Question

Possible Duplicate:
Why i am not getting the expected output in the following c programme?

i am having a doubt in order of evaluation of macros.like for the following code i am not able to understand the ouput:

#include <stdio.h>
#define f(a,b) a##b
#define g(a) #a
#define h(a) g(a) 
int main()
{
    printf("%s\n",h(f(1,2)));
    printf("%s\n",g(f(1,2)));
    return 0;
}

Output

12
f(1,2)

why not f is getting expanded first before g in the second printf ?

Answer 1

It’s a consequence of how macros are expanded, and has an impact on self-referential macros… This is quite nicely explained in detail in the GNU CPP manual