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-rw-r--r--NEWS2
-rw-r--r--Zend/tests/bug77345_gc_1.phpt42
-rw-r--r--Zend/tests/bug77345_gc_2.phpt48
-rw-r--r--Zend/zend_gc.c318
4 files changed, 327 insertions, 83 deletions
diff --git a/NEWS b/NEWS
index 309572d890..9bf6fdb3c7 100644
--- a/NEWS
+++ b/NEWS
@@ -3,6 +3,8 @@ PHP NEWS
?? ??? ????, PHP 7.4.0alpha1
- Core:
+ . Fixed bug #77345 (Stack Overflow caused by circular reference in garbage
+ collection). (Alexandru Patranescu, Nikita, Dmitry)
. Implemented request #76148 (Add array_key_exists() to the list of
specially compiled functions). (Majkl578)
. Fixed bug #76430 (__METHOD__ inconsistent outside of method).
diff --git a/Zend/tests/bug77345_gc_1.phpt b/Zend/tests/bug77345_gc_1.phpt
new file mode 100644
index 0000000000..eabb94ce7d
--- /dev/null
+++ b/Zend/tests/bug77345_gc_1.phpt
@@ -0,0 +1,42 @@
+--TEST--
+Bug #77345 (Segmentation faults stack overflow in cyclic garbage collector) (Bug #77427)
+--INI--
+zend.enable_gc = 1
+--FILE--
+<?php
+
+class Node
+{
+ /** @var Node */
+ public $previous;
+ /** @var Node */
+ public $next;
+}
+
+var_dump(gc_enabled());
+var_dump('start');
+
+$firstNode = new Node();
+$firstNode->previous = $firstNode;
+$firstNode->next = $firstNode;
+
+$circularDoublyLinkedList = $firstNode;
+
+for ($i = 0; $i < 200000; $i++) {
+ $currentNode = $circularDoublyLinkedList;
+ $nextNode = $circularDoublyLinkedList->next;
+
+ $newNode = new Node();
+
+ $newNode->previous = $currentNode;
+ $currentNode->next = $newNode;
+ $newNode->next = $nextNode;
+ $nextNode->previous = $newNode;
+
+ $circularDoublyLinkedList = $nextNode;
+}
+var_dump('end');
+--EXPECT--
+bool(true)
+string(5) "start"
+string(3) "end" \ No newline at end of file
diff --git a/Zend/tests/bug77345_gc_2.phpt b/Zend/tests/bug77345_gc_2.phpt
new file mode 100644
index 0000000000..9d39b6b969
--- /dev/null
+++ b/Zend/tests/bug77345_gc_2.phpt
@@ -0,0 +1,48 @@
+--TEST--
+Bug #77345 (Segmentation faults stack overflow in cyclic garbage collector) (Bug #77427)
+--INI--
+zend.enable_gc = 1
+--FILE--
+<?php
+
+class Node
+{
+ /** @var Node */
+ public $previous;
+ /** @var Node */
+ public $next;
+}
+
+var_dump(gc_enabled());
+var_dump('start');
+
+function xxx() {
+ $firstNode = new Node();
+ $firstNode->previous = $firstNode;
+ $firstNode->next = $firstNode;
+
+ $circularDoublyLinkedList = $firstNode;
+
+ for ($i = 0; $i < 300000; $i++) {
+ $currentNode = $circularDoublyLinkedList;
+ $nextNode = $circularDoublyLinkedList->next;
+
+ $newNode = new Node();
+
+ $newNode->previous = $currentNode;
+ $currentNode->next = $newNode;
+ $newNode->next = $nextNode;
+ $nextNode->previous = $newNode;
+
+ $circularDoublyLinkedList = $nextNode;
+ }
+}
+
+xxx();
+gc_collect_cycles();
+
+var_dump('end');
