Handle signals in the registered object's thread

Do not call `sender()` from a different thread. As the API documentation
indicates, that is not supported and can lead to crashes as experienced
on the CI frequently.

Instead, we now have per-thread SignalHandlers and use those to get
notified about signals and metacall events.

Moving a registered object into a different thread isn't supported once
it was registered. But the object can be deregistered, moved, and then
re-registered.

[ChangeLog] Signals from objects living in a different thread than the
QWebChannel are now handled correctly.

Task-number: QTBUG-51366
Change-Id: I1edb0694b946a494b6c0d4a8a6dc6b452dcb2c7a
Reviewed-by: Arno Rehn <a.rehn@menlosystems.com>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/src/webchannel/signalhandler_p.h b/src/webchannel/signalhandler_p.h
index 8fdf598..942c020 100644
--- a/src/webchannel/signalhandler_p.h
+++ b/src/webchannel/signalhandler_p.h
@@ -56,6 +56,7 @@
 #include <QList>
 #include <QMetaMethod>
 #include <QDebug>
+#include <QThread>
 
 QT_BEGIN_NAMESPACE
 
@@ -71,6 +72,7 @@ static const int s_destroyedSignalIndex = QObject::staticMetaObject.indexOfMetho
 template<class Receiver>
 class SignalHandler : public QObject
 {
+    Q_DISABLE_COPY(SignalHandler)
 public:
     SignalHandler(Receiver *receiver, QObject *parent = 0);
 
@@ -268,6 +270,7 @@ int SignalHandler<Receiver>::qt_metacall(QMetaObject::Call call, int methodId, v
     if (call == QMetaObject::InvokeMetaMethod) {
         const QObject *object = sender();
         Q_ASSERT(object);
+        Q_ASSERT(QThread::currentThread() == object->thread());
         Q_ASSERT(senderSignalIndex() == methodId);
         Q_ASSERT(m_connectionsCounter.contains(object));
         Q_ASSERT(m_connectionsCounter.value(object).contains(methodId));