Fix undefined return value of fiber after bailout (#7103)

Author: twose

Zend/tests/fibers/get-return-after-bailout.phpt

@@ -0,0 +1,25 @@
+--TEST--
+Fiber::getReturn() after bailout
+--FILE--
+<?php
+
+register_shutdown_function(static function (): void {
+    global $fiber;
+    var_dump($fiber->getReturn());
+});
+
+$fiber = new Fiber(static function (): void {
+    str_repeat('X', PHP_INT_MAX);
+});
+$fiber->start();
+
+?>
+--EXPECTF--
+Fatal error: Allowed memory size of %d bytes exhausted%s(tried to allocate %d bytes) %sget-return-after-bailout.php on line %d
+
+Fatal error: Uncaught FiberError: Cannot get fiber return value: The fiber exited with a fatal error in %sget-return-after-bailout.php:%d
+Stack trace:
+#0 %sget-return-after-bailout.php(%d): Fiber->getReturn()
+#1 [internal function]: {closure}()
+#2 {main}
+  thrown in %sget-return-after-bailout.php on line %d

Zend/zend_fibers.c

@@ -673,6 +673,8 @@ ZEND_METHOD(Fiber, getReturn)
 	if (fiber->status == ZEND_FIBER_STATUS_DEAD) {
 		if (fiber->flags & ZEND_FIBER_FLAG_THREW) {
 			message = "The fiber threw an exception";
+		} else if (fiber->flags & ZEND_FIBER_FLAG_BAILOUT) {
+			message = "The fiber exited with a fatal error";
 		} else {
 			RETURN_COPY(&fiber->value);
 		}