20 files changed, 1136 insertions, 422 deletions

diff --git a/src/corelib/tools/qarraydata.cpp b/src/corelib/tools/qarraydata.cpp
index 234a44f6b6..3879b48cbb 100644
--- a/src/corelib/tools/qarraydata.cpp
+++ b/src/corelib/tools/qarraydata.cpp
@@ -143,7 +143,7 @@ qCalculateGrowingBlockSize(size_t elementCount, size_t elementSize, size_t heade
     }
 
     result.elementCount = (bytes - unsigned(headerSize)) / unsigned(elementSize);
-    result.size = bytes;
+    result.size = result.elementCount * elementSize + headerSize;
     return result;
 }
 
@@ -265,7 +265,7 @@ void QArrayData::deallocate(QArrayData *data, size_t objectSize,
         return;
 #endif
 
-    Q_ASSERT_X(data == 0 || !data->ref.isStatic(), "QArrayData::deallocate",
+    Q_ASSERT_X(data == nullptr || !data->ref.isStatic(), "QArrayData::deallocate",
                "Static data cannot be deleted");
     ::free(data);
 }
diff --git a/src/corelib/tools/qcontainerfwd.h b/src/corelib/tools/qcontainerfwd.h
index 532b4c95ce..00a8c85b66 100644
--- a/src/corelib/tools/qcontainerfwd.h
+++ b/src/corelib/tools/qcontainerfwd.h
@@ -47,7 +47,7 @@ QT_BEGIN_NAMESPACE
 
 template <class Key, class T> class QCache;
 template <class Key, class T> class QHash;
-#ifndef QT_NO_LINKED_LIST
+#if !defined(QT_NO_LINKED_LIST) && QT_DEPRECATED_SINCE(5, 15)
 template <class T> class QLinkedList;
 #endif
 template <class T> class QList;
diff --git a/src/corelib/tools/qduplicatetracker_p.h b/src/corelib/tools/qduplicatetracker_p.h
new file mode 100644
index 0000000000..99068c01a3
--- /dev/null
+++ b/src/corelib/tools/qduplicatetracker_p.h
@@ -0,0 +1,94 @@
+/****************************************************************************
+**
+** Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz <marc.mutz@kdab.com>
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the QtCore module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+#ifndef QDUPLICATETRACKER_P_H
+#define QDUPLICATETRACKER_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <qglobal.h>
+
+#if QT_HAS_INCLUDE(<memory_resource>) && __cplusplus > 201402L
+#  include <unordered_set>
+#  include <memory_resource>
+#else
+#  include <qset.h>
+#endif
+
+QT_BEGIN_NAMESPACE
+
+template <typename T, size_t Prealloc = 32>
+class QDuplicateTracker {
+#ifdef __cpp_lib_memory_resource
+    char buffer[Prealloc * sizeof(T)];
+    std::pmr::monotonic_buffer_resource res{buffer, sizeof buffer};
+    std::pmr::unordered_set<T> set{&res};
+#else
+    QSet<T> set;
+    int setSize = 0;
+#endif
+    Q_DISABLE_COPY_MOVE(QDuplicateTracker);
+public:
+    QDuplicateTracker() = default;
+    void reserve(int n) { set.reserve(n); }
+    Q_REQUIRED_RESULT bool hasSeen(const T &s)
+    {
+        bool inserted;
+#ifdef __cpp_lib_memory_resource
+        inserted = set.insert(s).second;
+#else
+        set.insert(s);
+        const int n = set.size();
+        inserted = qExchange(setSize, n) != n;
+#endif
+        return !inserted;
+    }
+};
+
+QT_END_NAMESPACE
+
+#endif /* QDUPLICATETRACKER_P_H */
diff --git a/src/corelib/tools/qeasingcurve.cpp b/src/corelib/tools/qeasingcurve.cpp
index bf2fd2e401..84430ae49a 100644
--- a/src/corelib/tools/qeasingcurve.cpp
+++ b/src/corelib/tools/qeasingcurve.cpp
@@ -443,12 +443,12 @@ class QEasingCurvePrivate
 public:
     QEasingCurvePrivate()
         : type(QEasingCurve::Linear),
-          config(0),
+          config(nullptr),
           func(&easeNone)
     { }
     QEasingCurvePrivate(const QEasingCurvePrivate &other)
         : type(other.type),
-          config(other.config ? other.config->copy() : 0),
+          config(other.config ? other.config->copy() : nullptr),
           func(other.func)
     { }
     ~QEasingCurvePrivate() { delete config; }
@@ -590,7 +590,7 @@ struct BezierEase : public QEasingCurveFunction
         if (!(x < 1))
             return 1;
 
-        SingleCubicBezier *singleCubicBezier = 0;
+        SingleCubicBezier *singleCubicBezier = nullptr;
         getBezierSegment(singleCubicBezier, x);
 
         return evaluateSegmentForY(*singleCubicBezier, findTForX(*singleCubicBezier, x));
@@ -1097,7 +1097,7 @@ static QEasingCurve::EasingFunction curveToFunc(QEasingCurve::Type curve)
     case QEasingCurve::CosineCurve:
         return &easeCosineCurve;
     default:
-        return 0;
+        return nullptr;
     };
 }
 
@@ -1127,7 +1127,7 @@ static QEasingCurveFunction *curveToFunctionObject(QEasingCurve::Type type)
         return new QEasingCurveFunction(type, qreal(0.3), qreal(1.0), qreal(1.70158));
     }
 
-    return 0;
+    return nullptr;
 }
 
 /*!
@@ -1422,7 +1422,7 @@ void QEasingCurvePrivate::setType_helper(QEasingCurve::Type newType)
         tcbPoints = std::move(config->_tcbPoints);
 
         delete config;
-        config = 0;
+        config = nullptr;
     }
 
     if (isConfigFunction(newType) || (amp != -1.0) || (period != -1.0) || (overshoot != -1.0) ||
@@ -1436,11 +1436,11 @@ void QEasingCurvePrivate::setType_helper(QEasingCurve::Type newType)
             config->_o = overshoot;
         config->_bezierCurves = std::move(bezierCurves);
         config->_tcbPoints = std::move(tcbPoints);
-        func = 0;
+        func = nullptr;
     } else if (newType != QEasingCurve::Custom) {
         func = curveToFunc(newType);
     }
-    Q_ASSERT((func == 0) == (config != 0));
+    Q_ASSERT((func == nullptr) == (config != nullptr));
     type = newType;
 }
 
@@ -1487,7 +1487,7 @@ void QEasingCurve::setCustomType(EasingFunction func)
 */
 QEasingCurve::EasingFunction QEasingCurve::customType() const
 {
-    return d_ptr->type == Custom ? d_ptr->func : 0;
+    return d_ptr->type == Custom ? d_ptr->func : nullptr;
 }
 
