introduce a new StartShutdown() function, which starts a thread with Shutdown() if no GUI is used and calls uiInterface.QueueShutdown() if a GUI is used / all direct uiInterface.QueueShutdown() calls are replaced with Shutdown() - this ensures a clean GUI shutdown, even when catching a SIGTERM and allows the BitcoinGUI destructor to get called (which fixes a tray-icon issue and keeps the tray-icon until Bitcoin-Qt exits)

src/init.cpp

@@ -38,6 +38,17 @@ void ExitTimeout(void* parg)
 #endif
 }
 
+void StartShutdown()
+{
+#ifdef QT_GUI
+    // ensure we leave the Qt main loop for a clean GUI exit (Shutdown() is called in bitcoin.cpp afterwards)
+    uiInterface.QueueShutdown();
+#else
+    // Without UI, Shutdown() can simply be started in a new thread
+    CreateThread(Shutdown, NULL);
+#endif
+}
+
 void Shutdown(void* parg)
 {
     static CCriticalSection cs_Shutdown;
@@ -66,7 +77,10 @@ void Shutdown(void* parg)
         Sleep(50);
         printf("Bitcoin exited\n\n");
         fExit = true;
+#ifndef QT_GUI
+        // ensure non UI client get's exited here, but let Bitcoin-Qt reach return 0; in bitcoin.cpp
         exit(0);
+#endif
     }
     else
     {