/* Compares binary trees rooted at |a| and |b|,
   making sure that they are identical. */
static int
compare_trees (struct rtrb_node *a, struct rtrb_node *b)
{
  int okay;

  if (a == NULL || b == NULL)
    {
      if (a != NULL || b != NULL)
        {
          printf (" a=%d b=%d\n",
                  a ? *(int *) a->rtrb_data : -1,
                  b ? *(int *) b->rtrb_data : -1);
          assert (0);
        }
      return 1;
    }
  assert (a != b);

  if (*(int *) a->rtrb_data != *(int *) b->rtrb_data
      || a->rtrb_rtag != b->rtrb_rtag
      || a->rtrb_color != b->rtrb_color)
    {
      printf (" Copied nodes differ: a=%d%c b=%d%c a:",
              *(int *) a->rtrb_data, a->rtrb_color == RTRB_RED ? 'r' : 'b',
              *(int *) b->rtrb_data, b->rtrb_color == RTRB_RED ? 'r' : 'b');

      if (a->rtrb_rtag == RTRB_CHILD)
        printf ("r");

      printf (" b:");
      if (b->rtrb_rtag == RTRB_CHILD)
        printf ("r");

      printf ("\n");
      return 0;
    }

  if (a->rtrb_rtag == RTRB_THREAD)
    assert ((a->rtrb_link[1] == NULL) != (a->rtrb_link[1] != b->rtrb_link[1]));

  okay = compare_trees (a->rtrb_link[0], b->rtrb_link[0]);
  if (a->rtrb_rtag == RTRB_CHILD)
    okay &= compare_trees (a->rtrb_link[1], b->rtrb_link[1]);
  return okay;
}