init_prec_nodes (void)
{
  prec_nodes = xcalloc (nsyms, sizeof *prec_nodes);
  for (int i = 0; i < nsyms; ++i)
    {
      prec_nodes[i] = xmalloc (sizeof *prec_nodes[i]);
      symgraph *s = prec_nodes[i];
      s->id = i;
      s->succ = 0;
      s->pred = 0;
    }
}
init_prec_nodes (void)
{
  prec_nodes = xcalloc (nsyms, sizeof *prec_nodes);
  for (int i = 0; i < nsyms; ++i)
    {
      prec_nodes[i] = xmalloc (sizeof *prec_nodes[i]);
      symgraph *s = prec_nodes[i];
      s->id = i;
      s->succ = 0;
      s->pred = 0;
    }
}