C preprocessor Macro defining Macro

Question

Can you do something like this with a macro in C?

#define SUPERMACRO(X,Y) #define X Y  then  SUPERMACRO(A,B) expands to #define A B 

I have a feeling not because the preprocessor only does one pass.

Official gcc only. No third-party tools please.

Answer 1

Macros can't expand into preprocessing directives. From C99 6.10.3.4/3 "Rescanning and further replacement":

The resulting completely macro-replaced preprocessing token sequence is not processed as a preprocessing directive even if it resembles one,

Answer 2

You cannot define macros in other macros, but you can call a macro from your macro, which can get you essentially the same results.

#define B(x) do {printf("%d", (x)) }while(0) #define A(x) B(x) 

so, A(y) is expanded to do {printf("%d", (y)) }while(0)