assoc_free (void)
{
  for (int i = 0; i < nsyms; ++i)
    {
      linkedlist_free (prec_nodes[i]->pred);
      linkedlist_free (prec_nodes[i]->succ);
      free (prec_nodes[i]);
    }
  free (prec_nodes);
}
assoc_free (void)
{
  for (int i = 0; i < nsyms; ++i)
    {
      linkedlist_free (prec_nodes[i]->pred);
      linkedlist_free (prec_nodes[i]->succ);
      free (prec_nodes[i]);
    }
  free (prec_nodes);
}