> __FUNCTION__ is expanded as string by the preprocessor and merges
> with other strings.

Are you sure about that?  The preprocessor contains enough of a
codewalker to know whether it's in a function, and which function if
so?  I thought __LINE__ and __FILE__ were done by the preprocessor but
__FUNCTION__ was compile-phase magic.  Certainly the gcc version whose
docs I have most readily at hand, while rather old, does say that

	These names [__FUNCTION__ and __PRETTY_FUNCTION__] are not
	macros: they are predefined string variables.  For example,
	@samp{#ifdef __FUNCTION__} does not have any special meaning
	inside a function, since the preprocessor does not do anything
	special with the identifier @code{__FUNCTION__}.

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