nm(1) [opendarwin man page]
NM(1) General Commands Manual NM(1) NAME
nm - display name list (symbol table) SYNOPSIS
nm [ -agnoprumxjlf [ s segname sectname ]] [ file ... ] DESCRIPTION
Nm displays the name list (symbol table) of each object file in the argument list. If an argument is an archive, a listing for each object file in the archive will be produced. File can be of the form libx.a(x.o), in which case only symbols from that member of the object file are listed. (The parentheses have to be quoted to get by the shell.) If no file is given, the symbols in a.out are listed. Each symbol name is preceded by its value (blanks if undefined). Unless the -m option is specified, this value is followed by one of the following characters, representing the symbol type: U (undefined), A (absolute), T (text section symbol), D (data section symbol), B (bss section symbol), C (common symbol), - (for debugger symbol table entries; see -a below), S (symbol in a section other than those above), or I (indirect symbol). If the symbol is local (non-external), the symbol's type is instead represented by the corresponding lowercase let- ter. A lower case u in a dynamic shared library indicates a undefined reference to a private external in another module in the same library. If the symbol is a Objective C method, the symbol name is +-[Class_name(category_name) method:name:], where `+' is for class methods, `-' is for instance methods, and (category_name) is present only when the method is in a category. The output is sorted alphabetically by default. Options are: -a Display all symbol table entries, including those inserted for use by debuggers. -g Display only global (external) symbols. -n Sort numerically rather than alphabetically. -o Prepend file or archive element name to each output line, rather than only once. -p Don't sort; display in symbol-table order. -r Sort in reverse order. -u Display only undefined symbols. -m Display the N_SECT type symbols (Mach-O symbols) as (segment_name, section_name) followed by either external or non-external and then the symbol name. Undefined, common, absolute and indirect symbols get displayed as (undefined), (common), (absolute), and (indirect), respectively. -x Display the symbol table entry's fields in hexadecimal, along with the name as a string. -j Just display the symbol names (no value or type). -s segname sectname List only those symbols in the section (segname,sectname). -l List a pseudo symbol .section_start if no symbol has as its value the starting address of the section. (This is used with the -s option above.) -arch arch_type Specifies the architecture, arch_type, of the file for nm(1) to operate on when the file is a fat file (see arch(3) for the cur- rently known arch_types). The arch_type can be "all" to operate on all architectures in the file. The default is to display the symbols from only the host architecture, if the file contains it; otherwise, symbols for all architectures in the file are dis- played. -f Display the symbol table of a dynamic library flat (as one file not separate modules). SEE ALSO
ar(1), ar(5), Mach-O(5), stab(5), nlist(3) BUGS
Displaying Mach-O symbols with -m is too verbose. Without the -m, symbols in the Objective C sections get displayed as an `s'. Apple Computer, Inc. October 23, 1997 NM(1)
Check Out this Related Man Page
STRIP(1) General Commands Manual 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 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 refer- enced 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 sym- bols 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 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 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 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 ALSO
ld(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)