text: 
  struct mystruct {
      int f1;
      int f2;
  };
  
  typedef int size_t;
  
  #define edg_offsetof(t, memb) ((size_t)__INTADDR__(&(((t *)0)->memb)))
  
  void f(void) {
      int i1 = __builtin_offsetof(struct mystruct,f2);
      int i2 = edg_offsetof(struct mystruct,f2);
  }
  
  