NM(1) - phpMan

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:

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 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 the read-only data 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.

o 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.

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 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).

-U [d|i|l|e|x|h]
--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.

-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
--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.

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-2.38 2024-01-23 NM(1)

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