NMEDIT(1)

💖 NAME 💖

okay so bestie, this whole page is about nmedit(1) — the iconic little tool that changes global symbols to local symbols. no cap, that's literally the name vibe. 💅

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✨ SYNOPSIS ✨

here's the syntax, copy it exactly because we do not freestyle flags in this house:

nmedit -s list_file [-R list_file] [-p] [-A] [-] [[-arch arch_type] ...]
       object_file ... [-o output]

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🦋 DESCRIPTION 🦋

so nmedit takes the global symbols that are not listed in the list_file file you pass to the -s list_file option and turns them into static symbols. Undefined symbols and common symbols are not affected, and they shouldn't be listed in list_file — leave them out of the group chat, bestie. 🫶

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. slay, internal consistency ✨

nmedit differs from strip(1) in that it also changes the symbolic debugging information (produced 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. yes, she edits the debug info too — the debugger is still invited to the party. 🎀

nmedit is like strip(1) in that it's 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. interface boundaries? we love to see it.

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. iykyk 💛

Another example is an object that is made up of a number of other objects that will be loaded into an executable — it would be 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. literally surgical. 🧚

okay so one or more of the following options is required for nmedit(1) — required, not optional, bestie:

💅 the required options

• -s filename — Leave the symbol table entries for the global symbols listed in filename global (yep, keep those listed ones 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. drama, but organized. 💅
• -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.

and the other nmedit(1) options are:

🎀 the other options

• -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. runtime loading besties, this one's for you.
• -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. iconic little dash behavior.
• -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 known 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.

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🌈 SEE ALSO 🌈

go give these a read too, bestie: strip(1), ld(1), libtool(1), arch(3). ✨

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💀 BUGS 💀

warning warning warning: 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. fr fr, do not treat this as a flawless queen — debugger chaos is on the table. 😭💀

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okay that's the whole vibe — source/version energy: Apple Inc., dated May 29, 2007, for the NMEDIT(1) page. 💅✨