+--EXPECT--
+bool(true)
+string(5) "start"
+string(3) "end" \ No newline at end of file
diff --git a/Zend/zend_gc.c b/Zend/zend_gc.c
index 1954c360c9..2b39030d96 100644
--- a/Zend/zend_gc.c
+++ b/Zend/zend_gc.c
@@ -245,6 +245,73 @@ static zend_gc_globals gc_globals;
# define GC_TRACE(str)
#endif
+
+#define GC_STACK_SEGMENT_SIZE (((4096 - ZEND_MM_OVERHEAD) / sizeof(void*)) - 2)
+
+typedef struct _gc_stack gc_stack;
+
+struct _gc_stack {
+ gc_stack *prev;
+ gc_stack *next;
+ zend_refcounted *data[GC_STACK_SEGMENT_SIZE];
+};
+
+#define GC_STACK_DCL(init) \
+ gc_stack *_stack = init; \
+ size_t _top = 0;
+
+#define GC_STACK_PUSH(ref) \
+ gc_stack_push(&_stack, &_top, ref);
+
+#define GC_STACK_POP() \
+ gc_stack_pop(&_stack, &_top)
+
+static zend_never_inline gc_stack* gc_stack_next(gc_stack *stack)
+{
+ if (UNEXPECTED(!stack->next)) {
+ gc_stack *segment = emalloc(sizeof(gc_stack));
+ segment->prev = stack;
+ segment->next = NULL;
+ stack->next = segment;
+ }
+ return stack->next;
+}
+
+static zend_always_inline void gc_stack_push(gc_stack **stack, size_t *top, zend_refcounted *ref)
+{
+ if (UNEXPECTED(*top == GC_STACK_SEGMENT_SIZE)) {
+ (*stack) = gc_stack_next(*stack);
+ (*top) = 0;
+ }
+ (*stack)->data[(*top)++] = ref;
+}
+
+static zend_always_inline zend_refcounted* gc_stack_pop(gc_stack **stack, size_t *top)
+{
+ if (UNEXPECTED((*top) == 0)) {
+ if (!(*stack)->prev) {
+ return NULL;
+ } else {
+ (*stack) = (*stack)->prev;
+ (*top) = GC_STACK_SEGMENT_SIZE - 1;
+ return (*stack)->data[GC_STACK_SEGMENT_SIZE - 1];
+ }
+ } else {
+ return (*stack)->data[--(*top)];
+ }
+}
+
+static void gc_stack_free(gc_stack *stack)
+{
+ gc_stack *p = stack->next;
+
+ while (p) {
+ stack = p->next;
+ efree(p);
+ p = stack;
+ }
+}
+
static zend_always_inline uint32_t gc_compress(uint32_t idx)
{
return idx % GC_MAX_UNCOMPRESSED;
@@ -606,16 +673,14 @@ ZEND_API void ZEND_FASTCALL gc_remove_from_buffer(zend_refcounted *ref)
gc_remove_from_roots(root);
}
-static void gc_scan_black(zend_refcounted *ref)
+static void gc_scan_black(zend_refcounted *ref, gc_stack *stack)
{
- HashTable *ht;
+ HashTable *ht = NULL;
Bucket *p, *end;
zval *zv;
+ GC_STACK_DCL(stack);
tail_call:
- ht = NULL;
- GC_REF_SET_BLACK(ref);
-
if (GC_TYPE(ref) == IS_OBJECT) {
zend_object *obj = (zend_object*)ref;
@@ -628,9 +693,9 @@ tail_call:
ht = obj->handlers->get_gc(&tmp, &zv, &n);
end = zv + n;
if (EXPECTED(!ht)) {
- if (!n) return;
+ if (!n) goto next;
while (!Z_REFCOUNTED_P(--end)) {
- if (zv == end) return;
+ if (zv == end) goto next;
}
}
while (zv != end) {
@@ -638,7 +703,8 @@ tail_call:
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (!GC_REF_CHECK_COLOR(ref, GC_BLACK)) {
- gc_scan_black(ref);
+ GC_REF_SET_BLACK(ref);
+ GC_STACK_PUSH(ref);
}
}
zv++;
@@ -647,33 +713,35 @@ tail_call:
