File: binutils.info, Node: nm, Next: objcopy, Prev: ar, Up: Top
2 nm
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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...]
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. For more details on
common symbols, see the discussion of -warn-common in *note
Linker options: (ld.info)Options.
'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.
* The symbol name.
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. *Note c++filt::, for more information on demangling.
'--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. *Note Target Selection::, for more information.
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