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 <h3 class="section">6.47 Function Names as Strings</h3>

 <p><a name="index-g_t_0040code_007b_005f_005ffunc_005f_005f_007d-identifier-2883"></a><a name="index-g_t_0040code_007b_005f_005fFUNCTION_005f_005f_007d-identifier-2884"></a><a name="index-g_t_0040code_007b_005f_005fPRETTY_005fFUNCTION_005f_005f_007d-identifier-2885"></a>
 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>The identifier <code>__func__</code> is implicitly declared by the translator
 as if, immediately following the opening brace of each function
 definition, the declaration

 <pre class="smallexample">     static const char __func__[] = "function-name";
 </pre>
  <p class="noindent">appeared, where function-name is the name of the lexically-enclosing
 function.  This name is the unadorned name of the function.

  <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:

 <pre class="smallexample">     #if __STDC_VERSION__ &lt; 199901L
      # if __GNUC__ &gt;= 2
      #  define __func__ __FUNCTION__
      # else
      #  define __func__ "&lt;unknown&gt;"
      # endif
      #endif
 </pre>
  <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:

 <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>
  <p class="noindent">gives this output:

 <pre class="smallexample">     __FUNCTION__ = sub
      __PRETTY_FUNCTION__ = void a::sub(int)
 </pre>
  <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.

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	<h3 class="section">6.47 Function Names as Strings</h3>

	<p><a name="index-g_t_0040code_007b_005f_005ffunc_005f_005f_007d-identifier-2883"></a><a name="index-g_t_0040code_007b_005f_005fFUNCTION_005f_005f_007d-identifier-2884"></a><a name="index-g_t_0040code_007b_005f_005fPRETTY_005fFUNCTION_005f_005f_007d-identifier-2885"></a>
	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>The identifier <code>__func__</code> is implicitly declared by the translator
	as if, immediately following the opening brace of each function
	definition, the declaration

	<pre class="smallexample"> static const char __func__[] = "function-name";
	</pre>
	<p class="noindent">appeared, where function-name is the name of the lexically-enclosing
	function. This name is the unadorned name of the function.

	<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:

	<pre class="smallexample"> #if __STDC_VERSION__ < 199901L
	# if __GNUC__ >= 2
	# define __func__ __FUNCTION__
	# else
	# define __func__ "<unknown>"
	# endif
	#endif
	</pre>
	<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:

	<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>
	<p class="noindent">gives this output:

	<pre class="smallexample"> __FUNCTION__ = sub
	__PRETTY_FUNCTION__ = void a::sub(int)
	</pre>
	<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.

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