 /*!
diff --git a/src/corelib/tools/qhash.cpp b/src/corelib/tools/qhash.cpp
index 6ec8019ba3..15f731a603 100644
--- a/src/corelib/tools/qhash.cpp
+++ b/src/corelib/tools/qhash.cpp
@@ -1120,21 +1120,6 @@ uint qHash(long double key, uint seed) noexcept
 
     \snippet code/src_corelib_tools_qhash.cpp 9
 
-    However, you can store multiple values per key by using
-    insertMulti() instead of insert() (or using the convenience
-    subclass QMultiHash). If you want to retrieve all
-    the values for a single key, you can use values(const Key &key),
-    which returns a QList<T>:
-
-    \snippet code/src_corelib_tools_qhash.cpp 10
-
-    The items that share the same key are available from most
-    recently to least recently inserted. A more efficient approach is
-    to call find() to get the iterator for the first item with a key
-    and iterate from there:
-
-    \snippet code/src_corelib_tools_qhash.cpp 11
-
     If you only need to extract the values from a hash (not the keys),
     you can also use \l{foreach}:
 
@@ -1435,9 +1420,8 @@ uint qHash(long double key, uint seed) noexcept
 /*! \fn template <class Key, class T> int QHash<Key, T>::remove(const Key &key)
 
     Removes all the items that have the \a key from the hash.
-    Returns the number of items removed which is usually 1 but will
-    be 0 if the key isn't in the hash, or greater than 1 if
-    insertMulti() has been used with the \a key.
+    Returns the number of items removed which is 1 if the key exists in the hash,
+    and 0 otherwise.
 
     \sa clear(), take(), QMultiHash::remove()
 */
@@ -1507,27 +1491,25 @@ uint qHash(long double key, uint seed) noexcept
 
 /*! \fn template <class Key, class T> QList<Key> QHash<Key, T>::uniqueKeys() const
     \since 4.2
+    \obsolete
 
     Returns a list containing all the keys in the map. Keys that occur multiple
     times in the map (because items were inserted with insertMulti(), or
     unite() was used) occur only once in the returned list.
 
-    \sa keys(), values()
+    \sa QMultiHash::uniqueKeys()
 */
 
 /*! \fn template <class Key, class T> QList<Key> QHash<Key, T>::keys() const
 
     Returns a list containing all the keys in the hash, in an
     arbitrary order. Keys that occur multiple times in the hash
-    (because items were inserted with insertMulti(), or unite() was
-    used) also occur multiple times in the list.
-
-    To obtain a list of unique keys, where each key from the map only
-    occurs once, use uniqueKeys().
+    (because the method is operating on a QMultiHash) also occur
+    multiple times in the list.
 
     The order is guaranteed to be the same as that used by values().
 
-    \sa uniqueKeys(), values(), key()
+    \sa QMultiMap::uniqueKeys(), values(), key()
 */
 
 /*! \fn template <class Key, class T> QList<Key> QHash<Key, T>::keys(const T &value) const
@@ -1555,7 +1537,7 @@ uint qHash(long double key, uint seed) noexcept
 */
 
 /*! \fn template <class Key, class T> QList<T> QHash<Key, T>::values(const Key &key) const
-
+    \obsolete
     \overload
 
     Returns a list of all the values associated with the \a key,
@@ -1592,6 +1574,7 @@ uint qHash(long double key, uint seed) noexcept
 */
 
 /*! \fn template <class Key, class T> int QHash<Key, T>::count(const Key &key) const
+    \obsolete
 
     Returns the number of items associated with the \a key.
 
@@ -1803,11 +1786,22 @@ uint qHash(long double key, uint seed) noexcept
 
     If there are multiple items with the \a key, the most
     recently inserted item's value is replaced with \a value.
+*/
+
+/*! \fn template <class Key, class T> void QHash<Key, T>::insert(const QHash &other)
+    \since 5.15
+
+    Inserts all the items in the \a other hash into this hash.
+
+    If a key is common to both hashes, its value will be replaced with the
+    value stored in \a other.
 
-    \sa insertMulti()
+    \note If \a other contains multiple entries with the same key then the
+    final value of the key is undefined.
 */
 
 /*! \fn template <class Key, class T> QHash<Key, T>::iterator QHash<Key, T>::insertMulti(const Key &key, const T &value)
+    \obsolete
 
     Inserts a new item with the \a key and a value of \a value.
 
@@ -1816,16 +1810,17 @@ uint qHash(long double key, uint seed) noexcept
     different from insert(), which overwrites the value of an
     existing item.)
 
+    This function is obsolete. Use QMultiHash or QMultiMap instead.
+
     \sa insert(), values()
 */
 
 /*! \fn template <class Key, class T> QHash &QHash<Key, T>::unite(const QHash &other)
+    \obsolete
 
     Inserts all the items in the \a other hash into this hash. If a
     key is common to both hashes, the resulting hash will contain the
     key multiple times.
-
-    \sa insertMulti()
 */
 
 /*! \fn template <class Key, class T> bool QHash<Key, T>::empty() const
@@ -1966,10 +1961,7 @@ uint qHash(long double key, uint seed) noexcept
     \snippet code/src_corelib_tools_qhash.cpp 17
 
     Unlike QMap, which orders its items by key, QHash stores its
-    items in an arbitrary order. The only guarantee is that items that
-    share the same key (because they were inserted using
-    QHash::insertMulti()) will appear consecutively, from the most
-    recently to the least recently inserted value.
+    items in an arbitrary order.
 
     Let's see a few examples of things we can do with a
     QHash::iterator that we cannot do with a QHash::const_iterator.
@@ -2036,7 +2028,7 @@ uint qHash(long double key, uint seed) noexcept
 
     There is no direct way of changing an item's key through an
     iterator, although it can be done by calling QHash::erase()
-    followed by QHash::insert() or QHash::insertMulti().
+    followed by QHash::insert().
 
     \sa value()
 */
@@ -2198,7 +2190,7 @@ uint qHash(long double key, uint seed) noexcept
     Unlike QMap, which orders its items by key, QHash stores its
     items in an arbitrary order. The only guarantee is that items that
     share the same key (because they were inserted using
-    QHash::insertMulti()) will appear consecutively, from the most
+    a QMultiHash) will appear consecutively, from the most
     recently to the least recently inserted value.
 
     Multiple iterators can be used on the same hash. However, be aware
@@ -2531,18 +2523,22 @@ uint qHash(long double key, uint seed) noexcept
     It inherits QHash and extends it with a few convenience functions
     that make it more suitable than QHash for storing multi-valued
     hashes. A multi-valued hash is a hash that allows multiple values
-    with the same key; QHash normally doesn't allow that, unless you
-    call QHash::insertMulti().
+    with the same key.
 
     Because QMultiHash inherits QHash, all of QHash's functionality also
     applies to QMultiHash. For example, you can use isEmpty() to test
     whether the hash is empty, and you can traverse a QMultiHash using
-    QHash's iterator classes (for example, QHashIterator). But in
-    addition, it provides an insert() function that corresponds to
-    QHash::insertMulti(), and a replace() function that corresponds to
+    QHash's iterator classes (for example, QHashIterator). But opposed to
+    QHash, it provides an insert() function will allow the insertion of
+    multiple items with the same key. The replace() function corresponds to
     QHash::insert(). It also provides convenient operator+() and
     operator+=().
 
