为什么会出错？

#include <stdio.h>

#define f  (x) *((x)-1)

/*

case1 : function1  complied right
case2 : function2  complied right
case3 : function1 and function2 complied error
why?

*/

int main(){

///*function1

 int x = 3;
 int reslut = 0;
 reslut = f*10;
 printf("%d/n",reslut);

//*/

///*function2
 char *p;
 p = NULL;
 printf("%d/n",*p);

//*/
 return 1;
}