Differenciate WeakMaps from bare HashTables used as weak maps in GC

Author: arnaud-lb

Zend/zend_weakrefs.c

@@ -36,19 +36,21 @@ typedef struct _zend_weakmap_iterator {
 	uint32_t ht_iter;
 } zend_weakmap_iterator;
 
-/* EG(weakrefs) is a map from a key corresponding to a zend_object pointer to all the WeakReference and/or WeakMap entries relating to that pointer.
+/* EG(weakrefs) is a map from a key corresponding to a zend_object pointer to all the WeakReference, WeakMap, and/or bare HashTable entries relating to that pointer.
  *
  * 1. For a single WeakReference,
  *    the HashTable's corresponding value's tag is a ZEND_WEAKREF_TAG_REF and the pointer is a singleton WeakReference instance (zend_weakref *) for that zend_object pointer (from WeakReference::create()).
  * 2. For a single WeakMap, the HashTable's corresponding value's tag is a ZEND_WEAKREF_TAG_MAP and the pointer is a WeakMap instance (zend_weakmap *).
- * 3. For multiple values associated with the same zend_object pointer, the HashTable entry's tag is a ZEND_WEAKREF_TAG_HT with a HashTable mapping
- *    tagged pointers of at most 1 WeakReference and 1 or more WeakMaps to the same tagged pointer.
+ * 3. For a single bare HashTable, the HashTable's corresponding value's tag is a ZEND_WEAKREF_TAG_BARE_HT and the pointer is a HashTable*.
+ * 4. For multiple values associated with the same zend_object pointer, the HashTable entry's tag is a ZEND_WEAKREF_TAG_HT with a HashTable mapping
+ *    tagged pointers of at most 1 WeakReference and 1 or more WeakMap or bare HashTable to the same tagged pointer.
  *
  * ZEND_MM_ALIGNED_OFFSET_LOG2 is at least 2 on supported architectures (pointers to the objects in question are aligned to 4 bytes (1<<2) even on 32-bit systems),
  * i.e. the least two significant bits of the pointer can be used as a tag (ZEND_WEAKREF_TAG_*). */
-#define ZEND_WEAKREF_TAG_REF 0
-#define ZEND_WEAKREF_TAG_MAP 1
-#define ZEND_WEAKREF_TAG_HT  2
+#define ZEND_WEAKREF_TAG_REF     0
+#define ZEND_WEAKREF_TAG_MAP     1
+#define ZEND_WEAKREF_TAG_HT      2
+#define ZEND_WEAKREF_TAG_BARE_HT 3
 #define ZEND_WEAKREF_GET_TAG(p) (((uintptr_t) (p)) & 3)
 #define ZEND_WEAKREF_GET_PTR(p) ((void *) (((uintptr_t) (p)) & ~3))
 #define ZEND_WEAKREF_ENCODE(p, t) ((void *) (((uintptr_t) (p)) | (t)))
@@ -72,8 +74,8 @@ static inline void zend_weakref_unref_single(
 		zend_weakref *wr = ptr;
 		wr->referent = NULL;
 	} else {
-		/* unreferencing WeakMap entry (at ptr) with a key of object. */
-		ZEND_ASSERT(tag == ZEND_WEAKREF_TAG_MAP);
+		/* unreferencing WeakMap or bare HashTable entry (at ptr) with a key of object. */
+		ZEND_ASSERT(tag == ZEND_WEAKREF_TAG_MAP || tag == ZEND_WEAKREF_TAG_BARE_HT);
 		zend_hash_index_del((HashTable *) ptr, zend_object_to_weakref_key(object));
 	}
 }
@@ -166,18 +168,20 @@ static void zend_weakref_unregister(zend_object *object, void *payload, bool wea
 	}
 }
 
+/* Insert 'pData' into bare HashTable 'ht', with the given 'key'. 'key' is
+ * weakly referenced. 'ht' is considered to be a bare HashTable, not a WeakMap. */
 ZEND_API zval *zend_weakrefs_hash_add(HashTable *ht, zend_object *key, zval *pData) {
 	zval *zv = zend_hash_index_add(ht, zend_object_to_weakref_key(key), pData);
 	if (zv) {
-		zend_weakref_register(key, ZEND_WEAKREF_ENCODE(ht, ZEND_WEAKREF_TAG_MAP));
+		zend_weakref_register(key, ZEND_WEAKREF_ENCODE(ht, ZEND_WEAKREF_TAG_BARE_HT));
 	}
 	return zv;
 }
 
 ZEND_API zend_result zend_weakrefs_hash_del(HashTable *ht, zend_object *key) {
 	zval *zv = zend_hash_index_find(ht, zend_object_to_weakref_key(key));
 	if (zv) {
-		zend_weakref_unregister(key, ZEND_WEAKREF_ENCODE(ht, ZEND_WEAKREF_TAG_MAP), 1);
+		zend_weakref_unregister(key, ZEND_WEAKREF_ENCODE(ht, ZEND_WEAKREF_TAG_BARE_HT), 1);
 		return SUCCESS;
 	}
 	return FAILURE;