Merge remote-tracking branch 'origin/dev' into wip/qt6

Change-Id: I4ea2b77cc201daed94fbe321f146dfd20365a534

37 files changed, 502 insertions, 303 deletions

diff --git a/src/corelib/kernel/qabstracteventdispatcher.cpp b/src/corelib/kernel/qabstracteventdispatcher.cpp
index 186c2e743b..7215b3f2bd 100644
--- a/src/corelib/kernel/qabstracteventdispatcher.cpp
+++ b/src/corelib/kernel/qabstracteventdispatcher.cpp
@@ -170,7 +170,7 @@ QAbstractEventDispatcher::~QAbstractEventDispatcher()
 QAbstractEventDispatcher *QAbstractEventDispatcher::instance(QThread *thread)
 {
     QThreadData *data = thread ? QThreadData::get2(thread) : QThreadData::current();
-    return data->eventDispatcher.load();
+    return data->eventDispatcher.loadRelaxed();
 }
 
 /*!
diff --git a/src/corelib/kernel/qbasictimer.cpp b/src/corelib/kernel/qbasictimer.cpp
index b16833b34c..ea8f8e2c77 100644
--- a/src/corelib/kernel/qbasictimer.cpp
+++ b/src/corelib/kernel/qbasictimer.cpp
@@ -105,6 +105,7 @@ QT_BEGIN_NAMESPACE
     \sa stop(), isActive(), swap()
 */
 
+#if QT_DEPRECATED_SINCE(5, 14)
 #if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
 /*!
     \internal
@@ -125,6 +126,7 @@ QBasicTimer &QBasicTimer::operator=(const QBasicTimer &other)
     return *this;
 }
 #endif
+#endif
 
 /*!
     \fn QBasicTimer::~QBasicTimer()
diff --git a/src/corelib/kernel/qcore_mac_objc.mm b/src/corelib/kernel/qcore_mac_objc.mm
index 6b51eb65d9..15b69acbd4 100644
--- a/src/corelib/kernel/qcore_mac_objc.mm
+++ b/src/corelib/kernel/qcore_mac_objc.mm
@@ -514,5 +514,36 @@ Q_CONSTRUCTOR_FUNCTION(qt_apple_check_os_version);
 
 // -------------------------------------------------------------------------
 
+void QMacKeyValueObserver::addObserver()
+{
+    [object addObserver:observer forKeyPath:keyPath
+        options:NSKeyValueObservingOptionNew context:callback.get()];
+}
+
+void QMacKeyValueObserver::removeObserver() {
+    if (object)
+        [object removeObserver:observer forKeyPath:keyPath context:callback.get()];
+    object = nil;
+}
+
+KeyValueObserver *QMacKeyValueObserver::observer = [[KeyValueObserver alloc] init];
+
+QT_END_NAMESPACE
+@implementation KeyValueObserver
+- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object
+        change:(NSDictionary<NSKeyValueChangeKey, id> *)change context:(void *)context
+{
+    Q_UNUSED(keyPath);
+    Q_UNUSED(object);
+    Q_UNUSED(change);
+
+    (*reinterpret_cast<QMacKeyValueObserver::Callback*>(context))();
+}
+@end
+QT_BEGIN_NAMESPACE
+
+// -------------------------------------------------------------------------
+
+
 QT_END_NAMESPACE
 
diff --git a/src/corelib/kernel/qcore_mac_p.h b/src/corelib/kernel/qcore_mac_p.h
index 920105ee9e..0e1a5fe345 100644
--- a/src/corelib/kernel/qcore_mac_p.h
+++ b/src/corelib/kernel/qcore_mac_p.h
@@ -67,6 +67,7 @@
 
 #ifdef __OBJC__
 #include <Foundation/Foundation.h>
+#include <functional>
 #endif
 
 #include "qstring.h"
@@ -295,13 +296,13 @@ QT_MAC_WEAK_IMPORT(_os_activity_current);
 // -------------------------------------------------------------------------
 
 #if defined( __OBJC__)
-class QMacScopedObserver
+class QMacNotificationObserver
 {
 public:
-    QMacScopedObserver() {}
+    QMacNotificationObserver() {}
 
     template<typename Functor>
-    QMacScopedObserver(id object, NSNotificationName name, Functor callback) {
+    QMacNotificationObserver(id object, NSNotificationName name, Functor callback) {
         observer = [[NSNotificationCenter defaultCenter] addObserverForName:name
             object:object queue:nil usingBlock:^(NSNotification *) {
                 callback();
@@ -309,13 +310,13 @@ public:
         ];
     }
 
-    QMacScopedObserver(const QMacScopedObserver& other) = delete;
-    QMacScopedObserver(QMacScopedObserver&& other) : observer(other.observer) {
+    QMacNotificationObserver(const QMacNotificationObserver& other) = delete;
+    QMacNotificationObserver(QMacNotificationObserver&& other) : observer(other.observer) {
         other.observer = nil;
     }
 
-    QMacScopedObserver &operator=(const QMacScopedObserver& other) = delete;
-    QMacScopedObserver &operator=(QMacScopedObserver&& other) {
+    QMacNotificationObserver &operator=(const QMacNotificationObserver& other) = delete;
+    QMacNotificationObserver &operator=(QMacNotificationObserver&& other) {
         if (this != &other) {
             remove();
             observer = other.observer;
@@ -329,11 +330,65 @@ public:
             [[NSNotificationCenter defaultCenter] removeObserver:observer];
         observer = nil;
     }
-    ~QMacScopedObserver() { remove(); }
+    ~QMacNotificationObserver() { remove(); }
 
 private:
     id observer = nil;
 };
+
+QT_END_NAMESPACE
+@interface QT_MANGLE_NAMESPACE(KeyValueObserver) : NSObject
+@end
+QT_NAMESPACE_ALIAS_OBJC_CLASS(KeyValueObserver);
+QT_BEGIN_NAMESPACE
+
+class Q_CORE_EXPORT QMacKeyValueObserver
+{
+public:
+    using Callback = std::function<void()>;
+
+    QMacKeyValueObserver() {}
+
+    // Note: QMacKeyValueObserver must not outlive the object observed!
+    QMacKeyValueObserver(id object, NSString *keyPath, Callback callback)
+        : object(object), keyPath(keyPath), callback(new Callback(callback)) { addObserver(); }
+
+    QMacKeyValueObserver(const QMacKeyValueObserver &other)
+         : QMacKeyValueObserver(other.object, other.keyPath, *other.callback.get()) {}
+
+    QMacKeyValueObserver(QMacKeyValueObserver &&other) { swap(other, *this); }
+
+    ~QMacKeyValueObserver() { removeObserver(); }
+
+    QMacKeyValueObserver &operator=(const QMacKeyValueObserver &other) {
+        QMacKeyValueObserver tmp(other);
+        swap(tmp, *this);
+        return *this;
+    }
+
+    QMacKeyValueObserver &operator=(QMacKeyValueObserver &&other) {
+        QMacKeyValueObserver tmp(std::move(other));
+        swap(tmp, *this);
+        return *this;
+    }
+
+    void removeObserver();
+
+private:
+    void swap(QMacKeyValueObserver &first, QMacKeyValueObserver &second) {
+        std::swap(first.object, second.object);
+        std::swap(first.keyPath, second.keyPath);
+        std::swap(first.callback, second.callback);
+    }
+
+    void addObserver();
+
+    id object = nil;
+    NSString *keyPath = nullptr;
+    std::unique_ptr<Callback> callback;
+
+    static KeyValueObserver *observer;
+};
 #endif
 
 // -------------------------------------------------------------------------
diff --git a/src/corelib/kernel/qcore_unix_p.h b/src/corelib/kernel/qcore_unix_p.h
index 7f58813535..b56c2b9732 100644
--- a/src/corelib/kernel/qcore_unix_p.h
+++ b/src/corelib/kernel/qcore_unix_p.h
@@ -164,7 +164,7 @@ inline void qt_ignore_sigpipe()
 {
     // Set to ignore SIGPIPE once only.
     static QBasicAtomicInt atom = Q_BASIC_ATOMIC_INITIALIZER(0);
-    if (!atom.load()) {
+    if (!atom.loadRelaxed()) {
         // More than one thread could turn off SIGPIPE at the same time
         // But that's acceptable because they all would be doing the same
         // action
@@ -172,7 +172,7 @@ inline void qt_ignore_sigpipe()
         memset(&noaction, 0, sizeof(noaction));
         noaction.sa_handler = SIG_IGN;
         ::sigaction(SIGPIPE, &noaction, nullptr);
-        atom.store(1);
+        atom.storeRelaxed(1);
     }
 }
 
diff --git a/src/corelib/kernel/qcoreapplication.cpp b/src/corelib/kernel/qcoreapplication.cpp
index 865e16a3f0..9bc3fea23b 100644
--- a/src/corelib/kernel/qcoreapplication.cpp
+++ b/src/corelib/kernel/qcoreapplication.cpp
@@ -120,6 +120,7 @@
 
 #ifdef Q_OS_WASM
 #include <emscripten.h>
+#include <emscripten/val.h>
 #endif
 
 #ifdef QT_BOOTSTRAPPED
@@ -216,11 +217,11 @@ QString QCoreApplicationPrivate::appVersion() const
 }
 #endif
 
-QString *QCoreApplicationPrivate::cachedApplicationFilePath = 0;
+QString *QCoreApplicationPrivate::cachedApplicationFilePath = nullptr;
 
 bool QCoreApplicationPrivate::checkInstance(const char *function)
 {
-    bool b = (QCoreApplication::self != 0);
+    bool b = (QCoreApplication::self != nullptr);
     if (!b)
         qWarning("QApplication::%s: Please instantiate the QApplication object first", function);
     return b;
@@ -257,7 +258,7 @@ void QCoreApplicationPrivate::processCommandLineArguments()
     }
 
     if (j < argc) {
-        argv[j] = 0;
+        argv[j] = nullptr;
         argc = j;
     }
 }
@@ -367,11 +368,11 @@ Q_CORE_EXPORT uint qGlobalPostedEventsCount()
     return currentThreadData->postEventList.size() - currentThreadData->postEventList.startOffset;
 }
 
-QAbstractEventDispatcher *QCoreApplicationPrivate::eventDispatcher = 0;
+QAbstractEventDispatcher *QCoreApplicationPrivate::eventDispatcher = nullptr;
 
 #endif // QT_NO_QOBJECT
 
-QCoreApplication *QCoreApplication::self = 0;
+QCoreApplication *QCoreApplication::self = nullptr;
 uint QCoreApplicationPrivate::attribs =
     (1 << Qt::AA_SynthesizeMouseForUnhandledTouchEvents) |
     (1 << Qt::AA_SynthesizeMouseForUnhandledTabletEvents);
@@ -455,12 +456,12 @@ QCoreApplicationPrivate::QCoreApplicationPrivate(int &aargc, char **aargv, uint
     , aboutToQuitEmitted(false)
     , threadData_clean(false)
 #else
-    , q_ptr(0)
+    , q_ptr(nullptr)
 #endif
 {
     app_compile_version = flags & 0xffffff;
     static const char *const empty = "";
-    if (argc == 0 || argv == 0) {
+    if (argc == 0 || argv == nullptr) {
         argc = 0;
         argv = const_cast<char **>(&empty);
     }
@@ -551,8 +552,8 @@ void QCoreApplicationPrivate::eventDispatcherReady()
 QBasicAtomicPointer<QThread> QCoreApplicationPrivate::theMainThread = Q_BASIC_ATOMIC_INITIALIZER(0);
 QThread *QCoreApplicationPrivate::mainThread()
 {
-    Q_ASSERT(theMainThread.load() != 0);
-    return theMainThread.load();
+    Q_ASSERT(theMainThread.loadRelaxed() != 0);
+    return theMainThread.loadRelaxed();
 }
 
 bool QCoreApplicationPrivate::threadRequiresCoreApplication()
@@ -799,6 +800,10 @@ void QCoreApplicationPrivate::init()
                 Module.print(err);
         });
     );
+
+#if QT_CONFIG(thread)
+    QThreadPrivate::idealThreadCount = emscripten::val::global("navigator")["hardwareConcurrency"].as<int>();
+#endif
 #endif
 
     // Store app name/version (so they're still available after QCoreApplication is destroyed)
@@ -849,7 +854,7 @@ void QCoreApplicationPrivate::init()
 #ifndef QT_NO_QOBJECT
     // use the event dispatcher created by the app programmer (if any)
     Q_ASSERT(!eventDispatcher);
-    eventDispatcher = threadData->eventDispatcher.load();
+    eventDispatcher = threadData->eventDispatcher.loadRelaxed();
 
     // otherwise we create one
     if (!eventDispatcher)
@@ -886,7 +891,7 @@ QCoreApplication::~QCoreApplication()
 {
     qt_call_post_routines();
 
-    self = 0;
+    self = nullptr;
 #ifndef QT_NO_QOBJECT
     QCoreApplicationPrivate::is_app_closing = true;
     QCoreApplicationPrivate::is_app_running = false;
@@ -894,7 +899,7 @@ QCoreApplication::~QCoreApplication()
 
 #if QT_CONFIG(thread)
     // Synchronize and stop the global thread pool threads.
-    QThreadPool *globalThreadPool = 0;
+    QThreadPool *globalThreadPool = nullptr;
     QT_TRY {
         globalThreadPool = QThreadPool::globalInstance();
     } QT_CATCH (...) {
@@ -905,10 +910,10 @@ QCoreApplication::~QCoreApplication()
 #endif
 
 #ifndef QT_NO_QOBJECT
-    d_func()->threadData->eventDispatcher = 0;
+    d_func()->threadData->eventDispatcher = nullptr;
     if (QCoreApplicationPrivate::eventDispatcher)
         QCoreApplicationPrivate::eventDispatcher->closingDown();
-    QCoreApplicationPrivate::eventDispatcher = 0;
+    QCoreApplicationPrivate::eventDispatcher = nullptr;
 #endif
 
