int needed_size = prime_size (ht->count * 3);
ht->size = MAX (old_size, needed_size);
+#if 0
printf ("growing from %d to %d\n", old_size, ht->size);
+#endif
ht->mappings = xmalloc (ht->size * sizeof (struct mapping));
memset (ht->mappings, '\0', ht->size * sizeof (struct mapping));