9 files changed, 107 insertions, 63 deletions
diff --git a/src/corelib/kernel/qbasictimer.cpp b/src/corelib/kernel/qbasictimer.cpp
index b843ec1ecfd..62e5a7347d4 100644
--- a/src/corelib/kernel/qbasictimer.cpp
+++ b/src/corelib/kernel/qbasictimer.cpp
@@ -86,6 +86,11 @@ QT_BEGIN_NAMESPACE
 
 /*!
     \fn QBasicTimer::swap(QBasicTimer &other)
+    \since 5.14
+    \memberswap{timer}
+*/
+
+/*!
     \fn swap(QBasicTimer &lhs, QBasicTimer &rhs)
     \since 5.14
 
diff --git a/src/corelib/kernel/qdeadlinetimer.cpp b/src/corelib/kernel/qdeadlinetimer.cpp
index a5d16ddf65d..ea7a23c2dbc 100644
--- a/src/corelib/kernel/qdeadlinetimer.cpp
+++ b/src/corelib/kernel/qdeadlinetimer.cpp
@@ -978,8 +978,7 @@ QDeadlineTimer operator+(QDeadlineTimer dt, qint64 msecs)
 
 /*!
   \fn void QDeadlineTimer::swap(QDeadlineTimer &other)
-
-  Swaps this deadline timer with the \a other deadline timer.
+    \memberswap{deadline timer}
  */
 
 /*!
diff --git a/src/corelib/kernel/qmetaobject.cpp b/src/corelib/kernel/qmetaobject.cpp
index 792fe986563..a9036e02032 100644
--- a/src/corelib/kernel/qmetaobject.cpp
+++ b/src/corelib/kernel/qmetaobject.cpp
@@ -1734,9 +1734,7 @@ bool QMetaObject::invokeMethodImpl(QObject *object, QtPrivate::QSlotObjectBase *
 /*!
     \fn QMetaObject::Connection::swap(Connection &other)
     \since 5.15
-
-    Swaps this Connection instance with \a other. This operation is very fast
-    and never fails.
+    \memberswap{Connection instance}
 */
 
 /*!
diff --git a/src/corelib/kernel/qpointer.qdoc b/src/corelib/kernel/qpointer.qdoc
index aebdd68428b..65b4dd649e5 100644
--- a/src/corelib/kernel/qpointer.qdoc
+++ b/src/corelib/kernel/qpointer.qdoc
@@ -100,9 +100,7 @@
 /*!
     \fn template <class T> void QPointer<T>::swap(QPointer &other)
     \since 5.6
-
-    Swaps the contents of this QPointer with the contents of \a other.
-    This operation is very fast and never fails.
+    \memberswap{QPointer}
 */
 
 /*!
diff --git a/src/corelib/kernel/qproperty.cpp b/src/corelib/kernel/qproperty.cpp
index 68f6f424104..a9021822b56 100644
--- a/src/corelib/kernel/qproperty.cpp
+++ b/src/corelib/kernel/qproperty.cpp
@@ -226,8 +226,8 @@ void Qt::endPropertyUpdateGroup()
         data = data->next;
     }
     // notify all delayed notifications from binding evaluation
-    for (const QBindingObserverPtr &observer: bindingObservers) {
-        QPropertyBindingPrivate *binding = observer.binding();
+    for (const auto &bindingPtr: bindingObservers) {
+        auto *binding = static_cast<QPropertyBindingPrivate *>(bindingPtr.get());
         binding->notifyNonRecursive();
     }
     // do the same for properties which only have observers
@@ -307,8 +307,9 @@ void QPropertyBindingPrivate::notifyRecursive()
 void QPropertyBindingPrivate::notifyNonRecursive(const PendingBindingObserverList &bindingObservers)
 {
     notifyNonRecursive();
-    for (auto &&bindingObserver: bindingObservers) {
-        bindingObserver.binding()->notifyNonRecursive();
+    for (auto &&bindingPtr: bindingObservers) {
+        auto *binding = static_cast<QPropertyBindingPrivate *>(bindingPtr.get());
+        binding->notifyNonRecursive();
     }
 }
 