 #if QT_CONFIG(library)
@@ -972,7 +977,11 @@ void QCoreApplication::setAttribute(Qt::ApplicationAttribute attribute, bool on)
         QCoreApplicationPrivate::attribs |= 1 << attribute;
     else
         QCoreApplicationPrivate::attribs &= ~(1 << attribute);
+#if defined(QT_NO_QOBJECT)
     if (Q_UNLIKELY(qApp)) {
+#else
+    if (Q_UNLIKELY(QCoreApplicationPrivate::is_app_running)) {
+#endif
         switch (attribute) {
             case Qt::AA_EnableHighDpiScaling:
             case Qt::AA_DisableHighDpiScaling:
@@ -1297,7 +1306,7 @@ void QCoreApplication::processEvents(QEventLoop::ProcessEventsFlags flags)
     QThreadData *data = QThreadData::current();
     if (!data->hasEventDispatcher())
         return;
-    data->eventDispatcher.load()->processEvents(flags);
+    data->eventDispatcher.loadRelaxed()->processEvents(flags);
 }
 
 /*!
@@ -1329,7 +1338,7 @@ void QCoreApplication::processEvents(QEventLoop::ProcessEventsFlags flags, int m
         return;
     QElapsedTimer start;
     start.start();
-    while (data->eventDispatcher.load()->processEvents(flags & ~QEventLoop::WaitForMoreEvents)) {
+    while (data->eventDispatcher.loadRelaxed()->processEvents(flags & ~QEventLoop::WaitForMoreEvents)) {
         if (start.elapsed() > ms)
             break;
     }
@@ -1733,7 +1742,7 @@ void QCoreApplicationPrivate::sendPostedEvents(QObject *receiver, int event_type
 
             --data->postEventList.recursion;
             if (!data->postEventList.recursion && !data->canWait && data->hasEventDispatcher())
-                data->eventDispatcher.load()->wakeUp();
+                data->eventDispatcher.loadRelaxed()->wakeUp();
 
             // clear the global list, i.e. remove everything that was
             // delivered.
@@ -1984,7 +1993,7 @@ void QCoreApplicationPrivate::deref()
 
 void QCoreApplicationPrivate::maybeQuit()
 {
-    if (quitLockRef.load() == 0 && in_exec && quitLockRefEnabled && shouldQuit())
+    if (quitLockRef.loadRelaxed() == 0 && in_exec && quitLockRefEnabled && shouldQuit())
         QCoreApplication::postEvent(QCoreApplication::instance(), new QEvent(QEvent::Quit));
 }
 
@@ -2953,7 +2962,7 @@ bool QCoreApplication::hasPendingEvents()
 QAbstractEventDispatcher *QCoreApplication::eventDispatcher()
 {
     if (QCoreApplicationPrivate::theMainThread)
-        return QCoreApplicationPrivate::theMainThread.load()->eventDispatcher();
+        return QCoreApplicationPrivate::theMainThread.loadRelaxed()->eventDispatcher();
     return 0;
 }
 
diff --git a/src/corelib/kernel/qcoreapplication_win.cpp b/src/corelib/kernel/qcoreapplication_win.cpp
index 6995f9bbab..3f22c309ff 100644
--- a/src/corelib/kernel/qcoreapplication_win.cpp
+++ b/src/corelib/kernel/qcoreapplication_win.cpp
@@ -688,6 +688,12 @@ static const char *winPosInsertAfter(quintptr h)
 
 static const char *sessionMgrLogOffOption(uint p)
 {
+#ifndef ENDSESSION_CLOSEAPP
+#define ENDSESSION_CLOSEAPP 0x00000001
+#endif
+#ifndef ENDSESSION_CRITICAL
+#define ENDSESSION_CRITICAL 0x40000000
+#endif
     static const QWinMessageMapping<uint> values[] = {
         {ENDSESSION_CLOSEAPP, "Close application"},
         {ENDSESSION_CRITICAL, "Force application end"},
@@ -881,12 +887,6 @@ QString decodeMSG(const MSG& msg)
                 parameters += QLatin1Char(')');
             }
             break;
-#ifndef ENDSESSION_CLOSEAPP
-#define ENDSESSION_CLOSEAPP 0x00000001
-#endif
-#ifndef ENDSESSION_CRITICAL
-#define ENDSESSION_CRITICAL 0x40000000
-#endif
         case WM_QUERYENDSESSION:
             parameters = QLatin1String("End session: ");
             if (const char *logoffOption = sessionMgrLogOffOption(uint(wParam)))
diff --git a/src/corelib/kernel/qcoreevent.cpp b/src/corelib/kernel/qcoreevent.cpp
index aabd32b4a8..4cfc749386 100644
--- a/src/corelib/kernel/qcoreevent.cpp
+++ b/src/corelib/kernel/qcoreevent.cpp
@@ -424,7 +424,7 @@ struct QBasicAtomicBitField {
     bool allocateSpecific(int which) noexcept
     {
         QBasicAtomicInteger<uint> &entry = data[which / BitsPerInt];
-        const uint old = entry.load();
+        const uint old = entry.loadRelaxed();
         const uint bit = 1U << (which % BitsPerInt);
         return !(old & bit) // wasn't taken
             && entry.testAndSetRelaxed(old, old | bit); // still wasn't taken
@@ -445,10 +445,10 @@ struct QBasicAtomicBitField {
 
         // Then again, this should never execute many iterations, so
         // leave like this for now:
-        for (uint i = next.load(); i < NumBits; ++i) {
+        for (uint i = next.loadRelaxed(); i < NumBits; ++i) {
             if (allocateSpecific(i)) {
                 // remember next (possibly) free id:
-                const uint oldNext = next.load();
+                const uint oldNext = next.loadRelaxed();
                 next.testAndSetRelaxed(oldNext, qMax(i + 1, oldNext));
                 return i;
             }
diff --git a/src/corelib/kernel/qcoreglobaldata.cpp b/src/corelib/kernel/qcoreglobaldata.cpp
index 104be1b87b..7ff222f170 100644
--- a/src/corelib/kernel/qcoreglobaldata.cpp
+++ b/src/corelib/kernel/qcoreglobaldata.cpp
@@ -48,7 +48,7 @@ Q_GLOBAL_STATIC(QCoreGlobalData, globalInstance)
 
 QCoreGlobalData::QCoreGlobalData()
 #if QT_CONFIG(textcodec)
-    : codecForLocale(0)
+    : codecForLocale(nullptr)
 #endif
 {
 }
@@ -56,7 +56,7 @@ QCoreGlobalData::QCoreGlobalData()
 QCoreGlobalData::~QCoreGlobalData()
 {
 #if QT_CONFIG(textcodec)
-    codecForLocale = 0;
+    codecForLocale = nullptr;
     QList<QTextCodec *> tmp = allCodecs;
     allCodecs.clear();
     codecCache.clear();
diff --git a/src/corelib/kernel/qelapsedtimer.cpp b/src/corelib/kernel/qelapsedtimer.cpp
index adb554b624..57825583dd 100644
--- a/src/corelib/kernel/qelapsedtimer.cpp
+++ b/src/corelib/kernel/qelapsedtimer.cpp
@@ -65,7 +65,7 @@ QT_BEGIN_NAMESPACE
     \snippet qelapsedtimer/main.cpp 0
 
     In this example, the timer is started by a call to start() and the
-    elapsed timer is calculated by the elapsed() function.
+    elapsed time is calculated by the elapsed() function.
 
     The time elapsed can also be used to recalculate the time available for
     another operation, after the first one is complete. This is useful when
diff --git a/src/corelib/kernel/qeventdispatcher_glib.cpp b/src/corelib/kernel/qeventdispatcher_glib.cpp
index 34c2dde6a8..d9746ef6e2 100644
--- a/src/corelib/kernel/qeventdispatcher_glib.cpp
+++ b/src/corelib/kernel/qeventdispatcher_glib.cpp
@@ -261,7 +261,7 @@ static gboolean postEventSourcePrepare(GSource *s, gint *timeout)
     *timeout = canWait ? -1 : 0;
 
     GPostEventSource *source = reinterpret_cast<GPostEventSource *>(s);
-    source->d->wakeUpCalled = source->serialNumber.load() != source->lastSerialNumber;
+    source->d->wakeUpCalled = source->serialNumber.loadRelaxed() != source->lastSerialNumber;
     return !canWait || source->d->wakeUpCalled;
 }
 
@@ -273,7 +273,7 @@ static gboolean postEventSourceCheck(GSource *source)
 static gboolean postEventSourceDispatch(GSource *s, GSourceFunc, gpointer)
 {
     GPostEventSource *source = reinterpret_cast<GPostEventSource *>(s);
-    source->lastSerialNumber = source->serialNumber.load();
+    source->lastSerialNumber = source->serialNumber.loadRelaxed();
     QCoreApplication::sendPostedEvents();
     source->d->runTimersOnceWithNormalPriority();
     return true; // i dunno, george...
@@ -320,7 +320,7 @@ QEventDispatcherGlibPrivate::QEventDispatcherGlibPrivate(GMainContext *context)
     // setup post event source
     postEventSource = reinterpret_cast<GPostEventSource *>(g_source_new(&postEventSourceFuncs,
                                                                         sizeof(GPostEventSource)));
-    postEventSource->serialNumber.store(1);
+    postEventSource->serialNumber.storeRelaxed(1);
     postEventSource->d = this;
     g_source_set_can_recurse(&postEventSource->source, true);
     g_source_attach(&postEventSource->source, mainContext);
diff --git a/src/corelib/kernel/qeventdispatcher_unix.cpp b/src/corelib/kernel/qeventdispatcher_unix.cpp
index df0cac0239..5bc65b7110 100644
--- a/src/corelib/kernel/qeventdispatcher_unix.cpp
+++ b/src/corelib/kernel/qeventdispatcher_unix.cpp
@@ -459,7 +459,7 @@ void QEventDispatcherUNIX::unregisterSocketNotifier(QSocketNotifier *notifier)
 bool QEventDispatcherUNIX::processEvents(QEventLoop::ProcessEventsFlags flags)
 {
     Q_D(QEventDispatcherUNIX);
-    d->interrupt.store(0);
+    d->interrupt.storeRelaxed(0);
 
     // we are awake, broadcast it
     emit awake();
@@ -470,13 +470,13 @@ bool QEventDispatcherUNIX::processEvents(QEventLoop::ProcessEventsFlags flags)
     const bool wait_for_events = flags & QEventLoop::WaitForMoreEvents;
 
     const bool canWait = (d->threadData->canWaitLocked()
-                          && !d->interrupt.load()
+                          && !d->interrupt.loadRelaxed()
                           && wait_for_events);
 
     if (canWait)
         emit aboutToBlock();
 
-    if (d->interrupt.load())
+    if (d->interrupt.loadRelaxed())
         return false;
 
     timespec *tm = nullptr;
@@ -545,7 +545,7 @@ void QEventDispatcherUNIX::wakeUp()
 void QEventDispatcherUNIX::interrupt()
 {
     Q_D(QEventDispatcherUNIX);
-    d->interrupt.store(1);
+    d->interrupt.storeRelaxed(1);
     wakeUp();
 }
 
diff --git a/src/corelib/kernel/qeventdispatcher_win.cpp b/src/corelib/kernel/qeventdispatcher_win.cpp
index e0641a0282..c2e57a7924 100644
--- a/src/corelib/kernel/qeventdispatcher_win.cpp
+++ b/src/corelib/kernel/qeventdispatcher_win.cpp
@@ -247,7 +247,7 @@ LRESULT QT_WIN_CALLBACK qt_internal_proc(HWND hwnd, UINT message, WPARAM wp, LPA
         Q_ASSERT(d != 0);
 
         // Allow posting WM_QT_SENDPOSTEDEVENTS message.
-        d->wakeUps.store(0);
+        d->wakeUps.storeRelaxed(0);
 
         // We send posted events manually, if the window procedure was invoked
         // by the foreign event loop (e.g. from the native modal dialog).
@@ -526,7 +526,7 @@ bool QEventDispatcherWin32::processEvents(QEventLoop::ProcessEventsFlags flags)
         wakeUp(); // trigger a call to sendPostedEvents()
     }
 
-    d->interrupt.store(false);
+    d->interrupt.storeRelaxed(false);
     emit awake();
 
     // To prevent livelocks, send posted events once per iteration.
@@ -545,7 +545,7 @@ bool QEventDispatcherWin32::processEvents(QEventLoop::ProcessEventsFlags flags)
             pHandles = &d->winEventNotifierActivatedEvent;
         }
         QVarLengthArray<MSG> processedTimers;
-        while (!d->interrupt.load()) {
+        while (!d->interrupt.loadRelaxed()) {
             MSG msg;
             bool haveMessage;
 
@@ -590,7 +590,7 @@ bool QEventDispatcherWin32::processEvents(QEventLoop::ProcessEventsFlags flags)
                 if (d->internalHwnd == msg.hwnd && msg.message == WM_QT_SENDPOSTEDEVENTS) {
                     // Set result to 'true', if the message was sent by wakeUp().
                     if (msg.wParam == WMWP_QT_FROMWAKEUP) {
-                        d->wakeUps.store(0);
+                        d->wakeUps.storeRelaxed(0);
                         retVal = true;
                     }
                     needWM_QT_SENDPOSTEDEVENTS = true;
@@ -639,7 +639,7 @@ bool QEventDispatcherWin32::processEvents(QEventLoop::ProcessEventsFlags flags)
 
         // still nothing - wait for message or signalled objects
         canWait = (!retVal
-                   && !d->interrupt.load()
+                   && !d->interrupt.loadRelaxed()
                    && (flags & QEventLoop::WaitForMoreEvents));
         if (canWait) {
             emit aboutToBlock();
@@ -949,7 +949,7 @@ void QEventDispatcherWin32::activateEventNotifiers()
         for (int i = 0; i < d->winEventNotifierList.count(); ++i) {
             QWinEventNotifier *notifier = d->winEventNotifierList.at(i);
             QWinEventNotifierPrivate *nd = QWinEventNotifierPrivate::get(notifier);
-            if (nd->signaledCount.load() != 0) {
+            if (nd->signaledCount.loadRelaxed() != 0) {
                 --nd->signaledCount;
                 nd->unregisterWaitObject();
                 d->activateEventNotifier(notifier);
@@ -1014,7 +1014,7 @@ void QEventDispatcherWin32::wakeUp()
 void QEventDispatcherWin32::interrupt()
 {
     Q_D(QEventDispatcherWin32);
-    d->interrupt.store(true);
+    d->interrupt.storeRelaxed(true);
     wakeUp();
 }
 
diff --git a/src/corelib/kernel/qeventloop.cpp b/src/corelib/kernel/qeventloop.cpp
index a6cc51621a..2104b22095 100644
--- a/src/corelib/kernel/qeventloop.cpp
+++ b/src/corelib/kernel/qeventloop.cpp
@@ -135,7 +135,7 @@ bool QEventLoop::processEvents(ProcessEventsFlags flags)
     Q_D(QEventLoop);
     if (!d->threadData->hasEventDispatcher())
         return false;
-    return d->threadData->eventDispatcher.load()->processEvents(flags);
+    return d->threadData->eventDispatcher.loadRelaxed()->processEvents(flags);
 }
 
