STRIP(1)STRIP(1)NAMEstrip - remove symbols
SYNOPSISstrip [ option ] name ...
DESCRIPTIONstrip 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.
SEE ALSOld(1), cc(1)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. April 21, 2001 STRIP(1)
