Pin QtDBus shared library on Windows after being loaded by X-Plane

refs #850

src/blackmisc/dbus.cpp

@@ -0,0 +1,34 @@
+/* Copyright (C) 2016
+ * swift Project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ */
+
+#include "dbus.h"
+
+#ifdef Q_OS_WIN
+#include <QDBusConnection>
+#include <qt_windows.h>
+
+// https://blogs.msdn.microsoft.com/oldnewthing/20131105-00/?p=2733
+// See https://bugreports.qt.io/browse/QTBUG-53031 for more details
+// why this is necessary.
+void preventQtDBusDllUnload()
+{
+    // Only Qt 5.8.0 is affected.
+    if (qVersion() != QByteArray("5.8.0")) { return; }
+
+    static HMODULE dbusDll;
+    GetModuleHandleEx(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS |
+                      GET_MODULE_HANDLE_EX_FLAG_PIN,
+                      reinterpret_cast<LPCTSTR >(&QDBusConnection::staticMetaObject),
+                      &dbusDll);
+    Q_ASSERT(dbusDll);
+}
+#else
+void preventQtDBusDllUnload()
+{ }
+#endif

src/blackmisc/dbus.h

@@ -12,6 +12,7 @@
 #ifndef BLACKMISC_DBUS_H
 #define BLACKMISC_DBUS_H
 
+#include "blackmisc/blackmiscexport.h"
 #include "blackmisc/metaclass.h"
 #include "blackmisc/inheritancetraits.h"
 #include <QDBusArgument>
@@ -159,4 +160,9 @@ const QDBusArgument &operator>>(const QDBusArgument &argument, QPixmap &pixmap);
  */
 QDBusArgument &operator<<(QDBusArgument &argument, const QPixmap &pixmap);
 
+//! Windows: prevents unloading of QtDBus shared library until the process is terminated.
+//! QtDBus must have been loaded already by the calling process.
+//! Does nothing on non-Windows platforms.
+BLACKMISC_EXPORT void preventQtDBusDllUnload();
+
 #endif // guard

src/xbus/main.cpp

@@ -14,6 +14,7 @@
 #include "utils.h"
 #include "traffic.h"
 #include "service.h"
+#include "blackmisc/dbus.h"
 #include <XPLM/XPLMPlanes.h>
 
 #if ! defined(XPLM210)
@@ -57,6 +58,10 @@ PLUGIN_API int XPluginEnable()
     QXPlaneEventLoop::exec();
 
     g_plugin = new XBus::CPlugin;
+
+    // Here we can be safely assume that QtDBus was loaded by the process
+    preventQtDBusDllUnload();
+
     return 1;
 }