Improve suppression of spurious socket notifications under Windows

There were still two cases where spurious notifications would be
possible:

    - user calls hasPendingDatagrams()/pendingDatagramSize() on UDP
      socket somewhere outside the slot connected to readyRead()
      signal (::WSARecvFrom posts FD_READ notification, even if
      a notification for incoming datagram already exists in the
      message queue);
    - a socket was registered to receive several types of event and
      WM_QT_ACTIVATENOTIFIERS message is located between the
      different events for this socket in the queue.

Provided patch ensures that the message queue is synchronized with
the Qt event processing mechanism and adds a way to detect spurious
notifications inside the window procedure.

Task-number: QTBUG-58214
Change-Id: I49609dace601f300de09875ff1653617efabd72f
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Peter Seiderer <ps.report@gmx.net>

1 files changed, 5 insertions, 0 deletions

diff --git a/tests/auto/corelib/kernel/qsocketnotifier/tst_qsocketnotifier.cpp b/tests/auto/corelib/kernel/qsocketnotifier/tst_qsocketnotifier.cpp
index 1598382959..a52b80170f 100644
--- a/tests/auto/corelib/kernel/qsocketnotifier/tst_qsocketnotifier.cpp
+++ b/tests/auto/corelib/kernel/qsocketnotifier/tst_qsocketnotifier.cpp
@@ -360,11 +360,16 @@ void tst_QSocketNotifier::asyncMultipleDatagram()
     QSignalSpy spy(m_asyncReceiver, &QIODevice::readyRead);
     connect(m_asyncReceiver, &QIODevice::readyRead, this,
             &tst_QSocketNotifier::async_readDatagramSlot);
+
+    // activate socket notifiers
+    QTestEventLoop::instance().enterLoopMSecs(100);
+
     m_asyncSender->writeDatagram("1", makeNonAny(m_asyncReceiver->localAddress()), port);
     m_asyncSender->writeDatagram("2", makeNonAny(m_asyncReceiver->localAddress()), port);
     // wait a little to ensure that the datagrams we've just sent
     // will be delivered on receiver side.
     QTest::qSleep(100);
+    QVERIFY(m_asyncReceiver->hasPendingDatagrams());
 
     QTimer::singleShot(500, this, &tst_QSocketNotifier::async_writeDatagramSlot);