Improve reliability of GC related tests

Fixes propertyVarCircular2 in clang release builds for example.

Some of the QML/GC related tests had functions like

   function deassign()
   {
       someVariableThatWasholdingSomethingThatShouldBeCollectedNow = null;
       gc();
   }

which work fine with an exact GC like in v8, but with our conservative
collector they are not that reliable and much more vulnerable to a reference
to the object still being around somewhere. So to improve the reliability
of the test, this patch moves the gc() calls out of the JavaScript function
and back to the C++ caller side (these functions are invoked via QMetaObject::invokeMethod),
where the existing gc() helper function will call the collector and also
process posted deferred deletion events for QObjects.

Change-Id: I8c1f715d56d66bc567ea8bd1575f171460b15ac8
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@digia.com>

1 files changed, 16 insertions, 25 deletions

diff --git a/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp b/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
index 5df580b865..fd563f6304 100644
--- a/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
+++ b/tests/auto/qml/qqmlecmascript/tst_qqmlecmascript.cpp
@@ -298,6 +298,13 @@ private:
     QQmlEngine engine;
 };
 
+static void gc(QQmlEngine &engine)
+{
+    engine.collectGarbage();
+    QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete);
+    QCoreApplication::processEvents();
+}
+
 void tst_qqmlecmascript::initTestCase()
 {
     QQmlDataTest::initTestCase();
@@ -4171,6 +4178,7 @@ void tst_qqmlecmascript::scarceResources_other()
     QMetaObject::invokeMethod(object, "assignVarProperty");
     QVERIFY(v4->scarceResources.isEmpty());             // the scarce resource is a VME property.
     QMetaObject::invokeMethod(object, "deassignVarProperty");
+    gc(engine);
     QVERIFY(v4->scarceResources.isEmpty());             // should still be empty; the resource should have been released on gc.
     delete object;
 
@@ -4641,13 +4649,6 @@ void tst_qqmlecmascript::propertyVarCpp()
     delete object;
 }
 
