int  x=1;
int main() {
  int *p = &x;
  uintptr_t i = (uintptr_t)p;
  int uintptr_t_width = sizeof(uintptr_t) * CHAR_BIT;
  uintptr_t bit, j;
  int k;
  j=0;
  for (k=0; k<uintptr_t_width; k++) {
    bit = (i & (((uintptr_t)1) << k)) >> k;
    if (bit == 1) 
      j = j | ((uintptr_t)1 << k);
    else
      j = j;
  }
  int *q = (int *)j;
  *q = 11; // is this free of undefined behaviour?
  printf("*p=%d  *q=%d\n",*p,*q);  
}