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| |
| <h2 class="chapter">2 nm</h2> |
| |
| <p><a name="index-symbols-38"></a><a name="index-nm-39"></a> |
| <!-- man title nm list symbols from object files --> |
| |
| <pre class="smallexample"> <!-- man begin SYNOPSIS nm --> |
| nm [<samp><span class="option">-A</span></samp>|<samp><span class="option">-o</span></samp>|<samp><span class="option">--print-file-name</span></samp>] [<samp><span class="option">-a</span></samp>|<samp><span class="option">--debug-syms</span></samp>] |
| [<samp><span class="option">-B</span></samp>|<samp><span class="option">--format=bsd</span></samp>] [<samp><span class="option">-C</span></samp>|<samp><span class="option">--demangle</span></samp>[=<var>style</var>]] |
| [<samp><span class="option">-D</span></samp>|<samp><span class="option">--dynamic</span></samp>] [<samp><span class="option">-f</span></samp><var>format</var>|<samp><span class="option">--format=</span></samp><var>format</var>] |
| [<samp><span class="option">-g</span></samp>|<samp><span class="option">--extern-only</span></samp>] [<samp><span class="option">-h</span></samp>|<samp><span class="option">--help</span></samp>] |
| [<samp><span class="option">-l</span></samp>|<samp><span class="option">--line-numbers</span></samp>] [<samp><span class="option">--inlines</span></samp>] |
| [<samp><span class="option">-n</span></samp>|<samp><span class="option">-v</span></samp>|<samp><span class="option">--numeric-sort</span></samp>] |
| [<samp><span class="option">-P</span></samp>|<samp><span class="option">--portability</span></samp>] [<samp><span class="option">-p</span></samp>|<samp><span class="option">--no-sort</span></samp>] |
| [<samp><span class="option">-r</span></samp>|<samp><span class="option">--reverse-sort</span></samp>] [<samp><span class="option">-S</span></samp>|<samp><span class="option">--print-size</span></samp>] |
| [<samp><span class="option">-s</span></samp>|<samp><span class="option">--print-armap</span></samp>] [<samp><span class="option">-t</span></samp> <var>radix</var>|<samp><span class="option">--radix=</span></samp><var>radix</var>] |
| [<samp><span class="option">-u</span></samp>|<samp><span class="option">--undefined-only</span></samp>] [<samp><span class="option">-V</span></samp>|<samp><span class="option">--version</span></samp>] |
| [<samp><span class="option">-X 32_64</span></samp>] [<samp><span class="option">--defined-only</span></samp>] [<samp><span class="option">--no-demangle</span></samp>] |
| [<samp><span class="option">--plugin</span></samp> <var>name</var>] |
| [<samp><span class="option">--no-recurse-limit</span></samp>|<samp><span class="option">--recurse-limit</span></samp>]] |
| [<samp><span class="option">--size-sort</span></samp>] [<samp><span class="option">--special-syms</span></samp>] |
| [<samp><span class="option">--synthetic</span></samp>] [<samp><span class="option">--with-symbol-versions</span></samp>] [<samp><span class="option">--target=</span></samp><var>bfdname</var>] |
| [<var>objfile</var>...] |
| <!-- man end --> |
| </pre> |
| <!-- man begin DESCRIPTION nm --> |
| <p><span class="sc">gnu</span> <samp><span class="command">nm</span></samp> lists the symbols from object files <var>objfile</var><small class="dots">...</small>. |
| If no object files are listed as arguments, <samp><span class="command">nm</span></samp> assumes the file |
| <samp><span class="file">a.out</span></samp>. |
| |
| <p>For each symbol, <samp><span class="command">nm</span></samp> shows: |
| |
| <ul> |
| <li>The symbol value, in the radix selected by options (see below), or |
| hexadecimal by default. |
| |
| <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>). |
| |
| <!-- Some more detail on exactly what these symbol types are used for --> |
| <!-- would be nice. --> |
| <dl> |
| <dt><code>A</code><dd>The symbol's value is absolute, and will not be changed by further |
| linking. |
| |
| <br><dt><code>B</code><dt><code>b</code><dd>The symbol is in the BSS data section. This section typically |
| contains zero-initialized or uninitialized data, although the exact |
| behavior is system dependent. |
| |
| <br><dt><code>C</code><dd>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 <a href="../ld/Options.html#Options">Linker options</a>. |
| |
| <br><dt><code>D</code><dt><code>d</code><dd>The symbol is in the initialized data section. |
| |
| <br><dt><code>G</code><dt><code>g</code><dd>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. |
| |
| <br><dt><code>i</code><dd>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. |
| |
| <br><dt><code>I</code><dd>The symbol is an indirect reference to another symbol. |
| |
| <br><dt><code>N</code><dd>The symbol is a debugging symbol. |
| |
| <br><dt><code>n</code><dd>The symbol is in the read-only data section. |
| |
| <br><dt><code>p</code><dd>The symbol is in a stack unwind section. |
| |
