QObject: fix a memory leak in moveToThread

For some reason it seems to be supported to call moveToThread(0).
That call will allocate a new QThreadData for the object. However,
if we then detect that we're calling moveToThread from a thread
which is not the one the QObject has affinity with,
we error out leaking that QThreadData object.

Change-Id: I0fe6625a2a9887535e457f3897b514d2a03d1480
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/src/corelib/kernel/qobject.cpp b/src/corelib/kernel/qobject.cpp
index e588808ee8..9ab952362c 100644
--- a/src/corelib/kernel/qobject.cpp
+++ b/src/corelib/kernel/qobject.cpp
@@ -1461,14 +1461,14 @@ void QObject::moveToThread(QThread *targetThread)
     }
 
     QThreadData *currentData = QThreadData::current();
-    QThreadData *targetData = targetThread ? QThreadData::get2(targetThread) : new QThreadData(0);
+    QThreadData *targetData = targetThread ? QThreadData::get2(targetThread) : Q_NULLPTR;
     if (d->threadData->thread == 0 && currentData == targetData) {
         // one exception to the rule: we allow moving objects with no thread affinity to the current thread
         currentData = d->threadData;
     } else if (d->threadData != currentData) {
         qWarning("QObject::moveToThread: Current thread (%p) is not the object's thread (%p).\n"
                  "Cannot move to target thread (%p)\n",
-                 currentData->thread, d->threadData->thread, targetData->thread);
+                 currentData->thread, d->threadData->thread, targetData ? targetData->thread : Q_NULLPTR);
 
 #ifdef Q_OS_MAC
         qWarning("On Mac OS X, you might be loading two sets of Qt binaries into the same process. "
@@ -1482,6 +1482,9 @@ void QObject::moveToThread(QThread *targetThread)
     // prepare to move
     d->moveToThread_helper();
 
+    if (!targetData)
+        targetData = new QThreadData(0);
+
     QOrderedMutexLocker locker(&currentData->postEventList.mutex,
                                &targetData->postEventList.mutex);