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Commit d74901a

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arnaud-lbTimWolla
andcommitted
Differenciate WeakMaps from bare HashTables used as weak maps for GC purposes
Since cbf67e4, the GC needs to find all WeakMaps referencing a weakly referenced object. Doing so, it treats all ZEND_WEAKREF_TAG_MAP as WeakMap instances. However, a ZEND_WEAKREF_TAG_MAP reference may be a bare HashTable when zend_weakrefs_hash_add() is used. Introduce a new tag, ZEND_WEAKREF_TAG_BARE_HT, and use this tag when weakly referencing an object from a bare HashTable. Ignore such references in GC. Fixes GH-19543 Closes GH-19544 Co-authored-by: Tim Düsterhus <tim@tideways-gmbh.com>
1 parent 0a12aaa commit d74901a

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5 files changed

+72
-18
lines changed

5 files changed

+72
-18
lines changed

‎Zend/tests/gh19543-001.phpt‎

Lines changed: 17 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,17 @@
1+
--TEST--
2+
GH-19543 001: GC treats ZEND_WEAKREF_TAG_MAP references as WeakMap references
3+
--EXTENSIONS--
4+
zend_test
5+
--FILE--
6+
<?php
7+
8+
$e = new Exception();
9+
$a = new stdClass();
10+
zend_weakmap_attach($e, $a);
11+
unset($a);
12+
gc_collect_cycles();
13+
14+
?>
15+
==DONE==
16+
--EXPECT--
17+
==DONE==

‎Zend/tests/gh19543-002.phpt‎

Lines changed: 19 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,19 @@
1+
--TEST--
2+
GH-19543 002: GC treats ZEND_WEAKREF_TAG_MAP references as WeakMap references
3+
--EXTENSIONS--
4+
zend_test
5+
--FILE--
6+
<?php
7+
8+
$e = new Exception();
9+
$a = new stdClass();
10+
zend_weakmap_attach($e, $a);
11+
unset($a);
12+
$e2 = $e;
13+
unset($e2); // add to roots
14+
gc_collect_cycles();
15+
16+
?>
17+
==DONE==
18+
--EXPECT--
19+
==DONE==

‎Zend/zend_weakrefs.c‎

Lines changed: 26 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -36,19 +36,21 @@ typedef struct _zend_weakmap_iterator {
3636
uint32_t ht_iter;
3737
} zend_weakmap_iterator;
3838

39-
/* EG(weakrefs) is a map from a key corresponding to a zend_object pointer to all the WeakReferenceand/or WeakMap entries relating to that pointer.
39+
/* 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.
4040
*
4141
* 1. For a single WeakReference,
4242
* 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()).
4343
* 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 *).
44-
* 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
45-
* tagged pointers of at most 1 WeakReference and 1 or more WeakMaps to the same tagged pointer.
44+
* 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*.
45+
* 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
46+
* tagged pointers of at most 1 WeakReference and 1 or more WeakMap or bare HashTable to the same tagged pointer.
4647
*
4748
* 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),
4849
* i.e. the least two significant bits of the pointer can be used as a tag (ZEND_WEAKREF_TAG_*). */
49-
#define ZEND_WEAKREF_TAG_REF 0
50-
#define ZEND_WEAKREF_TAG_MAP 1
51-
#define ZEND_WEAKREF_TAG_HT 2
50+
#define ZEND_WEAKREF_TAG_REF 0
51+
#define ZEND_WEAKREF_TAG_MAP 1
52+
#define ZEND_WEAKREF_TAG_HT 2
53+
#define ZEND_WEAKREF_TAG_BARE_HT 3
5254
#define ZEND_WEAKREF_GET_TAG(p) (((uintptr_t) (p)) & 3)
5355
#define ZEND_WEAKREF_GET_PTR(p) ((void *) (((uintptr_t) (p)) & ~3))
5456
#define ZEND_WEAKREF_ENCODE(p, t) ((void *) (((uintptr_t) (p)) | (t)))
@@ -72,8 +74,8 @@ static inline void zend_weakref_unref_single(
7274
zend_weakref *wr = ptr;
7375
wr->referent = NULL;
7476
} else {
75-
/* unreferencing WeakMap entry (at ptr) with a key of object. */
76-
ZEND_ASSERT(tag == ZEND_WEAKREF_TAG_MAP);
77+
/* unreferencing WeakMap or bare HashTable entry (at ptr) with a key of object. */
78+
ZEND_ASSERT(tag == ZEND_WEAKREF_TAG_MAP||tag==ZEND_WEAKREF_TAG_BARE_HT);
7779
zend_hash_index_del((HashTable *) ptr, zend_object_to_weakref_key(object));
7880
}
7981
}
@@ -166,18 +168,20 @@ static void zend_weakref_unregister(zend_object *object, void *payload, bool wea
166168
}
167169
}
168170

