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 sym-bols. symbols.
bols.
strip no longer removes relocation entries under any condition. Instead, it updates the external
relocation entries (and indirect symbol 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 relocation 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 referenced 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 exe-cutable executable
cutable also must not be stripped. In this case, you should list the global symbols that the exe-cutable executable
cutable 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 symbols 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 num-ber number
ber 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 ta-ble. table.
ble.
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 relocatable objects to save symbols
referred to by external relocation 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
symbol 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 filename 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 directories.
-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 combina-tion combination
tion 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)
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