  found  in  the  loaded objects but not in the
              orderfile, as well as the number of symbol names listed  in  the
              orderfile  but not found in the loaded objects.  (The summary is
              omitted if both values are zero.)  To instead produce a detailed
              list  of  these  symbols, use the -sectorder_detail flag.  If an
              object file-symbol name pair is listed multiple times, a warning
              is generated, and the first occurrence is used.

       -sectobjectsymbols segname sectname
              This  causes  the  link  editor to generate local symbols in the
              section sectname in the segment segname.  Each object file  that
              has one of these sections will have a local symbol created whose
              name is that of the object file, or of the  member  of  the  ar-
              chive.   The symbol's value will be the first address where that
              object file's section was  loaded.   The  symbol  has  the  type
              N_SECT  and  its  section  number is the the same as that of the
              section (segname,sectname) in the output file.  This symbol will
              be  placed  in the symbol table just before all other local sym-
              bols for the object file.  This feature is typically used  where
              the  section  is  (__TEXT,__text), in order to help the debugger
              debug object files produced by old versions of the  compiler  or
              by non-Apple compilers.


       The following flags are related to name spaces:

       -twolevel_namespace
              Specifies the output to be built as a two-level namespace image.
              This option can also be specified  by  setting  the  environment
              variable LD_TWOLEVEL_NAMESPACE.  This is the default.

       -flat_namespace
              Specifies  the  output  to  be  built as a flat namespace image.
              This is not the default (but was the default in MacOS X 10.0).

       -force_flat_namespace
              Specifies the executable output to be built and executed  treat-
              ing  all  its  dynamic libraries as flat namespace images.  This
              marks the executable so that the dynamic link editor treats  all
              dynamic  libraries  as flat namespace images when the program is
              executed.

       -bundle_loader executable
              This specifies the executable that will be  loading  the  bundle
              output file being linked.  Undefined symbols from the bundle are
              checked against the specified executable like it was one of  the
              dynamic  libraries  the  bundle  was linked with.  If the bundle
              being  created  with  -twolevel_namespace  in  effect  then  the
              searching  of  the executable for symbols is based on the place-
              ment  of  the  -bundle_loader  flag  relative  to  the   dynamic
              libraries.  If the the bundle being created with -flat_namespace
              then the searching of the executable is done before all  dynamic
              libraries.

       -private_bundle
              This  allows symbols defined in the output to also be defined in
              executable in the -bundle_loader argument  when  -flat_namespace
              is  in  effect.   This implies that the bundle output file being
              created is going  to  be  loaded  by  the  executable  with  the
              NSLINKMODULE_OPTION_PRIVATE option to NSLinkModule(3).

       -twolevel_namespace_hints
              Specifies  to  create  the  output  with the two-level namespace
              hints table to be used by  the  dynamic  linker.   This  is  the
              default  except  when the -bundle flag is specified.  If this is
              used when the -bundle flag is specified the bundle will fail  to
              load on a MacOS X 10.0 system with a malformed object error.

       -multiply_defined treatment
              Specifies how multiply defined symbols in dynamic libraries when
              -twolevel_namespace is in effect are to be  treated.   treatment
              can  be: error, warning, or suppress.  Which cause the treatment
              of multiply defined symbols  in  dynamic  libraries  as  either,
              errors, warnings, or suppresses the checking of multiply symbols
              from dynamic libraries when -twolevel_namespace  is  in  effect.
              The  default  is  to  treat  multiply defined symbols in dynamic
              libraries as warnings when -twolevel_namespace is in effect.

       -multiply_defined_unused treatment
              Specifies  how  unused  multiply  defined  symbols  in   dynamic
              libraries  when  -twolevel_namespace  is  in  effect  are  to be
              treated.  An unused multiply defined  symbol  is  one  in  which
              there  is a symbol defined in the output that is also defined in
              the dynamic libraries the output is linked with but  the  symbol
              in  the dynamic library is not used by any reference in the out-
              put.  treatment  can  be:  error,  warning,  or  suppress.   The
              default for unused multiply defined symbols is to suppress these
              messages.