171+
/* Insert 'pData' into bare HashTable 'ht', with the given 'key'. 'key' is
172+
* weakly referenced. 'ht' is considered to be a bare HashTable, not a WeakMap. */
169173
ZEND_API zval *zend_weakrefs_hash_add(HashTable *ht, zend_object *key, zval *pData) {
170174
zval *zv = zend_hash_index_add(ht, zend_object_to_weakref_key(key), pData);
171175
if (zv) {
172-
zend_weakref_register(key, ZEND_WEAKREF_ENCODE(ht, ZEND_WEAKREF_TAG_MAP));
176+
zend_weakref_register(key, ZEND_WEAKREF_ENCODE(ht, ZEND_WEAKREF_TAG_BARE_HT));
173177
}
174178
return zv;
175179
}
176180

177181
ZEND_API zend_result zend_weakrefs_hash_del(HashTable *ht, zend_object *key) {
178182
zval *zv = zend_hash_index_find(ht, zend_object_to_weakref_key(key));
179183
if (zv) {
180-
zend_weakref_unregister(key, ZEND_WEAKREF_ENCODE(ht, ZEND_WEAKREF_TAG_MAP), 1);
184+
zend_weakref_unregister(key, ZEND_WEAKREF_ENCODE(ht, ZEND_WEAKREF_TAG_BARE_HT), 1);
181185
return SUCCESS;
182186
}
183187
return FAILURE;
@@ -520,6 +524,10 @@ HashTable *zend_weakmap_get_object_key_entry_gc(zend_object *object, zval **tabl
520524
ZEND_ASSERT(zv);
521525
zend_get_gc_buffer_add_ptr(gc_buffer, zv);
522526
zend_get_gc_buffer_add_obj(gc_buffer, &wm->std);
527+
} else if (ZEND_WEAKREF_GET_TAG(tagged_ptr) == ZEND_WEAKREF_TAG_BARE_HT) {
528+
/* Bare HashTables are intentionally ignored, since they are
529+
* intended for internal usage by extensions and might not be
530+
* collectable. */
523531
}
524532
} ZEND_HASH_FOREACH_END();
525533
} else if (tag == ZEND_WEAKREF_TAG_MAP) {
@@ -528,6 +536,8 @@ HashTable *zend_weakmap_get_object_key_entry_gc(zend_object *object, zval **tabl
528536
ZEND_ASSERT(zv);
529537
zend_get_gc_buffer_add_ptr(gc_buffer, zv);
530538
zend_get_gc_buffer_add_obj(gc_buffer, &wm->std);
539+
} else if (tag == ZEND_WEAKREF_TAG_BARE_HT) {
540+
/* Bare HashTables are intentionally ignored (see above) */
531541
}
532542

533543
zend_get_gc_buffer_use(gc_buffer, table, n);
@@ -554,13 +564,19 @@ HashTable *zend_weakmap_get_object_entry_gc(zend_object *object, zval **table, i
554564
zval *zv = zend_hash_index_find(&wm->ht, obj_key);
555565
ZEND_ASSERT(zv);
556566
zend_get_gc_buffer_add_ptr(gc_buffer, zv);
567+
} else if (ZEND_WEAKREF_GET_TAG(tagged_ptr) == ZEND_WEAKREF_TAG_BARE_HT) {
568+
/* Bare HashTables are intentionally ignored
569+
* (see zend_weakmap_get_object_key_entry_gc) */
557570
}
558571
} ZEND_HASH_FOREACH_END();
559572
} else if (tag == ZEND_WEAKREF_TAG_MAP) {
560573
zend_weakmap *wm = (zend_weakmap*) ptr;
561574
zval *zv = zend_hash_index_find(&wm->ht, obj_key);
562575
ZEND_ASSERT(zv);
563576
zend_get_gc_buffer_add_ptr(gc_buffer, zv);
577+
} else if (tag == ZEND_WEAKREF_TAG_BARE_HT) {
578+
/* Bare HashTables are intentionally ignored
579+
* (see zend_weakmap_get_object_key_entry_gc) */
564580
}
565581

