5 files changed, 63 insertions, 6 deletions

diff --git a/src/corelib/kernel/qcoreapplication.cpp b/src/corelib/kernel/qcoreapplication.cpp
index e47dc0dff2..9ad7970807 100644
--- a/src/corelib/kernel/qcoreapplication.cpp
+++ b/src/corelib/kernel/qcoreapplication.cpp
@@ -538,6 +538,14 @@ QThread *QCoreApplicationPrivate::mainThread()
     return theMainThread;
 }
 
+bool QCoreApplicationPrivate::threadRequiresCoreApplication()
+{
+    QThreadData *data = QThreadData::current(false);
+    if (!data)
+        return true;    // default setting
+    return data->requiresCoreApplication;
+}
+
 void QCoreApplicationPrivate::checkReceiverThread(QObject *receiver)
 {
     QThread *currentThread = QThread::currentThread();
@@ -926,6 +934,8 @@ bool QCoreApplication::isQuitLockEnabled()
     return quitLockRefEnabled;
 }
 
+static bool doNotify(QObject *, QEvent *);
+
 /*!
     Enables the ability of the QEventLoopLocker feature to quit
     the application.
@@ -960,7 +970,8 @@ bool QCoreApplication::notifyInternal(QObject *receiver, QEvent *event)
 */
 bool QCoreApplication::notifyInternal2(QObject *receiver, QEvent *event)
 {
-    if (!self)
+    bool selfRequired = QCoreApplicationPrivate::threadRequiresCoreApplication();
+    if (!self && selfRequired)
         return false;
 
     // Make it possible for Qt Script to hook into events even
@@ -978,6 +989,8 @@ bool QCoreApplication::notifyInternal2(QObject *receiver, QEvent *event)
     QObjectPrivate *d = receiver->d_func();
     QThreadData *threadData = d->threadData;
     QScopedLoopLevelCounter loopLevelCounter(threadData);
+    if (!selfRequired)
+        return doNotify(receiver, event);
     return self->notify(receiver, event);
 }
 
@@ -1039,7 +1052,11 @@ bool QCoreApplication::notify(QObject *receiver, QEvent *event)
     // no events are delivered after ~QCoreApplication() has started
     if (QCoreApplicationPrivate::is_app_closing)
         return true;
+    return doNotify(receiver, event);
+}
 
+static bool doNotify(QObject *receiver, QEvent *event)
+{
     if (receiver == 0) {                        // serious error
         qWarning("QCoreApplication::notify: Unexpected null receiver");
         return true;
@@ -1054,7 +1071,10 @@ bool QCoreApplication::notify(QObject *receiver, QEvent *event)
 
 bool QCoreApplicationPrivate::sendThroughApplicationEventFilters(QObject *receiver, QEvent *event)
 {
-    if (receiver->d_func()->threadData == this->threadData && extraData) {
+    // We can't access the application event filters outside of the main thread (race conditions)
+    Q_ASSERT(receiver->d_func()->threadData->thread == mainThread());
+
+    if (extraData) {
         // application event filters are only called for objects in the GUI thread
         for (int i = 0; i < extraData->eventFilters.size(); ++i) {
             QObject *obj = extraData->eventFilters.at(i);
@@ -1097,7 +1117,9 @@ bool QCoreApplicationPrivate::sendThroughObjectEventFilters(QObject *receiver, Q
 bool QCoreApplicationPrivate::notify_helper(QObject *receiver, QEvent * event)
 {
     // send to all application event filters (only does anything in the main thread)
-    if (QCoreApplication::self->d_func()->sendThroughApplicationEventFilters(receiver, event))
+    if (QCoreApplication::self
+            && receiver->d_func()->threadData->thread == mainThread()
+            && QCoreApplication::self->d_func()->sendThroughApplicationEventFilters(receiver, event))
         return true;
     // send to all receiver event filters
     if (sendThroughObjectEventFilters(receiver, event))
diff --git a/src/corelib/kernel/qcoreapplication_p.h b/src/corelib/kernel/qcoreapplication_p.h
index 5fed850c2b..21f59d8197 100644
--- a/src/corelib/kernel/qcoreapplication_p.h
+++ b/src/corelib/kernel/qcoreapplication_p.h
@@ -107,6 +107,8 @@ public:
 
