Fix phpGH-10496: Fibers must not be garbage collected while implicitly suspended by resumption of another fiber

Author: bwoebi

Zend/tests/fibers/gh10496.phpt renamed to Zend/tests/fibers/gh10496-001.phpt

@@ -1,5 +1,5 @@
 --TEST--
-Bug GH-10496 (Segfault when garbage collector is invoked inside of fiber)
+Bug GH-10496 001 (Segfault when garbage collector is invoked inside of fiber)
 --FILE--
 <?php
 

Zend/tests/fibers/gh10496-002.phpt

@@ -0,0 +1,26 @@
+--TEST--
+Bug GH-10496 002 (Segfault when garbage collector is invoked inside of fiber)
+--FILE--
+<?php
+
+function pollute_stack_and_suspend($a = 1, $b = 2, $c = 3) {
+    Fiber::suspend();
+}
+
+$f = new Fiber(function() use (&$f) {
+    pollute_stack_and_suspend();
+    (function() {
+        (function() {
+            (new Fiber(function() {
+                gc_collect_cycles();
+                echo "Success\n";
+            }))->start();
+        })();
+    })();
+});
+$f->start();
+$f->resume();
+
+?>
+--EXPECT--
+Success

Zend/zend_fibers.c

@@ -644,7 +644,7 @@ static HashTable *zend_fiber_object_gc(zend_object *object, zval **table, int *n
 	zend_get_gc_buffer_add_zval(buf, &fiber->fci.function_name);
 	zend_get_gc_buffer_add_zval(buf, &fiber->result);
 
-	if (fiber->context.status != ZEND_FIBER_STATUS_SUSPENDED) {
+	if (fiber->context.status != ZEND_FIBER_STATUS_SUSPENDED || fiber->caller != NULL) {
 		zend_get_gc_buffer_use(buf, table, num);
 		return NULL;
 	}