wisejohn
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buildtool


			
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<a name="nm"></a>
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<p>
Next: <a href="objcopy.html#objcopy" accesskey="n" rel="next">objcopy</a>, Previous: <a href="ar.html#ar" accesskey="p" rel="prev">ar</a>, Up: <a href="index.html#Top" accesskey="u" rel="up">Top</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Binutils-Index.html#Binutils-Index" title="Index" rel="index">Index</a>]</p>
</div>
<hr>
<a name="nm-1"></a>
<h2 class="chapter">2 nm</h2>
<a name="index-symbols"></a>
<a name="index-nm"></a>


<div class="smallexample">
<pre class="smallexample">nm [<samp>-A</samp>|<samp>-o</samp>|<samp>--print-file-name</samp>] [<samp>-a</samp>|<samp>--debug-syms</samp>]
   [<samp>-B</samp>|<samp>--format=bsd</samp>] [<samp>-C</samp>|<samp>--demangle</samp>[=<var>style</var>]]
   [<samp>-D</samp>|<samp>--dynamic</samp>] [<samp>-f</samp><var>format</var>|<samp>--format=</samp><var>format</var>]
   [<samp>-g</samp>|<samp>--extern-only</samp>] [<samp>-h</samp>|<samp>--help</samp>]
   [<samp>--ifunc-chars=<var>CHARS</var></samp>]
   [<samp>-l</samp>|<samp>--line-numbers</samp>] [<samp>--inlines</samp>]
   [<samp>-n</samp>|<samp>-v</samp>|<samp>--numeric-sort</samp>]
   [<samp>-P</samp>|<samp>--portability</samp>] [<samp>-p</samp>|<samp>--no-sort</samp>]
   [<samp>-r</samp>|<samp>--reverse-sort</samp>] [<samp>-S</samp>|<samp>--print-size</samp>]
   [<samp>-s</samp>|<samp>--print-armap</samp>] [<samp>-t</samp> <var>radix</var>|<samp>--radix=</samp><var>radix</var>]
   [<samp>-u</samp>|<samp>--undefined-only</samp>] [<samp>-V</samp>|<samp>--version</samp>]
   [<samp>-X 32_64</samp>] [<samp>--defined-only</samp>] [<samp>--no-demangle</samp>]
   [<samp>--plugin</samp> <var>name</var>]
   [<samp>--no-recurse-limit</samp>|<samp>--recurse-limit</samp>]]
   [<samp>--size-sort</samp>] [<samp>--special-syms</samp>]
   [<samp>--synthetic</samp>] [<samp>--target=</samp><var>bfdname</var>]
   [<var>objfile</var>&hellip;]
</pre></div>

<p><small>GNU</small> <code>nm</code> lists the symbols from object files <var>objfile</var>&hellip;.
If no object files are listed as arguments, <code>nm</code> assumes the file
<samp>a.out</samp>.
</p>
<p>For each symbol, <code>nm</code> shows:
</p>
<ul>
<li> The symbol value, in the radix selected by options (see below), or
hexadecimal by default.

</li><li> 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 (<code>u</code>, <code>v</code> and <code>w</code>).

<dl compact="compact">
<dt><code>A</code></dt>
<dd><p>The symbol&rsquo;s value is absolute, and will not be changed by further
linking.
</p>
</dd>
<dt><code>B</code></dt>
<dt><code>b</code></dt>
<dd><p>The symbol is in the BSS data section.  This section typically
contains zero-initialized or uninitialized data, although the exact
behavior is system dependent.
</p>
</dd>
<dt><code>C</code></dt>
<dt><code>c</code></dt>
<dd><p>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
&ndash;warn-common in <a href="http://sourceware.org/binutils/docs/ld/Options.html#Options">Linker options</a> in <cite>The GNU linker</cite>.
The lower case <var>c</var> character is used when the symbol is in a
special section for small commons.
</p>
</dd>
<dt><code>D</code></dt>
<dt><code>d</code></dt>
<dd><p>The symbol is in the initialized data section.
</p>
</dd>
<dt><code>G</code></dt>
<dt><code>g</code></dt>
<dd><p>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.
</p>
</dd>
<dt><code>i</code></dt>
<dd><p>For PE format files this indicates that the symbol is in a section
specific to the implementation of DLLs.
</p>
<p>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.
</p>
<p>Note - the actual symbols display for GNU indirect symbols is
controlled by the <samp>--ifunc-chars</samp> 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.
</p>
</dd>
<dt><code>I</code></dt>
<dd><p>The symbol is an indirect reference to another symbol.
</p>
</dd>
<dt><code>N</code></dt>
<dd><p>The symbol is a debugging symbol.
</p>
</dd>
<dt><code>n</code></dt>
<dd><p>The symbol is in the read-only data section.
</p>
</dd>
<dt><code>p</code></dt>
<dd><p>The symbol is in a stack unwind section.
</p>
</dd>
<dt><code>R</code></dt>
<dt><code>r</code></dt>
<dd><p>The symbol is in a read only data section.
</p>
</dd>
<dt><code>S</code></dt>
<dt><code>s</code></dt>
<dd><p>The symbol is in an uninitialized or zero-initialized data section
for small objects.
</p>
</dd>
<dt><code>T</code></dt>
<dt><code>t</code></dt>
<dd><p>The symbol is in the text (code) section.
</p>
</dd>
<dt><code>U</code></dt>
<dd><p>The symbol is undefined.
</p>
</dd>
<dt><code>u</code></dt>
<dd><p>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.
</p>
</dd>
<dt><code>V</code></dt>
<dt><code>v</code></dt>
<dd><p>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.
</p>
</dd>
<dt><code>W</code></dt>
<dt><code>w</code></dt>
<dd><p>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.
</p>
</dd>
<dt><code>-</code></dt>
<dd><p>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.
</p>
</dd>
<dt><code>?</code></dt>
<dd><p>The symbol type is unknown, or object file format specific.
</p></dd>
</dl>