+    Unlike QMultiMap, QMultiHash does not provide and ordering of the
+    inserted items. The only guarantee is that items that
+    share the same key will appear consecutively, from the most
+    recently to the least recently inserted value.
+
     Example:
     \snippet code/src_corelib_tools_qhash.cpp 24
 
@@ -2633,7 +2629,8 @@ uint qHash(long double key, uint seed) noexcept
     \sa replace()
 */
 
-/*! \fn template <class Key, class T> QMultiHash &QMultiHash<Key, T>::operator+=(const QMultiHash &other)
+/*! \fn template <class Key, class T> QMultiHash &QMultiHash<Key, T>::unite(const QMultiHash &other)
+    \since 5.13
 
     Inserts all the items in the \a other hash into this hash
     and returns a reference to this hash.
@@ -2641,6 +2638,32 @@ uint qHash(long double key, uint seed) noexcept
     \sa insert()
 */
 
+/*! \fn template <class Key, class T> QList<Key> QMultiHash<Key, T>::uniqueKeys() const
+    \since 5.13
+
+    Returns a list containing all the keys in the map. Keys that occur multiple
+    times in the map occur only once in the returned list.
+
+    \sa keys(), values()
+*/
+
+/*! \fn template <class Key, class T> QList<T> QMultiHash<Key, T>::values(const Key &key) const
+    \overload
+
+    Returns a list of all the values associated with the \a key,
+    from the most recently inserted to the least recently inserted.
+
+    \sa count(), insert()
+*/
+
+/*! \fn template <class Key, class T> QMultiHash &QMultiHash<Key, T>::operator+=(const QMultiHash &other)
+
+    Inserts all the items in the \a other hash into this hash
+    and returns a reference to this hash.
+
+    \sa unite(), insert()
+*/
+
 /*! \fn template <class Key, class T> QMultiHash QMultiHash<Key, T>::operator+(const QMultiHash &other) const
 
     Returns a hash that contains all the items in this hash in
@@ -2670,6 +2693,13 @@ uint qHash(long double key, uint seed) noexcept
     \sa QHash::remove()
 */
 
+/*! \fn template <class Key, class T> int QMultiHash<Key, T>::count(const Key &key) const
+
+    Returns the number of items associated with the \a key.
+
+    \sa contains(), insert()
+*/
+
 /*!
     \fn template <class Key, class T> int QMultiHash<Key, T>::count(const Key &key, const T &value) const
     \since 4.3
diff --git a/src/corelib/tools/qhash.h b/src/corelib/tools/qhash.h
index 236e433101..921b781f4a 100644
--- a/src/corelib/tools/qhash.h
+++ b/src/corelib/tools/qhash.h
@@ -308,12 +308,14 @@ public:
     T &operator[](const Key &key);
     const T operator[](const Key &key) const;
 
-    QList<Key> uniqueKeys() const;
     QList<Key> keys() const;
     QList<Key> keys(const T &value) const;
     QList<T> values() const;
-    QList<T> values(const Key &key) const;
-    int count(const Key &key) const;
+#if QT_DEPRECATED_SINCE(5, 15)
+    QT_DEPRECATED_X("Use QMultiHash for hashes storing multiple values with the same key.") QList<Key> uniqueKeys() const;
+    QT_DEPRECATED_X("Use QMultiHash for hashes storing multiple values with the same key.") QList<T> values(const Key &key) const;
+    QT_DEPRECATED_X("Use QMultiHash for hashes storing multiple values with the same key.") int count(const Key &key) const;
+#endif
 
     class const_iterator;
 
@@ -325,7 +327,11 @@ public:
         QHashData::Node *i;
 
     public:
+#if QT_DEPRECATED_SINCE(5, 15)
         typedef std::bidirectional_iterator_tag iterator_category;
+#else
+        typedef std::forward_iterator_tag iterator_category;
+#endif
         typedef qptrdiff difference_type;
         typedef T value_type;
         typedef T *pointer;
@@ -350,21 +356,25 @@ public:
             i = QHashData::nextNode(i);
             return r;
         }
-        inline iterator &operator--() {
+#if QT_DEPRECATED_SINCE(5, 15)
+        inline QT_DEPRECATED iterator &operator--()
+        {
             i = QHashData::previousNode(i);
             return *this;
         }
-        inline iterator operator--(int) {
+        inline QT_DEPRECATED iterator operator--(int)
+        {
             iterator r = *this;
             i = QHashData::previousNode(i);
             return r;
         }
-        inline iterator operator+(int j) const
+        inline QT_DEPRECATED iterator operator+(int j) const
         { iterator r = *this; if (j > 0) while (j--) ++r; else while (j++) --r; return r; }
-        inline iterator operator-(int j) const { return operator+(-j); }
-        inline iterator &operator+=(int j) { return *this = *this + j; }
-        inline iterator &operator-=(int j) { return *this = *this - j; }
-        friend inline iterator operator+(int j, iterator k) { return k + j; }
+        inline QT_DEPRECATED iterator operator-(int j) const { return operator+(-j); }
+        inline QT_DEPRECATED iterator &operator+=(int j) { return *this = *this + j; }
+        inline QT_DEPRECATED iterator &operator-=(int j) { return *this = *this - j; }
+        friend inline QT_DEPRECATED iterator operator+(int j, iterator k) { return k + j; }
+#endif
 
 #ifndef QT_STRICT_ITERATORS
     public:
@@ -380,11 +390,16 @@ public:
     {
         friend class iterator;
         friend class QHash<Key, T>;
+        friend class QMultiHash<Key, T>;
         friend class QSet<Key>;
         QHashData::Node *i;
 
     public:
+#if QT_DEPRECATED_SINCE(5, 15)
         typedef std::bidirectional_iterator_tag iterator_category;
+#else
+        typedef std::forward_iterator_tag iterator_category;
+#endif
         typedef qptrdiff difference_type;
         typedef T value_type;
         typedef const T *pointer;
@@ -416,21 +431,28 @@ public:
             i = QHashData::nextNode(i);
             return r;
         }
-        inline const_iterator &operator--() {
+#if QT_DEPRECATED_SINCE(5, 15)
+        inline QT_DEPRECATED const_iterator &operator--()
+        {
             i = QHashData::previousNode(i);
             return *this;
         }
-        inline const_iterator operator--(int) {
+        inline QT_DEPRECATED const_iterator operator--(int)
+        {
             const_iterator r = *this;
             i = QHashData::previousNode(i);
             return r;
         }
-        inline const_iterator operator+(int j) const
+        inline QT_DEPRECATED const_iterator operator+(int j) const
         { const_iterator r = *this; if (j > 0) while (j--) ++r; else while (j++) --r; return r; }
-        inline const_iterator operator-(int j) const { return operator+(-j); }
-        inline const_iterator &operator+=(int j) { return *this = *this + j; }
-        inline const_iterator &operator-=(int j) { return *this = *this - j; }
-        friend inline const_iterator operator+(int j, const_iterator k) { return k + j; }
+        inline QT_DEPRECATED const_iterator operator-(int j) const { return operator+(-j); }
+        inline QT_DEPRECATED const_iterator &operator+=(int j) { return *this = *this + j; }
+        inline QT_DEPRECATED const_iterator &operator-=(int j) { return *this = *this - j; }
+        friend inline QT_DEPRECATED const_iterator operator+(int j, const_iterator k)
+        {
+            return k + j;
+        }
+#endif
 
