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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | SEE ALSO | COPYRIGHT | COLOPHON |
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NM(1) GNU Development Tools NM(1)
nm - list symbols from object files
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]
[--ifunc-chars=CHARS]
[-j|--format=just-symbols]
[-l|--line-numbers] [--inlines]
[-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]
[-U|--defined-only]
[-V|--version]
[-W|--no-weak]
[-X 32_64]
[--no-demangle]
[--no-recurse-limit|--recurse-limit]]
[--plugin name]
[--size-sort]
[--special-syms]
[--synthetic]
[--target=bfdname]
[--unicode=method]
[--with-symbol-versions]
[--without-symbol-versions]
[objfile...]
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 BSS data section. This section
typically contains zero-initialized or uninitialized
data, although the exact behavior is system dependent.
"C"
"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.
The lower case c character is used when the symbol is in
a special section for small commons.
"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.
Note - the actual symbols display for GNU indirect
symbols is controlled by the --ifunc-chars command line
option. If this option has been provided then the first
character in the string will be used for global indirect
function symbols. If the string contains a second
character then that will be used for local indirect
function symbols.
"I" The symbol is an indirect reference to another symbol.
"N" The symbol is a debugging symbol.
"n" The symbol is in a non-data, non-code, non-debug read-
only section.
"p" The symbol 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 or zero-initialized
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.
• The symbol name. If a symbol has version information
associated with it, then the version information is displayed
as well. If the versioned symbol is undefined or hidden from
linker, the version string is displayed as a suffix to the
symbol name, preceded 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 preceded by two @ characters. For
example foo@@VER_2.
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 infinite 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 2048 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",
"posix" or "just-symbols". 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.
--ifunc-chars=CHARS
When display GNU indirect function symbols nm will default to
using the "i" character for both local indirect functions and
global indirect functions. The --ifunc-chars option allows
the user to specify a string containing one or two
characters. The first character will be used for global
indirect function symbols and the second character, if
present, will be used for local indirect function symbols.
j The same as --format=just-symbols.
-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). By default both defined and undefined symbols are
displayed.
-U
--defined-only
Display only defined symbols for each object file. By
default both defined and undefined symbols are displayed.
-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.
--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.
Note - this option does not work if --undefined-only has been
enabled as undefined symbols have no size.
--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.
--unicode=[default|invalid|locale|escape|hex|highlight]
Controls the display of UTF-8 encoded multibyte 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.
-W
--no-weak
Do not display weak symbols.
--with-symbol-versions
--without-symbol-versions
Enables or disables the display of symbol version
information. The version string is displayed as a suffix to
the symbol name, preceded 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 preceded by two @ characters. For
example foo@@VER_2. By default, symbol version information
is displayed.
--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.
ar(1), objdump(1), ranlib(1), and the Info entries for binutils.
Copyright (c) 1991-2024 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".
This page is part of the binutils (a collection of tools for
working with executable binaries) project. Information about the
project can be found at ⟨http://www.gnu.org/software/binutils/⟩.
If you have a bug report for this manual page, see
⟨http://sourceware.org/bugzilla/enter_bug.cgi?product=binutils⟩.
This page was obtained from the tarball binutils-2.42.tar.gz
fetched from ⟨https://ftp.gnu.org/gnu/binutils/⟩ on 2024-06-14.
If you discover any rendering problems in this HTML version of
the page, or you believe there is a better or more up-to-date
source for the page, or you have corrections or improvements to
the information in this COLOPHON (which is not part of the
original manual page), send a mail to [email protected]
binutils-2.42 2024-06-14 NM(1)
Pages that refer to this page: ar(1), ld(1), objdump(1), ranlib(1), strings(1), elf(5)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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