       -nomultidefs
              specifying this flag marks the umbrella being created such  that
              the dynamic linker is guaranteed that no multiple definitions of
              symbols in the umbrella's  sub-images  will  ever  exist.   This
              allows  the dynamic linker to always use the two-level namespace
              lookup hints even if the timestamps of  the  sub-images  do  not
              match.  This flag implies -multiply_defined error.


       The following flags are related to symbols.  These flags' arguments are
       external symbols whose names have `_' prepended to the C,  FORTRAN,  or
       Pascal variable name.

       -ysym  Display  each  file  in which sym appears, its type, and whether
              the file defines or references it.  Any multiply defined symbols
              are automatically traced.  Like most of the other symbol-related
              flags, -y takes only one argument; the  flag  may  be  specified
              more  than  once in the command line to trace more than one sym-
              bol.

       -Y number
              For the first number undefined symbols, displays  each  file  in
              which  the symbol appears, its type and whether the file defines
              or references it (that is, the same style of output produced  by
              the  -y option). To keep the output manageable, this option dis-
              plays at most number references.

       -keep_private_externs
              Don't turn private external symbols  into  static  symbols,  but
              rather  leave  them  as private external in the resulting output
              file.

       -m     Don't treat multiply defined symbols from the linked objects  as
              a hard error; instead, simply print a warning.  The first linked
              object defining such a symbol is used for linking; its value  is
              used  for the symbol in the symbol table.  The code and data for
              all such symbols are copied into the output.  The duplicate sym-
              bols  other than the first symbol may still end up being used in
              the resulting output file through local  references.   This  can
              still  produce  a  resulting output file that is in error.  This
              flag's use is strongly discouraged!

       -whyload
              Indicate why each member of  a  library  is  loaded.   In  other
              words,  indicate  which  currently  undefined  symbol  is  being
              resolved, causing that member to be loaded.  This in combination
              with  the above -ysym flag can help determine exactly why a link
              edit is failing due to multiply defined symbols.

       -u sym Enter the argument sym into the symbol  table  as  an  undefined
              symbol.  This is useful for loading wholly from a library, since
              initially the symbol table is empty and an unresolved  reference
              is needed to force the loading of the first object file.

       -e sym The  argument  sym  is  taken to be the symbol name of the entry
              point of the resulting file.  By default, the entry point is the
              address of the first section in the first segment.

       -idefinition:indirect
              Create  an  indirect symbol for the symbol name definition which
              is defined to be the same as the symbol name indirect (which  is
              taken  to  be undefined).  When a definition of the symbol named
              indirect is linked, both symbols will take on the  defined  type
              and value.

              This  option  overlaps  with  a compiler option.  If you use the
              compiler driver cc(1) to invoke ld_classic, invoke  this  option
              in this way: -Wl,-idefinition:indirect.


       -undefined treatment
              Specifies  how  undefined  symbols are to be treated.  treatment
              can be: error, warning, or suppress.  Which cause the  treatment
              of  undefined symbols as either, errors, warnings, or suppresses
              the checking of undefined symbols.   The  default  is  to  treat
              undefined  symbols  as  errors.   When  the environment variable
              MACOSX_DEPLOYMENT_TARGET is set to 10.3 or  higher  then  -unde-
              fined  dynamic_lookup  can  also  be used to allow any undefined
              symbols to be looked up dynamically at runtime.  Use of a binary
              built  with  this  flag  requires a system with a dynamic linker
              from Mac OS X 10.3 or later.  The flag  -undefined  define_a_way
              can  also be used to cause the static linker to create a private
              definition for all undefined symbols.  This flag should only  be
              used  if  it  is known that the undefined symbols are not refer-
              enced as any use of them may cause a crash.

       -U sym Allow the symbol sym to be undefined, even if the -r flag is not
              given.  Produce an executable file if the only undefined symbols
              are those specified with -U.

              This option overlaps with a compiler option.   If  you  use  the
              compiler  driver  cc(1) to invoke ld_classic, invoke this option
              in this way: -Wl,-U,sym.

       -bind_at_load
              Causes the output file to be marked such that the dynamic linker
              will  bind  all  undefined references when the file is loaded or
              launched.


       The following flags are related to  stripping  link  edit  information.
       This  information  can also be removed by strip(1), which uses the same
       options.  (The exception is the -s flag below, but this is the same  as
       strip(1)  with  no  arguments.)   The  following  flags  are  listed in
       decreasing level of stripping.

