function and function-like macro

if we use the same name for those things. avoid the prepocessor will expand the function first, we usaully add parenthese to prevent.

simple example

#include <stdio.h>
#define test(x) __test(x)
#define __test(x) printf("\n%d\n", x + 1);

int test(int x);
#undef test

int main()
{
    test(1);
}
int (test)(int x)
{
    printf("\n%d\n", x);
}

Referemce

http://stackoverflow.com/questions/13600790/what-do-the-parentheses-around-a-function-name-mean