Is there a way to force C preprocessor to evaluate macro arguments before the macro

Question

I have a number of macros in the form

#define F(A,B)   Some function of A and B

and for readability I would like to define arguments for these macros e.g.

#define C A,B

so that I can say

F(C)

but the preprocessor tries to expand F before C and complains that F needs 2 arguments. Is there a way to make it expand C before it expands F so that the error does not occur?

Answer 1

You can use an intermediate macro that takes a variable number of arguments:

#define F1(A,B) 
#define F(...) F1(__VA_ARGS__)

#define C A,B

int main(void) {
    F(C)
    F(1,2)
    return 0;
}

This should compile. You will still get a compilation failure if you pass more or less than two arguments, or arguments that don't expand to exactly two arguments.