Fix TQThreadStorage destruction in the main thread

Before that the allocations of TQThreadStorage objects from the main
thread were never destroyed and memory associated with them were never
freed. The second one isn't a huge problem as at that point program is
terminating anyway (but it still makes valgrind complain). The first one
is the bigger issue as destructors might contain some essential external
cleanups like removing temporary files.

Also make `TQApplication::guiThread()` return `0` when the thread is
destroyed (may happen on the program exiting during destruction of
statics).

Signed-off-by: Alexander Golubev <fatzer2@gmail.com>

src/kernel/ntqthread.h

@@ -120,6 +120,7 @@ protected:
 private:
     TQThreadInstance * d;
     friend class TQThreadInstance;
+    friend class TQThreadStorageData;
     friend class TQCoreApplicationThread;
     friend class TQApplication;
     friend class TQEventLoop;

src/kernel/qapplication.cpp

@@ -542,12 +542,19 @@ TQClipboard	      *tqt_clipboard = 0;	// global clipboard object
 TQWidgetList * tqt_modal_stack=0;		// stack of modal widgets
 
 #ifdef TQT_THREAD_SUPPORT
+
 // thread wrapper for the main() thread
 class TQCoreApplicationThread : public TQThread
 {
 public:
     inline TQCoreApplicationThread()
     {
+#ifdef QT_CHECK_STATE
+        if ( tqt_gui_thread_self )
+            tqWarning( "TQCoreApplicationThread: there should be exactly one main thread object" );
+#endif
+        tqt_gui_thread_self = this;
+
         TQThreadInstance::setCurrentThread(this);
 
         // thread should be running and not finished for the lifetime
@@ -556,11 +563,19 @@ public:
         d->finished = false;
         d->eventLoop = NULL;
     }
+
     inline ~TQCoreApplicationThread()
     {
+        tqt_gui_thread_self = nullptr;
+
         // avoid warning from TQThread
         d->running = false;
+        // do some cleanup, namely clean up the thread-local storage associated with the GUI thread
+        TQThreadInstance::finishGuiThread(d);
     }
+
+    static TQCoreApplicationThread* self() { return tqt_gui_thread_self; }
+
 private:
     inline void run()
     {
@@ -568,10 +583,15 @@ private:
         // only so that we can instantiate the object
         tqFatal("TQCoreApplicationThread: internal error");
     }
+
+    static TQCoreApplicationThread* tqt_gui_thread_self;
 };
 
+TQCoreApplicationThread* TQCoreApplicationThread::tqt_gui_thread_self = nullptr;
+
+// construct exactly one instance of the core thread with static storage duration. Do it static
+// rather than in the heap as we need it to be properly destroyed on the exit from the program.
 static TQCoreApplicationThread tqt_main_thread;
-static TQThread *mainThread() { return &tqt_main_thread; }
 #endif
 
 // Definitions for posted events
@@ -1035,7 +1055,7 @@ TQApplication::TQApplication(Display *dpy, int argc, char **argv,
 
 #ifdef TQT_THREAD_SUPPORT
 TQThread* TQApplication::guiThread() {
-	return mainThread();
+	return TQCoreApplicationThread::self();
 }
 
 bool TQApplication::isGuiThread() {

src/kernel/qthread_unix.cpp

@@ -180,6 +180,11 @@ void TQThreadInstance::finish( void * )
     }
 }
 
+void TQThreadInstance::finishGuiThread(TQThreadInstance *d) {
+    TQThreadStorageData::finish( d->thread_storage );
+    d->thread_storage = 0;
+}
+
 TQMutex *TQThreadInstance::mutex() const
 {
     return qt_thread_mutexpool ? qt_thread_mutexpool->get( (void *) this ) : 0;

src/tools/qthreadinstance_p.h

@@ -100,6 +100,8 @@ public:
     static void finish( TQThreadInstance * );
 #endif // Q_OS_WIN32
 
+    static void finishGuiThread( TQThreadInstance *d );
+
     TQEventLoop* eventLoop;
     int cleanupType;
     bool disableThreadPostedEvents : 1;

src/tools/qthreadstorage_unix.cpp

@@ -38,6 +38,8 @@
 
 #ifdef TQT_THREAD_SUPPORT
 
+#include "ntqapplication.h"
+#include "ntqthread.h"
 #include "qplatformdefs.h"
 
 #include "ntqthreadstorage.h"
@@ -88,6 +90,21 @@ TQThreadStorageData::TQThreadStorageData( void (*func)( void * ) )
 
 TQThreadStorageData::~TQThreadStorageData()
 {
+    // The Gui thread has static storage duration, TQThreadStorage are almost always static (it's
+    // technically possible to allocate those in the heap, but it's quite unusual). It's impossible
+    // to predict whichever of those one gets destroyed first, but usually it's a TQThreadStorage.
+    // In that case we have to do the cleanup of its storage ourself as it won't be possible after
+    // nullifying the destructor below.
+    TQThread *guiThread = TQApplication::guiThread();
+    if (guiThread) {
+	TQThreadInstance *d = guiThread->d;
+	TQMutexLocker locker( d->mutex() );
+	if (d->thread_storage && d->thread_storage[id]) {
+	    thread_storage_usage[id].func( d->thread_storage[id] );
+	    d->thread_storage[id] = nullptr;
+	}
+    }
+
     pthread_mutex_lock( &thread_storage_mutex );
     thread_storage_usage[id].used = FALSE;
     thread_storage_usage[id].func = 0;