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<h3 class="section">6.46 Function Names as Strings</h3>
<p><a name="index-g_t_0040code_007b_005f_005ffunc_005f_005f_007d-identifier-3511"></a><a name="index-g_t_0040code_007b_005f_005fFUNCTION_005f_005f_007d-identifier-3512"></a><a name="index-g_t_0040code_007b_005f_005fPRETTY_005fFUNCTION_005f_005f_007d-identifier-3513"></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>, provided for
backward compatibility with old versions of GCC.
<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 variables, not preprocessor macros, and may not
be used to initialize <code>char</code> arrays or be concatenated with other string
literals.
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