NM(1) GNU Development Tools NM(1)
NAME
nm - list symbols from object files
SYNOPSIS
nm [-A|-o|--print-file-name] [-a|--debug-syms]
[-B|--format=bsd] [-C|--demangle[=style]]
[-D|--dynamic] [-fformat|--format=format]
[-g|--extern-only] [-h|--help]
[-l|--line-numbers] [--inlines]
[-U method] [--unicode=method]
[-n|-v|--numeric-sort]
[-P|--portability] [-p|--no-sort]
[-r|--reverse-sort] [-S|--print-size]
[-s|--print-armap] [-t radix|--radix=radix]
[-u|--undefined-only] [-V|--version]
[-X 32_64] [--defined-only] [--no-demangle]
[--plugin name]
[--no-recurse-limit|--recurse-limit]]
[--size-sort] [--special-syms]
[--synthetic] [--with-symbol-versions] [--target=bfdname]
[objfile...]
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:
o The symbol value, in the radix selected by options (see below), or
hexadecimal by default.
o 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.
"p" The symbols is in a stack unwind section.
"R"
"r" The symbol is in a read only data section.
"S"
"s" The symbol is in an uninitialized data section for small
objects.
"T"
"t" The symbol is in the text (code) section.
"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.
o 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.
--recurse-limit
--no-recurse-limit
--recursion-limit
--no-recursion-limit
Enables or disables a limit on the amount of recursion performed
whilst demangling strings. Since the name mangling formats allow
for an inifinite level of recursion it is possible to create
strings whose decoding will exhaust the amount of stack space
available on the host machine, triggering a memory fault. The
limit tries to prevent this from happening by restricting recursion
to 1024 levels of nesting.
The default is for this limit to be enabled, but disabling it may
be necessary in order to demangle truly complicated names. Note
however that if the recursion limit is disabled then stack
exhaustion is possible and any bug reports about such an event will
be rejected.
-D
--dynamic
Display the dynamic symbols rather than the normal symbols. This
is only meaningful for dynamic objects, such as certain types of
shared libraries.
-f format
--format=format
Use the output format format, which can be "bsd", "sysv", or
"posix". The default is "bsd". Only the first character of format
is significant; it can be either upper or lower case.
-g
--extern-only
Display only external symbols.
-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.
--inlines
When option -l is active, if the address belongs to a function that
was inlined, then this option causes the source information for all
enclosing scopes back to the first non-inlined function to be
printed as well. For example, if "main" inlines "callee1" which
inlines "callee2", and address is from "callee2", the source
information for "callee1" and "main" will also be printed.
-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).
-U [d|i|l|e|x|h]
--unicode=[default|invalid|locale|escape|hex|highlight]
Controls the display of UTF-8 encoded mulibyte characters in
strings. The default (--unicode=default) is to give them no
special treatment. The --unicode=locale option displays the
sequence in the current locale, which may or may not support them.
The options --unicode=hex and --unicode=invalid display them as hex
byte sequences enclosed by either angle brackets or curly braces.
The --unicode=escape option displays them as escape sequences
(\uxxxx) and the --unicode=highlight option displays them as escape
sequences highlighted in red (if supported by the output device).
The colouring is intended to draw attention to the presence of
unicode sequences where they might not be expected.
-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.
--defined-only
Display only defined symbols for each object file.
--plugin name
Load the plugin called name to add support for extra target types.
This option is only available if the toolchain has been built with
plugin support enabled.
If --plugin is not provided, but plugin support has been enabled
then nm iterates over the files in ${libdir}/bfd-plugins in
alphabetic order and the first plugin that claims the object in
question is used.
Please note that this plugin search directory is not the one used
by ld's -plugin option. In order to make nm use the linker plugin
it must be copied into the ${libdir}/bfd-plugins directory. For
GCC based compilations the linker plugin is called
liblto_plugin.so.0.0.0. For Clang based compilations it is called
LLVMgold.so. The GCC plugin is always backwards compatible with
earlier versions, so it is sufficient to just copy the newest one.
--size-sort
Sort symbols by size. For ELF objects symbol sizes are read from
the ELF, for other object types the symbol sizes are computed as
the difference between the value of the symbol and the value of the
symbol with the next higher value. If the "bsd" output format is
used the size of the symbol is printed, rather than the value, and
-S must be used in order both size and value to be printed.
--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.
--with-symbol-versions
Enables the display of symbol version information if any exists.
The version string is displayed as a suffix to the symbol name,
preceeded by an @ character. For example foo@VER_1. If the
version is the default version to be used when resolving
unversioned references to the symbol then it is displayed as a
suffix preceeded by two @ characters. For example foo@@VER_2.
--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.
COPYRIGHT
Copyright (c) 1991-2018 Free Software Foundation, Inc.
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-2.30 2024-11-15 NM(1)
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