       -s     Completely strip the output; that is, remove  the  symbol  table
              and relocation information.

       -x     Strips the non-global symbols; only saves external symbols.

              This  option  overlaps  with  a compiler option.  If you use the
              compiler driver cc(1) to invoke ld_classic, invoke  this  option
              in this way: -Wl,-x.

       -S     Strip debugging symbols; only save local and global symbols.

       -X     Strip  local  symbols whose names begin with `L'; save all other
              symbols.  (The compiler  and  assembler  currently  strip  these
              internally-generated labels by default, so they generally do not
              appear in object files seen by the link editor.)

       -Sp    Strip, edit and add debugging symbols so the debugger  can  used
              most of the debugging symbols from the object files.

       -Si    Strip  duplicate  debugging symbols from include files.  This is
              the default.

       -b     Strip the base file's symbols from the output file.   (The  base
              file is given as the argument to the -A option.)

              This  option  overlaps  with  a compiler option.  If you use the
              compiler driver cc(1) to invoke ld_classic, invoke  this  option
              in this way: -Wl,-b.

       -Sn    Don't strip any symbols.

       -exported_symbols_list filename
              The  specified  filename  contains  lists of global symbol names
              that will remain as global symbols  in  the  output  file.   All
              other  global  symbols will be treated as if they were marked as
              __private_extern__ and will not be global in  the  output  file.
              The  symbol names listed in filename must be one per line. Lead-
              ing and trailing white space are not part of  the  symbol  name.
              Lines  starting with # are ignored, as are lines with only white
              space.

       -unexported_symbols_list filename
              The specified filename contains lists  of  global  symbol  names
              that  will not remain as global symbols in the output file.  The
              symbols will be  treated  as  if  they  were  marked  as  __pri-
              vate_extern__  and  will  not  be global in the output file. The
              symbol names listed in filename must be one  per  line.  Leading
              and trailing white space are not part of the symbol name.  Lines
              starting with # are ignored, as are lines with only white space.

       -no_uuid
              Do not emit an LC_UUID load command in the linked output file.


       -dead_strip
              Remove blocks of code and data that are unreachable by the entry
              point or exported symbols.

       -no_dead_strip_inits_and_terms
              When specified along with -dead_strip cause all constructors and
              destructors to never be dead stripped.


       The remaining options are infrequently used:

       -v     Print the version of the linker.

       -w     Suppresses all warning messages.

       -no_arch_warnings
              Suppresses  warning  messages  about  files  that have the wrong
              architecture for the -arch flag.

       -arch_errors_fatal
              Cause the errors having to do with files  that  have  the  wrong
              architecture to be fatal and stop the link editor.

       -M     Produce  a load map, listing all the segments and sections.  The
              list includes  the  address  where  each  input  file's  section
              appears in the output file, as well as the section's size.

              This  option  overlaps  with  a compiler option.  If you use the
              compiler driver cc(1) to invoke ld_classic, invoke  this  option
              in this way: -Wl,-M.

       -whatsloaded
              Display  a  single line listing each object file that is loaded.
              Names of objects in archives have the form libfoo.a(bar.o).

       -filelist listfile[,dirname]
              Specifies that the linker should link the files listed in  list-
              file  .  This is an alternative to listing the files on the com-
              mand line. The file names are listed one per line separated only
              by newlines. (Spaces and tabs are assumed to be part of the file
              name.)  If the optional directory name, dirname is specified, it
              is prepended to each name in the list file.

       -headerpad value
              Specifies  the minimum amount of space ("padding") following the
              headers for the MH_EXECUTE format and all output file types with
              the dynamic linker.  value is a hexadecimal number.  When a seg-
              ment's size is rounded up to the  segment  alignment,  there  is
              extra  space  left over, which is placed between the headers and
              the sections, rather than at the end of the segment.  The  head-
              erpad  option  specifies the minimum size of this padding, which
              can be useful if the headers will be altered later.  The default
              value is the larger of 2 * sizeof(struct section) so the program
              /usr/bin/objcunique can always add two section  headers,  or  if
              the output is an MH_EXECUTE filetype and -prebind is specified 3
              times the size of  the  LC_PREBOUND_DYLIB  load  commands.   The
              actual amount of pad will be as large as the amount of the first
              segment's round-off.  (That is, take the total size of the first
              segments'  headers and non-zerofill sections, round this size up
              to the segment alignment, and use  the  difference  between  the
              rounded and unrounded sizes as the minimum amount of padding.)