 /*!
@@ -225,7 +225,7 @@ int QEventLoop::exec(ProcessEventsFlags flags)
         processEvents(flags | WaitForMoreEvents | EventLoopExec);
 
     ref.exceptionCaught = false;
-    return d->returnCode.load();
+    return d->returnCode.loadRelaxed();
 }
 
 /*!
@@ -279,9 +279,9 @@ void QEventLoop::exit(int returnCode)
     if (!d->threadData->hasEventDispatcher())
         return;
 
-    d->returnCode.store(returnCode);
+    d->returnCode.storeRelaxed(returnCode);
     d->exit.storeRelease(true);
-    d->threadData->eventDispatcher.load()->interrupt();
+    d->threadData->eventDispatcher.loadRelaxed()->interrupt();
 
 #ifdef Q_OS_WASM
     // QEventLoop::exec() never returns in emscripten. We implement approximate behavior here.
@@ -318,7 +318,7 @@ void QEventLoop::wakeUp()
     Q_D(QEventLoop);
     if (!d->threadData->hasEventDispatcher())
         return;
-    d->threadData->eventDispatcher.load()->wakeUp();
+    d->threadData->eventDispatcher.loadRelaxed()->wakeUp();
 }
 
 
diff --git a/src/corelib/kernel/qeventloop_p.h b/src/corelib/kernel/qeventloop_p.h
index dcbb5c63c6..4ad6d92007 100644
--- a/src/corelib/kernel/qeventloop_p.h
+++ b/src/corelib/kernel/qeventloop_p.h
@@ -63,8 +63,8 @@ public:
     inline QEventLoopPrivate()
         : inExec(false)
     {
-        returnCode.store(-1);
-        exit.store(true);
+        returnCode.storeRelaxed(-1);
+        exit.storeRelaxed(true);
     }
 
     QAtomicInt quitLockRef;
diff --git a/src/corelib/kernel/qjni.cpp b/src/corelib/kernel/qjni.cpp
index 75a2436d9d..5f652d70e3 100644
--- a/src/corelib/kernel/qjni.cpp
+++ b/src/corelib/kernel/qjni.cpp
@@ -47,9 +47,9 @@
 
 QT_BEGIN_NAMESPACE
 
-static inline QString keyBase()
+static inline QLatin1String keyBase()
 {
-    return QStringLiteral("%1%2:%3");
+    return QLatin1String("%1%2:%3");
 }
 
 static QString qt_convertJString(jstring string)
@@ -154,7 +154,7 @@ static jmethodID getCachedMethodID(JNIEnv *env,
     if (className.isEmpty())
         return getMethodID(env, clazz, name, sig, isStatic);
 
-    const QString key = keyBase().arg(QLatin1String(className)).arg(QLatin1String(name)).arg(QLatin1String(sig));
+    const QString key = keyBase().arg(QLatin1String(className), QLatin1String(name), QLatin1String(sig));
     QHash<QString, jmethodID>::const_iterator it;
 
     {
@@ -206,7 +206,7 @@ static jfieldID getCachedFieldID(JNIEnv *env,
     if (className.isNull())
         return getFieldID(env, clazz, name, sig, isStatic);
 
-    const QString key = keyBase().arg(QLatin1String(className)).arg(QLatin1String(name)).arg(QLatin1String(sig));
+    const QString key = keyBase().arg(QLatin1String(className), QLatin1String(name), QLatin1String(sig));
     QHash<QString, jfieldID>::const_iterator it;
 
     {
diff --git a/src/corelib/kernel/qmetatype.cpp b/src/corelib/kernel/qmetatype.cpp
index 855d36794d..754f5a13e4 100644
--- a/src/corelib/kernel/qmetatype.cpp
+++ b/src/corelib/kernel/qmetatype.cpp
@@ -517,12 +517,12 @@ static const struct { const char * typeName; int typeNameLength; int type; } typ
     QT_FOR_EACH_STATIC_TYPE(QT_ADD_STATIC_METATYPE)
     QT_FOR_EACH_STATIC_ALIAS_TYPE(QT_ADD_STATIC_METATYPE_ALIASES_ITER)
     QT_FOR_EACH_STATIC_HACKS_TYPE(QT_ADD_STATIC_METATYPE_HACKS_ITER)
-    {0, 0, QMetaType::UnknownType}
+    {nullptr, 0, QMetaType::UnknownType}
 };
 
-Q_CORE_EXPORT const QMetaTypeInterface *qMetaTypeGuiHelper = 0;
-Q_CORE_EXPORT const QMetaTypeInterface *qMetaTypeWidgetsHelper = 0;
-Q_CORE_EXPORT const QMetaObject *qMetaObjectWidgetsHelper = 0;
+Q_CORE_EXPORT const QMetaTypeInterface *qMetaTypeGuiHelper = nullptr;
+Q_CORE_EXPORT const QMetaTypeInterface *qMetaTypeWidgetsHelper = nullptr;
+Q_CORE_EXPORT const QMetaObject *qMetaObjectWidgetsHelper = nullptr;
 
 class QCustomTypeInfo : public QMetaTypeInterface
 {
@@ -557,7 +557,7 @@ public:
     {
         const QWriteLocker locker(&lock);
         const T* &fun = map[k];
-        if (fun != 0)
+        if (fun)
             return false;
         fun = f;
         return true;
@@ -566,7 +566,7 @@ public:
     const T *function(Key k) const
     {
         const QReadLocker locker(&lock);
-        return map.value(k, 0);
+        return map.value(k, nullptr);
     }
 
     void remove(int from, int to)
@@ -587,13 +587,7 @@ QMetaTypeComparatorRegistry;
 typedef QMetaTypeFunctionRegistry<QtPrivate::AbstractDebugStreamFunction,int>
 QMetaTypeDebugStreamRegistry;
 
-namespace
-{
-union CheckThatItIsPod
-{   // This should break if QMetaTypeInterface is not a POD type
-    QMetaTypeInterface iface;
-};
-}
+Q_STATIC_ASSERT(std::is_pod<QMetaTypeInterface>::value);
 
 Q_DECLARE_TYPEINFO(QCustomTypeInfo, Q_MOVABLE_TYPE);
 Q_GLOBAL_STATIC(QVector<QCustomTypeInfo>, customTypes)
@@ -973,7 +967,7 @@ static inline int qMetaTypeStaticType(const char *typeName, int length)
     The extra \a firstInvalidIndex parameter is an easy way to avoid
     iterating over customTypes() a second time in registerNormalizedType().
 */
-static int qMetaTypeCustomType_unlocked(const char *typeName, int length, int *firstInvalidIndex = 0)
+static int qMetaTypeCustomType_unlocked(const char *typeName, int length, int *firstInvalidIndex = nullptr)
 {
     const QVector<QCustomTypeInfo> * const ct = customTypes();
     if (!ct)
@@ -1006,7 +1000,7 @@ int QMetaType::registerType(const char *typeName, Deleter deleter,
 {
     return registerType(typeName, deleter, creator,
                         QtMetaTypePrivate::QMetaTypeFunctionHelper<void>::Destruct,
-                        QtMetaTypePrivate::QMetaTypeFunctionHelper<void>::Construct, 0, TypeFlags(), 0);
+                        QtMetaTypePrivate::QMetaTypeFunctionHelper<void>::Construct, 0, TypeFlags(), nullptr);
 }
 
 /*!
@@ -1613,7 +1607,7 @@ void *QMetaType::create(int type, const void *copy)
     QMetaType info(type);
     if (int size = info.sizeOf())
         return info.construct(operator new(size), copy);
-    return 0;
+    return nullptr;
 }
 
 /*!
@@ -1639,14 +1633,18 @@ class TypeConstructor {
         static void *Construct(const int type, void *where, const void *copy)
         {
             if (QModulesPrivate::QTypeModuleInfo<T>::IsGui)
-                return Q_LIKELY(qMetaTypeGuiHelper) ? qMetaTypeGuiHelper[type - QMetaType::FirstGuiType].constructor(where, copy) : 0;
+                return Q_LIKELY(qMetaTypeGuiHelper)
+                    ? qMetaTypeGuiHelper[type - QMetaType::FirstGuiType].constructor(where, copy)
+                    : nullptr;
 
             if (QModulesPrivate::QTypeModuleInfo<T>::IsWidget)
-                return Q_LIKELY(qMetaTypeWidgetsHelper) ? qMetaTypeWidgetsHelper[type - QMetaType::FirstWidgetsType].constructor(where, copy) : 0;
+                return Q_LIKELY(qMetaTypeWidgetsHelper)
+                    ? qMetaTypeWidgetsHelper[type - QMetaType::FirstWidgetsType].constructor(where, copy)
+                    : nullptr;
 
             // This point can be reached only for known types that definition is not available, for example
             // in bootstrap mode. We have no other choice then ignore it.
-            return 0;
+            return nullptr;
         }
     };
 public:
@@ -1670,7 +1668,7 @@ private:
         {
             QReadLocker locker(customTypesLock());
             if (Q_UNLIKELY(type < QMetaType::User || !ct || ct->count() <= type - QMetaType::User))
-                return 0;
+                return nullptr;
             const auto &typeInfo = ct->at(type - QMetaType::User);
             ctor = typeInfo.constructor;
             tctor = typeInfo.typedConstructor;
@@ -1715,7 +1713,7 @@ private:
 void *QMetaType::construct(int type, void *where, const void *copy)
 {
     if (!where)
-        return 0;
+        return nullptr;
     TypeConstructor constructor(type, where);
     return QMetaTypeSwitcher::switcher<void*>(constructor, type, copy);
 }
@@ -1861,7 +1859,7 @@ private:
 int QMetaType::sizeOf(int type)
 {
     SizeOf sizeOf(type);
-    return QMetaTypeSwitcher::switcher<int>(sizeOf, type, 0);
+    return QMetaTypeSwitcher::switcher<int>(sizeOf, type);
 }
 
 namespace {
@@ -1925,7 +1923,7 @@ private:
 QMetaType::TypeFlags QMetaType::typeFlags(int type)
 {
     Flags flags(type);
-    return static_cast<QMetaType::TypeFlags>(QMetaTypeSwitcher::switcher<quint32>(flags, type, 0));
+    return static_cast<QMetaType::TypeFlags>(QMetaTypeSwitcher::switcher<quint32>(flags, type));
 }
 
 #ifndef QT_BOOTSTRAPPED
@@ -1948,17 +1946,21 @@ public:
     {
         static const QMetaObject *MetaObject(int type) {
             if (QModulesPrivate::QTypeModuleInfo<T>::IsGui)
-                return Q_LIKELY(qMetaTypeGuiHelper) ? qMetaTypeGuiHelper[type - QMetaType::FirstGuiType].metaObject : 0;
+                return Q_LIKELY(qMetaTypeGuiHelper)
+                    ? qMetaTypeGuiHelper[type - QMetaType::FirstGuiType].metaObject
+                    : nullptr;
             if (QModulesPrivate::QTypeModuleInfo<T>::IsWidget)
-                return Q_LIKELY(qMetaTypeWidgetsHelper) ? qMetaTypeWidgetsHelper[type - QMetaType::FirstWidgetsType].metaObject : 0;
+                return Q_LIKELY(qMetaTypeWidgetsHelper)
+                    ? qMetaTypeWidgetsHelper[type - QMetaType::FirstWidgetsType].metaObject
+                    : nullptr;
             return 0;
         }
     };
 
     template <typename T>
     const QMetaObject *delegate(const T *) { return MetaObjectImpl<T>::MetaObject(m_type); }
-    const QMetaObject *delegate(const void*) { return 0; }
-    const QMetaObject *delegate(const QMetaTypeSwitcher::UnknownType*) { return 0; }
+    const QMetaObject *delegate(const void*) { return nullptr; }
+    const QMetaObject *delegate(const QMetaTypeSwitcher::UnknownType*) { return nullptr; }
     const QMetaObject *delegate(const QMetaTypeSwitcher::NotBuiltinType*) { return customMetaObject(m_type); }
 private:
     const int m_type;
@@ -1966,10 +1968,10 @@ private:
     {
         const QVector<QCustomTypeInfo> * const ct = customTypes();
         if (Q_UNLIKELY(!ct || type < QMetaType::User))
-            return 0;
+            return nullptr;
         QReadLocker locker(customTypesLock());
         if (Q_UNLIKELY(ct->count() <= type - QMetaType::User))
-            return 0;
+            return nullptr;
         return ct->at(type - QMetaType::User).metaObject;
     }
 };
@@ -1987,10 +1989,10 @@ const QMetaObject *QMetaType::metaObjectForType(int type)
 {
 #ifndef QT_BOOTSTRAPPED
     MetaObject mo(type);
-    return QMetaTypeSwitcher::switcher<const QMetaObject*>(mo, type, 0);
+    return QMetaTypeSwitcher::switcher<const QMetaObject*>(mo, type);
 #else
     Q_UNUSED(type);
-    return 0;
+    return nullptr;
 #endif
 }
 
@@ -2187,7 +2189,7 @@ private:
 QMetaType QMetaType::typeInfo(const int type)
 {
     TypeInfo typeInfo(type);
-    QMetaTypeSwitcher::switcher<void>(typeInfo, type, 0);
+    QMetaTypeSwitcher::switcher<void>(typeInfo, type);
     return (typeInfo.info.constructor || typeInfo.info.typedConstructor)
                 ? QMetaType(static_cast<ExtensionFlag>(QMetaType::CreateEx | QMetaType::DestroyEx |
                                                        (typeInfo.info.typedConstructor ? QMetaType::ConstructEx | QMetaType::DestructEx : 0))
@@ -2307,7 +2309,7 @@ void QMetaType::dtor()
 void *QMetaType::createExtended(const void *copy) const
 {
     if (m_typeId == QMetaType::UnknownType)
-        return 0;
+        return nullptr;
     if (Q_UNLIKELY(m_typedConstructor && !m_constructor))
         return m_typedConstructor(m_typeId, operator new(m_size), copy);
     return m_constructor(operator new(m_size), copy);
@@ -2387,7 +2389,7 @@ uint QMetaType::sizeExtended() const
 */
 QMetaType::TypeFlags QMetaType::flagsExtended() const
 {
-    return 0;
+    return { };
 }
 