         // ### Qt 5: not sure this is necessary anymore
 #ifdef QT_STRICT_ITERATORS
@@ -462,8 +484,14 @@ public:
 
         inline key_iterator &operator++() { ++i; return *this; }
         inline key_iterator operator++(int) { return key_iterator(i++);}
-        inline key_iterator &operator--() { --i; return *this; }
-        inline key_iterator operator--(int) { return key_iterator(i--); }
+#if QT_DEPRECATED_SINCE(5, 15)
+        inline QT_DEPRECATED key_iterator &operator--()
+        {
+            --i;
+            return *this;
+        }
+        inline QT_DEPRECATED key_iterator operator--(int) { return key_iterator(i--); }
+#endif
         const_iterator base() const { return i; }
     };
 
@@ -501,8 +529,11 @@ public:
     const_iterator find(const Key &key) const;
     const_iterator constFind(const Key &key) const;
     iterator insert(const Key &key, const T &value);
-    iterator insertMulti(const Key &key, const T &value);
-    QHash &unite(const QHash &other);
+    void insert(const QHash &hash);
+#if QT_DEPRECATED_SINCE(5, 15)
+    QT_DEPRECATED_X("Use QMultiHash for hashes storing multiple values with the same key.") iterator insertMulti(const Key &key, const T &value);
+    QT_DEPRECATED_X("Use QMultiHash for hashes storing multiple values with the same key.") QHash &unite(const QHash &other);
+#endif
 
     // STL compatibility
     typedef T mapped_type;
@@ -544,6 +575,7 @@ private:
 #endif
     }
     friend class QSet<Key>;
+    friend class QMultiHash<Key, T>;
 };
 
 
@@ -582,22 +614,6 @@ QHash<Key, T>::createNode(uint ah, const Key &akey, const T &avalue, Node **anex
 }
 
 template <class Key, class T>
-Q_INLINE_TEMPLATE QHash<Key, T> &QHash<Key, T>::unite(const QHash &other)
-{
-    if (d == &QHashData::shared_null) {
-        *this = other;
-    } else {
-        QHash copy(other);
-        const_iterator it = copy.constEnd();
-        while (it != copy.constBegin()) {
-            --it;
-            insertMulti(it.key(), it.value());
-        }
-    }
-    return *this;
-}
-
-template <class Key, class T>
 Q_OUTOFLINE_TEMPLATE void QHash<Key, T>::freeData(QHashData *x)
 {
     x->free_helper(deleteNode2);
@@ -656,26 +672,6 @@ Q_INLINE_TEMPLATE const T QHash<Key, T>::value(const Key &akey, const T &adefaul
 }
 
 template <class Key, class T>
-Q_OUTOFLINE_TEMPLATE QList<Key> QHash<Key, T>::uniqueKeys() const
-{
-    QList<Key> res;
-    res.reserve(size()); // May be too much, but assume short lifetime
-    const_iterator i = begin();
-    if (i != end()) {
-        for (;;) {
-            const Key &aKey = i.key();
-            res.append(aKey);
-            do {
-                if (++i == end())
-                    goto break_out_of_outer_loop;
-            } while (aKey == i.key());
-        }
-    }
-break_out_of_outer_loop:
-    return res;
-}
-
-template <class Key, class T>
 Q_OUTOFLINE_TEMPLATE QList<Key> QHash<Key, T>::keys() const
 {
     QList<Key> res;
@@ -734,32 +730,6 @@ Q_OUTOFLINE_TEMPLATE QList<T> QHash<Key, T>::values() const
 }
 
 template <class Key, class T>
-Q_OUTOFLINE_TEMPLATE QList<T> QHash<Key, T>::values(const Key &akey) const
-{
-    QList<T> res;
-    Node *node = *findNode(akey);
-    if (node != e) {
-        do {
-            res.append(node->value);
-        } while ((node = node->next) != e && node->key == akey);
-    }
-    return res;
-}
-
-template <class Key, class T>
-Q_OUTOFLINE_TEMPLATE int QHash<Key, T>::count(const Key &akey) const
-{
-    int cnt = 0;
-    Node *node = *findNode(akey);
-    if (node != e) {
-        do {
-            ++cnt;
-        } while ((node = node->next) != e && node->key == akey);
-    }
-    return cnt;
-}
-
-template <class Key, class T>
 Q_INLINE_TEMPLATE const T QHash<Key, T>::operator[](const Key &akey) const
 {
     return value(akey);
@@ -800,15 +770,28 @@ Q_INLINE_TEMPLATE typename QHash<Key, T>::iterator QHash<Key, T>::insert(const K
 }
 
 template <class Key, class T>
-Q_INLINE_TEMPLATE typename QHash<Key, T>::iterator QHash<Key, T>::insertMulti(const Key &akey,
-                                                                              const T &avalue)
+Q_INLINE_TEMPLATE void QHash<Key, T>::insert(const QHash &hash)
 {
+    if (d == hash.d)
+        return;
+
     detach();
-    d->willGrow();
 
-    uint h;
-    Node **nextNode = findNode(akey, &h);
-    return iterator(createNode(h, akey, avalue, nextNode));
+    QHashData::Node *i = hash.d->firstNode();
+    QHashData::Node *end = reinterpret_cast<QHashData::Node *>(hash.e);
+    while (i != end) {
+        Node *n = concrete(i);
+        Node **node = findNode(n->key, n->h);
+        if (*node == e) {
+            if (d->willGrow())
+                node = findNode(n->key, n->h);
+            createNode(n->h, n->key, n->value, node);
+        } else {
+            if (!std::is_same<T, QHashDummyValue>::value)
+                (*node)->value = n->value;
+        }
+        i = QHashData::nextNode(i);
+    }
 }
 
 template <class Key, class T>
@@ -1061,11 +1044,12 @@ public:
     inline typename QHash<Key, T>::iterator replace(const Key &key, const T &value)
     { return QHash<Key, T>::insert(key, value); }
 
-    inline typename QHash<Key, T>::iterator insert(const Key &key, const T &value)
-    { return QHash<Key, T>::insertMulti(key, value); }
+    typename QHash<Key, T>::iterator insert(const Key &key, const T &value);
+
+    inline QMultiHash &unite(const QMultiHash &other);
 
     inline QMultiHash &operator+=(const QMultiHash &other)
-    { this->unite(other); return *this; }
+    { return unite(other); }
     inline QMultiHash operator+(const QMultiHash &other) const
     { QMultiHash result = *this; result += other; return result; }
 