       -headerpad_max_install_names
              Add  to  the  header  padding enough space to allow changing all
              dynamic shared library paths recorded in the output file  to  be
              changed to MAXPATHLEN in length.

       -t     Trace  the progress of the link editor; display the name of each
              file that is loaded as it is processed in the first  and  second
              pass of the link editor.

       -A basefile
              Incremental loading: linking is to be done in a manner that lets
              the resulting object be read into an already executing  program,
              the basefile.  basefile is the name of a file whose symbol table
              will be taken as a basis on which to define additional  symbols.
              Only  newly linked material will be entered into the a.out file,
              but the new symbol table will reflect every  symbol  defined  in
              the  base file and the newly linked files.  Option(s) to specify
              the addresses of the segments are typically  needed,  since  the
              default  addresses  tend  to  overlap  with  the  basefile.  The
              default format of the object file is  MH_OBJECT.   Note:  It  is
              strongly  recommended  that this option NOT be used, because the
              dyld package described in dyld(3) is a much easier  alternative.

       -dylib_install_name name
              For dynamic shared library files, specifies the name of the file
              the library will be installed in for programs that use  it.   If
              this  is not specified, the name specified in the -o name option
              will  be  used.   This  option  is  used   as   the   libtool(1)
              -install_name name option when its -dynamic option is specified.

       -umbrella framework_name
              Specifies this is a subframework  where  framework_name  is  the
              name  of  the umbrella framework this subframework is a part of.
              Where framework_name is the same as the argument to the  -frame-
              work  framework_name option.  This subframework can then only be
              linked into the umbrella framework with the same  framework_name
              or  another  subframework with the same umbrella framework name.
              Any other attempt to statically link this subframework  directly
              will result in an error stating to link with the umbrella frame-
              work instead.  When building the umbrella  framework  that  uses
              this  subframework  no additional options are required.  However
              the install name of the umbrella framework, required to be spec-
              ified  with -dylib_install_name, must have the proper format for
              an install name of a framework for  the  framework_name  of  the
              umbrella framework to be determined.

       -allowable_client client_name
              Specifies  that  for  this subframework the client_name can link
              with this subframework without error even though it is not  part
              of  the  umbrella  framework  that this subframework is part of.
              The client_name can be another framework name or a name used  by
              bundles (see the -client_name client_name option below).

       -client_name client_name
              Specifies  the client_name of a bundle for checking of allowable
              clients of subframeworks (see the -allowable_client  client_name
              option above).

       -sub_umbrella framework_name
              Specifies  that  the  framework_name  being  linked by a dynamic
              library is to be  treated  as  one  of  the  subframeworks  with
              respect to twolevel namespace.

       -sub_library library_name
              Specifies  that  the  library_name  being  linked  by  a dynamic
              library is to be treated as one of the sublibraries with respect
              to   twolevel  namespace.   For  example  the  library_name  for
              /usr/lib/libobjc_profile.A.dylib would be libobjc.

       -init sym
              The argument sym is taken to be the symbol name of  the  dynamic
              shared  library  initialization  routine.  If any module is used
              from the dynamic library the library initialization  routine  is
              called  before any symbol is used from the library including C++

       -run_init_lazily
              This option is obsolete.

       -dylib_compatibility_version number
              For dynamic shared library files, this specifies the compatibil-
              ity  version number of the library.  When a library is used by a
              program, the compatibility version is checked and  if  the  pro-
              gram's  version  is greater that the library's version, it is an
              error.  The format of number is X[.Y[.Z]] where X must be a pos-
              itive non-zero number less than or equal to 65535, and .Y and .Z
              are optional and if present must be  non-negative  numbers  less
              than  or  equal  to 255.  If the compatibility version number is
              not specified, it has a value of 0 and no checking is done  when
              the  library  is  used.   This  option is used as the libtool(1)
              -compatibility_version number option when its -dynamic option is
              set.