@@ -622,8 +623,10 @@ void QPropertyBindingData::notifyObservers(QUntypedPropertyData *propertyDataPtr
                 d = QPropertyBindingDataPointer {storage->bindingData(propertyDataPtr)};
             if (QPropertyObserverPointer observer = d.firstObserver())
                 observer.notifyOnlyChangeHandler(propertyDataPtr);
-            for (auto &&bindingObserver: bindingObservers)
-                bindingObserver.binding()->notifyNonRecursive();
+            for (auto &&bindingPtr: bindingObservers) {
+                auto *binding = static_cast<QPropertyBindingPrivate *>(bindingPtr.get());
+                binding->notifyNonRecursive();
+            }
         }
     }
 }
@@ -784,9 +787,11 @@ void QPropertyObserverPointer::evaluateBindings(PendingBindingObserverList &bind
         if (QPropertyObserver::ObserverTag(observer->next.tag()) == QPropertyObserver::ObserverNotifiesBinding) {
             auto bindingToEvaluate = observer->binding;
             QPropertyObserverNodeProtector protector(observer);
-            QBindingObserverPtr bindingObserver(observer); // binding must not be gone after evaluateRecursive_inline
-            if (bindingToEvaluate->evaluateRecursive_inline(bindingObservers, status))
-                bindingObservers.push_back(std::move(bindingObserver));
+            // binding must not be gone after evaluateRecursive_inline
+            QPropertyBindingPrivatePtr currentBinding(observer->binding);
+            const bool evalStatus = bindingToEvaluate->evaluateRecursive_inline(bindingObservers, status);
+            if (evalStatus)
+                bindingObservers.push_back(std::move(currentBinding));
             next = protector.next();
         }
 
diff --git a/src/corelib/kernel/qproperty_p.h b/src/corelib/kernel/qproperty_p.h
index 15dff50312b..6c5c73b955d 100644
--- a/src/corelib/kernel/qproperty_p.h
+++ b/src/corelib/kernel/qproperty_p.h
@@ -58,7 +58,7 @@ public:
     inline QPropertyObserver *operator ->();
 };
 
-using PendingBindingObserverList = QVarLengthArray<QBindingObserverPtr>;
+using PendingBindingObserverList = QVarLengthArray<QPropertyBindingPrivatePtr>;
 
 // Keep all classes related to QProperty in one compilation unit. Performance of this code is crucial and
 // we need to allow the compiler to inline where it makes sense.
@@ -234,21 +234,12 @@ struct CompatPropertySafePoint
 struct CurrentCompatPropertyThief
 {
     Q_DISABLE_COPY_MOVE(CurrentCompatPropertyThief)
+    QScopedValueRollback<CompatPropertySafePoint *> m_guard;
 public:
     CurrentCompatPropertyThief(QBindingStatus *status)
-        : status(&status->currentCompatProperty)
-        , stolen(std::exchange(status->currentCompatProperty, nullptr))
+        : m_guard(status->currentCompatProperty, nullptr)
     {
     }
-
-    ~CurrentCompatPropertyThief()
-    {
-        *status = stolen;
-    }
-
-private:
-    CompatPropertySafePoint **status = nullptr;
-    CompatPropertySafePoint *stolen = nullptr;
 };
 