 /*!
@@ -2400,7 +2402,7 @@ QMetaType::TypeFlags QMetaType::flagsExtended() const
 */
 const QMetaObject *QMetaType::metaObjectExtended() const
 {
-    return 0;
+    return nullptr;
 }
 
 
@@ -2409,7 +2411,7 @@ namespace QtPrivate
 const QMetaObject *metaObjectForQWidget()
 {
     if (!qMetaTypeWidgetsHelper)
-        return 0;
+        return nullptr;
     return qMetaObjectWidgetsHelper;
 }
 }
diff --git a/src/corelib/kernel/qmetatype.h b/src/corelib/kernel/qmetatype.h
index 12d4bc97aa..a97764ede4 100644
--- a/src/corelib/kernel/qmetatype.h
+++ b/src/corelib/kernel/qmetatype.h
@@ -1715,12 +1715,17 @@ namespace QtPrivate {
         }
     };
 
+    // hack to delay name lookup to instantiation time by making
+    // EnableInternalData a dependent name:
+    template <typename T>
+    struct EnableInternalDataWrap;
+
     template<typename T>
     struct QSmartPointerConvertFunctor<QWeakPointer<T> >
     {
         QObject* operator()(const QWeakPointer<T> &p) const
         {
-            return p.internalData();
+            return QtPrivate::EnableInternalDataWrap<T>::internalData(p);
         }
     };
 }
@@ -1994,7 +1999,7 @@ struct QMetaTypeId< SINGLE_ARG_TEMPLATE<T> > \
     static int qt_metatype_id() \
     { \
         static QBasicAtomicInt metatype_id = Q_BASIC_ATOMIC_INITIALIZER(0); \
-        if (const int id = metatype_id.load()) \
+        if (const int id = metatype_id.loadRelaxed()) \
             return id; \
         const char *tName = QMetaType::typeName(qMetaTypeId<T>()); \
         Q_ASSERT(tName); \
diff --git a/src/corelib/kernel/qmetatype_p.h b/src/corelib/kernel/qmetatype_p.h
index 0846193e66..97d6001937 100644
--- a/src/corelib/kernel/qmetatype_p.h
+++ b/src/corelib/kernel/qmetatype_p.h
@@ -140,12 +140,12 @@ public:
     /*saveOp*/(QtMetaTypePrivate::QMetaTypeFunctionHelper<Type, QtMetaTypePrivate::TypeDefinition<Type>::IsAvailable>::Save), \
     /*loadOp*/(QtMetaTypePrivate::QMetaTypeFunctionHelper<Type, QtMetaTypePrivate::TypeDefinition<Type>::IsAvailable>::Load),
 #  define QT_METATYPE_INTERFACE_INIT_EMPTY_DATASTREAM_IMPL(Type) \
-    /*saveOp*/ 0, \
-    /*loadOp*/ 0,
+    /*saveOp*/ nullptr, \
+    /*loadOp*/ nullptr,
 #else
 #  define QT_METATYPE_INTERFACE_INIT_EMPTY_DATASTREAM_IMPL(Type) \
-    /*saveOp*/ 0, \
-    /*loadOp*/ 0,
+    /*saveOp*/ nullptr, \
+    /*loadOp*/ nullptr,
 #  define QT_METATYPE_INTERFACE_INIT_DATASTREAM_IMPL(Type) \
     QT_METATYPE_INTERFACE_INIT_EMPTY_DATASTREAM_IMPL(Type)
 #endif
@@ -153,7 +153,7 @@ public:
 #ifndef QT_BOOTSTRAPPED
 #define METAOBJECT_DELEGATE(Type) (QtPrivate::MetaObjectForType<Type>::value())
 #else
-#define METAOBJECT_DELEGATE(Type) 0
+#define METAOBJECT_DELEGATE(Type) nullptr
 #endif
 
 #define QT_METATYPE_INTERFACE_INIT_IMPL(Type, DATASTREAM_DELEGATE) \
@@ -184,11 +184,11 @@ public:
 #define QT_METATYPE_INTERFACE_INIT_EMPTY() \
 { \
     QT_METATYPE_INTERFACE_INIT_EMPTY_DATASTREAM_IMPL(void) \
-    /*constructor*/ 0, \
-    /*destructor*/ 0, \
+    /*constructor*/ nullptr, \
+    /*destructor*/ nullptr, \
     /*size*/ 0, \
     /*flags*/ 0, \
-    /*metaObject*/ 0 , \
+    /*metaObject*/ nullptr , \
     /*typedConstructor*/ nullptr, \
     /*typedDestructor*/ nullptr \
 }
diff --git a/src/corelib/kernel/qmetatypeswitcher_p.h b/src/corelib/kernel/qmetatypeswitcher_p.h
index 154fb8ab7f..dabc70f4b0 100644
--- a/src/corelib/kernel/qmetatypeswitcher_p.h
+++ b/src/corelib/kernel/qmetatypeswitcher_p.h
@@ -60,7 +60,7 @@ public:
     class NotBuiltinType;   // type is not a built-in type, but it may be a custom type or an unknown type
     class UnknownType;      // type not known to QMetaType system
     template<class ReturnType, class DelegateObject>
-    static ReturnType switcher(DelegateObject &logic, int type, const void *data);
+    static ReturnType switcher(DelegateObject &logic, int type, const void *data = nullptr);
 };
 
 
diff --git a/src/corelib/kernel/qobject.cpp b/src/corelib/kernel/qobject.cpp
index 965857d408..8f80be30bd 100644
--- a/src/corelib/kernel/qobject.cpp
+++ b/src/corelib/kernel/qobject.cpp
@@ -58,6 +58,7 @@
 #include <qdebug.h>
 #include <qpair.h>
 #include <qvarlengtharray.h>
+#include <qscopeguard.h>
 #include <qset.h>
 #if QT_CONFIG(thread)
 #include <qsemaphore.h>
@@ -81,7 +82,7 @@ Q_CORE_EXPORT QBasicAtomicPointer<QSignalSpyCallbackSet> qt_signal_spy_callback_
 
 void qt_register_signal_spy_callbacks(QSignalSpyCallbackSet *callback_set)
 {
-    qt_signal_spy_callback_set.store(callback_set);
+    qt_signal_spy_callback_set.storeRelease(callback_set);
 }
 
 QDynamicMetaObjectData::~QDynamicMetaObjectData()
@@ -221,7 +222,7 @@ QObjectPrivate::~QObjectPrivate()
         if (Q_LIKELY(threadData->thread == QThread::currentThread())) {
             // unregister pending timers
             if (threadData->hasEventDispatcher())
-                threadData->eventDispatcher.load()->unregisterTimers(q_ptr);
+                threadData->eventDispatcher.loadRelaxed()->unregisterTimers(q_ptr);
 
             // release the timer ids back to the pool
             for (int i = 0; i < extraData->runningTimers.size(); ++i)
@@ -267,17 +268,17 @@ bool QObjectPrivate::isSender(const QObject *receiver, const char *signal) const
 {
     Q_Q(const QObject);
     int signal_index = signalIndex(signal);
-    ConnectionData *cd = connections.load();
+    ConnectionData *cd = connections.loadRelaxed();
     if (signal_index < 0 || !cd)
         return false;
     QBasicMutexLocker locker(signalSlotLock(q));
     if (signal_index < cd->signalVectorCount()) {
-        const QObjectPrivate::Connection *c = cd->signalVector.load()->at(signal_index).first.load();
+        const QObjectPrivate::Connection *c = cd->signalVector.loadRelaxed()->at(signal_index).first.loadRelaxed();
 
         while (c) {
-            if (c->receiver.load() == receiver)
+            if (c->receiver.loadRelaxed() == receiver)
                 return true;
-            c = c->nextConnectionList.load();
+            c = c->nextConnectionList.loadRelaxed();
         }
     }
     return false;
@@ -288,17 +289,17 @@ QObjectList QObjectPrivate::receiverList(const char *signal) const
 {
     QObjectList returnValue;
     int signal_index = signalIndex(signal);
-    ConnectionData *cd = connections.load();
+    ConnectionData *cd = connections.loadRelaxed();
     if (signal_index < 0 || !cd)
         return returnValue;
     if (signal_index < cd->signalVectorCount()) {
-        const QObjectPrivate::Connection *c = cd->signalVector.load()->at(signal_index).first.load();
+        const QObjectPrivate::Connection *c = cd->signalVector.loadRelaxed()->at(signal_index).first.loadRelaxed();
 
         while (c) {
-            QObject *r = c->receiver.load();
+            QObject *r = c->receiver.loadRelaxed();
             if (r)
                 returnValue << r;
-            c = c->nextConnectionList.load();
+            c = c->nextConnectionList.loadRelaxed();
         }
     }
     return returnValue;
@@ -308,7 +309,7 @@ QObjectList QObjectPrivate::receiverList(const char *signal) const
 QObjectList QObjectPrivate::senderList() const
 {
     QObjectList returnValue;
-    ConnectionData *cd = connections.load();
+    ConnectionData *cd = connections.loadRelaxed();
     if (cd) {
         QBasicMutexLocker locker(signalSlotLock(q_func()));
         for (Connection *c = cd->senders; c; c = c->next)
@@ -331,24 +332,24 @@ void QObjectPrivate::addConnection(int signal, Connection *c)
 {
     Q_ASSERT(c->sender == q_ptr);
     ensureConnectionData();
-    ConnectionData *cd = connections.load();
+    ConnectionData *cd = connections.loadRelaxed();
     cd->resizeSignalVector(signal + 1);
 
     ConnectionList &connectionList = cd->connectionsForSignal(signal);
-    if (connectionList.last.load()) {
-        Q_ASSERT(connectionList.last.load()->receiver.load());
-        connectionList.last.load()->nextConnectionList.store(c);
+    if (connectionList.last.loadRelaxed()) {
+        Q_ASSERT(connectionList.last.loadRelaxed()->receiver.loadRelaxed());
+        connectionList.last.loadRelaxed()->nextConnectionList.storeRelaxed(c);
     } else {
-        connectionList.first.store(c);
+        connectionList.first.storeRelaxed(c);
     }
     c->id = ++cd->currentConnectionId;
-    c->prevConnectionList = connectionList.last.load();
-    connectionList.last.store(c);
+    c->prevConnectionList = connectionList.last.loadRelaxed();
+    connectionList.last.storeRelaxed(c);
 
-    QObjectPrivate *rd = QObjectPrivate::get(c->receiver.load());
+    QObjectPrivate *rd = QObjectPrivate::get(c->receiver.loadRelaxed());
     rd->ensureConnectionData();
 
-    c->prev = &(rd->connections.load()->senders);
+    c->prev = &(rd->connections.loadRelaxed()->senders);
     c->next = *c->prev;
     *c->prev = c;
     if (c->next)
@@ -357,17 +358,17 @@ void QObjectPrivate::addConnection(int signal, Connection *c)
 
 void QObjectPrivate::ConnectionData::removeConnection(QObjectPrivate::Connection *c)
 {
-    Q_ASSERT(c->receiver.load());
-    ConnectionList &connections = signalVector.load()->at(c->signal_index);
-    c->receiver.store(nullptr);
-    QThreadData *td = c->receiverThreadData.load();
+    Q_ASSERT(c->receiver.loadRelaxed());
+    ConnectionList &connections = signalVector.loadRelaxed()->at(c->signal_index);
+    c->receiver.storeRelaxed(nullptr);
+    QThreadData *td = c->receiverThreadData.loadRelaxed();
     if (td)
         td->deref();
-    c->receiverThreadData.store(nullptr);
+    c->receiverThreadData.storeRelaxed(nullptr);
 
 #ifndef QT_NO_DEBUG
     bool found = false;
-    for (Connection *cc = connections.first.load(); cc; cc = cc->nextConnectionList.load()) {
+    for (Connection *cc = connections.first.loadRelaxed(); cc; cc = cc->nextConnectionList.loadRelaxed()) {
         if (cc == c) {
             found = true;
             break;
@@ -382,29 +383,29 @@ void QObjectPrivate::ConnectionData::removeConnection(QObjectPrivate::Connection
         c->next->prev = c->prev;
     c->prev = nullptr;
 
-    if (connections.first.load() == c)
-        connections.first.store(c->nextConnectionList.load());
-    if (connections.last.load() == c)
-        connections.last.store(c->prevConnectionList);
-    Q_ASSERT(signalVector.load()->at(c->signal_index).first.load() != c);
-    Q_ASSERT(signalVector.load()->at(c->signal_index).last.load() != c);
+    if (connections.first.loadRelaxed() == c)
+        connections.first.storeRelaxed(c->nextConnectionList.loadRelaxed());
+    if (connections.last.loadRelaxed() == c)
+        connections.last.storeRelaxed(c->prevConnectionList);
+    Q_ASSERT(signalVector.loadRelaxed()->at(c->signal_index).first.loadRelaxed() != c);
+    Q_ASSERT(signalVector.loadRelaxed()->at(c->signal_index).last.loadRelaxed() != c);
 
     // keep c->nextConnectionList intact, as it might still get accessed by activate
-    Connection *n = c->nextConnectionList.load();
+    Connection *n = c->nextConnectionList.loadRelaxed();
     if (n)
         n->prevConnectionList = c->prevConnectionList;
     if (c->prevConnectionList)
-        c->prevConnectionList->nextConnectionList.store(n);
+        c->prevConnectionList->nextConnectionList.storeRelaxed(n);
     c->prevConnectionList = nullptr;
 
-    Q_ASSERT(c != orphaned.load());
+    Q_ASSERT(c != orphaned.loadRelaxed());
     // add c to orphanedConnections
-    c->nextInOrphanList = orphaned.load();
-    orphaned.store(c);
+    c->nextInOrphanList = orphaned.loadRelaxed();
+    orphaned.storeRelaxed(c);
 