</li><li> 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
&lsquo;<samp>foo@VER_1</samp>&rsquo;.  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 &lsquo;<samp>foo@@VER_2</samp>&rsquo;.
</li></ul>


<p>The long and short forms of options, shown here as alternatives, are
equivalent.
</p>
<dl compact="compact">
<dt><code>-A</code></dt>
<dt><code>-o</code></dt>
<dt><code>--print-file-name</code></dt>
<dd><a name="index-input-file-name"></a>
<a name="index-file-name"></a>
<a name="index-source-file-name"></a>
<p>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.
</p>
</dd>
<dt><code>-a</code></dt>
<dt><code>--debug-syms</code></dt>
<dd><a name="index-debugging-symbols"></a>
<p>Display all symbols, even debugger-only symbols; normally these are not
listed.
</p>
</dd>
<dt><code>-B</code></dt>
<dd><a name="index-nm-format"></a>
<a name="index-nm-compatibility"></a>
<p>The same as <samp>--format=bsd</samp> (for compatibility with the MIPS <code>nm</code>).
</p>
</dd>
<dt><code>-C</code></dt>
<dt><code>--demangle[=<var>style</var>]</code></dt>
<dd><a name="index-demangling-in-nm"></a>
<p>Decode (<em>demangle</em>) 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. See <a href="c_002b_002bfilt.html#c_002b_002bfilt">c++filt</a>,
for more information on demangling.
</p>
</dd>
<dt><code>--no-demangle</code></dt>
<dd><p>Do not demangle low-level symbol names.  This is the default.
</p>
</dd>
<dt><code>--recurse-limit</code></dt>
<dt><code>--no-recurse-limit</code></dt>
<dt><code>--recursion-limit</code></dt>
<dt><code>--no-recursion-limit</code></dt>
<dd><p>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.
</p>
<p>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.
</p>
</dd>
<dt><code>-D</code></dt>
<dt><code>--dynamic</code></dt>
<dd><a name="index-dynamic-symbols"></a>
<p>Display the dynamic symbols rather than the normal symbols.  This is
only meaningful for dynamic objects, such as certain types of shared
libraries.
</p>
</dd>
<dt><code>-f <var>format</var></code></dt>
<dt><code>--format=<var>format</var></code></dt>
<dd><a name="index-nm-format-1"></a>
<a name="index-nm-compatibility-1"></a>
<p>Use the output format <var>format</var>, which can be <code>bsd</code>,
<code>sysv</code>, or <code>posix</code>.  The default is <code>bsd</code>.
Only the first character of <var>format</var> is significant; it can be
either upper or lower case.
</p>
</dd>
<dt><code>-g</code></dt>
<dt><code>--extern-only</code></dt>
<dd><a name="index-external-symbols"></a>
<p>Display only external symbols.
</p>
</dd>
<dt><code>-h</code></dt>
<dt><code>--help</code></dt>
<dd><p>Show a summary of the options to <code>nm</code> and exit.
</p>
</dd>
<dt><code>--ifunc-chars=<var>CHARS</var></code></dt>
<dd><p>When display GNU indirect function symbols <code>nm</code> will default
to using the <code>i</code> character for both local indirect functions and
global indirect functions.  The <samp>--ifunc-chars</samp> 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.
</p>
</dd>
<dt><code>-l</code></dt>
<dt><code>--line-numbers</code></dt>
<dd><a name="index-symbol-line-numbers"></a>
<p>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.
</p>
</dd>
<dt><code>--inlines</code></dt>
<dd><a name="index-objdump-inlines"></a>
<p>When option <samp>-l</samp> 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 <code>main</code> inlines
<code>callee1</code> which inlines <code>callee2</code>, and address is from
<code>callee2</code>, the source information for <code>callee1</code> and <code>main</code>
will also be printed.
</p>
</dd>
<dt><code>-n</code></dt>
<dt><code>-v</code></dt>
<dt><code>--numeric-sort</code></dt>
<dd><p>Sort symbols numerically by their addresses, rather than alphabetically
by their names.
</p>
</dd>
<dt><code>-p</code></dt>
<dt><code>--no-sort</code></dt>
<dd><a name="index-sorting-symbols"></a>
<p>Do not bother to sort the symbols in any order; print them in the order
encountered.
</p>
</dd>
<dt><code>-P</code></dt>
<dt><code>--portability</code></dt>
<dd><p>Use the POSIX.2 standard output format instead of the default format.