     static QThread *theMainThread;
     static QThread *mainThread();
+    static bool threadRequiresCoreApplication();
+
     static void sendPostedEvents(QObject *receiver, int event_type, QThreadData *data);
 
     static void checkReceiverThread(QObject *receiver);
diff --git a/src/corelib/kernel/qeventloop.cpp b/src/corelib/kernel/qeventloop.cpp
index 1723db0ab9..dca25ce968 100644
--- a/src/corelib/kernel/qeventloop.cpp
+++ b/src/corelib/kernel/qeventloop.cpp
@@ -93,7 +93,7 @@ QEventLoop::QEventLoop(QObject *parent)
     : QObject(*new QEventLoopPrivate, parent)
 {
     Q_D(QEventLoop);
-    if (!QCoreApplication::instance()) {
+    if (!QCoreApplication::instance() && QCoreApplicationPrivate::threadRequiresCoreApplication()) {
         qWarning("QEventLoop: Cannot be used without QApplication");
     } else if (!d->threadData->eventDispatcher.load()) {
         QThreadPrivate::createEventDispatcher(d->threadData);
diff --git a/src/corelib/thread/qthread.cpp b/src/corelib/thread/qthread.cpp
index 0c009db930..590479d68c 100644
--- a/src/corelib/thread/qthread.cpp
+++ b/src/corelib/thread/qthread.cpp
@@ -50,7 +50,8 @@ QT_BEGIN_NAMESPACE
 
 QThreadData::QThreadData(int initialRefCount)
     : _ref(initialRefCount), loopLevel(0), thread(0), threadId(0),
-      eventDispatcher(0), quitNow(false), canWait(true), isAdopted(false)
+      eventDispatcher(0),
+      quitNow(false), canWait(true), isAdopted(false), requiresCoreApplication(true)
 {
     // fprintf(stderr, "QThreadData %p created\n", this);
 }
@@ -867,4 +868,28 @@ bool QThread::isInterruptionRequested() const
     return d->interruptionRequested;
 }
 
+/*!
+    \class QDaemonThread
+    \since 5.5
+    \brief The QDaemonThread provides a class to manage threads that outlive QCoreApplication
+    \internal
+
+    Note: don't try to deliver events from the started() signal.
+*/
+static void setThreadDoesNotRequireCoreApplication()
+{
+    QThreadData::current()->requiresCoreApplication = false;
+}
+
+QDaemonThread::QDaemonThread(QObject *parent)
+    : QThread(parent)
+{
+    // QThread::started() is emitted from the thread we start
+    connect(this, &QThread::started, setThreadDoesNotRequireCoreApplication);
+}
+
+QDaemonThread::~QDaemonThread()
+{
+}
+
 QT_END_NAMESPACE
diff --git a/src/corelib/thread/qthread_p.h b/src/corelib/thread/qthread_p.h
index 1ecd682ad1..ffefe0b1d1 100644
--- a/src/corelib/thread/qthread_p.h
+++ b/src/corelib/thread/qthread_p.h
@@ -135,6 +135,13 @@ private:
 
 #ifndef QT_NO_THREAD
 
+class Q_CORE_EXPORT QDaemonThread : public QThread
+{
+public:
+    QDaemonThread(QObject *parent = 0);
+    ~QDaemonThread();
+};
+
 class QThreadPrivate : public QObjectPrivate
 {
     Q_DECLARE_PUBLIC(QThread)
@@ -224,7 +231,7 @@ public:
     QThreadData(int initialRefCount = 1);
     ~QThreadData();
 
-    static QThreadData *current(bool createIfNecessary = true);
+    static Q_AUTOTEST_EXPORT QThreadData *current(bool createIfNecessary = true);
     static void clearCurrentThreadData();
     static QThreadData *get2(QThread *thread)
     { Q_ASSERT_X(thread != 0, "QThread", "internal error"); return thread->d_func()->data; }
@@ -278,6 +285,7 @@ public:
     bool quitNow;
     bool canWait;
     bool isAdopted;
+    bool requiresCoreApplication;
 };
 
 class QScopedLoopLevelCounter