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (!GC_REF_CHECK_COLOR(ref, GC_BLACK)) {
+ GC_REF_SET_BLACK(ref);
goto tail_call;
}
- return;
+ goto next;
}
} else {
- return;
+ goto next;
}
} else if (GC_TYPE(ref) == IS_ARRAY) {
if ((zend_array*)ref != &EG(symbol_table)) {
ht = (zend_array*)ref;
} else {
- return;
+ goto next;
}
} else if (GC_TYPE(ref) == IS_REFERENCE) {
if (Z_REFCOUNTED(((zend_reference*)ref)->val)) {
ref = Z_COUNTED(((zend_reference*)ref)->val);
GC_ADDREF(ref);
if (!GC_REF_CHECK_COLOR(ref, GC_BLACK)) {
+ GC_REF_SET_BLACK(ref);
goto tail_call;
}
}
- return;
+ goto next;
} else {
- return;
+ goto next;
}
- if (!ht->nNumUsed) return;
+ if (!ht->nNumUsed) goto next;
p = ht->arData;
end = p + ht->nNumUsed;
while (1) {
@@ -685,7 +753,7 @@ tail_call:
if (Z_REFCOUNTED_P(zv)) {
break;
}
- if (p == end) return;
+ if (p == end) goto next;
}
while (p != end) {
zv = &p->val;
@@ -696,7 +764,8 @@ tail_call:
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (!GC_REF_CHECK_COLOR(ref, GC_BLACK)) {
- gc_scan_black(ref);
+ GC_REF_SET_BLACK(ref);
+ GC_STACK_PUSH(ref);
}
}
p++;
@@ -708,21 +777,26 @@ tail_call:
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
if (!GC_REF_CHECK_COLOR(ref, GC_BLACK)) {
+ GC_REF_SET_BLACK(ref);
+ goto tail_call;
+ }
+
+next:
+ ref = GC_STACK_POP();
+ if (ref) {
goto tail_call;
}
}
-static void gc_mark_grey(zend_refcounted *ref)
+static void gc_mark_grey(zend_refcounted *ref, gc_stack *stack)
{
- HashTable *ht;
+ HashTable *ht = NULL;
Bucket *p, *end;
zval *zv;
+ GC_STACK_DCL(stack);
-tail_call:
- if (!GC_REF_CHECK_COLOR(ref, GC_GREY)) {
- ht = NULL;
+ do {
GC_BENCH_INC(zval_marked_grey);
- GC_REF_SET_COLOR(ref, GC_GREY);
if (GC_TYPE(ref) == IS_OBJECT) {
zend_object *obj = (zend_object*)ref;
@@ -736,31 +810,38 @@ tail_call:
ht = obj->handlers->get_gc(&tmp, &zv, &n);
end = zv + n;
if (EXPECTED(!ht)) {
- if (!n) return;
+ if (!n) goto next;
while (!Z_REFCOUNTED_P(--end)) {
- if (zv == end) return;
+ if (zv == end) goto next;
}
}
while (zv != end) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_DELREF(ref);
- gc_mark_grey(ref);
+ if (!GC_REF_CHECK_COLOR(ref, GC_GREY)) {
+ GC_REF_SET_COLOR(ref, GC_GREY);
+ GC_STACK_PUSH(ref);
+ }
}
zv++;
}
if (EXPECTED(!ht)) {
ref = Z_COUNTED_P(zv);
GC_DELREF(ref);
- goto tail_call;
+ if (!GC_REF_CHECK_COLOR(ref, GC_GREY)) {
+ GC_REF_SET_COLOR(ref, GC_GREY);
+ continue;
+ }
+ goto next;
}
} else {
- return;
+ goto next;
}
} else if (GC_TYPE(ref) == IS_ARRAY) {
if (((zend_array*)ref) == &EG(symbol_table)) {
GC_REF_SET_BLACK(ref);
- return;
+ goto next;
} else {
ht = (zend_array*)ref;
}
@@ -768,14 +849,17 @@ tail_call:
if (Z_REFCOUNTED(((zend_reference*)ref)->val)) {
ref = Z_COUNTED(((zend_reference*)ref)->val);
GC_DELREF(ref);
- goto tail_call;
