Differences in Macro ## concatenation operator between Visual-C++ and gcc

Question

I\'m having a macro like this ( not exactly, but function is quite equivalent):

#define STRUCTMEMBER(Member,Value) GlobalStructInstance. ## Member = Value
..         


        

Answer 1

Maybe Visual C++ is pasting a couple of spaces together to make another space. Not that whitespaces are tokens, but it would allow your code to work.

object.member is not a token, it's three tokens, so you don't need token-pasting to implement the macro you describe. Just remove the '##' and it should work everywhere.

[Edit: just checked, and the result of using ## to form something that isn't a valid token is undefined. So GCC is allowed to reject it and MSVC is allowed to ignore it and perform no paste, as far as I can tell.]