       -dylib_current_version number
              For  dynamic shared library files, specifies the current version
              number of the library.  The current version of the  library  can
              be  obtained  programmatically  by the user of the library so it
              can determine exactly which version of the library it is  using.
              The  format  of  number  is X[.Y[.Z]] where X must be a positive
              non-zero number less than or equal to 65535, and .Y and  .Z  are
              optional  and  if present must be non-negative numbers less than
              or equal to 255.  If the version number is not specified, it has
              a  value  of  0.   This  option  is used as the libtool(1) -cur-
              rent_version number option when its -dynamic option is set.

       -single_module
              When building a dynamic library build the  library  so  that  it
              contains only one module.

       -multi_module
              When  building  a  dynamic  library build the library so that it
              contains one module for each object file linked in.  This is the
              default.

       -dylinker_install_name name
              For  dynamic  link  editor files, specifies the name of the file
              the dynamic link editor will be installed in for  programs  that
              use it.

       -macosx_version_min version
              This overrides the MACOSX_DEPLOYMENT_TARGET environment variable
              (see below).  Unlike other linker options, this one may be spec-
              ified multiple times; only the last occurrence is effective.

       The following environment variable is used to control the use of incom-
       patible features in the output with respect to Mac OS X releases.

       MACOSX_DEPLOYMENT_TARGET
              This is set to indicate the oldest Mac OS X  version  that  that
              the output is to be used on.  When this is set to a release that
              is older than the current release features that are incompatible
              with that release will be disabled.  If a feature is seen in the
              input that can't be in the output due to this setting a  warning
              is issued.  The current allowable values for this are 10.1, 10.2
              10.3, and 10.4 with the default being 10.4 for the  i386  archi-
              tecture and 10.1 for all other architectures.

       The following environment variables are used by Apple's Build and Inte-
       gration team:

       LD_TRACE_ARCHIVES
              When this is set it causes a message of the form ``[Logging  for
              XBS]  Used  static  archive:  filename'' for each static archive
              that has members linked into the output.

       LD_TRACE_DYLIBS
              When this is set it causes a message of the form ``[Logging  for
              XBS]  Used  dynamic library: filename'' for each dynamic library
              linked into the output.

       RC_TRACE_PREBINDING_DISABLED
              When this is set it causes a message of the form ``[Logging  for
              XBS  prebinding  disabled  for filename because reason''.  Where
              filename is the value of the -final_output argument if specified
              or the value of the -o argument.

       -final_output filename
              The  argument  filename  is  used  in  the  above  message  when
              RC_TRACE_PREBINDING_DISABLED is set.

       LD_TRACE_FILE
              When this is set, messages displayed  due  to  the  LD_TRACE_AR-
              CHIVES  ,  LD_TRACE_DYLIBS  ,  and  LD_TRACE_PREBINDING_DISABLED
              environment variables are printed to  the  file  whose  path  is
              specified by this variable instead of stdout.

       LD_SPLITSEGS_NEW_LIBRARIES
              When  set and MACOSX_DEPLOYMENT_TARGET is set to 10.4 or greater
              and the output is a dynamic library, and if the install name  of
              the  library is not listed the segment address table, and if the
              environment variable LD_UNPREBOUND_LIBRARIES is set with a  file
              name  with  a list of library install names and the install name
              is not listed, then this is built as a split shared library.


       Options available in early versions of the Mach-O link  editor  may  no
       longer be supported.



FILES

       /lib/lib*.{a,dylib}                        libraries
       /usr/lib/lib*.{a,dylib}
       /usr/local/lib/lib*.{a,dylib}
       /Library/Frameworks/*.framework/*          framework libraries
       /Network/Library/Frameworks/*.framework/*  framework libraries
       /System/Library/Frameworks/*.framework/*   framework libraries
       a.out                                      output file


SEE ALSO

       as(1),  ar(1),  cc(1),  libtool(1), ranlib(1), nm(1), otool(1) lipo(1),
       ld(1), arch(3), dyld(3), Mach-O(5), strip(1), redo_prebinding(1)



Apple Computer, Inc.            August 4, 2006                   ld_classic(1)

Mac OS X 10.6 - Generated Thu Sep 17 20:07:59 CDT 2009
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