Cherry pick fix for #79657

Author: nikic

NEWS

@@ -2,15 +2,14 @@ PHP                                                                        NEWS
 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 ?? ??? ????, PHP 7.4.7
 
-
-28 May 2020, PHP 7.4.7RC1
-
 - Core:
   . Fixed bug #79599 (coredump in set_error_handler). (Laruence)
   . Fixed bug #79566 (Private SHM is not private on Windows). (cmb)
   . Fixed bug #79489 (.user.ini does not inherit). (cmb)
   . Fixed bug #79600 (Regression in 7.4.6 when yielding an array based
     generator). (Nikita)
+  . Fixed bug #79657 ("yield from" hangs when invalid value encountered).
+    (Nikita)
 
 - FFI:
   . Fixed bug #79571 (FFI: var_dumping unions may segfault). (cmb)

Zend/tests/bug79657.phpt

@@ -0,0 +1,42 @@
+--TEST--
+Bug #79657: "yield from" hangs when invalid value encountered
+--FILE--
+<?php
+
+function throwException(): iterable
+{
+    throw new Exception();
+}
+
+function loop(): iterable
+{
+    $callbacks = [
+        function () {
+            yield 'first';
+        },
+        function () {
+            yield from throwException();
+        }
+    ];
+
+    foreach ($callbacks as $callback) {
+        yield from $callback();
+    }
+}
+
+function get(string $first, int $second): array
+{
+    return [];
+}
+
+get(...loop());
+
+?>
+--EXPECTF--
+Fatal error: Uncaught Exception in %s:%d
+Stack trace:
+#0 %s(%d): throwException()
+#1 %s(%d): {closure}()
+#2 %s(%d): loop()
+#3 {main}
+  thrown in %s on line %d

Zend/zend_generators.c

@@ -857,6 +857,7 @@ ZEND_API void zend_generator_resume(zend_generator *orig_generator) /* {{{ */
 			} else {
 				generator = zend_generator_get_current(orig_generator);
 				zend_generator_throw_exception(generator, NULL);
+				orig_generator->flags &= ~ZEND_GENERATOR_DO_INIT;
 				goto try_again;
 			}
 		}