+ if (!GC_REF_CHECK_COLOR(ref, GC_GREY)) {
+ GC_REF_SET_COLOR(ref, GC_GREY);
+ continue;
+ }
}
- return;
+ goto next;
} else {
- return;
+ goto next;
}
- if (!ht->nNumUsed) return;
+ if (!ht->nNumUsed) goto next;
p = ht->arData;
end = p + ht->nNumUsed;
while (1) {
@@ -787,7 +871,7 @@ tail_call:
if (Z_REFCOUNTED_P(zv)) {
break;
}
- if (p == end) return;
+ if (p == end) goto next;
}
while (p != end) {
zv = &p->val;
@@ -797,7 +881,10 @@ tail_call:
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_DELREF(ref);
- gc_mark_grey(ref);
+ if (!GC_REF_CHECK_COLOR(ref, GC_GREY)) {
+ GC_REF_SET_COLOR(ref, GC_GREY);
+ GC_STACK_PUSH(ref);
+ }
}
p++;
}
@@ -807,8 +894,14 @@ tail_call:
}
ref = Z_COUNTED_P(zv);
GC_DELREF(ref);
- goto tail_call;
- }
+ if (!GC_REF_CHECK_COLOR(ref, GC_GREY)) {
+ GC_REF_SET_COLOR(ref, GC_GREY);
+ continue;
+ }
+
+next:
+ ref = GC_STACK_POP();
+ } while (ref);
}
/* Two-Finger compaction algorithm */
@@ -848,7 +941,7 @@ static void gc_compact(void)
}
}
-static void gc_mark_roots(void)
+static void gc_mark_roots(gc_stack *stack)
{
gc_root_buffer *current, *last;
@@ -859,25 +952,35 @@ static void gc_mark_roots(void)
while (current != last) {
if (GC_IS_ROOT(current->ref)) {
if (GC_REF_CHECK_COLOR(current->ref, GC_PURPLE)) {
- gc_mark_grey(current->ref);
+ GC_REF_SET_COLOR(current->ref, GC_GREY);
+ gc_mark_grey(current->ref, stack);
}
}
current++;
}
}
-static void gc_scan(zend_refcounted *ref)
+static void gc_scan(zend_refcounted *ref, gc_stack *stack)
{
- HashTable *ht;
+ HashTable *ht = NULL;
Bucket *p, *end;
zval *zv;
+ GC_STACK_DCL(stack);
tail_call:
- if (GC_REF_CHECK_COLOR(ref, GC_GREY)) {
+ if (GC_REF_CHECK_COLOR(ref, GC_WHITE)) {
if (GC_REFCOUNT(ref) > 0) {
- gc_scan_black(ref);
+ if (!GC_REF_CHECK_COLOR(ref, GC_BLACK)) {
+ GC_REF_SET_BLACK(ref);
+ if (UNEXPECTED(!_stack->next)) {
+ gc_stack_next(_stack);
+ }
+ /* Split stack and reuse the tail */
+ _stack->next->prev = NULL;
+ gc_scan_black(ref, _stack->next);
+ _stack->next->prev = _stack;
+ }
} else {
- GC_REF_SET_COLOR(ref, GC_WHITE);
if (GC_TYPE(ref) == IS_OBJECT) {
zend_object *obj = (zend_object*)ref;
@@ -890,43 +993,53 @@ tail_call:
ht = obj->handlers->get_gc(&tmp, &zv, &n);
end = zv + n;
if (EXPECTED(!ht)) {
- if (!n) return;
+ if (!n) goto next;
while (!Z_REFCOUNTED_P(--end)) {
- if (zv == end) return;
+ if (zv == end) goto next;
}
}
while (zv != end) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
- gc_scan(ref);
+ if (GC_REF_CHECK_COLOR(ref, GC_GREY)) {
+ GC_REF_SET_COLOR(ref, GC_WHITE);
+ GC_STACK_PUSH(ref);
+ }
}
zv++;
}
if (EXPECTED(!ht)) {
ref = Z_COUNTED_P(zv);
- goto tail_call;
+ if (GC_REF_CHECK_COLOR(ref, GC_GREY)) {
+ GC_REF_SET_COLOR(ref, GC_WHITE);
+ goto tail_call;
+ }
+ goto next;
}
} else {
- return;
+ goto next;
}