 #ifndef QT_NO_DEBUG
     found = false;
-    for (Connection *cc = connections.first.load(); cc; cc = cc->nextConnectionList.load()) {
+    for (Connection *cc = connections.first.loadRelaxed(); cc; cc = cc->nextConnectionList.loadRelaxed()) {
         if (cc == c) {
             found = true;
             break;
@@ -426,8 +427,8 @@ void QObjectPrivate::ConnectionData::cleanOrphanedConnectionsImpl(QObject *sende
         // Since ref == 1, no activate() is in process since we locked the mutex. That implies,
         // that nothing can reference the orphaned connection objects anymore and they can
         // be safely deleted
-        c = orphaned.load();
-        orphaned.store(nullptr);
+        c = orphaned.loadRelaxed();
+        orphaned.storeRelaxed(nullptr);
     }
     deleteOrphaned(c);
 }
@@ -442,7 +443,7 @@ void QObjectPrivate::ConnectionData::deleteOrphaned(QObjectPrivate::ConnectionOr
         } else {
             QObjectPrivate::Connection *c = static_cast<Connection *>(o);
             next = c->nextInOrphanList;
-            Q_ASSERT(!c->receiver.load());
+            Q_ASSERT(!c->receiver.loadRelaxed());
             Q_ASSERT(!c->prev);
             c->freeSlotObject();
             c->deref();
@@ -462,22 +463,22 @@ bool QObjectPrivate::isSignalConnected(uint signalIndex, bool checkDeclarative)
     if (checkDeclarative && isDeclarativeSignalConnected(signalIndex))
         return true;
 
-    ConnectionData *cd = connections.load();
+    ConnectionData *cd = connections.loadRelaxed();
     if (!cd)
         return false;
-    SignalVector *signalVector = cd->signalVector.load();
+    SignalVector *signalVector = cd->signalVector.loadRelaxed();
     if (!signalVector)
         return false;
 
-    if (signalVector->at(-1).first.load())
+    if (signalVector->at(-1).first.loadRelaxed())
         return true;
 
     if (signalIndex < uint(cd->signalVectorCount())) {
-        const QObjectPrivate::Connection *c = signalVector->at(signalIndex).first.load();
+        const QObjectPrivate::Connection *c = signalVector->at(signalIndex).first.loadRelaxed();
         while (c) {
-            if (c->receiver.load())
+            if (c->receiver.loadRelaxed())
                 return true;
-            c = c->nextConnectionList.load();
+            c = c->nextConnectionList.loadRelaxed();
         }
     }
     return false;
@@ -485,10 +486,10 @@ bool QObjectPrivate::isSignalConnected(uint signalIndex, bool checkDeclarative)
 
 bool QObjectPrivate::maybeSignalConnected(uint signalIndex) const
 {
-    ConnectionData *cd = connections.load();
+    ConnectionData *cd = connections.loadRelaxed();
     if (!cd)
         return false;
-    SignalVector *signalVector = cd->signalVector.load();
+    SignalVector *signalVector = cd->signalVector.loadRelaxed();
     if (!signalVector)
         return false;
 
@@ -851,6 +852,8 @@ static bool check_parent_thread(QObject *parent,
 QObject::QObject(QObject *parent)
     : d_ptr(new QObjectPrivate)
 {
+    Q_ASSERT_X(this != parent, Q_FUNC_INFO, "Cannot parent a QObject to itself");
+
     Q_D(QObject);
     d_ptr->q_ptr = this;
     d->threadData = (parent && !parent->thread()) ? parent->d_func()->threadData : QThreadData::current();
@@ -879,6 +882,8 @@ QObject::QObject(QObject *parent)
 QObject::QObject(QObjectPrivate &dd, QObject *parent)
     : d_ptr(&dd)
 {
+    Q_ASSERT_X(this != parent, Q_FUNC_INFO, "Cannot parent a QObject to itself");
+
     Q_D(QObject);
     d_ptr->q_ptr = this;
     d->threadData = (parent && !parent->thread()) ? parent->d_func()->threadData : QThreadData::current();
@@ -939,15 +944,15 @@ QObject::~QObject()
     d->wasDeleted = true;
     d->blockSig = 0; // unblock signals so we always emit destroyed()
 
-    QtSharedPointer::ExternalRefCountData *sharedRefcount = d->sharedRefcount.load();
+    QtSharedPointer::ExternalRefCountData *sharedRefcount = d->sharedRefcount.loadRelaxed();
     if (sharedRefcount) {
-        if (sharedRefcount->strongref.load() > 0) {
+        if (sharedRefcount->strongref.loadRelaxed() > 0) {
             qWarning("QObject: shared QObject was deleted directly. The program is malformed and may crash.");
             // but continue deleting, it's too late to stop anyway
         }
 
         // indicate to all QWeakPointers that this QObject has now been deleted
-        sharedRefcount->strongref.store(0);
+        sharedRefcount->strongref.storeRelaxed(0);
         if (!sharedRefcount->weakref.deref())
             delete sharedRefcount;
     }
@@ -966,7 +971,7 @@ QObject::~QObject()
         }
     }
 
-    QObjectPrivate::ConnectionData *cd = d->connections.load();
+    QObjectPrivate::ConnectionData *cd = d->connections.loadRelaxed();
     if (cd) {
         if (cd->currentSender) {
             cd->currentSender->receiverDeleted();
@@ -981,14 +986,14 @@ QObject::~QObject()
         for (int signal = -1; signal < receiverCount; ++signal) {
             QObjectPrivate::ConnectionList &connectionList = cd->connectionsForSignal(signal);
 
-            while (QObjectPrivate::Connection *c = connectionList.first.load()) {
+            while (QObjectPrivate::Connection *c = connectionList.first.loadRelaxed()) {
                 Q_ASSERT(c->receiver);
 
-                QBasicMutex *m = signalSlotLock(c->receiver.load());
+                QBasicMutex *m = signalSlotLock(c->receiver.loadRelaxed());
                 bool needToUnlock = QOrderedMutexLocker::relock(signalSlotMutex, m);
                 if (c->receiver) {
                     cd->removeConnection(c);
-                    Q_ASSERT(connectionList.first.load() != c);
+                    Q_ASSERT(connectionList.first.loadRelaxed() != c);
                 }
                 if (needToUnlock)
                     m->unlock();
@@ -1014,7 +1019,7 @@ QObject::~QObject()
                 continue;
             }
 
-            QObjectPrivate::ConnectionData *senderData = sender->d_func()->connections.load();
+            QObjectPrivate::ConnectionData *senderData = sender->d_func()->connections.loadRelaxed();
             Q_ASSERT(senderData);
 
             QtPrivate::QSlotObjectBase *slotObj = nullptr;
@@ -1036,11 +1041,11 @@ QObject::~QObject()
 
         // invalidate all connections on the object and make sure
         // activate() will skip them
-        cd->currentConnectionId.store(0);
+        cd->currentConnectionId.storeRelaxed(0);
     }
     if (cd && !cd->ref.deref())
         delete cd;
-    d->connections.store(nullptr);
+    d->connections.storeRelaxed(nullptr);
 
     if (!d->children.isEmpty())
         d->deleteChildren();
@@ -1060,7 +1065,7 @@ QObject::~QObject()
 QObjectPrivate::Connection::~Connection()
 {
     if (ownArgumentTypes) {
-        const int *v = argumentTypes.load();
+        const int *v = argumentTypes.loadRelaxed();
         if (v != &DIRECT_CONNECTION_ONLY)
             delete [] v;
     }
@@ -1269,7 +1274,7 @@ bool QObject::event(QEvent *e)
         {
             QAbstractMetaCallEvent *mce = static_cast<QAbstractMetaCallEvent*>(e);
 
-            if (!d_func()->connections.load()) {
+            if (!d_func()->connections.loadRelaxed()) {
                 QBasicMutexLocker locker(signalSlotLock(this));
                 d_func()->ensureConnectionData();
             }
@@ -1282,7 +1287,7 @@ bool QObject::event(QEvent *e)
     case QEvent::ThreadChange: {
         Q_D(QObject);
         QThreadData *threadData = d->threadData;
-        QAbstractEventDispatcher *eventDispatcher = threadData->eventDispatcher.load();
+        QAbstractEventDispatcher *eventDispatcher = threadData->eventDispatcher.loadRelaxed();
         if (eventDispatcher) {
             QList<QAbstractEventDispatcher::TimerInfo> timers = eventDispatcher->registeredTimers(this);
             if (!timers.isEmpty()) {
@@ -1517,7 +1522,7 @@ void QObject::moveToThread(QThread *targetThread)
     } else if (d->threadData != currentData) {
         qWarning("QObject::moveToThread: Current thread (%p) is not the object's thread (%p).\n"
                  "Cannot move to target thread (%p)\n",
-                 currentData->thread.load(), d->threadData->thread.load(), targetData ? targetData->thread.load() : nullptr);
+                 currentData->thread.loadRelaxed(), d->threadData->thread.loadRelaxed(), targetData ? targetData->thread.loadRelaxed() : nullptr);
 
 #ifdef Q_OS_MAC
         qWarning("You might be loading two sets of Qt binaries into the same process. "
@@ -1582,11 +1587,11 @@ void QObjectPrivate::setThreadData_helper(QThreadData *currentData, QThreadData
     }
     if (eventsMoved > 0 && targetData->hasEventDispatcher()) {
         targetData->canWait = false;
-        targetData->eventDispatcher.load()->wakeUp();
+        targetData->eventDispatcher.loadRelaxed()->wakeUp();
     }
 
     // the current emitting thread shouldn't restore currentSender after calling moveToThread()
-    ConnectionData *cd = connections.load();
+    ConnectionData *cd = connections.loadRelaxed();
     if (cd) {
         if (cd->currentSender) {
             cd->currentSender->receiverDeleted();
@@ -1597,14 +1602,14 @@ void QObjectPrivate::setThreadData_helper(QThreadData *currentData, QThreadData
         if (cd) {
             auto *c = cd->senders;
             while (c) {
-                QObject *r = c->receiver.load();
+                QObject *r = c->receiver.loadRelaxed();
                 if (r) {
                     Q_ASSERT(r == q);
                     targetData->ref();
-                    QThreadData *old = c->receiverThreadData.load();
+                    QThreadData *old = c->receiverThreadData.loadRelaxed();
                     if (old)
                         old->deref();
-                    c->receiverThreadData.store(targetData);
+                    c->receiverThreadData.storeRelaxed(targetData);
                 }
                 c = c->next;
             }
@@ -1627,7 +1632,7 @@ void QObjectPrivate::_q_reregisterTimers(void *pointer)
 {
     Q_Q(QObject);
     QList<QAbstractEventDispatcher::TimerInfo> *timerList = reinterpret_cast<QList<QAbstractEventDispatcher::TimerInfo> *>(pointer);
-    QAbstractEventDispatcher *eventDispatcher = threadData->eventDispatcher.load();
+    QAbstractEventDispatcher *eventDispatcher = threadData->eventDispatcher.loadRelaxed();
     for (int i = 0; i < timerList->size(); ++i) {
         const QAbstractEventDispatcher::TimerInfo &ti = timerList->at(i);
         eventDispatcher->registerTimer(ti.timerId, ti.interval, ti.timerType, q);
@@ -1693,7 +1698,7 @@ int QObject::startTimer(int interval, Qt::TimerType timerType)
         qWarning("QObject::startTimer: Timers cannot be started from another thread");
         return 0;
     }
-    int timerId = d->threadData->eventDispatcher.load()->registerTimer(interval, timerType, this);
+    int timerId = d->threadData->eventDispatcher.loadRelaxed()->registerTimer(interval, timerType, this);
     if (!d->extraData)
         d->extraData = new QObjectPrivate::ExtraData;
     d->extraData->runningTimers.append(timerId);
@@ -1768,7 +1773,7 @@ void QObject::killTimer(int id)
         }
 
         if (d->threadData->hasEventDispatcher())
-            d->threadData->eventDispatcher.load()->unregisterTimer(id);
+            d->threadData->eventDispatcher.loadRelaxed()->unregisterTimer(id);
 
         d->extraData->runningTimers.remove(at);
         QAbstractEventDispatcherPrivate::releaseTimerId(id);
@@ -2069,8 +2074,25 @@ void QObjectPrivate::deleteChildren()
 void QObjectPrivate::setParent_helper(QObject *o)
 {
     Q_Q(QObject);
+    Q_ASSERT_X(q != o, Q_FUNC_INFO, "Cannot parent a QObject to itself");
+#ifdef QT_DEBUG
+    const auto checkForParentChildLoops = qScopeGuard([&](){
+        int depth = 0;
+        auto p = parent;
+        while (p) {
+            if (++depth == CheckForParentChildLoopsWarnDepth) {
+                qWarning("QObject %p (class: '%s', object name: '%s') may have a loop in its parent-child chain; "
+                         "this is undefined behavior",
+                         q, q->metaObject()->className(), qPrintable(q->objectName()));
+            }
+            p = p->parent();
+        }
+    });
+#endif
+
     if (o == parent)
         return;
+
     if (parent) {
         QObjectPrivate *parentD = parent->d_func();
         if (parentD->isDeletingChildren && wasDeleted
@@ -2420,7 +2442,7 @@ QObject *QObject::sender() const
     Q_D(const QObject);
 
     QBasicMutexLocker locker(signalSlotLock(this));
-    QObjectPrivate::ConnectionData *cd = d->connections.load();
+    QObjectPrivate::ConnectionData *cd = d->connections.loadRelaxed();
     if (!cd || !cd->currentSender)
         return nullptr;
 
@@ -2462,7 +2484,7 @@ int QObject::senderSignalIndex() const
     Q_D(const QObject);
 
     QBasicMutexLocker locker(signalSlotLock(this));
-    QObjectPrivate::ConnectionData *cd = d->connections.load();
+    QObjectPrivate::ConnectionData *cd = d->connections.loadRelaxed();
     if (!cd || !cd->currentSender)
         return -1;
 
@@ -2525,13 +2547,13 @@ int QObject::receivers(const char *signal) const
                                                              signal_index);
         }
 
-        QObjectPrivate::ConnectionData *cd = d->connections.load();
+        QObjectPrivate::ConnectionData *cd = d->connections.loadRelaxed();
         QBasicMutexLocker locker(signalSlotLock(this));
         if (cd && signal_index < cd->signalVectorCount()) {
-            const QObjectPrivate::Connection *c = cd->signalVector.load()->at(signal_index).first.load();
+            const QObjectPrivate::Connection *c = cd->signalVector.loadRelaxed()->at(signal_index).first.loadRelaxed();
             while (c) {
-                receivers += c->receiver.load() ? 1 : 0;
-                c = c->nextConnectionList.load();
+                receivers += c->receiver.loadRelaxed() ? 1 : 0;
+                c = c->nextConnectionList.loadRelaxed();
             }
         }
     }
@@ -3340,17 +3362,17 @@ QObjectPrivate::Connection *QMetaObjectPrivate::connect(const QObject *sender,
     QOrderedMutexLocker locker(signalSlotLock(sender),
                                signalSlotLock(receiver));
 
