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 <a name="Function-Names"></a>
 <div class="header">
 <p>
 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> &nbsp; [<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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 <hr>
 <a name="Function-Names-as-Strings"></a>
 <h3 class="section">6.47 Function Names as Strings</h3>
 <a name="index-_005f_005ffunc_005f_005f-identifier"></a>
 <a name="index-_005f_005fFUNCTION_005f_005f-identifier"></a>
 <a name="index-_005f_005fPRETTY_005fFUNCTION_005f_005f-identifier"></a>

 <p>GCC provides three magic variables that hold the name of the current
 function, as a string.  The first of these is <code>__func__</code>, which
 is part of the C99 standard:
 </p>
 <p>The identifier <code>__func__</code> is implicitly declared by the translator
 as if, immediately following the opening brace of each function
 definition, the declaration
 </p>
 <div class="smallexample">
 <pre class="smallexample">static const char __func__[] = &quot;function-name&quot;;
 </pre></div>

 <p>appeared, where function-name is the name of the lexically-enclosing
 function.  This name is the unadorned name of the function.
 </p>
 <p><code>__FUNCTION__</code> is another name for <code>__func__</code>.  Older
 versions of GCC recognize only this name.  However, it is not
 standardized.  For maximum portability, we recommend you use
 <code>__func__</code>, but provide a fallback definition with the
 preprocessor:
 </p>
 <div class="smallexample">
 <pre class="smallexample">#if __STDC_VERSION__ &lt; 199901L
 # if __GNUC__ &gt;= 2
 #  define __func__ __FUNCTION__
 # else
 #  define __func__ &quot;&lt;unknown&gt;&quot;
 # endif
 #endif
 </pre></div>

 <p>In C, <code>__PRETTY_FUNCTION__</code> is yet another name for
 <code>__func__</code>.  However, in C++, <code>__PRETTY_FUNCTION__</code> contains
 the type signature of the function as well as its bare name.  For
 example, this program:
 </p>
 <div class="smallexample">
 <pre class="smallexample">extern &quot;C&quot; {
 extern int printf (char *, ...);
 }

 class a {
  public:
   void sub (int i)
     {
       printf (&quot;__FUNCTION__ = %s\n&quot;, __FUNCTION__);
       printf (&quot;__PRETTY_FUNCTION__ = %s\n&quot;, __PRETTY_FUNCTION__);
     }
 };

 int
 main (void)
 {
   a ax;
   ax.sub (0);
   return 0;
 }
 </pre></div>

 <p>gives this output:
 </p>
 <div class="smallexample">
 <pre class="smallexample">__FUNCTION__ = sub
 __PRETTY_FUNCTION__ = void a::sub(int)
 </pre></div>

 <p>These identifiers are not preprocessor macros.  In GCC 3.3 and
 earlier, in C only, <code>__FUNCTION__</code> and <code>__PRETTY_FUNCTION__</code>
 were treated as string literals; they could be used to initialize
 <code>char</code> arrays, and they could be concatenated with other string
 literals.  GCC 3.4 and later treat them as variables, like
 <code>__func__</code>.  In C++, <code>__FUNCTION__</code> and
 <code>__PRETTY_FUNCTION__</code> have always been variables.
 </p>
 <hr>
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	<a name="Function-Names"></a>
	<div class="header">
	<p>
	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>
	</div>
	<hr>
	<a name="Function-Names-as-Strings"></a>
	<h3 class="section">6.47 Function Names as Strings</h3>
	<a name="index-_005f_005ffunc_005f_005f-identifier"></a>
	<a name="index-_005f_005fFUNCTION_005f_005f-identifier"></a>
	<a name="index-_005f_005fPRETTY_005fFUNCTION_005f_005f-identifier"></a>

	<p>GCC provides three magic variables that hold the name of the current
	function, as a string. The first of these is <code>__func__</code>, which
	is part of the C99 standard:
	</p>
	<p>The identifier <code>__func__</code> is implicitly declared by the translator
	as if, immediately following the opening brace of each function
	definition, the declaration
	</p>
	<div class="smallexample">
	<pre class="smallexample">static const char __func__[] = "function-name";
	</pre></div>

	<p>appeared, where function-name is the name of the lexically-enclosing
	function. This name is the unadorned name of the function.
	</p>
	<p><code>__FUNCTION__</code> is another name for <code>__func__</code>. Older
	versions of GCC recognize only this name. However, it is not
	standardized. For maximum portability, we recommend you use
	<code>__func__</code>, but provide a fallback definition with the
	preprocessor:
	</p>
	<div class="smallexample">
	<pre class="smallexample">#if __STDC_VERSION__ < 199901L
	# if __GNUC__ >= 2
	# define __func__ __FUNCTION__
	# else
	# define __func__ "<unknown>"
	# endif
	#endif
	</pre></div>

	<p>In C, <code>__PRETTY_FUNCTION__</code> is yet another name for
	<code>__func__</code>. However, in C++, <code>__PRETTY_FUNCTION__</code> contains
	the type signature of the function as well as its bare name. For
	example, this program:
	</p>
	<div class="smallexample">
	<pre class="smallexample">extern "C" {
	extern int printf (char *, ...);
	}

	class a {
	public:
	void sub (int i)
	{
	printf ("__FUNCTION__ = %s\n", __FUNCTION__);
	printf ("__PRETTY_FUNCTION__ = %s\n", __PRETTY_FUNCTION__);
	}
	};

	int
	main (void)
	{
	a ax;
	ax.sub (0);
	return 0;
	}
	</pre></div>

	<p>gives this output:
	</p>
	<div class="smallexample">
	<pre class="smallexample">__FUNCTION__ = sub
	__PRETTY_FUNCTION__ = void a::sub(int)
	</pre></div>

	<p>These identifiers are not preprocessor macros. In GCC 3.3 and
	earlier, in C only, <code>__FUNCTION__</code> and <code>__PRETTY_FUNCTION__</code>
	were treated as string literals; they could be used to initialize
	<code>char</code> arrays, and they could be concatenated with other string
	literals. GCC 3.4 and later treat them as variables, like
	<code>__func__</code>. In C++, <code>__FUNCTION__</code> and
	<code>__PRETTY_FUNCTION__</code> have always been variables.
	</p>
	<hr>
	<div class="header">
	<p>
	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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