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strip(1)                                                              strip(1)




NAME

       strip - remove symbols


SYNOPSIS

       strip [ option ] name ...


DESCRIPTION

       strip  removes  or  modifies the symbol table attached to the output of
       the assembler and link editor.  This is useful to save  space  after  a
       program has been debugged and to limit dynamically bound symbols.

       strip  no  longer  removes  relocation  entries  under  any  condition.
       Instead, it updates the external relocation entries (and indirect  sym-
       bol table entries) to reflect the resulting symbol table.  strip prints
       an error message for those symbols not in the  resulting  symbol  table
       that  are  needed by an external relocation entry or an indirect symbol
       table.  The link editor ld(1) is the only program that can strip  relo-
       cation entries and know if it is safe to do so.

       When  strip  is  used  with no options on an executable file, it checks
       that file to see if it uses the dynamic link editor.  If it  does,  the
       effect of the strip command is the same as using the -u and -r options.
       If the file does not use the dynamic link editor, the effect  of  strip
       without  any  options is the same as using the -s option of ld(1).  The
       options -S, -x, and -X have the same effect as the ld(1) options.   The
       options  to  strip(1)  can be combined to trim the symbol table to just
       what is desired.

       You should trim the symbol table of files used with dynamic linking  so
       that  only  those symbols intended to be external interfaces are saved.
       Files used with dynamic linking include executables, objects  that  are
       loaded  (usually  bundles),  and dynamic shared libraries.  Only global
       symbols are used by the dynamic linking process. You should  strip  all
       non-global symbols.

       When  an  executable  is  built  with  all its dependent dynamic shared
       libraries, it is typically stripped with:
              % strip -u -r executable
       which saves all undefined  symbols  (usually  defined  in  the  dynamic
       shared libraries) and all global symbols defined in the executable ref-
       erenced by the dynamic libraries (as marked by the static  link  editor
       when  the executable was built).  This is the maximum level of striping
       for an executable that will still allow the program  to  run  correctly
       with its libraries.

       If  the  executable loads objects, however, the global symbols that the
       objects reference from the executable also must not  be  stripped.   In
       this case, you should list the global symbols that the executable wants
       to allow the objects to reference in a file, and those  global  symbols
       are then saved when the executable is stripped. For example:
              % strip -u -r -s interface_symbols executable
       where  the  file interface_symbols would contain only those global sym-
       bols from the executable that the executable wants the  loaded  objects
       to have access to.

       For objects that will be loaded into an executable, you should trim the
       symbol table to limit the global symbols the executable will see.  This
       would be done with:
              % strip -s interface_symbols -u object
       which  would leave only the undefined symbols and symbols listed in the
       file interface_symbols in the object file.  In this case, strip(1)  has
       updated the relocation entries and indirect symbol table to reflect the
       new symbol table.

       For dynamic shared libraries, the maximum level of stripping is usually
       -x (to remove all non-global symbols).


STRIPPING FILES FOR USE WITH RUNTIME LOADED CODE

       Trimming the symbol table for programs that load code at runtime allows
       you to control the interface that the executable wants  to  provide  to
       the objects that it will load; it will not have to publish symbols that
       are not part of its interface.  For example, an executable that  wishes
       to  allow only a subset of its global symbols but all of the statically
       linked shared library's globals to be used would be stripped with:
              % strip -s interface_symbols -A executable
       where the file interface_symbols would contain only those symbols  from
       the executable that it wishes the code loaded at runtime to have access
       to.  Another example is an object that is made up of a number of  other
       objects  that  will  be  loaded into an executable would built and then
       stripped with:
              % ld -o relocatable.o -r a.o b.o c.o
              % strip -s interface_symbols -u relocatable.o
       which would leave only the undefined symbols and symbols listed in  the
       file  interface_symbols  in the object file.  In this case strip(1) has
       updated the relocation entries to reflect the new symbol table.


OPTIONS

       The first set of options indicate symbols that are to be  save  in  the
       resulting output file.

       -u     Save all undefined symbols.  This is intended for use with relo-
              catable objects to save symbols referred to by external  reloca-
              tion  entries.  Note that common symbols are also referred to by
              external relocation entries and this flag does  not  save  those
              symbols.

       -r     Save all symbols referenced dynamically.

       -s filename
              Save  the  symbol table entries for the global symbols listed in
              filename.  The symbol names listed in filename must be  one  per
              line.  Leading and trailing white space are not part of the sym-
              bol name.  Lines starting with # are ignored, as are lines  with
              only white space.

       -R filename
              Remove the symbol table entries for the global symbols listed in
              filename.  This file has the same  format  as  the  -s  filename
              option  above.   This option is usually used in combination with
              other options that save some symbols, -S, -x, etc.

       -i     Ignore symbols listed in the -s filename or -R filename  options
              that  are  not  in the files to be stripped (this is normally an
              error).

       -d filename
              Save the debugging symbol table entries  for  each  source  file
              name  listed in filename.  The source file names listed in file-
              name must be one per line with no other white space in the  file
              except  the  newlines on the end of each line.  And they must be
              just the base name of the source file without any leading direc-
              tories.

       -A     Save  all  global  absolute symbols except those with a value of
              zero, and save Objective C class symbols.  This is intended  for
              use  of  programs  that load code at runtime and want the loaded
              code to use symbols from the shared libraries (this is only used
              with NEXTSTEP 3.3 and earlier releases).

       -n     Save  all  N_SECT global symbols.  This is intended for use with
              executable programs in combination with -A to remove the symbols
              needed  for correct static link editing which are not needed for
              use with runtime loading interfaces where using the -s  filename
              would  be  too much trouble (this is only used with NEXTSTEP 3.3
              and earlier releases).

       These options specify symbols to be removed from the  resulting  output
       file.

       -S     Remove  the debugging symbol table entries (those created by the
              -g option to cc(1) and other compilers).

       -X     Remove the local symbols whose names begin with `L'.

       -x     Remove all local symbols (saving only global symbols).

       -c     Remove the section contents of a dynamic library creating a stub
              library output file.

       And the last options:

       -      Treat all remaining arguments as file names and not options.

       -o output
              Write the result into the file output.

       -no_uuid
              Remove any LC_UUID load commands.

       -arch arch_type
              Specifies  the architecture, arch_type, of the file for strip(1)
              to operate on when the file is a universal file.   (See  arch(3)
              for  the currently know arch_types.)  The arch_type can be "all"
              to operate on all  architectures  in  the  file,  which  is  the
              default.


SEE ALSO

       ld(1), cc(1)


EXAMPLES

       When creating a stub library the -c and -x are typically used:

              strip -x -c libfoo -o libfoo.stripped


LIMITATIONS

       Not every layout of a Mach-O file can be stripped by this program.  But
       all layouts produced by the Apple compiler system can be stripped.



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

Mac OS X 10.6 - Generated Thu Sep 17 20:09:16 CDT 2009
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