Do not hold fiber after suspension

Author: arnaud-lb

Zend/tests/fibers/destructors_005.phpt

@@ -8,36 +8,53 @@ register_shutdown_function(function () {
 });
 
 class Cycle {
-    public static $counter = 0;
     public $self;
-    public function __construct() {
+    public function __construct(public int $id) {
         $this->self = $this;
     }
     public function __destruct() {
-        $id = self::$counter++;
-        printf("%d: Start destruct\n", $id);
+        printf("%d: Start destruct\n", $this->id);
         try {
-            if ($id === 0) {
+            if ($this->id === 0) {
+                /* Fiber will be collected by GC because it's not referenced */
+                Fiber::suspend(new stdClass);
+            } else if ($this->id === 1) {
+                /* Fiber will be dtor during shutdown */
+                global $f2;
+                $f2 = Fiber::getCurrent();
                 Fiber::suspend(new stdClass);
             }
         } finally {
-            printf("%d: End destruct\n", $id);
+            printf("%d: End destruct\n", $this->id);
         }
     }
 }
 
-$f = new Fiber(function () {
-    new Cycle();
-    new Cycle();
+$refs = [];
+$f = new Fiber(function () use (&$refs) {
+    $refs[] = WeakReference::create(new Cycle(0));
+    $refs[] = WeakReference::create(new Cycle(1));
+    $refs[] = WeakReference::create(new Cycle(2));
     gc_collect_cycles();
 });
 
 $f->start();
 
+gc_collect_cycles();
+
+foreach ($refs as $id => $ref) {
+    printf("%d: %s\n", $id, $ref->get() ? 'Live' : 'Collected');
+}
+
 ?>
 --EXPECT--
+2: Start destruct
+2: End destruct
 0: Start destruct
+0: End destruct
 1: Start destruct
-1: End destruct
+0: Collected
+1: Live
+2: Collected
 Shutdown
-0: End destruct
+1: End destruct

Zend/zend_gc.c

@@ -1838,10 +1838,6 @@ static zend_always_inline zend_result gc_call_destructors(uint32_t idx, uint32_t
 				if (UNEXPECTED(fiber != NULL && GC_G(dtor_fiber) != fiber)) {
 					/* We resumed after suspension */
 					gc_check_possible_root((zend_refcounted*)&obj->gc);
-
-					GC_DELREF(&fiber->std);
-					gc_check_possible_root((zend_refcounted*)&fiber->std.gc);
-
 					return FAILURE;
 				}
 			}
@@ -1901,6 +1897,9 @@ static zend_never_inline void gc_call_destructors_in_fiber(uint32_t end)
 			GC_TRACE("destructor fiber suspended by destructor");
 			GC_G(dtor_fiber) = NULL;
 			GC_G(dtor_idx)++;
+			/* We do not own the fiber anymore. It may be collected if the
+			 * application does not reference it. */
+			zend_object_release(&fiber->std);
 			fiber = gc_create_destructor_fiber();
 			continue;
 		} else {