QFileSystemWatcher: Do not require QApplication in the destructor.

QThread::quit() is threadsafe, and can safely (and should) be called
from the parent thread.
Using invokeMethod requires an instance of QCoreApplication. There
is no reason we should depend on that.

Task-number: QTBUG-15255
Task-number:  QT-3305
Reviewed-by: Denis
Reviewed-by: Brad

4 files changed, 23 insertions, 8 deletions

diff --git a/src/corelib/io/qfilesystemwatcher.cpp b/src/corelib/io/qfilesystemwatcher.cpp
index 34eff75..9739067 100644
--- a/src/corelib/io/qfilesystemwatcher.cpp
+++ b/src/corelib/io/qfilesystemwatcher.cpp
@@ -198,7 +198,7 @@ QStringList QPollingFileSystemWatcherEngine::removePaths(const QStringList &path
 
 void QPollingFileSystemWatcherEngine::stop()
 {
-    QMetaObject::invokeMethod(this, "quit");
+    quit();
 }
 
 void QPollingFileSystemWatcherEngine::timeout()
@@ -432,11 +432,6 @@ QFileSystemWatcher::QFileSystemWatcher(const QStringList &paths, QObject *parent
 
 /*!
     Destroys the file system watcher.
-
-    \note To avoid deadlocks on shutdown, all instances of QFileSystemWatcher
-    need to be destroyed before QCoreApplication. Note that passing
-    QCoreApplication::instance() as the parent object when creating
-    QFileSystemWatcher is not sufficient.
 */
 QFileSystemWatcher::~QFileSystemWatcher()
 {
diff --git a/src/corelib/io/qfilesystemwatcher_inotify.cpp b/src/corelib/io/qfilesystemwatcher_inotify.cpp
index 8c81de8..2eec117 100644
--- a/src/corelib/io/qfilesystemwatcher_inotify.cpp
+++ b/src/corelib/io/qfilesystemwatcher_inotify.cpp
@@ -340,7 +340,7 @@ QStringList QInotifyFileSystemWatcherEngine::removePaths(const QStringList &path
 
 void QInotifyFileSystemWatcherEngine::stop()
 {
-    QMetaObject::invokeMethod(this, "quit");
+    quit();
 }
 
 void QInotifyFileSystemWatcherEngine::readFromInotify()
diff --git a/src/corelib/io/qfilesystemwatcher_symbian.cpp b/src/corelib/io/qfilesystemwatcher_symbian.cpp
index 0d8f22e..95c65c0 100644
--- a/src/corelib/io/qfilesystemwatcher_symbian.cpp
+++ b/src/corelib/io/qfilesystemwatcher_symbian.cpp
@@ -215,7 +215,7 @@ void QSymbianFileSystemWatcherEngine::emitPathChanged(QNotifyChangeEvent *e)
 
 void QSymbianFileSystemWatcherEngine::stop()
 {
-    QMetaObject::invokeMethod(this, "quit");
+    quit();
     wait();
 }
 
diff --git a/tests/auto/qfilesystemwatcher/tst_qfilesystemwatcher.cpp b/tests/auto/qfilesystemwatcher/tst_qfilesystemwatcher.cpp
index 8e0c9fe..9d46a8d 100644
--- a/tests/auto/qfilesystemwatcher/tst_qfilesystemwatcher.cpp
+++ b/tests/auto/qfilesystemwatcher/tst_qfilesystemwatcher.cpp
@@ -82,6 +82,8 @@ private slots:
     void removeFileAndUnWatch();
 
     void cleanup();
+
+    void QTBUG15255_deadlock();
 private:
     QStringList do_force_engines;
     bool do_force_native;
@@ -550,5 +552,23 @@ void tst_QFileSystemWatcher::removeFileAndUnWatch()
     watcher.addPath(filename);
 }
 
+class SomeSingleton : public QObject
+{
+public:
+    SomeSingleton() : mFsWatcher(new QFileSystemWatcher(this)) { mFsWatcher->addPath(QLatin1String("/usr/lib"));}
+    void bla() const {}
+    QFileSystemWatcher* mFsWatcher;
+};
+
+Q_GLOBAL_STATIC(SomeSingleton, someSingleton)
+
+void tst_QFileSystemWatcher::QTBUG15255_deadlock()
+{
+    someSingleton()->bla();
+    //the test must still finish
+    QTest::qWait(30);
+}
+
+
 QTEST_MAIN(tst_QFileSystemWatcher)
 #include "tst_qfilesystemwatcher.moc"