 }
@@ -386,11 +377,11 @@ public:
     QPropertyBindingSourceLocation sourceLocation() const
     {
         if (!hasCustomVTable())
-            return this->location;
-        QPropertyBindingSourceLocation location;
+            return location;
+        QPropertyBindingSourceLocation result;
         constexpr auto msg = "Custom location";
-        location.fileName = msg;
-        return location;
+        result.fileName = msg;
+        return result;
     }
     QPropertyBindingError bindingError() const { return m_error; }
     QMetaType valueMetaType() const { return metaType; }
@@ -666,8 +657,10 @@ public:
                             // evaluateBindings() can trash the observers. We need to re-fetch here.
                             if (QPropertyObserverPointer observer = d.firstObserver())
                                 observer.notifyOnlyChangeHandler(this);
-                            for (auto&& bindingObserver: bindingObservers)
-                                bindingObserver.binding()->notifyNonRecursive();
+                            for (auto&& bindingPtr: bindingObservers) {
+                                auto *binding = static_cast<QPropertyBindingPrivate *>(bindingPtr.get());
+                                binding->notifyNonRecursive();
+                            }
                         }
                     }
                 }
diff --git a/src/corelib/kernel/qpropertyprivate.h b/src/corelib/kernel/qpropertyprivate.h
index aca6d14c968..f07ced20051 100644
--- a/src/corelib/kernel/qpropertyprivate.h
+++ b/src/corelib/kernel/qpropertyprivate.h
@@ -29,8 +29,8 @@ class QBindingStorage;
 template<typename Class, typename T, auto Offset, auto Setter, auto Signal, auto Getter>
 class QObjectCompatProperty;
 
-struct QBindingObserverPtr;
-using PendingBindingObserverList = QVarLengthArray<QBindingObserverPtr>;
+class QPropertyBindingPrivatePtr;
+using PendingBindingObserverList = QVarLengthArray<QPropertyBindingPrivatePtr>;
 
 namespace QtPrivate {
 // QPropertyBindingPrivatePtr operates on a RefCountingMixin solely so that we can inline
diff --git a/src/corelib/kernel/qtranslator.cpp b/src/corelib/kernel/qtranslator.cpp
index 2f02eef96c2..75cb0af7312 100644
--- a/src/corelib/kernel/qtranslator.cpp
+++ b/src/corelib/kernel/qtranslator.cpp
@@ -15,13 +15,16 @@
 #include "qdatastream.h"
 #include "qendian.h"
 #include "qfile.h"
-#include "qmap.h"
 #include "qalgorithms.h"
 #include "qtranslator_p.h"
 #include "qlocale.h"
+#include "qloggingcategory.h"
+#include "qdebug.h"
 #include "qendian.h"
 #include "qresource.h"
 
+#include <QtCore/private/qduplicatetracker_p.h>
+
 #if defined(Q_OS_UNIX) && !defined(Q_OS_INTEGRITY)
 #  define QT_USE_MMAP
 #  include "private/qcore_unix_p.h"
@@ -39,6 +42,8 @@
 
 QT_BEGIN_NAMESPACE
 
+static Q_LOGGING_CATEGORY(lcTranslator, "qt.core.qtranslator")
+
 namespace {
 enum Tag { Tag_End = 1, Tag_SourceText16, Tag_Translation, Tag_Context16, Tag_Obsolete1,
            Tag_SourceText, Tag_Context, Tag_Comment, Tag_Obsolete2 };
@@ -600,7 +605,10 @@ Q_NEVER_INLINE
 static bool is_readable_file(const QString &name)
 {
     const QFileInfo fi(name);
-    return fi.isReadable() && fi.isFile();
+    const bool isReadableFile = fi.isReadable() && fi.isFile();
+    qCDebug(lcTranslator) << "Testing file" << name << isReadableFile;
+
+    return isReadableFile;
 }
 
 static QString find_translation(const QLocale & locale,
@@ -609,6 +617,9 @@ static QString find_translation(const QLocale & locale,
                                 const QString & directory,
                                 const QString & suffix)
 {
+    qCDebug(lcTranslator).noquote().nospace() << "Searching translation for "
+                          << filename << prefix << locale << suffix
+                          << " in " << directory;
     QString path;
     if (QFileInfo(filename).isRelative()) {
         path = directory;
@@ -619,7 +630,7 @@ static QString find_translation(const QLocale & locale,
 
     QString realname;
     realname += path + filename + prefix; // using += in the hope for some reserve capacity
-    const int realNameBaseSize = realname.size();
+    const qsizetype realNameBaseSize = realname.size();
 
