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<title>Using the GNU Compiler Collection (GCC): Function Names</title>
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<a name="Function-Names"></a>
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<p>
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Next: <a href="Return-Address.html#Return-Address" accesskey="n" rel="next">Return Address</a>, Previous: <a href="Incomplete-Enums.html#Incomplete-Enums" accesskey="p" rel="prev">Incomplete Enums</a>, Up: <a href="C-Extensions.html#C-Extensions" accesskey="u" rel="up">C Extensions</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p>
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<a name="Function-Names-as-Strings"></a>
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<h3 class="section">6.47 Function Names as Strings</h3>
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<a name="index-_005f_005ffunc_005f_005f-identifier"></a>
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<a name="index-_005f_005fFUNCTION_005f_005f-identifier"></a>
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<a name="index-_005f_005fPRETTY_005fFUNCTION_005f_005f-identifier"></a>
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<p>GCC provides three magic variables that hold the name of the current
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function, as a string. The first of these is <code>__func__</code>, which
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is part of the C99 standard:
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</p>
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<p>The identifier <code>__func__</code> is implicitly declared by the translator
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as if, immediately following the opening brace of each function
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definition, the declaration
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</p>
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<div class="smallexample">
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<pre class="smallexample">static const char __func__[] = "function-name";
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</pre></div>
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<p>appeared, where function-name is the name of the lexically-enclosing
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function. This name is the unadorned name of the function.
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</p>
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<p><code>__FUNCTION__</code> is another name for <code>__func__</code>, provided for
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backward compatibility with old versions of GCC.
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</p>
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<p>In C, <code>__PRETTY_FUNCTION__</code> is yet another name for
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<code>__func__</code>. However, in C++, <code>__PRETTY_FUNCTION__</code> contains
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the type signature of the function as well as its bare name. For
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example, this program:
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</p>
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<div class="smallexample">
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<pre class="smallexample">extern "C" {
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extern int printf (char *, ...);
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}
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class a {
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public:
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void sub (int i)
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{
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printf ("__FUNCTION__ = %s\n", __FUNCTION__);
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printf ("__PRETTY_FUNCTION__ = %s\n", __PRETTY_FUNCTION__);
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}
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};
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int
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main (void)
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{
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a ax;
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ax.sub (0);
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return 0;
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}
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</pre></div>
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<p>gives this output:
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</p>
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<div class="smallexample">
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<pre class="smallexample">__FUNCTION__ = sub
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__PRETTY_FUNCTION__ = void a::sub(int)
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</pre></div>
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<p>These identifiers are variables, not preprocessor macros, and may not
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be used to initialize <code>char</code> arrays or be concatenated with other string
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literals.
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