| <br><dt><code>R</code><dt><code>r</code><dd>The symbol is in a read only data section. |
| |
| <br><dt><code>S</code><dt><code>s</code><dd>The symbol is in an uninitialized or zero-initialized data section |
| for small objects. |
| |
| <br><dt><code>T</code><dt><code>t</code><dd>The symbol is in the text (code) section. |
| |
| <br><dt><code>U</code><dd>The symbol is undefined. |
| |
| <br><dt><code>u</code><dd>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. |
| |
| <br><dt><code>V</code><dt><code>v</code><dd>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. |
| |
| <br><dt><code>W</code><dt><code>w</code><dd>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. |
| |
| <br><dt><code>-</code><dd>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. |
| |
| <br><dt><code>?</code><dd>The symbol type is unknown, or object file format specific. |
| </dl> |
| |
| <li>The symbol name. |
| </ul> |
| |
| <!-- man end --> |
| <!-- man begin OPTIONS nm --> |
| <p>The long and short forms of options, shown here as alternatives, are |
| equivalent. |
| |
| <dl> |
| <dt><samp><span class="env">-A</span></samp><dt><samp><span class="env">-o</span></samp><dt><samp><span class="env">--print-file-name</span></samp><dd><a name="index-input-file-name-40"></a><a name="index-file-name-41"></a><a name="index-source-file-name-42"></a>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. |
| |
| <br><dt><samp><span class="env">-a</span></samp><dt><samp><span class="env">--debug-syms</span></samp><dd><a name="index-debugging-symbols-43"></a>Display all symbols, even debugger-only symbols; normally these are not |
| listed. |
| |
| <br><dt><samp><span class="env">-B</span></samp><dd><a name="index-g_t_0040command_007bnm_007d-format-44"></a><a name="index-g_t_0040command_007bnm_007d-compatibility-45"></a>The same as <samp><span class="option">--format=bsd</span></samp> (for compatibility with the MIPS <samp><span class="command">nm</span></samp>). |
| |
| <br><dt><samp><span class="env">-C</span></samp><dt><samp><span class="env">--demangle[=</span><var>style</var><span class="env">]</span></samp><dd><a name="index-demangling-in-nm-46"></a>Decode (<dfn>demangle</dfn>) 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. |
| |
| <br><dt><samp><span class="env">--no-demangle</span></samp><dd>Do not demangle low-level symbol names. This is the default. |
| |
| <br><dt><samp><span class="env">--recurse-limit</span></samp><dt><samp><span class="env">--no-recurse-limit</span></samp><dt><samp><span class="env">--recursion-limit</span></samp><dt><samp><span class="env">--no-recursion-limit</span></samp><dd>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 2048 levels of nesting. |
| |
| <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. |
| |
| <br><dt><samp><span class="env">-D</span></samp><dt><samp><span class="env">--dynamic</span></samp><dd><a name="index-dynamic-symbols-47"></a>Display the dynamic symbols rather than the normal symbols. This is |
| only meaningful for dynamic objects, such as certain types of shared |
| libraries. |
| |
| <br><dt><samp><span class="env">-f </span><var>format</var></samp><dt><samp><span class="env">--format=</span><var>format</var></samp><dd><a name="index-g_t_0040command_007bnm_007d-format-48"></a><a name="index-g_t_0040command_007bnm_007d-compatibility-49"></a>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. |
| |
| <br><dt><samp><span class="env">-g</span></samp><dt><samp><span class="env">--extern-only</span></samp><dd><a name="index-external-symbols-50"></a>Display only external symbols. |
| |
| <br><dt><samp><span class="env">-h</span></samp><dt><samp><span class="env">--help</span></samp><dd>Show a summary of the options to <samp><span class="command">nm</span></samp> and exit. |
| |
| <br><dt><samp><span class="env">-l</span></samp><dt><samp><span class="env">--line-numbers</span></samp><dd><a name="index-symbol-line-numbers-51"></a>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. |
| |
| <br><dt><samp><span class="env">--inlines</span></samp><dd><a name="index-objdump-inlines-52"></a>When option <samp><span class="option">-l</span></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. |
| |
| <br><dt><samp><span class="env">-n</span></samp><dt><samp><span class="env">-v</span></samp><dt><samp><span class="env">--numeric-sort</span></samp><dd>Sort symbols numerically by their addresses, rather than alphabetically |
| by their names. |
| |
| <br><dt><samp><span class="env">-p</span></samp><dt><samp><span class="env">--no-sort</span></samp><dd><a name="index-sorting-symbols-53"></a>Do not bother to sort the symbols in any order; print them in the order |
| encountered. |
| |
| <br><dt><samp><span class="env">-P</span></samp><dt><samp><span class="env">--portability</span></samp><dd>Use the POSIX.2 standard output format instead of the default format. |
