Don't crash if the relayed signal was emitted from the wrong thread

Under normal circumstances, this should never happen. Signals exported
to D-Bus should only be emitted from the object's own thread. That's the
only way for the receiver (the QDBusAdaptorConnector object) to know
what the sender object and signal were. If they are emitted from another
thread, the sender will be null.

Task-number: QTBUG-31932
Change-Id: Ia5a45d648985e0645bffd4abc0881fca9da64f79
(cherry-picked from qtbase commit d94961d08f91696824d9035f666af5fe28d59ef6)
Reviewed-by: Peter Seiderer <ps.report@gmx.net>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 9 insertions, 1 deletions

diff --git a/src/dbus/qdbusabstractadaptor.cpp b/src/dbus/qdbusabstractadaptor.cpp
index 84c30cd..9ce843e 100644
--- a/src/dbus/qdbusabstractadaptor.cpp
+++ b/src/dbus/qdbusabstractadaptor.cpp
@@ -267,7 +267,15 @@ void QDBusAdaptorConnector::polish()
 void QDBusAdaptorConnector::relaySlot(void **argv)
 {
     QObjectPrivate *d = static_cast<QObjectPrivate *>(d_ptr.data());
-    relay(d->currentSender->sender, d->currentSender->signal, argv);
+    if (Q_LIKELY(d->currentSender)) {
+        relay(d->currentSender->sender, d->currentSender->signal, argv);
+    } else {
+        qWarning("QtDBus: cannot relay signals from parent %s(%p \"%s\") unless they are emitted in the object's thread %s(%p \"%s\"). "
+                 "Current thread is %s(%p \"%s\").",
+                 parent()->metaObject()->className(), parent(), qPrintable(parent()->objectName()),
+                 parent()->thread()->metaObject()->className(), parent()->thread(), qPrintable(parent()->thread()->objectName()),
+                 QThread::currentThread()->metaObject()->className(), QThread::currentThread(), qPrintable(QThread::currentThread()->objectName()));
+    }
 }
 
 void QDBusAdaptorConnector::relay(QObject *senderObj, int lastSignalIdx, void **argv)