-static void gc(QQmlEngine &engine)
-{
-    engine.collectGarbage();
-    QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete);
-    QCoreApplication::processEvents();
-}
-
 void tst_qqmlecmascript::propertyVarOwnership()
 {
     // Referenced JS objects are not collected
@@ -4748,8 +4749,7 @@ void tst_qqmlecmascript::propertyVarImplicitOwnership()
     QCoreApplication::processEvents();
     QVERIFY(!qobjectGuard.isNull());
     QMetaObject::invokeMethod(object, "deassignCircular");
-    QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete); // process deleteLater() events from QV8QObjectWrapper.
-    QCoreApplication::processEvents();
+    gc(engine);
     QVERIFY(qobjectGuard.isNull());                                // should have been collected now.
     delete object;
 }
@@ -4783,15 +4783,13 @@ void tst_qqmlecmascript::propertyVarReparent()
     // now reparent the "Image" object (currently, it has JS ownership)
     image->setParent(text);                                        // shouldn't be collected after deassignVp now, since has a parent.
     QMetaObject::invokeMethod(text2, "deassignVp");
-    QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete); // process deleteLater() events from QV8QObjectWrapper.
-    QCoreApplication::processEvents();
+    gc(engine);
     QCOMPARE(text->property("textCanary").toInt(), 11);
     QCOMPARE(text2->property("textCanary").toInt(), 22);
     QVERIFY(!imageGuard.isNull());                                 // should still be alive.
     QCOMPARE(image->property("imageCanary").toInt(), 13);          // still able to access var properties
     QMetaObject::invokeMethod(object, "deassignVarProp");          // now deassign the root-object's vp, causing gc of rect+text+text2
-    QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete); // process deleteLater() events from QV8QObjectWrapper.
-    QCoreApplication::processEvents();
+    gc(engine);
     QVERIFY(imageGuard.isNull());                                  // should now have been deleted, due to parent being deleted.
     delete object;
 }
@@ -4827,8 +4825,7 @@ void tst_qqmlecmascript::propertyVarReparentNullContext()
     // now reparent the "Image" object (currently, it has JS ownership)
     image->setParent(object);                                      // reparented to base object.  after deassignVarProp, the ctxt will be invalid.
     QMetaObject::invokeMethod(object, "deassignVarProp");          // now deassign the root-object's vp, causing gc of rect+text+text2
-    QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete); // process deleteLater() events from QV8QObjectWrapper.
-    QCoreApplication::processEvents();
+    gc(engine);
     QVERIFY(!imageGuard.isNull());                                 // should still be alive.
     QVERIFY(!image->property("imageCanary").isValid());            // but varProperties won't be available (null context).
     delete object;
@@ -4850,12 +4847,10 @@ void tst_qqmlecmascript::propertyVarCircular()
     QPixmap canaryResourcePixmap = canaryResourceVariant.value<QPixmap>();
     canaryResourceVariant = QVariant();                            // invalidate it to remove one copy of the pixmap from memory.
     QMetaObject::invokeMethod(object, "deassignCanaryResource");   // remove one copy of the pixmap from memory
-    QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete); // process deleteLater() events from QV8QObjectWrapper.
-    QCoreApplication::processEvents();
+    gc(engine);
     QVERIFY(!canaryResourcePixmap.isDetached());                   // two copies extant - this and the propertyVar.vp.vp.vp.vp.memoryHog.
     QMetaObject::invokeMethod(object, "deassignCircular");         // cause deassignment and gc
-    QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete); // process deleteLater() events from QV8QObjectWrapper.
-    QCoreApplication::processEvents();
+    gc(engine);
     QCOMPARE(object->property("canaryInt"), QVariant(2));
     QCOMPARE(object->property("canaryResource"), QVariant(1));
     QVERIFY(canaryResourcePixmap.isDetached());                    // now detached, since orig copy was member of qdvmemo which was deleted.
@@ -4884,8 +4879,7 @@ void tst_qqmlecmascript::propertyVarCircular2()
     QCOMPARE(rootObject->property("rectCanary").toInt(), 5);
     QCOMPARE(childObject->property("textCanary").toInt(), 10);
     QMetaObject::invokeMethod(object, "deassignCircular");
-    QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete); // process deleteLater() events from QV8QObjectWrapper.
-    QCoreApplication::processEvents();
+    gc(engine);
     QVERIFY(rootObjectTracker.isNull());                           // should have been collected
     QVERIFY(childObjectTracker.isNull());                          // should have been collected
     delete object;
@@ -4934,8 +4928,6 @@ void tst_qqmlecmascript::propertyVarInheritance()
     }
     // now we deassign the var prop, which should trigger collection of item subtrees.
     QMetaObject::invokeMethod(object, "deassignCircular");         // cause deassignment and gc
-    QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete); // process deleteLater() events from QV8QObjectWrapper.
-    QCoreApplication::processEvents();
     // ensure that there are only weak handles to the underlying varProperties array remaining.
     gc(engine);
     // an equivalent for pragma GCC optimize is still work-in-progress for CLang, so this test will fail.
@@ -4976,8 +4968,7 @@ void tst_qqmlecmascript::propertyVarInheritance2()
         QCOMPARE(childObject->property("textCanary").toInt(), 10);
     }
     QMetaObject::invokeMethod(object, "deassignCircular");
-    QCoreApplication::sendPostedEvents(0, QEvent::DeferredDelete); // process deleteLater() events from QV8QObjectWrapper.
-    QCoreApplication::processEvents();
+    gc(engine);
     // an equivalent for pragma GCC optimize is still work-in-progress for CLang, so this test will fail.
 #if !defined(Q_CC_CLANG)
     QVERIFY(childObjectVarArrayValueHandle.isEmpty()); // should have been collected now.