nm - list symbols from object files at Linux.org

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NM(1) GNU Development Tools NM(1)

NAME
nm - list symbols from object files

DESCRIPTION
GNU nm lists the symbols from object files objfile.... If no object files are listed as arguments, nm assumes
the file a.out.

For each symbol, nm shows:

· The symbol value, in the radix selected by options (see below), or hexadecimal by default.

· The symbol type. At least the following types are used; others are, as well, depending on the object file
format. If lowercase, the symbol is usually local; if uppercase, the symbol is global (external). There
are however a few lowercase symbols that are shown for special global symbols ("u", "v" and "w").

"A" The symbol's value is absolute, and will not be changed by further linking.

"B"
"b" The symbol is in the uninitialized data section (known as BSS).

"C" The symbol is common. Common symbols are uninitialized data. When linking, multiple common symbols
may appear with the same name. If the symbol is defined anywhere, the common symbols are treated as
undefined references.

"D"
"d" The symbol is in the initialized data section.

"G"
"g" The symbol is in an initialized data section for small objects. Some object file formats permit more
efficient access to small data objects, such as a global int variable as opposed to a large global
array.

"i" For PE format files this indicates that the symbol is in a section specific to the implementation of
DLLs. For ELF format files this indicates that the symbol is an indirect function. This is a GNU
extension to the standard set of ELF symbol types. It indicates a symbol which if referenced by a
relocation does not evaluate to its address, but instead must be invoked at runtime. The runtime
execution will then return the value to be used in the relocation.

"I" The symbol is an indirect reference to another symbol.

"N" The symbol is a debugging symbol.
"U" The symbol is undefined.

"u" The symbol is a unique global symbol. This is a GNU extension to the standard set of ELF symbol
bindings. For such a symbol the dynamic linker will make sure that in the entire process there is
just one symbol with this name and type in use.

"V"
"v" The symbol is a weak object. When a weak defined symbol is linked with a normal defined symbol, the
normal defined symbol is used with no error. When a weak undefined symbol is linked and the symbol is
not defined, the value of the weak symbol becomes zero with no error. On some systems, uppercase
indicates that a default value has been specified.

"W"
"w" The symbol is a weak symbol that has not been specifically tagged as a weak object symbol. When a
weak defined symbol is linked with a normal defined symbol, the normal defined symbol is used with no
error. When a weak undefined symbol is linked and the symbol is not defined, the value of the symbol
is determined in a system-specific manner without error. On some systems, uppercase indicates that a
default value has been specified.

"-" The symbol is a stabs symbol in an a.out object file. In this case, the next values printed are the
stabs other field, the stabs desc field, and the stab type. Stabs symbols are used to hold debugging
information.

"?" The symbol type is unknown, or object file format specific.

· The symbol name.

OPTIONS
The long and short forms of options, shown here as alternatives, are equivalent.

-A
-o
--print-file-name
Precede each symbol by the name of the input file (or archive member) in which it was found, rather than
identifying the input file once only, before all of its symbols.

-a
--debug-syms
Display all symbols, even debugger-only symbols; normally these are not listed.

-B The same as --format=bsd (for compatibility with the MIPS nm).

-C
--demangle[=style]
Decode (demangle) low-level symbol names into user-level names. Besides removing any initial underscore
prepended by the system, this makes C++ function names readable. Different compilers have different
mangling styles. The optional demangling style argument can be used to choose an appropriate demangling
style for your compiler.

--no-demangle
Do not demangle low-level symbol names. This is the default.

-D
--dynamic
-h
--help
Show a summary of the options to nm and exit.

-l
--line-numbers
For each symbol, use debugging information to try to find a filename and line number. For a defined
symbol, look for the line number of the address of the symbol. For an undefined symbol, look for the line
number of a relocation entry which refers to the symbol. If line number information can be found, print
it after the other symbol information.

-n
-v
--numeric-sort
Sort symbols numerically by their addresses, rather than alphabetically by their names.

-p
--no-sort
Do not bother to sort the symbols in any order; print them in the order encountered.

-P
--portability
Use the POSIX.2 standard output format instead of the default format. Equivalent to -f posix.

-r
--reverse-sort
Reverse the order of the sort (whether numeric or alphabetic); let the last come first.

-S
--print-size
Print both value and size of defined symbols for the "bsd" output style. This option has no effect for
object formats that do not record symbol sizes, unless --size-sort is also used in which case a calculated
size is displayed.

-s
--print-armap
When listing symbols from archive members, include the index: a mapping (stored in the archive by ar or
ranlib) of which modules contain definitions for which names.

-t radix
--radix=radix
Use radix as the radix for printing the symbol values. It must be d for decimal, o for octal, or x for
hexadecimal.

-u
--undefined-only
Display only undefined symbols (those external to each object file).

-V
--version
Show the version number of nm and exit.

-X This option is ignored for compatibility with the AIX version of nm. It takes one parameter which must be
the string 32_64. The default mode of AIX nm corresponds to -X 32, which is not supported by GNU nm.

--special-syms
Display symbols which have a target-specific special meaning. These symbols are usually used by the
target for some special processing and are not normally helpful when included in the normal symbol lists.
For example for ARM targets this option would skip the mapping symbols used to mark transitions between
ARM code, THUMB code and data.

--synthetic
Include synthetic symbols in the output. These are special symbols created by the linker for various
purposes. They are not shown by default since they are not part of the binary's original source code.

--target=bfdname
Specify an object code format other than your system's default format.

@file
Read command-line options from file. The options read are inserted in place of the original @file option.
If file does not exist, or cannot be read, then the option will be treated literally, and not removed.

Options in file are separated by whitespace. A whitespace character may be included in an option by
surrounding the entire option in either single or double quotes. Any character (including a backslash)
may be included by prefixing the character to be included with a backslash. The file may itself contain
additional @file options; any such options will be processed recursively.

SEE ALSO
ar(1), objdump(1), ranlib(1), and the Info entries for binutils.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free
Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is
included in the section entitled "GNU Free Documentation License".

binutils-2.25 2014-12-23 NM(1)