Feature: C preprocessor supports __func__ or __FUNCTION__?

[R. Bernstein]

Correct me if I am wrong, but it doesn't look like there is a macro
that can be used to test if the C preprocessor __func__ or
__FUNCTION__ "variables" work. I'd imagine such a test would produce
in config.h

#define __func__ __FUNCTION__ 

if only __FUNCTION__ works, or nothing if __func__ works or 

#define __func__ "" 

if neither works.

Is there a way to handle this already. If not, should I try to supply
a patch to provide such a feature?

Thanks.