566582
zend_get_gc_buffer_use(gc_buffer, table, n);

‎ext/zend_test/php_test.h‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -50,7 +50,7 @@ ZEND_BEGIN_MODULE_GLOBALS(zend_test)
5050
int observer_fiber_switch;
5151
int observer_fiber_destroy;
5252
int observer_execute_internal;
53-
HashTable global_weakmap;
53+
HashTable *global_weakmap;
5454
int replace_zend_execute_ex;
5555
int register_passes;
5656
bool print_stderr_mshutdown;

‎ext/zend_test/test.c‎

Lines changed: 9 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -340,7 +340,7 @@ static ZEND_FUNCTION(zend_weakmap_attach)
340340
Z_PARAM_ZVAL(value)
341341
ZEND_PARSE_PARAMETERS_END();
342342

343-
if (zend_weakrefs_hash_add(&ZT_G(global_weakmap), obj, value)) {
343+
if (zend_weakrefs_hash_add(ZT_G(global_weakmap), obj, value)) {
344344
Z_TRY_ADDREF_P(value);
345345
RETURN_TRUE;
346346
}
@@ -355,13 +355,13 @@ static ZEND_FUNCTION(zend_weakmap_remove)
355355
Z_PARAM_OBJ(obj)
356356
ZEND_PARSE_PARAMETERS_END();
357357

358-
RETURN_BOOL(zend_weakrefs_hash_del(&ZT_G(global_weakmap), obj) == SUCCESS);
358+
RETURN_BOOL(zend_weakrefs_hash_del(ZT_G(global_weakmap), obj) == SUCCESS);
359359
}
360360

361361
static ZEND_FUNCTION(zend_weakmap_dump)
362362
{
363363
ZEND_PARSE_PARAMETERS_NONE();
364-
RETURN_ARR(zend_array_dup(&ZT_G(global_weakmap)));
364+
RETURN_ARR(zend_array_dup(ZT_G(global_weakmap)));
365365
}
366366

367367
static ZEND_FUNCTION(zend_get_current_func_name)
@@ -1311,18 +1311,20 @@ PHP_MSHUTDOWN_FUNCTION(zend_test)
13111311

13121312
PHP_RINIT_FUNCTION(zend_test)
13131313
{
1314-
zend_hash_init(&ZT_G(global_weakmap), 8, NULL, ZVAL_PTR_DTOR, 0);
1314+
ALLOC_HASHTABLE(ZT_G(global_weakmap));
1315+
zend_hash_init(ZT_G(global_weakmap), 8, NULL, ZVAL_PTR_DTOR, 0);
13151316
ZT_G(observer_nesting_depth) = 0;
13161317
return SUCCESS;
13171318
}
13181319

13191320
PHP_RSHUTDOWN_FUNCTION(zend_test)
13201321
{
13211322
zend_ulong obj_key;
1322-
ZEND_HASH_FOREACH_NUM_KEY(&ZT_G(global_weakmap), obj_key) {
1323-
zend_weakrefs_hash_del(&ZT_G(global_weakmap), zend_weakref_key_to_object(obj_key));
1323+
ZEND_HASH_FOREACH_NUM_KEY(ZT_G(global_weakmap), obj_key) {
1324+
zend_weakrefs_hash_del(ZT_G(global_weakmap), zend_weakref_key_to_object(obj_key));
13241325
} ZEND_HASH_FOREACH_END();
1325-
zend_hash_destroy(&ZT_G(global_weakmap));
1326+
zend_hash_destroy(ZT_G(global_weakmap));
1327+
FREE_HASHTABLE(ZT_G(global_weakmap));
13261328

13271329
if (ZT_G(zend_test_heap)) {
13281330
free(ZT_G(zend_test_heap));

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