-    QObjectPrivate::ConnectionData *scd  = QObjectPrivate::get(s)->connections.load();
+    QObjectPrivate::ConnectionData *scd  = QObjectPrivate::get(s)->connections.loadRelaxed();
     if (type & Qt::UniqueConnection && scd) {
         if (scd->signalVectorCount() > signal_index) {
-            const QObjectPrivate::Connection *c2 = scd->signalVector.load()->at(signal_index).first.load();
+            const QObjectPrivate::Connection *c2 = scd->signalVector.loadRelaxed()->at(signal_index).first.loadRelaxed();
 
             int method_index_absolute = method_index + method_offset;
 
             while (c2) {
-                if (!c2->isSlotObject && c2->receiver.load() == receiver && c2->method() == method_index_absolute)
+                if (!c2->isSlotObject && c2->receiver.loadRelaxed() == receiver && c2->method() == method_index_absolute)
                     return nullptr;
-                c2 = c2->nextConnectionList.load();
+                c2 = c2->nextConnectionList.loadRelaxed();
             }
         }
         type &= Qt::UniqueConnection - 1;
@@ -3359,15 +3381,15 @@ QObjectPrivate::Connection *QMetaObjectPrivate::connect(const QObject *sender,
     QScopedPointer<QObjectPrivate::Connection> c(new QObjectPrivate::Connection);
     c->sender = s;
     c->signal_index = signal_index;
-    c->receiver.store(r);
+    c->receiver.storeRelaxed(r);
     QThreadData *td = r->d_func()->threadData;
     td->ref();
-    c->receiverThreadData.store(td);
+    c->receiverThreadData.storeRelaxed(td);
     c->method_relative = method_index;
     c->method_offset = method_offset;
     c->connectionType = type;
     c->isSlotObject = false;
-    c->argumentTypes.store(types);
+    c->argumentTypes.storeRelaxed(types);
     c->callFunction = callFunction;
 
     QObjectPrivate::get(s)->addConnection(signal_index, c.data());
@@ -3420,9 +3442,9 @@ bool QMetaObjectPrivate::disconnectHelper(QObjectPrivate::ConnectionData *connec
     bool success = false;
 
     auto &connectionList = connections->connectionsForSignal(signalIndex);
-    auto *c = connectionList.first.load();
+    auto *c = connectionList.first.loadRelaxed();
     while (c) {
-        QObject *r = c->receiver.load();
+        QObject *r = c->receiver.loadRelaxed();
         if (r && (receiver == nullptr || (r == receiver
                            && (method_index < 0 || (!c->isSlotObject && c->method() == method_index))
                            && (slot == nullptr || (c->isSlotObject && c->slotObj->compare(slot)))))) {
@@ -3433,7 +3455,7 @@ bool QMetaObjectPrivate::disconnectHelper(QObjectPrivate::ConnectionData *connec
                 // need to relock this receiver and sender in the correct order
                 needToUnlock = QOrderedMutexLocker::relock(senderMutex, receiverMutex);
             }
-            if (c->receiver.load())
+            if (c->receiver.loadRelaxed())
                 connections->removeConnection(c);
 
             if (needToUnlock)
@@ -3444,7 +3466,7 @@ bool QMetaObjectPrivate::disconnectHelper(QObjectPrivate::ConnectionData *connec
             if (disconnectType == DisconnectOne)
                 return success;
         }
-        c = c->nextConnectionList.load();
+        c = c->nextConnectionList.loadRelaxed();
     }
     return success;
 }
@@ -3466,7 +3488,7 @@ bool QMetaObjectPrivate::disconnect(const QObject *sender,
     QBasicMutex *senderMutex = signalSlotLock(sender);
     QBasicMutexLocker locker(senderMutex);
 
-    QObjectPrivate::ConnectionData *scd  = QObjectPrivate::get(s)->connections.load();
+    QObjectPrivate::ConnectionData *scd  = QObjectPrivate::get(s)->connections.loadRelaxed();
     if (!scd)
         return false;
 
@@ -3608,7 +3630,7 @@ void QMetaObject::connectSlotsByName(QObject *o)
 */
 static void queued_activate(QObject *sender, int signal, QObjectPrivate::Connection *c, void **argv)
 {
-    const int *argumentTypes = c->argumentTypes.load();
+    const int *argumentTypes = c->argumentTypes.loadRelaxed();
     if (!argumentTypes) {
         QMetaMethod m = QMetaObjectPrivate::signal(sender->metaObject(), signal);
         argumentTypes = queuedConnectionTypes(m.parameterTypes());
@@ -3617,7 +3639,7 @@ static void queued_activate(QObject *sender, int signal, QObjectPrivate::Connect
         if (!c->argumentTypes.testAndSetOrdered(0, argumentTypes)) {
             if (argumentTypes != &DIRECT_CONNECTION_ONLY)
                 delete [] argumentTypes;
-            argumentTypes = c->argumentTypes.load();
+            argumentTypes = c->argumentTypes.loadRelaxed();
         }
     }
     if (argumentTypes == &DIRECT_CONNECTION_ONLY) // cannot activate
@@ -3640,8 +3662,8 @@ static void queued_activate(QObject *sender, int signal, QObjectPrivate::Connect
             args[n] = QMetaType::create(types[n], argv[n]);
     }
 
-    QBasicMutexLocker locker(signalSlotLock(c->receiver.load()));
-    if (!c->receiver.load()) {
+    QBasicMutexLocker locker(signalSlotLock(c->receiver.loadRelaxed()));
+    if (!c->receiver.loadRelaxed()) {
         // the connection has been disconnected before we got the lock
         locker.unlock();
         for (int n = 1; n < nargs; ++n)
@@ -3654,7 +3676,7 @@ static void queued_activate(QObject *sender, int signal, QObjectPrivate::Connect
     QMetaCallEvent *ev = c->isSlotObject ?
         new QMetaCallEvent(c->slotObj, sender, signal, nargs, types, args) :
         new QMetaCallEvent(c->method_offset, c->method_relative, c->callFunction, sender, signal, nargs, types, args);
-    QCoreApplication::postEvent(c->receiver.load(), ev);
+    QCoreApplication::postEvent(c->receiver.loadRelaxed(), ev);
 }
 
 template <bool callbacks_enabled>
@@ -3674,7 +3696,7 @@ void doActivate(QObject *sender, int signal_index, void **argv)
                                                 signal_index, argv);
     }
 
-    const QSignalSpyCallbackSet *signal_spy_set = callbacks_enabled ? qt_signal_spy_callback_set.load() : nullptr;
+    const QSignalSpyCallbackSet *signal_spy_set = callbacks_enabled ? qt_signal_spy_callback_set.loadAcquire() : nullptr;
 
     void *empty_argv[] = { nullptr };
     if (!argv)
@@ -3695,8 +3717,8 @@ void doActivate(QObject *sender, int signal_index, void **argv)
     bool senderDeleted = false;
     {
     Q_ASSERT(sp->connections);
-    QObjectPrivate::ConnectionDataPointer connections(sp->connections.load());
-    QObjectPrivate::SignalVector *signalVector = connections->signalVector.load();
+    QObjectPrivate::ConnectionDataPointer connections(sp->connections.loadRelaxed());
+    QObjectPrivate::SignalVector *signalVector = connections->signalVector.loadRelaxed();
 
     const QObjectPrivate::ConnectionList *list;
     if (signal_index < signalVector->count())
@@ -3705,32 +3727,32 @@ void doActivate(QObject *sender, int signal_index, void **argv)
         list = &signalVector->at(-1);
 
     Qt::HANDLE currentThreadId = QThread::currentThreadId();
-    bool inSenderThread = currentThreadId == QObjectPrivate::get(sender)->threadData->threadId.load();
+    bool inSenderThread = currentThreadId == QObjectPrivate::get(sender)->threadData->threadId.loadRelaxed();
 
     // We need to check against the highest connection id to ensure that signals added
     // during the signal emission are not emitted in this emission.
-    uint highestConnectionId = connections->currentConnectionId.load();
+    uint highestConnectionId = connections->currentConnectionId.loadRelaxed();
     do {
-        QObjectPrivate::Connection *c = list->first.load();
+        QObjectPrivate::Connection *c = list->first.loadRelaxed();
         if (!c)
             continue;
 
         do {
-            QObject * const receiver = c->receiver.load();
+            QObject * const receiver = c->receiver.loadRelaxed();
             if (!receiver)
                 continue;
 
-            QThreadData *td = c->receiverThreadData.load();
+            QThreadData *td = c->receiverThreadData.loadRelaxed();
             if (!td)
                 continue;
 
             bool receiverInSameThread;
             if (inSenderThread) {
-                receiverInSameThread = currentThreadId == td->threadId.load();
+                receiverInSameThread = currentThreadId == td->threadId.loadRelaxed();
             } else {
                 // need to lock before reading the threadId, because moveToThread() could interfere
                 QMutexLocker lock(signalSlotLock(receiver));
-                receiverInSameThread = currentThreadId == td->threadId.load();
+                receiverInSameThread = currentThreadId == td->threadId.loadRelaxed();
             }
 
 
@@ -3803,17 +3825,17 @@ void doActivate(QObject *sender, int signal_index, void **argv)
                 if (callbacks_enabled && signal_spy_set->slot_end_callback != nullptr)
                     signal_spy_set->slot_end_callback(receiver, method);
             }
-        } while ((c = c->nextConnectionList.load()) != nullptr && c->id <= highestConnectionId);
+        } while ((c = c->nextConnectionList.loadRelaxed()) != nullptr && c->id <= highestConnectionId);
 
     } while (list != &signalVector->at(-1) &&
         //start over for all signals;
         ((list = &signalVector->at(-1)), true));
 
-        if (connections->currentConnectionId.load() == 0)
+        if (connections->currentConnectionId.loadRelaxed() == 0)
             senderDeleted = true;
     }
     if (!senderDeleted)
-        sp->connections.load()->cleanOrphanedConnections(sender);
+        sp->connections.loadRelaxed()->cleanOrphanedConnections(sender);
 
     if (callbacks_enabled && signal_spy_set->signal_end_callback != nullptr)
         signal_spy_set->signal_end_callback(sender, signal_index);
@@ -3827,7 +3849,7 @@ void QMetaObject::activate(QObject *sender, const QMetaObject *m, int local_sign
 {
     int signal_index = local_signal_index + QMetaObjectPrivate::signalOffset(m);
 
-    if (Q_UNLIKELY(qt_signal_spy_callback_set.load()))
+    if (Q_UNLIKELY(qt_signal_spy_callback_set.loadRelaxed()))
         doActivate<true>(sender, signal_index, argv);
     else
         doActivate<false>(sender, signal_index, argv);
@@ -3840,7 +3862,7 @@ void QMetaObject::activate(QObject *sender, int signalOffset, int local_signal_i
 {
     int signal_index = signalOffset + local_signal_index;
 
-    if (Q_UNLIKELY(qt_signal_spy_callback_set.load()))
+    if (Q_UNLIKELY(qt_signal_spy_callback_set.loadRelaxed()))
         doActivate<true>(sender, signal_index, argv);
     else
         doActivate<false>(sender, signal_index, argv);
@@ -4109,11 +4131,11 @@ void QObject::dumpObjectInfo() const
     // first, look for connections where this object is the sender
     qDebug("  SIGNALS OUT");
 
-    QObjectPrivate::ConnectionData *cd = d->connections.load();
+    QObjectPrivate::ConnectionData *cd = d->connections.loadRelaxed();
     if (cd && cd->signalVectorCount()) {
-        QObjectPrivate::SignalVector *signalVector = cd->signalVector.load();
+        QObjectPrivate::SignalVector *signalVector = cd->signalVector.loadRelaxed();
         for (int signal_index = 0; signal_index < signalVector->count(); ++signal_index) {
-            const QObjectPrivate::Connection *c = signalVector->at(signal_index).first.load();
+            const QObjectPrivate::Connection *c = signalVector->at(signal_index).first.loadRelaxed();
             if (!c)
                 continue;
             const QMetaMethod signal = QMetaObjectPrivate::signal(metaObject(), signal_index);
@@ -4121,23 +4143,23 @@ void QObject::dumpObjectInfo() const
 
             // receivers
             while (c) {
-                if (!c->receiver.load()) {
+                if (!c->receiver.loadRelaxed()) {
                     qDebug("          <Disconnected receiver>");
-                    c = c->nextConnectionList.load();
+                    c = c->nextConnectionList.loadRelaxed();
                     continue;
                 }
                 if (c->isSlotObject) {
                     qDebug("          <functor or function pointer>");
-                    c = c->nextConnectionList.load();
+                    c = c->nextConnectionList.loadRelaxed();
                     continue;
                 }
-                const QMetaObject *receiverMetaObject = c->receiver.load()->metaObject();
+                const QMetaObject *receiverMetaObject = c->receiver.loadRelaxed()->metaObject();
                 const QMetaMethod method = receiverMetaObject->method(c->method());
                 qDebug("          --> %s::%s %s",
                        receiverMetaObject->className(),
-                       c->receiver.load()->objectName().isEmpty() ? "unnamed" : qPrintable(c->receiver.load()->objectName()),
+                       c->receiver.loadRelaxed()->objectName().isEmpty() ? "unnamed" : qPrintable(c->receiver.loadRelaxed()->objectName()),
                        method.methodSignature().constData());
-                c = c->nextConnectionList.load();
+                c = c->nextConnectionList.loadRelaxed();
             }
         }
     } else {
@@ -4888,17 +4910,17 @@ QMetaObject::Connection QObjectPrivate::connectImpl(const QObject *sender, int s
     QOrderedMutexLocker locker(signalSlotLock(sender),
                                signalSlotLock(receiver));
 
