Fix assertion failure in generator dtor

Zend/tests/gh15866.phpt

@@ -0,0 +1,53 @@
+--TEST--
+GH-15866: Core dumped in Zend/zend_generators.c
+--FILE--
+<?php
+
+class Canary {
+    public function __construct(public mixed $value) {}
+    public function __destruct() {
+        printf("%s\n", __METHOD__);
+    }
+}
+
+function g() {
+    Fiber::suspend();
+}
+
+function f($canary) {
+    try {
+        var_dump(yield from g());
+    } finally {
+        print "Generator finally\n";
+    }
+}
+
+$canary = new Canary(null);
+$iterable = f($canary);
+$fiber = new Fiber(function () use ($iterable, $canary) {
+    try {
+        $iterable->next();
+    } finally {
+        print "Fiber finally\n";
+    }
+});
+$canary->value = $fiber;
+$fiber->start();
+
+// Reset roots
+gc_collect_cycles();
+
+// Add to roots, create garbage cycles
+$fiber = $iterable = $canary = null;
+
+print "Collect cycles\n";
+gc_collect_cycles();
+
+?>
+==DONE==
+--EXPECT--
+Collect cycles
+Canary::__destruct
+Generator finally
+Fiber finally
+==DONE==

Zend/zend_generators.c

@@ -218,43 +218,30 @@ static zend_always_inline void clear_link_to_root(zend_generator *generator) {
 	}
 }
 
-/* In the context of zend_generator_dtor_storage during shutdown, check if
- * the intermediate node 'generator' is running in a fiber */
+/* Check if the node 'generator' is running in a fiber */
 static inline bool check_node_running_in_fiber(zend_generator *generator) {
-	ZEND_ASSERT(EG(flags) & EG_FLAGS_IN_SHUTDOWN);
 	ZEND_ASSERT(generator->execute_data);
 
-	if (generator->flags & ZEND_GENERATOR_IN_FIBER) {
+	if (EXPECTED(generator->flags & ZEND_GENERATOR_IN_FIBER)) {
 		return true;
 	}
 
-	if (generator->node.children == 0) {
+	if (EXPECTED(generator->node.children == 0)) {
 		return false;
 	}
 
-	if (generator->flags & ZEND_GENERATOR_DTOR_VISITED) {
-		return false;
-	}
-	generator->flags |= ZEND_GENERATOR_DTOR_VISITED;
-
 	if (generator->node.children == 1) {
-		if (check_node_running_in_fiber(generator->node.child.single)) {
-			goto in_fiber;
-		}
-		return false;
+		return check_node_running_in_fiber(generator->node.child.single);
 	}
 
 	zend_generator *child;
 	ZEND_HASH_FOREACH_PTR(generator->node.child.ht, child) {
 		if (check_node_running_in_fiber(child)) {
-			goto in_fiber;
+			return true;
 		}
 	} ZEND_HASH_FOREACH_END();
-	return false;
 
-in_fiber:
-	generator->flags |= ZEND_GENERATOR_IN_FIBER;
-	return true;
+	return false;
 }
 
 static void zend_generator_dtor_storage(zend_object *object) /* {{{ */

Zend/zend_generators.h

@@ -93,7 +93,6 @@ static const zend_uchar ZEND_GENERATOR_FORCED_CLOSE      = 0x2;
 static const zend_uchar ZEND_GENERATOR_AT_FIRST_YIELD    = 0x4;
 static const zend_uchar ZEND_GENERATOR_DO_INIT           = 0x8;
 static const zend_uchar ZEND_GENERATOR_IN_FIBER          = 0x10;
-static const zend_uchar ZEND_GENERATOR_DTOR_VISITED      = 0x20;
 
 void zend_register_generator_ce(void);
 ZEND_API void zend_generator_close(zend_generator *generator, bool finished_execution);