@Kartoffel:
Ty, i was also thinking about such a solution and I think i will use it(however i'm not too happy about it, because it may cause undefined behaviour if the users saves the result in an expression(this wouldn't be the case if void is used...)

@MasterQ32:
I don't agree that it makes no sense... You think so, because you never needed it xD I looked up if it is allowed in C99, and you are right, it isn't. However in c++ it is:
Quote:
An expression of type void shall be used only as an expression statement (6.2), as an operand of a comma expression (5.18), as a second or third operand of ?: (5.16), as the operand of typeid, or as the expression in a return statement (6.6.3) for a function with the return type void.


In c++ it is useful for templates, so why shouldn't it be useful in c for macros?

Anyway, thanks for your help laugh