@@ -1074,13 +1058,27 @@ public:
     using QHash<Key, T>::count;
     using QHash<Key, T>::find;
     using QHash<Key, T>::constFind;
+    using QHash<Key, T>::values;
+    using QHash<Key, T>::findNode;
+    using QHash<Key, T>::createNode;
+    using QHash<Key, T>::concrete;
+    using QHash<Key, T>::detach;
+
+    using typename QHash<Key, T>::Node;
+    using typename QHash<Key, T>::iterator;
+    using typename QHash<Key, T>::const_iterator;
 
     bool contains(const Key &key, const T &value) const;
 
     int remove(const Key &key, const T &value);
 
+    int count(const Key &key) const;
     int count(const Key &key, const T &value) const;
 
+    QList<Key> uniqueKeys() const;
+
+    QList<T> values(const Key &akey) const;
+
     typename QHash<Key, T>::iterator find(const Key &key, const T &value) {
         typename QHash<Key, T>::iterator i(find(key));
         typename QHash<Key, T>::iterator end(this->end());
@@ -1109,6 +1107,50 @@ private:
 };
 
 template <class Key, class T>
+Q_INLINE_TEMPLATE typename QHash<Key, T>::iterator QMultiHash<Key, T>::insert(const Key &akey, const T &avalue)
+{
+    detach();
+    this->d->willGrow();
+
+    uint h;
+    Node **nextNode = findNode(akey, &h);
+    return iterator(createNode(h, akey, avalue, nextNode));
+}
+
+template <class Key, class T>
+Q_INLINE_TEMPLATE QMultiHash<Key, T> &QMultiHash<Key, T>::unite(const QMultiHash &other)
+{
+    if (this->d == &QHashData::shared_null) {
+        *this = other;
+    } else {
+#if QT_DEPRECATED_SINCE(5, 15)
+        QMultiHash copy(other);
+        const_iterator it = copy.constEnd();
+        while (it != copy.constBegin()) {
+            it.i = QHashData::previousNode(it.i);
+            insert(it.key(), it.value());
+        }
+#else
+        const QMultiHash copy(other);
+        const_iterator it = copy.cbegin();
+        const const_iterator end = copy.cend();
+        while (it != end) {
+            const auto rangeStart = it++;
+            while (it != end && rangeStart.key() == it.key())
+                ++it;
+            const qint64 last = std::distance(rangeStart, it) - 1;
+            for (qint64 i = last; i >= 0; --i) {
+                auto next = std::next(rangeStart, i);
+                insert(next.key(), next.value());
+            }
+        }
+#endif
+    }
+    return *this;
+}
+
+
+template <class Key, class T>
 Q_INLINE_TEMPLATE bool QMultiHash<Key, T>::contains(const Key &key, const T &value) const
 {
     return constFind(key, value) != QHash<Key, T>::constEnd();
@@ -1145,8 +1187,259 @@ Q_INLINE_TEMPLATE int QMultiHash<Key, T>::count(const Key &key, const T &value)
     return n;
 }
 