     // see http://www.unicode.org/reports/tr35/#LanguageMatching for inspiration
 
@@ -631,34 +642,71 @@ static QString find_translation(const QLocale & locale,
     // that the Qt resource system is always case-sensitive, even on
     // Windows (in other words: this codepath is *not* UNIX-only).
     QStringList languages = locale.uiLanguages();
-    for (int i = languages.size()-1; i >= 0; --i) {
-        QString lang = languages.at(i);
+    for (auto &localeName : languages)
+        localeName.replace(u'-', u'_');
+    qCDebug(lcTranslator) << "Requested UI languages" << languages;
+
+    QDuplicateTracker<QString> duplicates(languages.size() * 2);
+    for (const auto &l : std::as_const(languages))
+        (void)duplicates.hasSeen(l);
+
+    for (qsizetype i = languages.size() - 1; i >= 0; --i) {
+        QString language = languages.at(i);
+
+        // Add candidates for each entry where we progressively truncate sections
+        // from the end, until a matching language tag is found. For compatibility
+        // reasons (see QTBUG-124898) we add a special case: if we find a
+        // language_Script_Territory entry (i.e. an entry with two sections), try
+        // language_Territory as well as language_Script. Use QDuplicateTracker
+        // so that we don't add any entries as fallbacks that are already in the
+        // list anyway.
+        // This is a kludge, and such entries are added at the end of the candidate
+        // list; from 6.9 on, this is fixed in QLocale::uiLanguages().
+        QStringList fallbacks;
+        const auto addIfNew = [&duplicates, &fallbacks](const QString &fallback) {
+            if (!duplicates.hasSeen(fallback))
+                fallbacks.append(fallback);
+        };
+
+        while (true) {
+            const qsizetype last = language.lastIndexOf(u'_');
+            if (last < 0) // no more sections
+                break;
+
+            const qsizetype first = language.indexOf(u'_');
+            // two sections, add fallback without script
+            if (first != last && language.count(u'_') == 2) {
+                QString fallback = language.left(first) + language.mid(last);
+                addIfNew(fallback);
+            }
+            QString fallback = language.left(last);
+            addIfNew(fallback);
+
+            language.truncate(last);
+        }
+        for (qsizetype j = fallbacks.size() - 1; j >= 0; --j)
+            languages.insert(i + 1, fallbacks.at(j));
+    }
+
+    qCDebug(lcTranslator) << "Augmented UI languages" << languages;
+    for (qsizetype i = languages.size() - 1; i >= 0; --i) {
+        const QString &lang = languages.at(i);
         QString lowerLang = lang.toLower();
         if (lang != lowerLang)
             languages.insert(i + 1, lowerLang);
     }
 
     for (QString localeName : std::as_const(languages)) {
-        localeName.replace(u'-', u'_');
-
-        // try the complete locale name first and progressively truncate from
-        // the end until a matching language tag is found (with or without suffix)
-        for (;;) {
-            realname += localeName + suffixOrDotQM;
-            if (is_readable_file(realname))
-                return realname;
-
-            realname.truncate(realNameBaseSize + localeName.size());
-            if (is_readable_file(realname))
-                return realname;
+        // try each locale with and without suffix
+        realname += localeName + suffixOrDotQM;
+        if (is_readable_file(realname))
+            return realname;
 
-            realname.truncate(realNameBaseSize);
+        realname.truncate(realNameBaseSize + localeName.size());
+        if (is_readable_file(realname))
+            return realname;
 
-            int rightmost = localeName.lastIndexOf(u'_');
-            if (rightmost <= 0)
-                break; // no truncations anymore, break
-            localeName.truncate(rightmost);
-        }
+        realname.truncate(realNameBaseSize);
     }
 
     const int realNameBaseSizeFallbacks = path.size() + filename.size();
diff --git a/src/corelib/kernel/qvariant.cpp b/src/corelib/kernel/qvariant.cpp
index 221926d218f..931be20e42c 100644
--- a/src/corelib/kernel/qvariant.cpp
+++ b/src/corelib/kernel/qvariant.cpp
@@ -1016,9 +1016,7 @@ QVariant &QVariant::operator=(const QVariant &variant)
 /*!
     \fn void QVariant::swap(QVariant &other)
     \since 4.8
-
-    Swaps variant \a other with this variant. This operation is very
-    fast and never fails.
+    \memberswap{variant}
 */
 
 /*!