QGenericUnixServices: properly disconnect signals in dtor

Since QGenericUnixServices does not derive from QObject, the connection
to QDBusPendingCallWatcher made in the ctor might outlive the lifetime
of QGenericUnixServices.
Fix it by explicitly disconnecting it in the dtor.

Fixes: QTBUG-125239
Pick-to: 6.8 6.7 6.5
Change-Id: I5fac4fd5831b2dde16b3d7b479a8ee616bfb7e3a
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/gui/platform/unix/qgenericunixservices.cpp

@@ -385,7 +385,8 @@ QGenericUnixServices::QGenericUnixServices()
 
     QDBusPendingCall pendingCall = QDBusConnection::sessionBus().asyncCall(message);
     auto watcher = new QDBusPendingCallWatcher(pendingCall);
-    QObject::connect(watcher, &QDBusPendingCallWatcher::finished, watcher,
+    m_watcherConnection =
+            QObject::connect(watcher, &QDBusPendingCallWatcher::finished, watcher,
                      [this](QDBusPendingCallWatcher *watcher) {
                          watcher->deleteLater();
                          QDBusPendingReply<QVariant> reply = *watcher;
@@ -396,6 +397,13 @@ QGenericUnixServices::QGenericUnixServices()
 #endif
 }
 
+QGenericUnixServices::~QGenericUnixServices()
+{
+#if QT_CONFIG(dbus)
+    QObject::disconnect(m_watcherConnection);
+#endif
+}
+
 QPlatformServiceColorPicker *QGenericUnixServices::colorPicker(QWindow *parent)
 {
 #if QT_CONFIG(dbus)
@@ -534,6 +542,7 @@ bool QGenericUnixServices::openDocument(const QUrl &url)
 
 #else
 QGenericUnixServices::QGenericUnixServices() = default;
+QGenericUnixServices::~QGenericUnixServices() = default;
 
 QByteArray QGenericUnixServices::desktopEnvironment() const
 {

src/gui/platform/unix/qgenericunixservices_p.h

@@ -27,6 +27,7 @@ class Q_GUI_EXPORT QGenericUnixServices : public QPlatformServices
 {
 public:
     QGenericUnixServices();
+    ~QGenericUnixServices();
 
     QByteArray desktopEnvironment() const override;
 
@@ -41,6 +42,9 @@ public:
 private:
     QString m_webBrowser;
     QString m_documentLauncher;
+#if QT_CONFIG(dbus)
+    QMetaObject::Connection m_watcherConnection;
+#endif
     bool m_hasScreenshotPortalWithColorPicking = false;
 };