QThreadStorage: ensure global static exists when finish() is called

For the thread that calls ::exit() (usually, the main thread).
Otherwise, depending on construction order, it is possible for the
QThreadStorage's destructor list to have been destroyed by the time
destroy_current_thread_data() → QThreadData::finish() calls our
finish().

Fixes: QTBUG-135044
Pick-to: 6.9 6.8
Change-Id: Ic5a10367ff31e7faa039fffdc2067eba9642fbf9
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

src/corelib/CMakeLists.txt

@@ -748,7 +748,7 @@ qt_internal_extend_target(Core CONDITION QT_FEATURE_thread
         thread/qreadwritelock.cpp thread/qreadwritelock_p.h
         thread/qsemaphore.cpp thread/qsemaphore.h
         thread/qthreadpool.cpp thread/qthreadpool.h thread/qthreadpool_p.h
-        thread/qthreadstorage.cpp
+        thread/qthreadstorage.cpp thread/qthreadstorage_p.h
 )
 
 qt_internal_extend_target(Core CONDITION QT_FEATURE_thread AND UNIX

src/corelib/thread/qthread_p.h

@@ -17,18 +17,19 @@
 //
 //
 
-#include "qplatformdefs.h"
 #include "QtCore/qthread.h"
-#include "QtCore/qmutex.h"
+
-#include "QtCore/qstack.h"
-#if QT_CONFIG(thread)
-#include "QtCore/qwaitcondition.h"
-#endif
-#include "QtCore/qmap.h"
 #include "QtCore/qcoreapplication.h"
 #include "private/qobject_p.h"
+#include "QtCore/qmap.h"
+#include "QtCore/qmutex.h"
+#include "QtCore/qstack.h"
+
+#if QT_CONFIG(thread)
+#include "private/qthreadstorage_p.h"
+#include "QtCore/qwaitcondition.h"
+#endif
 
-#include <algorithm>
 #include <atomic>
 
 QT_BEGIN_NAMESPACE

src/corelib/thread/qthread_unix.cpp

@@ -223,6 +223,7 @@ struct QThreadDataDestroyer
     }
 
     struct EarlyMainThread {
+        EarlyMainThread() { QThreadStoragePrivate::init(); }
         ~EarlyMainThread()
         {
             // running function-local destructors upon ::exit()

src/corelib/thread/qthread_win.cpp

@@ -82,6 +82,7 @@ static void set_thread_data(QThreadData *data) noexcept
 {
     if (data) {
         struct Cleanup {
+            Cleanup() { QThreadStoragePrivate::init(); }
             ~Cleanup() { destroy_current_thread_data(currentThreadData); }
         };
         static thread_local Cleanup currentThreadCleanup;

src/corelib/thread/qthreadstorage.cpp

@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
 #include "qthreadstorage.h"
+#include "qthreadstorage_p.h"
 
 #include "private/qcoreapplication_p.h"
 #include "qthread.h"
@@ -133,6 +134,13 @@ void **QThreadStorageData::set(void *p)
     return &value;
 }
 
+void QThreadStoragePrivate::init()
+{
+    // Make sure the Q_GLOBAL_STATIC is initialized, ensuring consistent
+    // destruction order.
+    destructors();
+}
+
 void QThreadStorageData::finish(void **p)
 {
     QList<void *> *tls = reinterpret_cast<QList<void *> *>(p);

src/corelib/thread/qthreadstorage_p.h

@@ -0,0 +1,29 @@
+// Copyright (C) 2025 Intel Corporation.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
+
+#ifndef QTHREADSTORAGE_P_H
+#define QTHREADSTORAGE_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <qlist.h>
+#include <private/qglobal_p.h>
+
+QT_BEGIN_NAMESPACE
+
+namespace QThreadStoragePrivate {
+void init();
+} // namespace QThreadStoragePrivate
+
+QT_END_NAMESPACE
+
+#endif // QTHREADSTORAGE_P_H