QThreadStorage: make the internal finish() function really private

This class is very old and hasn't been modernized since C++98 became a
thing we could rely on. We hadn't come up with the concept of private
headers yet.

This commit moves the exported QThreadStorageData::finish() function
from the public header to QThreadStoragePrivate in a private header and
no longer exports it. It also removes the need to pass the QList as a
void **.

Task-number: QTBUG-135044
Change-Id: I736cb12a7c29716effd7fffd87c7b086a8cb7e19
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/corelib/kernel/qcoreapplication.cpp

@@ -491,8 +491,7 @@ void QCoreApplicationPrivate::cleanupThreadData()
 
     if (thisThreadData && !threadData_clean) {
 #if QT_CONFIG(thread)
-        void *data = &thisThreadData->tls;
-        QThreadStorageData::finish((void **)data);
+        QThreadStoragePrivate::finish(&thisThreadData->tls);
 #endif
 
         // need to clear the state of the mainData, just in case a new QCoreApplication comes along.

src/corelib/thread/qthread_unix.cpp

@@ -460,8 +460,7 @@ void QThreadPrivate::finish()
         emit thr->finished(QThread::QPrivateSignal());
         QCoreApplication::sendPostedEvents(nullptr, QEvent::DeferredDelete);
 
-        void *data = &d->data->tls;
-        QThreadStorageData::finish((void **)data);
+        QThreadStoragePrivate::finish(&d->data->tls);
     });
 
     if constexpr (QT_CONFIG(broken_threadlocal_dtors))

src/corelib/thread/qthread_win.cpp

@@ -242,12 +242,11 @@ void QThreadPrivate::finish(bool lockAnyway) noexcept
     QMutexLocker locker(lockAnyway ? &d->mutex : nullptr);
     d->threadState = QThreadPrivate::Finishing;
     d->priority = QThread::InheritPriority;
-    void **tls_data = reinterpret_cast<void **>(&d->data->tls);
     if (lockAnyway)
         locker.unlock();
     emit thr->finished(QThread::QPrivateSignal());
     QCoreApplicationPrivate::sendPostedEvents(nullptr, QEvent::DeferredDelete, d->data);
-    QThreadStorageData::finish(tls_data);
+    QThreadStoragePrivate::finish(&d->data->tls);
     if (lockAnyway)
         locker.relock();
 

src/corelib/thread/qthreadstorage.cpp

@@ -141,10 +141,9 @@ void QThreadStoragePrivate::init()
     destructors();
 }
 
-void QThreadStorageData::finish(void **p)
+void QThreadStoragePrivate::finish(QList<void *> *tls)
 {
-    QList<void *> *tls = reinterpret_cast<QList<void *> *>(p);
-    if (!tls || tls->isEmpty() || !destructors())
+    if (tls->isEmpty() || !destructors())
         return; // nothing to do
 
     DEBUG_MSG("QThreadStorageData: Destroying storage for thread %p", QThread::currentThread());

src/corelib/thread/qthreadstorage.h

@@ -35,7 +35,6 @@ public:
     void** get() const;
     void** set(void* p);
 
-    static void finish(void**);
     int id;
 };
 

src/corelib/thread/qthreadstorage_p.h

@@ -22,6 +22,7 @@ QT_BEGIN_NAMESPACE
 
 namespace QThreadStoragePrivate {
 void init();
+void finish(QList<void *> *tls);
 } // namespace QThreadStoragePrivate
 
 QT_END_NAMESPACE