Avoid calling gc in QQmlEngine destructor.

GC may be expensive. GC call in QQmlEngine doesn't have much sense
because V8 will destroy all objects living in a current context.
The only problem is that V8 may decide to not invoke weak callbacks
which may cause a memory leak. To avoid that we track all QObjects that
have JavaScript ownership set and we delete them explicitly.

The change reduce time of destroying QQmlEngine by 75%, which is really
visible in qquicklistmodel test.

Change-Id: I2a3668fd23630669114baee8c241a7ecc4100e33
Reviewed-by: Chris Adams <christopher.adams@nokia.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/tests/auto/qml/qjsengine/tst_qjsengine.cpp b/tests/auto/qml/qjsengine/tst_qjsengine.cpp
index e34304b258..5ebc42a453 100644
--- a/tests/auto/qml/qjsengine/tst_qjsengine.cpp
+++ b/tests/auto/qml/qjsengine/tst_qjsengine.cpp
@@ -120,6 +120,7 @@ private slots:
 #endif
     void newQObject_promoteNonObject();
     void newQObject_promoteNonQScriptObject();
+    void newQObject_deletedEngine();
 #if 0 // ### FIXME: No QScript Metaobject support right now
     void newQMetaObject();
     void newActivationObject();
@@ -1120,6 +1121,19 @@ void tst_QJSEngine::newQObject_promoteNonQScriptObject()
 #endif
 }
 
+void tst_QJSEngine::newQObject_deletedEngine()
+{
+    QJSValue object;
+    QObject *ptr = new QObject();
+    QSignalSpy spy(ptr, SIGNAL(destroyed()));
+    {
+        QJSEngine engine;
+        object = engine.newQObject(ptr);
+        engine.globalObject().setProperty("obj", object);
+    }
+    QTRY_VERIFY(spy.count());
+}
+
 #if 0 // ### FIXME: No QScript Metaobject support right now
 QT_BEGIN_NAMESPACE
 Q_SCRIPT_DECLARE_QMETAOBJECT(QObject, QObject*)