-void **pointer_map_contains (struct pointer_map_t *pmap, void *p);
-void **pointer_map_insert (struct pointer_map_t *pmap, void *p);
-void pointer_map_traverse (struct pointer_map_t *,
- bool (*) (void *, void **, void *), void *);
+void **pointer_map_contains (const struct pointer_map_t *pmap, const void *p);
+void **pointer_map_insert (struct pointer_map_t *pmap, const void *p);
+void pointer_map_traverse (const struct pointer_map_t *,
+ bool (*) (const void *, void **, void *), void *);