-/* The before-gc C hook only runs if GC_table_start_callback is available,
- so if not, fall back on a finalizer-based implementation. */
-static int
-weak_gc_callback (void **weak)
-{
- void *val = weak[0];
- void (*callback) (SCM) = weak[1];
-
- if (!val)
- return 0;
-
- callback (SCM_PACK_POINTER (val));
-
- return 1;
-}
-
-#ifdef HAVE_GC_TABLE_START_CALLBACK
-static void*
-weak_gc_hook (void *hook_data, void *fn_data, void *data)
-{
- if (!weak_gc_callback (fn_data))
- scm_c_hook_remove (&scm_before_gc_c_hook, weak_gc_hook, fn_data);
-
- return NULL;
-}
-#else
-static void
-weak_gc_finalizer (void *ptr, void *data)
-{
- if (weak_gc_callback (ptr))
- scm_i_set_finalizer (ptr, weak_gc_finalizer, data);
-}
-#endif
-
-static void
-scm_c_register_weak_gc_callback (SCM obj, void (*callback) (SCM))
-{
- void **weak = GC_MALLOC_ATOMIC (sizeof (void*) * 2);
-
- weak[0] = SCM_UNPACK_POINTER (obj);
- weak[1] = (void*)callback;
- GC_GENERAL_REGISTER_DISAPPEARING_LINK (weak, SCM2PTR (obj));
-
-#ifdef HAVE_GC_TABLE_START_CALLBACK
- scm_c_hook_add (&scm_after_gc_c_hook, weak_gc_hook, weak, 0);
-#else
- scm_i_set_finalizer (weak, weak_gc_finalizer, NULL);
-#endif
-}
-