-    if (type & Qt::UniqueConnection && slot && QObjectPrivate::get(s)->connections.load()) {
-        QObjectPrivate::ConnectionData *connections = QObjectPrivate::get(s)->connections.load();
+    if (type & Qt::UniqueConnection && slot && QObjectPrivate::get(s)->connections.loadRelaxed()) {
+        QObjectPrivate::ConnectionData *connections = QObjectPrivate::get(s)->connections.loadRelaxed();
         if (connections->signalVectorCount() > signal_index) {
-            const QObjectPrivate::Connection *c2 = connections->signalVector.load()->at(signal_index).first.load();
+            const QObjectPrivate::Connection *c2 = connections->signalVector.loadRelaxed()->at(signal_index).first.loadRelaxed();
 
             while (c2) {
-                if (c2->receiver.load() == receiver && c2->isSlotObject && c2->slotObj->compare(slot)) {
+                if (c2->receiver.loadRelaxed() == receiver && c2->isSlotObject && c2->slotObj->compare(slot)) {
                     slotObj->destroyIfLastRef();
                     return QMetaObject::Connection();
                 }
-                c2 = c2->nextConnectionList.load();
+                c2 = c2->nextConnectionList.loadRelaxed();
             }
         }
         type = static_cast<Qt::ConnectionType>(type ^ Qt::UniqueConnection);
@@ -4909,13 +4931,13 @@ QMetaObject::Connection QObjectPrivate::connectImpl(const QObject *sender, int s
     c->signal_index = signal_index;
     QThreadData *td = r->d_func()->threadData;
     td->ref();
-    c->receiverThreadData.store(td);
-    c->receiver.store(r);
+    c->receiverThreadData.storeRelaxed(td);
+    c->receiver.storeRelaxed(r);
     c->slotObj = slotObj;
     c->connectionType = type;
     c->isSlotObject = true;
     if (types) {
-        c->argumentTypes.store(types);
+        c->argumentTypes.storeRelaxed(types);
         c->ownArgumentTypes = false;
     }
 
@@ -4944,7 +4966,7 @@ bool QObject::disconnect(const QMetaObject::Connection &connection)
 
     if (!c)
         return false;
-    QObject *receiver = c->receiver.load();
+    QObject *receiver = c->receiver.loadRelaxed();
     if (!receiver)
         return false;
 
@@ -4956,11 +4978,11 @@ bool QObject::disconnect(const QMetaObject::Connection &connection)
         QOrderedMutexLocker locker(senderMutex, receiverMutex);
 
         // load receiver once again and recheck to ensure nobody else has removed the connection in the meantime
-        receiver = c->receiver.load();
+        receiver = c->receiver.loadRelaxed();
         if (!receiver)
             return false;
 
-        connections = QObjectPrivate::get(c->sender)->connections.load();
+        connections = QObjectPrivate::get(c->sender)->connections.loadRelaxed();
         Q_ASSERT(connections);
         connections->removeConnection(c);
     }
@@ -5152,7 +5174,7 @@ bool QMetaObject::Connection::isConnected_helper() const
     Q_ASSERT(d_ptr);    // we're only called from operator RestrictedBool() const
     QObjectPrivate::Connection *c = static_cast<QObjectPrivate::Connection *>(d_ptr);
 
-    return c->receiver.load();
+    return c->receiver.loadRelaxed();
 }
 
 
diff --git a/src/corelib/kernel/qobject.h b/src/corelib/kernel/qobject.h
index 12512e74c5..7f72b69c1a 100644
--- a/src/corelib/kernel/qobject.h
+++ b/src/corelib/kernel/qobject.h
@@ -113,12 +113,17 @@ public:
     int postedEvents;
     QDynamicMetaObjectData *metaObject;
     QMetaObject *dynamicMetaObject() const;
+
+#ifdef QT_DEBUG
+    enum { CheckForParentChildLoopsWarnDepth = 4096 };
+#endif
 };
 
 
 class Q_CORE_EXPORT QObject
 {
     Q_OBJECT
+
     Q_PROPERTY(QString objectName READ objectName WRITE setObjectName NOTIFY objectNameChanged)
     Q_DECLARE_PRIVATE(QObject)
 
@@ -129,7 +134,7 @@ public:
     virtual bool event(QEvent *event);
     virtual bool eventFilter(QObject *watched, QEvent *event);
 
-#if defined(QT_NO_TRANSLATION)
+#if defined(QT_NO_TRANSLATION) || defined(Q_CLANG_QDOC)
     static QString tr(const char *sourceText, const char * = nullptr, int = -1)
         { return QString::fromUtf8(sourceText); }
 #if QT_DEPRECATED_SINCE(5, 0)
diff --git a/src/corelib/kernel/qobject_p.h b/src/corelib/kernel/qobject_p.h
index e6e57b29b9..1953aea21e 100644
--- a/src/corelib/kernel/qobject_p.h
+++ b/src/corelib/kernel/qobject_p.h
@@ -184,7 +184,7 @@ public:
         }
         void deref() {
             if (!ref_.deref()) {
-                Q_ASSERT(!receiver.load());
+                Q_ASSERT(!receiver.loadRelaxed());
                 Q_ASSERT(!isSlotObject);
                 delete this;
             }
@@ -202,7 +202,7 @@ public:
             : receiver(receiver), sender(sender), signal(signal)
         {
             if (receiver) {
-                ConnectionData *cd = receiver->d_func()->connections.load();
+                ConnectionData *cd = receiver->d_func()->connections.loadRelaxed();
                 previous = cd->currentSender;
                 cd->currentSender = this;
             }
@@ -210,7 +210,7 @@ public:
         ~Sender()
         {
             if (receiver)
-                receiver->d_func()->connections.load()->currentSender = previous;
+                receiver->d_func()->connections.loadRelaxed()->currentSender = previous;
         }
         void receiverDeleted()
         {
@@ -268,8 +268,8 @@ public:
 
         ~ConnectionData()
         {
-            deleteOrphaned(orphaned.load());
-            SignalVector *v = signalVector.load();
+            deleteOrphaned(orphaned.loadRelaxed());
+            SignalVector *v = signalVector.loadRelaxed();
             if (v)
                 free(v);
         }
@@ -279,18 +279,18 @@ public:
         void removeConnection(Connection *c);
         void cleanOrphanedConnections(QObject *sender)
         {
-            if (orphaned.load() && ref == 1)
+            if (orphaned.loadRelaxed() && ref == 1)
                 cleanOrphanedConnectionsImpl(sender);
         }
         void cleanOrphanedConnectionsImpl(QObject *sender);
 
         ConnectionList &connectionsForSignal(int signal)
         {
-            return signalVector.load()->at(signal);
+            return signalVector.loadRelaxed()->at(signal);
         }
 
         void resizeSignalVector(uint size) {
-            SignalVector *vector = this->signalVector.load();
+            SignalVector *vector = this->signalVector.loadRelaxed();
             if (vector && vector->allocated > size)
                 return;
             size = (size + 7) & ~7;
@@ -305,14 +305,14 @@ public:
             newVector->next = nullptr;
             newVector->allocated = size;
 
-            signalVector.store(newVector);
+            signalVector.storeRelaxed(newVector);
             if (vector) {
-                vector->nextInOrphanList = orphaned.load();
-                orphaned.store(ConnectionOrSignalVector::fromSignalVector(vector));
+                vector->nextInOrphanList = orphaned.loadRelaxed();
+                orphaned.storeRelaxed(ConnectionOrSignalVector::fromSignalVector(vector));
             }
         }
         int signalVectorCount() const {
-            return  signalVector ? signalVector.load()->count() : -1;
+            return  signalVector ? signalVector.loadRelaxed()->count() : -1;
         }
 
         static void deleteOrphaned(ConnectionOrSignalVector *c);
@@ -366,11 +366,11 @@ public:
 
     void ensureConnectionData()
     {
-        if (connections.load())
+        if (connections.loadRelaxed())
             return;
         ConnectionData *cd = new ConnectionData;
         cd->ref.ref();
-        connections.store(cd);
+        connections.storeRelaxed(cd);
     }
 public:
     ExtraData *extraData;    // extra data set by the user
diff --git a/src/corelib/kernel/qobjectdefs.h b/src/corelib/kernel/qobjectdefs.h
index 0bceab6fb4..4d5ac4dcb2 100644
--- a/src/corelib/kernel/qobjectdefs.h
+++ b/src/corelib/kernel/qobjectdefs.h
@@ -138,6 +138,10 @@ class QString;
 # define QT_TR_FUNCTIONS
 #endif
 
+#ifdef Q_CLANG_QDOC
+#define QT_TR_FUNCTIONS
+#endif
+
 // ### Qt6: remove
 #define Q_OBJECT_CHECK  /* empty, unused since Qt 5.2 */
 
diff --git a/src/corelib/kernel/qpointer.h b/src/corelib/kernel/qpointer.h
index 80faef2990..7052bcf0d4 100644
--- a/src/corelib/kernel/qpointer.h
+++ b/src/corelib/kernel/qpointer.h
@@ -143,7 +143,8 @@ template<typename T>
 QPointer<T>
 qPointerFromVariant(const QVariant &variant)
 {
-    return QPointer<T>(qobject_cast<T*>(QtSharedPointer::weakPointerFromVariant_internal(variant).internalData()));
+    const auto wp = QtSharedPointer::weakPointerFromVariant_internal(variant);
+    return QPointer<T>{qobject_cast<T*>(QtPrivate::EnableInternalData::internalData(wp))};
 }
 
 template <class T>
diff --git a/src/corelib/kernel/qpoll.cpp b/src/corelib/kernel/qpoll.cpp
index 8e93c4d363..8b87bfe79d 100644
--- a/src/corelib/kernel/qpoll.cpp
+++ b/src/corelib/kernel/qpoll.cpp
@@ -39,6 +39,10 @@
 
 #include "qcore_unix_p.h"
 
+#ifdef Q_OS_RTEMS
+#include <rtems/rtems_bsdnet_internal.h>
+#endif
+
 QT_BEGIN_NAMESPACE
 
 #define QT_POLL_READ_MASK   (POLLIN | POLLRDNORM)
@@ -135,6 +139,11 @@ static inline int qt_poll_sweep(struct pollfd *fds, nfds_t nfds,
 
 static inline bool qt_poll_is_bad_fd(int fd)
 {
+#ifdef Q_OS_RTEMS
+    if (!rtems_bsdnet_fdToSocket(fd))
+        return true;
+#endif
+
     int ret;
     EINTR_LOOP(ret, fcntl(fd, F_GETFD));
     return (ret == -1 && errno == EBADF);
diff --git a/src/corelib/kernel/qsharedmemory.cpp b/src/corelib/kernel/qsharedmemory.cpp
index c952655cb8..39f3002394 100644
--- a/src/corelib/kernel/qsharedmemory.cpp
+++ b/src/corelib/kernel/qsharedmemory.cpp
@@ -150,11 +150,18 @@ QSharedMemoryPrivate::makePlatformSafeKey(const QString &key,
 
   \sa setKey()
  */
+
+#ifndef QT_NO_QOBJECT
 QSharedMemory::QSharedMemory(QObject *parent)
   : QObject(*new QSharedMemoryPrivate, parent)
 {
 }
-
+#else
+QSharedMemory::QSharedMemory()
+    : d_ptr(new QSharedMemoryPrivate)
+{
+}
+#endif
 /*!
   Constructs a shared memory object with the given \a parent and with
   its key set to \a key. Because its key is set, its create() and
@@ -162,11 +169,19 @@ QSharedMemory::QSharedMemory(QObject *parent)
 
   \sa setKey(), create(), attach()
  */
+#ifndef QT_NO_QOBJECT
 QSharedMemory::QSharedMemory(const QString &key, QObject *parent)
     : QObject(*new QSharedMemoryPrivate, parent)
 {
     setKey(key);
 }
+#else
+QSharedMemory::QSharedMemory(const QString &key)
+    : d_ptr(new QSharedMemoryPrivate)
+{
+    setKey(key);
+}
+#endif
 
 /*!
   The destructor clears the key, which forces the shared memory object
@@ -604,4 +619,6 @@ QString QSharedMemory::errorString() const
 
 QT_END_NAMESPACE
 
+#ifndef QT_NO_QOBJECT
 #include "moc_qsharedmemory.cpp"
+#endif
diff --git a/src/corelib/kernel/qsharedmemory.h b/src/corelib/kernel/qsharedmemory.h
index 67cf52ac17..6236c6aa4c 100644
--- a/src/corelib/kernel/qsharedmemory.h
+++ b/src/corelib/kernel/qsharedmemory.h
@@ -40,8 +40,14 @@
 #ifndef QSHAREDMEMORY_H
 #define QSHAREDMEMORY_H
 
-#include <QtCore/qobject.h>
-
+#include <QtCore/qglobal.h>
+#ifndef QT_NO_QOBJECT
+# include <QtCore/qobject.h>
+#else
+# include <QtCore/qobjectdefs.h>
+# include <QtCore/qscopedpointer.h>
+# include <QtCore/qstring.h>
+#endif
 QT_BEGIN_NAMESPACE
 
 
@@ -49,9 +55,14 @@ QT_BEGIN_NAMESPACE
 
 class QSharedMemoryPrivate;
 
-class Q_CORE_EXPORT QSharedMemory : public QObject
+class Q_CORE_EXPORT QSharedMemory
+#ifndef QT_NO_QOBJECT
+    : public QObject
+#endif
 {
+#ifndef QT_NO_QOBJECT
     Q_OBJECT
+#endif
     Q_DECLARE_PRIVATE(QSharedMemory)
 
 public:
@@ -74,8 +85,17 @@ public:
         UnknownError
     };
 
+#ifndef QT_NO_QOBJECT
     QSharedMemory(QObject *parent = nullptr);
     QSharedMemory(const QString &key, QObject *parent = nullptr);
+#else
+    QSharedMemory();
+    QSharedMemory(const QString &key);
+    static QString tr(const char * str)
+    {
+        return QString::fromLatin1(str);
+    }
+#endif
     ~QSharedMemory();
 
     void setKey(const QString &key);
@@ -104,6 +124,9 @@ public:
 
 private:
     Q_DISABLE_COPY(QSharedMemory)
+#ifdef QT_NO_QOBJECT
+    QScopedPointer<QSharedMemoryPrivate> d_ptr;
+#endif
 };
 
 #endif // QT_NO_SHAREDMEMORY
diff --git a/src/corelib/kernel/qsharedmemory_p.h b/src/corelib/kernel/qsharedmemory_p.h
index bf7c42dc62..e6e989abda 100644
--- a/src/corelib/kernel/qsharedmemory_p.h
+++ b/src/corelib/kernel/qsharedmemory_p.h
@@ -67,7 +67,10 @@ namespace QSharedMemoryPrivate
 #else
 
 #include "qsystemsemaphore.h"
-#include "private/qobject_p.h"
+
+#ifndef QT_NO_QOBJECT
+# include "private/qobject_p.h"
+#endif
 
 #if !defined(Q_OS_WIN) && !defined(Q_OS_ANDROID) && !defined(Q_OS_INTEGRITY) && !defined(Q_OS_RTEMS)
 #  include <sys/sem.h>
@@ -107,9 +110,14 @@ private:
 };
 #endif // QT_NO_SYSTEMSEMAPHORE
 