} else if (GC_TYPE(ref) == IS_ARRAY) {
if ((zend_array*)ref == &EG(symbol_table)) {
GC_REF_SET_BLACK(ref);
- return;
+ goto next;
} else {
ht = (zend_array*)ref;
}
} else if (GC_TYPE(ref) == IS_REFERENCE) {
if (Z_REFCOUNTED(((zend_reference*)ref)->val)) {
ref = Z_COUNTED(((zend_reference*)ref)->val);
- goto tail_call;
+ if (GC_REF_CHECK_COLOR(ref, GC_GREY)) {
+ GC_REF_SET_COLOR(ref, GC_WHITE);
+ goto tail_call;
+ }
}
- return;
+ goto next;
} else {
- return;
+ goto next;
}
- if (!ht->nNumUsed) return;
+ if (!ht->nNumUsed) goto next;
p = ht->arData;
end = p + ht->nNumUsed;
while (1) {
@@ -938,7 +1051,7 @@ tail_call:
if (Z_REFCOUNTED_P(zv)) {
break;
}
- if (p == end) return;
+ if (p == end) goto next;
}
while (p != end) {
zv = &p->val;
@@ -947,7 +1060,10 @@ tail_call:
}
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
- gc_scan(ref);
+ if (GC_REF_CHECK_COLOR(ref, GC_GREY)) {
+ GC_REF_SET_COLOR(ref, GC_WHITE);
+ GC_STACK_PUSH(ref);
+ }
}
p++;
}
@@ -956,19 +1072,31 @@ tail_call:
zv = Z_INDIRECT_P(zv);
}
ref = Z_COUNTED_P(zv);
- goto tail_call;
+ if (GC_REF_CHECK_COLOR(ref, GC_GREY)) {
+ GC_REF_SET_COLOR(ref, GC_WHITE);
+ goto tail_call;
+ }
}
}
+
+next:
+ ref = GC_STACK_POP();
+ if (ref) {
+ goto tail_call;
+ }
}
-static void gc_scan_roots(void)
+static void gc_scan_roots(gc_stack *stack)
{
gc_root_buffer *current = GC_IDX2PTR(GC_FIRST_ROOT);
gc_root_buffer *last = GC_IDX2PTR(GC_G(first_unused));
while (current != last) {
if (GC_IS_ROOT(current->ref)) {
- gc_scan(current->ref);
+ if (GC_REF_CHECK_COLOR(current->ref, GC_GREY)) {
+ GC_REF_SET_COLOR(current->ref, GC_WHITE);
+ gc_scan(current->ref, stack);
+ }
}
current++;
}
@@ -999,18 +1127,15 @@ static void gc_add_garbage(zend_refcounted *ref)
GC_G(num_roots)++;
}
-static int gc_collect_white(zend_refcounted *ref, uint32_t *flags)
+static int gc_collect_white(zend_refcounted *ref, uint32_t *flags, gc_stack *stack)
{
int count = 0;
- HashTable *ht;
+ HashTable *ht = NULL;
Bucket *p, *end;
zval *zv;
+ GC_STACK_DCL(stack);
-tail_call:
- if (GC_REF_CHECK_COLOR(ref, GC_WHITE)) {
- ht = NULL;
- GC_REF_SET_BLACK(ref);
-
+ do {
/* don't count references for compatibility ??? */
if (GC_TYPE(ref) != IS_REFERENCE) {
count++;
@@ -1036,20 +1161,23 @@ tail_call:
ht = obj->handlers->get_gc(&tmp, &zv, &n);
end = zv + n;
if (EXPECTED(!ht)) {
- if (!n) return count;
+ if (!n) goto next;
while (!Z_REFCOUNTED_P(--end)) {
/* count non-refcounted for compatibility ??? */
if (Z_TYPE_P(zv) != IS_UNDEF) {
count++;
}
- if (zv == end) return count;
+ if (zv == end) goto next;
}
}
while (zv != end) {
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
- count += gc_collect_white(ref, flags);
+ if (GC_REF_CHECK_COLOR(ref, GC_WHITE)) {
+ GC_REF_SET_BLACK(ref);
+ GC_STACK_PUSH(ref);
+ }
