nmedit - change global symbols to local symbols
nmedit -s list_file [-R list_file] [-p] [-A] [-] [[-arch
arch_type] ...] object_file ... [-o output]
Nmedit changes the global symbols not listed in the
list_file file of the -s list_file option to static
symbols. Undefined symbols and common symbols are not affected and shouldn't
be listed in list_file. For dynamic libraries symbols are turned into
private extern symbols that are no longer external (rather than static
symbols). This is done so that the references between modules of a dynamic
library are resolved to the symbols in the dynamic library. Nmedit
differs from strip(1) in that it also changes the symbolic debugging
information (produce by the -g option to cc(1)) for the global
symbols it changes to static symbols so that the resulting object can still
be used with the debugger.
Nmedit like strip(1) is useful to limit the symbols
for use with later linking. This allows control of the interface that the
executable wants to provide to the objects that it will dynamically load,
and 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 shared libraries globals to be used would have its
symbol table edited with:
% nmedit -s interface_symbols -A executable
where the file interface_symbols would contain only those symbols from
the executable that it wishes the objects 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 have its symbol table
edited with:
% ld -o relocatable.o -r a.o b.o c.o
% nmedit -s interface_symbols relocatable.o
which would leave only the symbols listed in the file interface_symbols
(and the undefined and common symbols) as global symbols in the object file.
The one or more of the following options is required to
nmedit(1) is:
- -s filename
- Leave the symbol table entries for the global symbols listed in
filename global but turn all other global symbols (except undefined
and common symbols) into static symbols. 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
- Change the symbol table entries for the global symbols listed in
filename into static symbols. This file has the same format as the
-s filename option above. If the -R filename
option is specified without the -s filename option, then all
symbols not listed in the -R filename option's filename are
left as globals. If both a -R filename and a -s
filename are given the symbols listed in the -R filename
are basically ignored and only those symbols listed in the -s
filename are saved.
- -p
- Change symbols to private externs instead of static. This is allowed as
the only option to change all defined global symbols to private
externs.
The options to nmedit(1) are:
- -A
- Leave all global absolute symbols except those with a value of zero, and
save objective-C class symbols as globals. This is intended for use of
programs that load code at runtime and want the loaded code to use symbols
from the shared libraries.
- -D
- When editing a static library, set the archive's SYMDEF file's user id,
group id, date, and file mode to reasonable defaults. See the
libtool(1) documentation for -D for more information.
- -
- Treat all remaining arguments as file names and not options.
- -arch
arch_type
- Specifies the architecture, arch_type, of the file for
nmedit(1) to process when the file is a universal file (see
arch(3) for the currently know arch_types). The
arch_type can be all to process all architectures in the
file. The default is to process all architectures that are contained in
the file.
- -o output
- Write the result into the file output.
strip(1), ld(1), libtool(1), arch(3)
The changing of the symbolic debugging information by
nmedit is not known to be totally correct and could cause the
debugger to crash, get confused or produce incorrect information.