-Q_DECLARE_ASSOCIATIVE_ITERATOR(Hash)
-Q_DECLARE_MUTABLE_ASSOCIATIVE_ITERATOR(Hash)
+template <class Key, class T>
+Q_OUTOFLINE_TEMPLATE QList<Key> QMultiHash<Key, T>::uniqueKeys() const
+{
+    QList<Key> res;
+    res.reserve(QHash<Key, T>::size()); // May be too much, but assume short lifetime
+    typename QHash<Key, T>::const_iterator i = QHash<Key, T>::begin();
+    if (i != QHash<Key, T>::end()) {
+        for (;;) {
+            const Key &aKey = i.key();
+            res.append(aKey);
+            do {
+                if (++i == QHash<Key, T>::end())
+                    goto break_out_of_outer_loop;
+            } while (aKey == i.key());
+        }
+    }
+break_out_of_outer_loop:
+    return res;
+}
+
+#if QT_DEPRECATED_SINCE(5, 15)
+
+template <class Key, class T>
+Q_OUTOFLINE_TEMPLATE typename QHash<Key, T>::iterator QHash<Key, T>::insertMulti(const Key &key, const T &value) {
+    return static_cast<QMultiHash<Key, T> *>(this)->insert(key, value);
+}
+
+template <class Key, class T>
+Q_OUTOFLINE_TEMPLATE QHash<Key, T> &QHash<Key, T>::unite(const QHash &other) {
+    return static_cast<QMultiHash<Key, T> *>(this)->unite(other);
+}
+
+template <class Key, class T>
+Q_OUTOFLINE_TEMPLATE QList<T> QHash<Key, T>::values(const Key &akey) const
+{
+    return static_cast<const QMultiHash<Key, T> *>(this)->values(akey);
+}
+
+template <class Key, class T>
+Q_OUTOFLINE_TEMPLATE int QHash<Key, T>::count(const Key &akey) const
+{
+    return static_cast<const QMultiHash<Key, T> *>(this)->count(akey);
+}
+
+template <class Key, class T>
+Q_OUTOFLINE_TEMPLATE QList<Key> QHash<Key, T>::uniqueKeys() const
+{
+    return static_cast<const QMultiHash<Key, T> *>(this)->uniqueKeys();
+}
+#endif
+
+template <class Key, class T>
+Q_OUTOFLINE_TEMPLATE QList<T> QMultiHash<Key, T>::values(const Key &akey) const
+{
+    QList<T> res;
+    Node *node = *findNode(akey);
+    if (node != this->e) {
+        do {
+            res.append(node->value);
+        } while ((node = node->next) != this->e && node->key == akey);
+    }
+    return res;
+}
+
+template <class Key, class T>
+Q_OUTOFLINE_TEMPLATE int QMultiHash<Key, T>::count(const Key &akey) const
+{
+    int cnt = 0;
+    Node *node = *findNode(akey);
+    if (node != this->e) {
+        do {
+            ++cnt;
+        } while ((node = node->next) != this->e && node->key == akey);
+    }
+    return cnt;
+}
+
+#if !defined(QT_NO_JAVA_STYLE_ITERATORS)
+template <class Key, class T>
+class QHashIterator
+{
+    typedef typename QHash<Key, T>::const_iterator const_iterator;
+    typedef const_iterator Item;
+    QHash<Key, T> c;
+    const_iterator i, n;
+    inline bool item_exists() const { return n != c.constEnd(); }
+
+public:
+    inline QHashIterator(const QHash<Key, T> &container)
+        : c(container), i(c.constBegin()), n(c.constEnd())
+    {
+    }
+    inline QHashIterator &operator=(const QHash<Key, T> &container)
+    {
+        c = container;
+        i = c.constBegin();
+        n = c.constEnd();
+        return *this;
+    }
+    inline void toFront()
+    {
+        i = c.constBegin();
+        n = c.constEnd();
+    }
+    inline void toBack()
+    {
+        i = c.constEnd();
+        n = c.constEnd();
+    }
+    inline bool hasNext() const { return i != c.constEnd(); }
+    inline Item next()
+    {
+        n = i++;
+        return n;
+    }
+    inline Item peekNext() const { return i; }
+    inline const T &value() const
+    {
+        Q_ASSERT(item_exists());
+        return *n;
+    }
+    inline const Key &key() const
+    {
+        Q_ASSERT(item_exists());
+        return n.key();
+    }
+    inline bool findNext(const T &t)
+    {
+        while ((n = i) != c.constEnd())
+            if (*i++ == t)
+                return true;
+        return false;
+    }
+#if QT_DEPRECATED_SINCE(5, 15)
+    inline QT_DEPRECATED bool hasPrevious() const { return i != c.constBegin(); }
+    inline QT_DEPRECATED Item previous()
+    {
+        n = --i;
+        return n;
+    }
+    inline QT_DEPRECATED Item peekPrevious() const
+    {
+        const_iterator p = i;
+        return --p;
+    }
+    inline bool QT_DEPRECATED findPrevious(const T &t)
+    {
+        while (i != c.constBegin())
+            if (*(n = --i) == t)
+                return true;
+        n = c.constEnd();
+        return false;
+    }
+#endif
+};
+
+template<class Key, class T>
+class QMutableHashIterator
+{
+    typedef typename QHash<Key, T>::iterator iterator;
+    typedef typename QHash<Key, T>::const_iterator const_iterator;
+    typedef iterator Item;
+    QHash<Key, T> *c;
+    iterator i, n;
+    inline bool item_exists() const { return const_iterator(n) != c->constEnd(); }
+
+public:
+    inline QMutableHashIterator(QHash<Key, T> &container) : c(&container)
+    {
+        i = c->begin();
+        n = c->end();
+    }
+    inline QMutableHashIterator &operator=(QHash<Key, T> &container)
+    {
+        c = &container;
+        i = c->begin();
+        n = c->end();
+        return *this;
+    }
+    inline void toFront()
+    {
+        i = c->begin();
+        n = c->end();
+    }
+    inline void toBack()
+    {
+        i = c->end();
+        n = c->end();
+    }
+    inline bool hasNext() const { return const_iterator(i) != c->constEnd(); }
+    inline Item next()
+    {
+        n = i++;
+        return n;
+    }
+    inline Item peekNext() const { return i; }
+    inline void remove()
+    {
+        if (const_iterator(n) != c->constEnd()) {
+            i = c->erase(n);
+            n = c->end();
+        }
+    }
+    inline void setValue(const T &t)
+    {
+        if (const_iterator(n) != c->constEnd())
+            *n = t;
+    }
+    inline T &value()
+    {
+        Q_ASSERT(item_exists());
+        return *n;
+    }
+    inline const T &value() const
+    {
+        Q_ASSERT(item_exists());
+        return *n;
+    }
+    inline const Key &key() const
+    {
+        Q_ASSERT(item_exists());
+        return n.key();
+    }
+    inline bool findNext(const T &t)
+    {
+        while (const_iterator(n = i) != c->constEnd())
+            if (*i++ == t)
+                return true;
+        return false;
+    }
+#if QT_DEPRECATED_SINCE(5, 15)
+    inline QT_DEPRECATED bool hasPrevious() const { return const_iterator(i) != c->constBegin(); }
+    inline QT_DEPRECATED Item previous()
+    {
+        n = --i;
+        return n;
+    }
+    inline QT_DEPRECATED Item peekPrevious() const
+    {
+        iterator p = i;
+        return --p;
+    }
+    inline QT_DEPRECATED bool findPrevious(const T &t)
+    {
+        while (const_iterator(i) != c->constBegin())
+            if (*(n = --i) == t)
+                return true;
+        n = c->end();
+        return false;
+    }
+#endif
+};
+#endif // !QT_NO_JAVA_STYLE_ITERATORS
 
 template <class Key, class T>
 uint qHash(const QHash<Key, T> &key, uint seed = 0)
diff --git a/src/corelib/tools/qiterator.qdoc b/src/corelib/tools/qiterator.qdoc
index b4d332b7b1..3531fb202c 100644
--- a/src/corelib/tools/qiterator.qdoc
+++ b/src/corelib/tools/qiterator.qdoc
@@ -203,6 +203,7 @@
 /*!
     \class QLinkedListIterator
     \inmodule QtCore
+    \obsolete
 
     \brief The QLinkedListIterator class provides a Java-style const iterator for QLinkedList.
 
@@ -416,6 +417,7 @@
 /*!
     \class QMutableLinkedListIterator
     \inmodule QtCore
+    \obsolete
 
     \brief The QMutableLinkedListIterator class provides a Java-style non-const iterator for QLinkedList.
 
diff --git a/src/corelib/tools/qlinkedlist.cpp b/src/corelib/tools/qlinkedlist.cpp
index 3b1bc8aab1..6a423545da 100644
--- a/src/corelib/tools/qlinkedlist.cpp
+++ b/src/corelib/tools/qlinkedlist.cpp
@@ -45,6 +45,11 @@
 
 QT_BEGIN_NAMESPACE
 
+#if QT_DEPRECATED_SINCE(5, 15)
+
+QT_WARNING_PUSH
+QT_WARNING_DISABLE_DEPRECATED
+
 const QLinkedListData QLinkedListData::shared_null = {
     const_cast<QLinkedListData *>(&QLinkedListData::shared_null),
     const_cast<QLinkedListData *>(&QLinkedListData::shared_null),
@@ -53,6 +58,7 @@ const QLinkedListData QLinkedListData::shared_null = {
 
 /*! \class QLinkedList
     \inmodule QtCore
+    \obsolete
     \brief The QLinkedList class is a template class that provides linked lists.
 
     \ingroup tools
@@ -60,6 +66,8 @@ const QLinkedListData QLinkedListData::shared_null = {
 
     \reentrant
 
+    \note This class is obsolete, please use std::list instead.
+
     QLinkedList\<T\> is one of Qt's generic \l{container classes}. It
     stores a list of values and provides iterator-based access as
     well as \l{constant time} insertions and removals.
@@ -720,6 +728,7 @@ const QLinkedListData QLinkedListData::shared_null = {
 
 /*! \class QLinkedList::iterator
     \inmodule QtCore
+    \obsolete
     \brief The QLinkedList::iterator class provides an STL-style non-const iterator for QLinkedList.
 
     QLinkedList features both \l{STL-style iterators} and
@@ -965,6 +974,7 @@ const QLinkedListData QLinkedListData::shared_null = {
 
 /*! \class QLinkedList::const_iterator
     \inmodule QtCore
+    \obsolete
     \brief The QLinkedList::const_iterator class provides an STL-style const iterator for QLinkedList.
 
