Control-Flow Flattening example

source: https://tigress.wtf/flatten.html

struct argStruct {

   int tmp ;
   int *x ;
   int returnv ;
   unsigned long next ;
};

void block_1(struct argStruct *arg ) {
  arg->returnv = *(arg->x) * arg->tmp;
  arg->next = 5;
  return;
}

void block_2(struct argStruct *arg ) {
  arg->tmp = fac(*(arg->x) - 1);
  arg->next = 1;
  return;
}

void block_4(struct argStruct *arg ) {
  if (*(arg->x) == 1) {
    arg->next = 3;
  } else {
    arg->next = 2;
  }
  return;
}

void block_3(struct argStruct *arg ) {
  arg->returnv = 1;
  arg->next = 5;
  return;
}

int fac(int x ){
  struct argStruct arg ;
  static void (*jumpTab[4])(struct argStruct *arg )  = {& block_1, & block_2,& block_3, & block_4};
  arg.next = 4;
  arg.x = & x;
  while (1) {
    if (arg.next > 4) {
      return (arg.returnv);
    } else {
      (*(jumpTab[arg.next - 1]))(& arg);
    }
  }
}