Sorry for the second post here but reading the code I thought of one more feature that may be possible.and will try to work out for myself, but I am unsure of the side effects.

If a SINGLE value is passed, how hard would it be to have it eval the passed expression and then return that from _trace()?

That way, the TRACE macro could be used in-situ in the code, and by a suitable test of some flag (possibly the systems debug settings) either Trace or not trace and the program would still fuction (possibly inefficiently).

Does this thought have any merit?