| Equivalent to ‘<samp><span class="samp">-f posix</span></samp>’. |
| |
| <br><dt><samp><span class="env">-r</span></samp><dt><samp><span class="env">--reverse-sort</span></samp><dd>Reverse the order of the sort (whether numeric or alphabetic); let the |
| last come first. |
| |
| <br><dt><samp><span class="env">-S</span></samp><dt><samp><span class="env">--print-size</span></samp><dd>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 ‘<samp><span class="samp">--size-sort</span></samp>’ is also used in which case a |
| calculated size is displayed. |
| |
| <br><dt><samp><span class="env">-s</span></samp><dt><samp><span class="env">--print-armap</span></samp><dd><a name="index-symbol-index_002c-listing-54"></a>When listing symbols from archive members, include the index: a mapping |
| (stored in the archive by <samp><span class="command">ar</span></samp> or <samp><span class="command">ranlib</span></samp>) of which modules |
| contain definitions for which names. |
| |
| <br><dt><samp><span class="env">-t </span><var>radix</var></samp><dt><samp><span class="env">--radix=</span><var>radix</var></samp><dd>Use <var>radix</var> as the radix for printing the symbol values. It must be |
| ‘<samp><span class="samp">d</span></samp>’ for decimal, ‘<samp><span class="samp">o</span></samp>’ for octal, or ‘<samp><span class="samp">x</span></samp>’ for hexadecimal. |
| |
| <br><dt><samp><span class="env">-u</span></samp><dt><samp><span class="env">--undefined-only</span></samp><dd><a name="index-external-symbols-55"></a><a name="index-undefined-symbols-56"></a>Display only undefined symbols (those external to each object file). |
| |
| <br><dt><samp><span class="env">-V</span></samp><dt><samp><span class="env">--version</span></samp><dd>Show the version number of <samp><span class="command">nm</span></samp> and exit. |
| |
| <br><dt><samp><span class="env">-X</span></samp><dd>This option is ignored for compatibility with the AIX version of |
| <samp><span class="command">nm</span></samp>. It takes one parameter which must be the string |
| <samp><span class="option">32_64</span></samp>. The default mode of AIX <samp><span class="command">nm</span></samp> corresponds |
| to <samp><span class="option">-X 32</span></samp>, which is not supported by <span class="sc">gnu</span> <samp><span class="command">nm</span></samp>. |
| |
| <br><dt><samp><span class="env">--defined-only</span></samp><dd><a name="index-external-symbols-57"></a><a name="index-undefined-symbols-58"></a>Display only defined symbols for each object file. |
| |
| <br><dt><samp><span class="env">--plugin </span><var>name</var></samp><dd><a name="index-plugins-59"></a>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>If <samp><span class="option">--plugin</span></samp> is not provided, but plugin support has been |
| enabled then <samp><span class="command">nm</span></samp> iterates over the files in |
| <samp><span class="file">${libdir}/bfd-plugins</span></samp> in alphabetic order and the first |
| plugin that claims the object in question is used. |
| |
| <p>Please note that this plugin search directory is <em>not</em> the one |
| used by <samp><span class="command">ld</span></samp>'s <samp><span class="option">-plugin</span></samp> option. In order to make |
| <samp><span class="command">nm</span></samp> use the linker plugin it must be copied into the |
| <samp><span class="file">${libdir}/bfd-plugins</span></samp> directory. For GCC based compilations |
| the linker plugin is called <samp><span class="file">liblto_plugin.so.0.0.0</span></samp>. For Clang |
| based compilations it is called <samp><span class="file">LLVMgold.so</span></samp>. The GCC plugin |
| is always backwards compatible with earlier versions, so it is |
| sufficient to just copy the newest one. |
| |
| <br><dt><samp><span class="env">--size-sort</span></samp><dd>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 |
| ‘<samp><span class="samp">-S</span></samp>’ must be used in order both size and value to be printed. |
| |
| <br><dt><samp><span class="env">--special-syms</span></samp><dd>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. |
| |
| <br><dt><samp><span class="env">--synthetic</span></samp><dd>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. |
| |
| <br><dt><samp><span class="env">--with-symbol-versions</span></samp><dd>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 ‘<samp><span class="samp">foo@VER_1</span></samp>’. 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 ‘<samp><span class="samp">foo@@VER_2</span></samp>’. |
| |
| <br><dt><samp><span class="env">--target=</span><var>bfdname</var></samp><dd><a name="index-object-code-format-60"></a>Specify an object code format other than your system's default format. |
| See <a href="Target-Selection.html#Target-Selection">Target Selection</a>, for more information. |
| |
| </dl> |
| |
| <!-- man end --> |
| </body></html> |
| |
