Function Names as Strings
【Function Names as Strings】
GCC provides three magic variables that hold the name of the current function, as a string. The first of these is __func__
, which is part of the C99 standard(old):
The identifier __func__
is implicitly declared by the translator as if, immediately following the opening brace of each function definition, the declaration
static const char __func__[] = "function-name";
appeared, where function-name is the name of the lexically-enclosing function. This name is the unadorned name of the function.
__FUNCTION__
is another name for __func__
. Older versions of GCC recognize only this name(GCC2.0以上版本没有__func__,只有__FUNCTION__,2.0以下版本编译器不认识__FUNCTION__). However, it is not standardized. For maximum portability, we recommend you use __func__
, but provide a fallback definition with the preprocessor(GCC2.0)(通过以下的宏使用__func__可以提供跨版本特性):
#if __STDC_VERSION__ < 199901L
# if __GNUC__ >= 2
# define __func__ __FUNCTION__
# else
# define __func__ "<unknown>"
# endif
#endif
In C, __PRETTY_FUNCTION__
is yet another name for __func__
. However, in C++, __PRETTY_FUNCTION__
contains the type signature of the function as well as its bare name(C++中__PRETTY_FUNCTION__包含函数签名). For example, this program:
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;
}
gives this output:
__FUNCTION__ = sub
__PRETTY_FUNCTION__ = void a::sub(int)
These identifiers are not preprocessor macros. In GCC 3.3 and earlier, in C only, __FUNCTION__
and __PRETTY_FUNCTION__
were treated as string literals; they could be used to initialize char
arrays, and they could be concatenated with other string literals. GCC 3.4 and later treat them as variables, like __func__(GCC3.4以后版本,此2种东西均为变量)
. In C++, __FUNCTION__
and__PRETTY_FUNCTION__
have always been variables.
参考:http://gcc.gnu.org/onlinedocs/gcc/Function-Names.html#Function-Names
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