     QLinkedList features both \l{STL-style iterators} and
@@ -1221,4 +1231,8 @@ const QLinkedListData QLinkedListData::shared_null = {
     \sa fromStdList()
 */
 
+QT_WARNING_POP
+
+#endif // QT_DEPRECATED_SINCE(5, 15)
+
 QT_END_NAMESPACE
diff --git a/src/corelib/tools/qlinkedlist.h b/src/corelib/tools/qlinkedlist.h
index 8970d39be0..64c6b4d326 100644
--- a/src/corelib/tools/qlinkedlist.h
+++ b/src/corelib/tools/qlinkedlist.h
@@ -55,10 +55,22 @@
 #include <iterator>
 #include <list>
 
-QT_BEGIN_NAMESPACE
 
+#if 0
+// This is needed because of QTBUG-80347
+#pragma qt_class(QLinkedList)
+#pragma qt_class(QLinkedListData)
+#pragma qt_class(QLinkedListNode)
+#endif
+
+#if QT_DEPRECATED_SINCE(5, 15)
+
+QT_WARNING_PUSH
+QT_WARNING_DISABLE_DEPRECATED
 
-struct Q_CORE_EXPORT QLinkedListData
+QT_BEGIN_NAMESPACE
+
+struct QT_DEPRECATED_VERSION_5_15 Q_CORE_EXPORT QLinkedListData
 {
     QLinkedListData *n, *p;
     QtPrivate::RefCount ref;
@@ -69,7 +81,7 @@ struct Q_CORE_EXPORT QLinkedListData
 };
 
 template <typename T>
-struct QLinkedListNode
+struct QT_DEPRECATED_VERSION_5_15 QLinkedListNode
 {
     inline QLinkedListNode(const T &arg): t(arg) { }
     QLinkedListNode *n, *p;
@@ -77,7 +89,7 @@ struct QLinkedListNode
 };
 
 template <class T>
-class QLinkedList
+class QT_DEPRECATED_VERSION_X_5_15("Use std::list instead") QLinkedList
 {
     typedef QLinkedListNode<T> Node;
     union { QLinkedListData *d; QLinkedListNode<T> *e; };
@@ -594,6 +606,10 @@ QT_END_NAMESPACE
 
 Q_DECLARE_SEQUENTIAL_CONTAINER_METATYPE(QLinkedList)
 
+QT_WARNING_POP
+
+#endif // QT_DEPRECATED_SINCE(5, 15)
+
 #endif // QT_NO_LINKED_LIST
 
 #endif // QLINKEDLIST_H
diff --git a/src/corelib/tools/qlist.cpp b/src/corelib/tools/qlist.cpp
index 66770f6866..5d5da20752 100644
--- a/src/corelib/tools/qlist.cpp
+++ b/src/corelib/tools/qlist.cpp
@@ -847,9 +847,10 @@ void **QListData::erase(void **xi)
 
 /*! \fn template <class T> void QList<T>::insert(int i, const T &value)
 
-    Inserts \a value at index position \a i in the list. If \a i <= 0,
-    the value is prepended to the list. If \a i >= size(), the
-    value is appended to the list.
+    Inserts \a value at index position \a i in the list.
+
+    If \a i == 0, the value is prepended to the list. If \a i == size(),
+    the value is appended to the list.
 
     Example:
     \snippet code/src_corelib_tools_qlistdata.cpp 8
diff --git a/src/corelib/tools/qlist.h b/src/corelib/tools/qlist.h
index 425ffa42a5..ffd470efcd 100644
--- a/src/corelib/tools/qlist.h
+++ b/src/corelib/tools/qlist.h
@@ -580,8 +580,16 @@ inline T &QList<T>::operator[](int i)
   detach(); return reinterpret_cast<Node *>(p.at(i))->t(); }
 template <typename T>
 inline void QList<T>::removeAt(int i)
-{ if(i >= 0 && i < p.size()) { detach();
- node_destruct(reinterpret_cast<Node *>(p.at(i))); p.remove(i); } }
+{
+#if !QT_DEPRECATED_SINCE(5, 15)
+    Q_ASSERT_X(i >= 0 && i < p.size(), "QList<T>::removeAt", "index out of range");
+#elif !defined(QT_NO_DEBUG)
+    if (i < 0 || i >= p.size())
+        qWarning("QList::removeAt(): Index out of range.");
+#endif
+    detach();
+    node_destruct(reinterpret_cast<Node *>(p.at(i))); p.remove(i);
+}
 template <typename T>
 inline T QList<T>::takeAt(int i)
 { Q_ASSERT_X(i >= 0 && i < p.size(), "QList<T>::take", "index out of range");
@@ -676,6 +684,12 @@ inline void QList<T>::prepend(const T &t)
 template <typename T>
 inline void QList<T>::insert(int i, const T &t)
 {
+#if !QT_DEPRECATED_SINCE(5, 15)
+    Q_ASSERT_X(i >= 0 && i <= p.size(), "QList<T>::insert", "index out of range");
+#elif !defined(QT_NO_DEBUG)
+    if (i < 0 || i > p.size())
+        qWarning("QList::insert(): Index out of range.");
+#endif
     if (d->ref.isShared()) {
         Node *n = detach_helper_grow(i, 1);
         QT_TRY {
diff --git a/src/corelib/tools/qmap.cpp b/src/corelib/tools/qmap.cpp
index a0ec372f9a..9b9c67e42b 100644
--- a/src/corelib/tools/qmap.cpp
+++ b/src/corelib/tools/qmap.cpp
@@ -468,10 +468,9 @@ void QMapDataBase::freeData(QMapDataBase *d)
     \snippet code/src_corelib_tools_qmap.cpp 9
 
     However, you can store multiple values per key by using
-    insertMulti() instead of insert() (or using the convenience
-    subclass QMultiMap). If you want to retrieve all the values for a
-    single key, you can use values(const Key &key), which returns a
-    QList<T>:
+    using the subclass QMultiMap. If you want
+    to retrieve all the values for a single key, you can use
+    values(const Key &key), which returns a QList<T>:
 
     \snippet code/src_corelib_tools_qmap.cpp 10
 
@@ -676,9 +675,8 @@ void QMapDataBase::freeData(QMapDataBase *d)
 /*! \fn template <class Key, class T> int QMap<Key, T>::remove(const Key &key)
 
     Removes all the items that have the key \a key from the map.
-    Returns the number of items removed which is usually 1 but will be
-    0 if the key isn't in the map, or \> 1 if insertMulti() has been
-    used with the \a key.
+    Returns the number of items removed which will be 1 if the key
+    exists in the map, and 0 otherwise.
 
     \sa clear(), take(), QMultiMap::remove()
 */
@@ -742,28 +740,26 @@ void QMapDataBase::freeData(QMapDataBase *d)
 
 /*! \fn template <class Key, class T> QList<Key> QMap<Key, T>::uniqueKeys() const
     \since 4.2
+    \obsolete
 
     Returns a list containing all the keys in the map in ascending
     order. Keys that occur multiple times in the map (because items
     were inserted with insertMulti(), or unite() was used) occur only
     once in the returned list.
 