/* count non-refcounted for compatibility ??? */
} else if (Z_TYPE_P(zv) != IS_UNDEF) {
count++;
@@ -1059,10 +1187,14 @@ tail_call:
if (EXPECTED(!ht)) {
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
- goto tail_call;
+ if (GC_REF_CHECK_COLOR(ref, GC_WHITE)) {
+ GC_REF_SET_BLACK(ref);
+ continue;
+ }
+ goto next;
}
} else {
- return count;
+ goto next;
}
} else if (GC_TYPE(ref) == IS_ARRAY) {
/* optimization: color is GC_BLACK (0) */
@@ -1074,14 +1206,17 @@ tail_call:
if (Z_REFCOUNTED(((zend_reference*)ref)->val)) {
ref = Z_COUNTED(((zend_reference*)ref)->val);
GC_ADDREF(ref);
- goto tail_call;
+ if (GC_REF_CHECK_COLOR(ref, GC_WHITE)) {
+ GC_REF_SET_BLACK(ref);
+ continue;
+ }
}
- return count;
+ goto next;
} else {
- return count;
+ goto next;
}
- if (!ht->nNumUsed) return count;
+ if (!ht->nNumUsed) goto next;
p = ht->arData;
end = p + ht->nNumUsed;
while (1) {
@@ -1097,7 +1232,7 @@ tail_call:
if (Z_TYPE_P(zv) != IS_UNDEF) {
count++;
}
- if (p == end) return count;
+ if (p == end) goto next;
}
while (p != end) {
zv = &p->val;
@@ -1107,7 +1242,10 @@ tail_call:
if (Z_REFCOUNTED_P(zv)) {
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
- count += gc_collect_white(ref, flags);
+ if (GC_REF_CHECK_COLOR(ref, GC_WHITE)) {
+ GC_REF_SET_BLACK(ref);
+ GC_STACK_PUSH(ref);
+ }
/* count non-refcounted for compatibility ??? */
} else if (Z_TYPE_P(zv) != IS_UNDEF) {
count++;
@@ -1120,12 +1258,19 @@ tail_call:
}
ref = Z_COUNTED_P(zv);
GC_ADDREF(ref);
- goto tail_call;
- }
+ if (GC_REF_CHECK_COLOR(ref, GC_WHITE)) {
+ GC_REF_SET_BLACK(ref);
+ continue;
+ }
+
+next:
+ ref = GC_STACK_POP();
+ } while (ref);
+
return count;
}
-static int gc_collect_roots(uint32_t *flags)
+static int gc_collect_roots(uint32_t *flags, gc_stack *stack)
{
uint32_t idx, end;
zend_refcounted *ref;
@@ -1156,7 +1301,8 @@ static int gc_collect_roots(uint32_t *flags)
ZEND_ASSERT(GC_IS_ROOT(ref));
current->ref = GC_MAKE_GARBAGE(ref);
if (GC_REF_CHECK_COLOR(ref, GC_WHITE)) {
- count += gc_collect_white(ref, flags);
+ GC_REF_SET_BLACK(ref);
+ count += gc_collect_white(ref, flags, stack);
}
idx++;
}
@@ -1269,6 +1415,10 @@ ZEND_API int zend_gc_collect_cycles(void)
zend_refcounted *p;
uint32_t gc_flags = 0;
uint32_t idx, end;
+ gc_stack stack;
+
+ stack.prev = NULL;
+ stack.next = NULL;
if (GC_G(gc_active)) {
return 0;
@@ -1279,12 +1429,14 @@ ZEND_API int zend_gc_collect_cycles(void)
GC_G(gc_active) = 1;
GC_TRACE("Marking roots");
- gc_mark_roots();
+ gc_mark_roots(&stack);
GC_TRACE("Scanning roots");
- gc_scan_roots();
+ gc_scan_roots(&stack);
GC_TRACE("Collecting roots");
- count = gc_collect_roots(&gc_flags);
+ count = gc_collect_roots(&gc_flags, &stack);
+
+ gc_stack_free(&stack);
if (!GC_G(num_roots)) {
/* nothing to free */
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