-class Q_AUTOTEST_EXPORT QSharedMemoryPrivate : public QObjectPrivate
+class Q_AUTOTEST_EXPORT QSharedMemoryPrivate
+#ifndef QT_NO_QOBJECT
+        : public QObjectPrivate
+#endif
 {
+#ifndef QT_NO_QOBJECT
     Q_DECLARE_PUBLIC(QSharedMemory)
+#endif
 
 public:
     QSharedMemoryPrivate();
diff --git a/src/corelib/kernel/qsharedmemory_unix.cpp b/src/corelib/kernel/qsharedmemory_unix.cpp
index d1d44747e0..f6d7e78441 100644
--- a/src/corelib/kernel/qsharedmemory_unix.cpp
+++ b/src/corelib/kernel/qsharedmemory_unix.cpp
@@ -64,8 +64,11 @@
 #ifndef QT_NO_SHAREDMEMORY
 QT_BEGIN_NAMESPACE
 
-QSharedMemoryPrivate::QSharedMemoryPrivate()
-    : QObjectPrivate(), memory(0), size(0), error(QSharedMemory::NoError),
+QSharedMemoryPrivate::QSharedMemoryPrivate() :
+#ifndef QT_NO_QOBJECT
+    QObjectPrivate(),
+#endif
+    memory(0), size(0), error(QSharedMemory::NoError),
 #ifndef QT_NO_SYSTEMSEMAPHORE
       systemSemaphore(QString()), lockedByMe(false),
 #endif
diff --git a/src/corelib/kernel/qsharedmemory_win.cpp b/src/corelib/kernel/qsharedmemory_win.cpp
index c1dba30e2b..02de2339a5 100644
--- a/src/corelib/kernel/qsharedmemory_win.cpp
+++ b/src/corelib/kernel/qsharedmemory_win.cpp
@@ -47,7 +47,10 @@ QT_BEGIN_NAMESPACE
 
 #ifndef QT_NO_SHAREDMEMORY
 
-QSharedMemoryPrivate::QSharedMemoryPrivate() : QObjectPrivate(),
+QSharedMemoryPrivate::QSharedMemoryPrivate() :
+#ifndef QT_NO_QOBJECT
+    QObjectPrivate(),
+#endif
         memory(0), size(0), error(QSharedMemory::NoError),
            systemSemaphore(QString()), lockedByMe(false), hand(0)
 {
diff --git a/src/corelib/kernel/qsocketnotifier.cpp b/src/corelib/kernel/qsocketnotifier.cpp
index 6ff8268978..2a246b1204 100644
--- a/src/corelib/kernel/qsocketnotifier.cpp
+++ b/src/corelib/kernel/qsocketnotifier.cpp
@@ -152,7 +152,7 @@ QSocketNotifier::QSocketNotifier(qintptr socket, Type type, QObject *parent)
     else if (!d->threadData->hasEventDispatcher())
         qWarning("QSocketNotifier: Can only be used with threads started with QThread");
     else
-        d->threadData->eventDispatcher.load()->registerSocketNotifier(this);
+        d->threadData->eventDispatcher.loadRelaxed()->registerSocketNotifier(this);
 }
 
 /*!
@@ -241,9 +241,9 @@ void QSocketNotifier::setEnabled(bool enable)
         return;
     }
     if (d->snenabled)
-        d->threadData->eventDispatcher.load()->registerSocketNotifier(this);
+        d->threadData->eventDispatcher.loadRelaxed()->registerSocketNotifier(this);
     else
-        d->threadData->eventDispatcher.load()->unregisterSocketNotifier(this);
+        d->threadData->eventDispatcher.loadRelaxed()->unregisterSocketNotifier(this);
 }
 
 
diff --git a/src/corelib/kernel/qsystemerror.cpp b/src/corelib/kernel/qsystemerror.cpp
index 9d0394e4a5..a735e12925 100644
--- a/src/corelib/kernel/qsystemerror.cpp
+++ b/src/corelib/kernel/qsystemerror.cpp
@@ -112,7 +112,7 @@ static QString windowsErrorString(int errorCode)
 
 static QString standardLibraryErrorString(int errorCode)
 {
-    const char *s = 0;
+    const char *s = nullptr;
     QString ret;
     switch (errorCode) {
     case 0:
diff --git a/src/corelib/kernel/qsystemsemaphore_systemv.cpp b/src/corelib/kernel/qsystemsemaphore_systemv.cpp
index 9e438ae2a6..2c38d74d2d 100644
--- a/src/corelib/kernel/qsystemsemaphore_systemv.cpp
+++ b/src/corelib/kernel/qsystemsemaphore_systemv.cpp
@@ -76,7 +76,7 @@ key_t QSystemSemaphorePrivate::handle(QSystemSemaphore::AccessMode mode)
 #if QT_CONFIG(translation)
             QCoreApplication::tr("%1: key is empty", "QSystemSemaphore")
 #else
-            QString::fromLatin1("%1: key is empty")
+            QLatin1String("%1: key is empty")
 #endif
                 .arg(QLatin1String("QSystemSemaphore::handle:"));
         error = QSystemSemaphore::KeyError;
@@ -94,7 +94,7 @@ key_t QSystemSemaphorePrivate::handle(QSystemSemaphore::AccessMode mode)
 #if QT_CONFIG(translation)
             QCoreApplication::tr("%1: unable to make key", "QSystemSemaphore")
 #else
-            QString::fromLatin1("%1: unable to make key")
+            QLatin1String("%1: unable to make key")
 #endif
                 .arg(QLatin1String("QSystemSemaphore::handle:"));
         error = QSystemSemaphore::KeyError;
@@ -111,7 +111,7 @@ key_t QSystemSemaphorePrivate::handle(QSystemSemaphore::AccessMode mode)
 #if QT_CONFIG(translation)
             QCoreApplication::tr("%1: ftok failed", "QSystemSemaphore")
 #else
-            QString::fromLatin1("%1: ftok failed")
+            QLatin1String("%1: ftok failed")
 #endif
                 .arg(QLatin1String("QSystemSemaphore::handle:"));
         error = QSystemSemaphore::KeyError;
diff --git a/src/corelib/kernel/qvariant.cpp b/src/corelib/kernel/qvariant.cpp
index 1ac47f3972..511dc3c81c 100644
--- a/src/corelib/kernel/qvariant.cpp
+++ b/src/corelib/kernel/qvariant.cpp
@@ -119,19 +119,19 @@ namespace { // annonymous used to hide QVariant handlers
 static void construct(QVariant::Private *x, const void *copy)
 {
     QVariantConstructor<CoreTypesFilter> constructor(x, copy);
-    QMetaTypeSwitcher::switcher<void>(constructor, x->type, 0);
+    QMetaTypeSwitcher::switcher<void>(constructor, x->type);
 }
 
 static void clear(QVariant::Private *d)
 {
     QVariantDestructor<CoreTypesFilter> cleaner(d);
-    QMetaTypeSwitcher::switcher<void>(cleaner, d->type, 0);
+    QMetaTypeSwitcher::switcher<void>(cleaner, d->type);
 }
 
 static bool isNull(const QVariant::Private *d)
 {
     QVariantIsNull<CoreTypesFilter> isNull(d);
-    return QMetaTypeSwitcher::switcher<bool>(isNull, d->type, 0);
+    return QMetaTypeSwitcher::switcher<bool>(isNull, d->type);
 }
 
 /*!
@@ -143,7 +143,7 @@ static bool isNull(const QVariant::Private *d)
 static bool compare(const QVariant::Private *a, const QVariant::Private *b)
 {
     QVariantComparator<CoreTypesFilter> comparator(a, b);
-    return QMetaTypeSwitcher::switcher<bool>(comparator, a->type, 0);
+    return QMetaTypeSwitcher::switcher<bool>(comparator, a->type);
 }
 
 /*!
@@ -1401,7 +1401,7 @@ static void streamDebug(QDebug dbg, const QVariant &v)
 {
     QVariant::Private *d = const_cast<QVariant::Private *>(&v.data_ptr());
     QVariantDebugStream<CoreTypesFilter> stream(dbg, d);
-    QMetaTypeSwitcher::switcher<void>(stream, d->type, 0);
+    QMetaTypeSwitcher::switcher<void>(stream, d->type);
 }
 #endif
 
@@ -1410,16 +1410,16 @@ const QVariant::Handler qt_kernel_variant_handler = {
     clear,
     isNull,
 #ifndef QT_NO_DATASTREAM
-    0,
-    0,
+    nullptr,
+    nullptr,
 #endif
     compare,
     convert,
-    0,
+    nullptr,
 #if !defined(QT_NO_DEBUG_STREAM)
     streamDebug
 #else
-    0
+    nullptr
 #endif
 };
 
@@ -1436,16 +1436,16 @@ const QVariant::Handler qt_dummy_variant_handler = {
     dummyClear,
     dummyIsNull,
 #ifndef QT_NO_DATASTREAM
-    0,
-    0,
+    nullptr,
+    nullptr,
 #endif
     dummyCompare,
     dummyConvert,
-    0,
+    nullptr,
 #if !defined(QT_NO_DEBUG_STREAM)
     dummyStreamDebug
 #else
-    0
+    nullptr
 #endif
 };
 
@@ -1555,16 +1555,16 @@ const QVariant::Handler qt_custom_variant_handler = {
     customClear,
     customIsNull,
 #ifndef QT_NO_DATASTREAM
-    0,
-    0,
+    nullptr,
+    nullptr,
 #endif
     customCompare,
     customConvert,
-    0,
+    nullptr,
 #if !defined(QT_NO_DEBUG_STREAM)
     customStreamDebug
 #else
-    0
+    nullptr
 #endif
 };
 
@@ -2125,7 +2125,7 @@ QVariant::QVariant(const char *val)
 */
 
 QVariant::QVariant(Type type)
-{ create(type, 0); }
+{ create(type, nullptr); }
 QVariant::QVariant(int typeId, const void *copy)
 { create(typeId, copy); d.is_null = false; }
 
@@ -2366,7 +2366,7 @@ QVariant& QVariant::operator=(const QVariant &variant)
 
 void QVariant::detach()
 {
-    if (!d.is_shared || d.data.shared->ref.load() == 1)
+    if (!d.is_shared || d.data.shared->ref.loadRelaxed() == 1)
         return;
 
     Private dd;
@@ -2667,7 +2667,7 @@ inline T qVariantToHelper(const QVariant::Private &d, const HandlersManager &han
             return ret;
     }
 
-    handlerManager[d.type]->convert(&d, targetType, &ret, 0);
+    handlerManager[d.type]->convert(&d, targetType, &ret, nullptr);
     return ret;
 }
 
@@ -3217,7 +3217,7 @@ bool QVariant::toBool() const
         return d.data.b;
 
     bool res = false;
-    handlerManager[d.type]->convert(&d, Bool, &res, 0);
+    handlerManager[d.type]->convert(&d, Bool, &res, nullptr);
 
     return res;
 }
@@ -3735,7 +3735,7 @@ bool QVariant::convert(int targetTypeId)
     if (!oldValue.canConvert(targetTypeId))
         return false;
 
-    create(targetTypeId, 0);
+    create(targetTypeId, nullptr);
     // Fail if the value is not initialized or was forced null by a previous failed convert.
     if (oldValue.d.is_null && oldValue.d.type != QMetaType::Nullptr)
         return false;
@@ -3760,7 +3760,7 @@ bool QVariant::convert(int targetTypeId)
 */
 bool QVariant::convert(const int type, void *ptr) const
 {
-    return handlerManager[type]->convert(&d, type, ptr, 0);
+    return handlerManager[type]->convert(&d, type, ptr, nullptr);
 }
 
 
diff --git a/src/corelib/kernel/qvariant.h b/src/corelib/kernel/qvariant.h
index e094ebff52..c8cb551863 100644
--- a/src/corelib/kernel/qvariant.h
+++ b/src/corelib/kernel/qvariant.h
@@ -577,7 +577,7 @@ Q_CORE_EXPORT QDataStream& operator<< (QDataStream& s, const QVariant::Type p);
 #endif
 
 inline bool QVariant::isDetached() const
-{ return !d.is_shared || d.data.shared->ref.load() == 1; }
+{ return !d.is_shared || d.data.shared->ref.loadRelaxed() == 1; }
 
 
 #ifdef Q_QDOC
diff --git a/src/corelib/kernel/qwineventnotifier.cpp b/src/corelib/kernel/qwineventnotifier.cpp
index 3c73c0b851..d2ae9668fe 100644
--- a/src/corelib/kernel/qwineventnotifier.cpp
+++ b/src/corelib/kernel/qwineventnotifier.cpp
@@ -124,7 +124,7 @@ QWinEventNotifier::QWinEventNotifier(HANDLE hEvent, QObject *parent)
  : QObject(*new QWinEventNotifierPrivate(hEvent, false), parent)
 {
     Q_D(QWinEventNotifier);
-    QAbstractEventDispatcher *eventDispatcher = d->threadData->eventDispatcher.load();
+    QAbstractEventDispatcher *eventDispatcher = d->threadData->eventDispatcher.loadRelaxed();
     if (Q_UNLIKELY(!eventDispatcher)) {
         qWarning("QWinEventNotifier: Can only be used with threads started with QThread");
         return;
@@ -197,7 +197,7 @@ void QWinEventNotifier::setEnabled(bool enable)
         return;
     d->enabled = enable;
 
-    QAbstractEventDispatcher *eventDispatcher = d->threadData->eventDispatcher.load();
+    QAbstractEventDispatcher *eventDispatcher = d->threadData->eventDispatcher.loadRelaxed();
     if (!eventDispatcher) { // perhaps application is shutting down
         if (!enable && d->waitHandle != nullptr)
             d->unregisterWaitObject();
@@ -256,7 +256,7 @@ void QWinEventNotifierPrivate::unregisterWaitObject()
 static void CALLBACK wfsoCallback(void *context, BOOLEAN /*ignore*/)
 {
     QWinEventNotifierPrivate *nd = reinterpret_cast<QWinEventNotifierPrivate *>(context);
-    QAbstractEventDispatcher *eventDispatcher = nd->threadData->eventDispatcher.load();
+    QAbstractEventDispatcher *eventDispatcher = nd->threadData->eventDispatcher.loadRelaxed();
 
     // Happens when Q(Core)Application is destroyed before QWinEventNotifier.
     // https://bugreports.qt.io/browse/QTBUG-70214