Add new special QObjectPrivate::{connect, disconnect} for QML

Original QML-specific connection mechanism ignores the receiver argument
and uses sender as receiver. This causes uncontrollable memory growth
in certain cases as connections on receiver persist even after receiver
is destroyed

New connect() with receiver parameter uses underlying API correctly,
disconnect is provided for the symmetry (not sure it's really needed)

Task-number: QTBUG-86368
Pick-to: 5.15 6.0
Change-Id: I4580d75b617cb2c4dfb971a4dfb8e943e325572b
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/tests/auto/corelib/kernel/qobject/tst_qobject.cpp b/tests/auto/corelib/kernel/qobject/tst_qobject.cpp
index 8513375a20..a7b47438e0 100644
--- a/tests/auto/corelib/kernel/qobject/tst_qobject.cpp
+++ b/tests/auto/corelib/kernel/qobject/tst_qobject.cpp
@@ -152,6 +152,7 @@ private slots:
     void connectBase();
     void connectWarnings();
     void qmlConnect();
+    void qmlConnectToQObjectReceiver();
     void exceptions();
     void noDeclarativeParentChangedOnDestruction();
     void deleteLaterInAboutToBlockHandler();
@@ -6790,6 +6791,33 @@ void tst_QObject::qmlConnect()
 #endif
 }
 
+void tst_QObject::qmlConnectToQObjectReceiver()
+{
+#ifdef QT_BUILD_INTERNAL
+    SenderObject sender;
+    QScopedPointer<QObject> receiver(new QObject);
+    QmlReceiver *slotObject = new QmlReceiver;
+    slotObject->magic = slotObject;
+    slotObject->ref(); // extra ref so that slot object is not implicitly deleted
+
+    QVERIFY(QObjectPrivate::connect(&sender, sender.metaObject()->indexOfSignal("signal1()"),
+                                    receiver.get(), slotObject, Qt::AutoConnection));
+
+    QCOMPARE(slotObject->callCount, 0);
+    sender.emitSignal1();
+    QCOMPARE(slotObject->callCount, 1);
+
+    receiver.reset(); // this should disconnect the slotObject
+
+    sender.emitSignal1();
+    QCOMPARE(slotObject->callCount, 1);
+
+    slotObject->destroyIfLastRef();
+#else
+    QSKIP("Needs QT_BUILD_INTERNAL");
+#endif
+}
+
 #ifndef QT_NO_EXCEPTIONS
 class ObjectException : public std::exception { };