Equivalent to &lsquo;<samp>-f posix</samp>&rsquo;.
</p>
</dd>
<dt><code>-r</code></dt>
<dt><code>--reverse-sort</code></dt>
<dd><p>Reverse the order of the sort (whether numeric or alphabetic); let the
last come first.
</p>
</dd>
<dt><code>-S</code></dt>
<dt><code>--print-size</code></dt>
<dd><p>Print both value and size of defined symbols for the <code>bsd</code> output style.
This option has no effect for object formats that do not record symbol
sizes, unless &lsquo;<samp>--size-sort</samp>&rsquo; is also used in which case a
calculated size is displayed.
</p>
</dd>
<dt><code>-s</code></dt>
<dt><code>--print-armap</code></dt>
<dd><a name="index-symbol-index_002c-listing"></a>
<p>When listing symbols from archive members, include the index: a mapping
(stored in the archive by <code>ar</code> or <code>ranlib</code>) of which modules
contain definitions for which names.
</p>
</dd>
<dt><code>-t <var>radix</var></code></dt>
<dt><code>--radix=<var>radix</var></code></dt>
<dd><p>Use <var>radix</var> as the radix for printing the symbol values.  It must be
&lsquo;<samp>d</samp>&rsquo; for decimal, &lsquo;<samp>o</samp>&rsquo; for octal, or &lsquo;<samp>x</samp>&rsquo; for hexadecimal.
</p>
</dd>
<dt><code>-u</code></dt>
<dt><code>--undefined-only</code></dt>
<dd><a name="index-external-symbols-1"></a>
<a name="index-undefined-symbols"></a>
<p>Display only undefined symbols (those external to each object file).
</p>
</dd>
<dt><code>-V</code></dt>
<dt><code>--version</code></dt>
<dd><p>Show the version number of <code>nm</code> and exit.
</p>
</dd>
<dt><code>-X</code></dt>
<dd><p>This option is ignored for compatibility with the AIX version of
<code>nm</code>.  It takes one parameter which must be the string
<samp>32_64</samp>.  The default mode of AIX <code>nm</code> corresponds
to <samp>-X 32</samp>, which is not supported by <small>GNU</small> <code>nm</code>.
</p>
</dd>
<dt><code>--defined-only</code></dt>
<dd><a name="index-external-symbols-2"></a>
<a name="index-undefined-symbols-1"></a>
<p>Display only defined symbols for each object file.
</p>
</dd>
<dt><code>--plugin <var>name</var></code></dt>
<dd><a name="index-plugins-1"></a>
<p>Load the plugin called <var>name</var> to add support for extra target
types.  This option is only available if the toolchain has been built
with plugin support enabled.
</p>
<p>If <samp>--plugin</samp> is not provided, but plugin support has been
enabled then <code>nm</code> iterates over the files in
<samp>${libdir}/bfd-plugins</samp> in alphabetic order and the first
plugin that claims the object in question is used.
</p>
<p>Please note that this plugin search directory is <em>not</em> the one
used by <code>ld</code>&rsquo;s <samp>-plugin</samp> option.  In order to make
<code>nm</code> use the  linker plugin it must be copied into the
<samp>${libdir}/bfd-plugins</samp> directory.  For GCC based compilations
the linker plugin is called <samp>liblto_plugin.so.0.0.0</samp>.  For Clang
based compilations it is called <samp>LLVMgold.so</samp>.  The GCC plugin
is always backwards compatible with earlier versions, so it is
sufficient to just copy the newest one.
</p>
</dd>
<dt><code>--size-sort</code></dt>
<dd><p>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 <code>bsd</code> output format is used
the size of the symbol is printed, rather than the value, and
&lsquo;<samp>-S</samp>&rsquo; must be used in order both size and value to be printed.
</p>
</dd>
<dt><code>--special-syms</code></dt>
<dd><p>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.
</p>
</dd>
<dt><code>--synthetic</code></dt>
<dd><p>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&rsquo;s original source code.
</p>
</dd>
<dt><code>--target=<var>bfdname</var></code></dt>
<dd><a name="index-object-code-format"></a>
<p>Specify an object code format other than your system&rsquo;s default format.
See <a href="Target-Selection.html#Target-Selection">Target Selection</a>, for more information.
</p>
</dd>
</dl>


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