-    \sa keys(), values()
+    \sa QMultiMap::uniqueKeys()
 */
 
 /*! \fn template <class Key, class T> QList<Key> QMap<Key, T>::keys() const
 
     Returns a list containing all the keys in the map in ascending
-    order. Keys that occur multiple times in the map (because items
-    were inserted with insertMulti(), or unite() was used) also
-    occur multiple times in the list.
-
-    To obtain a list of unique keys, where each key from the map only
-    occurs once, use uniqueKeys().
+    order. Keys that occur multiple times in the map (because the
+    method is operating on a QMultiMap) also occur multiple times
+    in the list.
 
     The order is guaranteed to be the same as that used by values().
 
-    \sa uniqueKeys(), values(), key()
+    \sa QMultiMap::uniqueKeys(), values(), key()
 */
 
 /*! \fn template <class Key, class T> QList<Key> QMap<Key, T>::keys(const T &value) const
@@ -806,6 +802,7 @@ void QMapDataBase::freeData(QMapDataBase *d)
 */
 
 /*! \fn template <class Key, class T> QList<T> QMap<Key, T>::values(const Key &key) const
+    \obsolete
 
     \overload
 
@@ -813,14 +810,15 @@ void QMapDataBase::freeData(QMapDataBase *d)
     \a key, from the most recently inserted to the least recently
     inserted one.
 
-    \sa count(), insertMulti()
+    \sa QMultiMap::values()
 */
 
 /*! \fn template <class Key, class T> int QMap<Key, T>::count(const Key &key) const
+    \obsolete
 
     Returns the number of items associated with key \a key.
 
-    \sa contains(), insertMulti(), QMultiMap::count()
+    \sa QMultiMap::count()
 */
 
 /*! \fn template <class Key, class T> int QMap<Key, T>::count() const
@@ -1118,7 +1116,7 @@ void QMapDataBase::freeData(QMapDataBase *d)
     If there are multiple items with the key \a key, the most
     recently inserted item's value is replaced with \a value.
 
-    \sa insertMulti()
+    \sa QMultiMap::insert()
 */
 
 /*! \fn template <class Key, class T> QMap<Key, T>::iterator QMap<Key, T>::insert(const_iterator pos, const Key &key, const T &value)
@@ -1147,10 +1145,25 @@ void QMapDataBase::freeData(QMapDataBase *d)
     \b {Note:} Be careful with the hint. Providing an iterator from an older shared instance might
     crash but there is also a risk that it will silently corrupt both the map and the \a pos map.
 
-    \sa insertMulti()
+    \sa QMultiMap::insert()
+*/
+
+/*! \fn template <class Key, class T> void QMap<Key, T>::insert(const QMap<Key, T> &map)
+    \since 5.15
+
+    Inserts all the items in \a map into this map.
+
+    If a key is common to both maps, its value will be replaced with
+    the value stored in \a map.
+
+    \note If \a map contains multiple entries with the same key then the
+    final value of the key is undefined.
+
+    \sa QMultiMap::insert()
 */
 
 /*! \fn template <class Key, class T> QMap<Key, T>::iterator QMap<Key, T>::insertMulti(const Key &key, const T &value)
+    \obsolete
 
     Inserts a new item with the key \a key and a value of \a value.
 
@@ -1159,12 +1172,13 @@ void QMapDataBase::freeData(QMapDataBase *d)
     different from insert(), which overwrites the value of an
     existing item.)
 
-    \sa insert(), values()
+    \sa QMultiMap::insert()
 */
 
 /*! \fn template <class Key, class T> QMap<Key, T>::iterator QMap<Key, T>::insertMulti(const_iterator pos, const Key &key, const T &value)
     \overload
     \since 5.1
+    \obsolete
     Inserts a new item with the key \a key and value \a value and with hint \a pos
     suggesting where to do the insert.
 
@@ -1178,17 +1192,18 @@ void QMapDataBase::freeData(QMapDataBase *d)
     \b {Note:} Be careful with the hint. Providing an iterator from an older shared instance might
     crash but there is also a risk that it will silently corrupt both the map and the \a pos map.
 
-    \sa insert()
+    \sa QMultiMap::insert()
 */
 
 
 /*! \fn template <class Key, class T> QMap<Key, T> &QMap<Key, T>::unite(const QMap<Key, T> &other)
+    \obsolete
 
     Inserts all the items in the \a other map into this map. If a
     key is common to both maps, the resulting map will contain the
     key multiple times.
 
-    \sa insertMulti()
+    \sa QMultiMap::unite()
 */
 
 /*! \typedef QMap::Iterator
@@ -1271,9 +1286,8 @@ void QMapDataBase::freeData(QMapDataBase *d)
 
     Unlike QHash, which stores its items in an arbitrary order, QMap
     stores its items ordered by key. Items that share the same key
-    (because they were inserted using QMap::insertMulti(), or due to a
-    unite()) will appear consecutively, from the most recently to the
-    least recently inserted value.
+    (because the map is a QMultiMap) will appear consecutively,
+    from the most recently to the least recently inserted value.
 
     Let's see a few examples of things we can do with a
     QMap::iterator that we cannot do with a QMap::const_iterator.
@@ -1519,9 +1533,8 @@ void QMapDataBase::freeData(QMapDataBase *d)
 
     Unlike QHash, which stores its items in an arbitrary order, QMap
     stores its items ordered by key. Items that share the same key
-    (because they were inserted using QMap::insertMulti()) will
-    appear consecutively, from the most recently to the least
-    recently inserted value.
+    (because the map is a QMultiMap) will appear consecutively,
+    from the most recently to the least recently inserted value.
 
     Multiple iterators can be used on the same map. If you add items
     to the map, existing iterators will remain valid. If you remove
@@ -1893,20 +1906,20 @@ void QMapDataBase::freeData(QMapDataBase *d)
     \reentrant
 
     QMultiMap\<Key, T\> is one of Qt's generic \l{container classes}.
-    It inherits QMap and extends it with a few convenience functions
-    that make it more suitable than QMap for storing multi-valued
-    maps. A multi-valued map is a map that allows multiple values
-    with the same key; QMap normally doesn't allow that, unless you
-    call QMap::insertMulti().
+    It inherits QMap and extends it with a few functions
+    that make it able to store multi-valued maps. A multi-valued map
+    is a map that allows multiple values with the same key; QMap
+    doesn't allow that.
 
     Because QMultiMap inherits QMap, all of QMap's functionality also
     applies to QMultiMap. For example, you can use isEmpty() to test
     whether the map is empty, and you can traverse a QMultiMap using
     QMap's iterator classes (for example, QMapIterator). But in
-    addition, it provides an insert() function that corresponds to
-    QMap::insertMulti(), and a replace() function that corresponds to
-    QMap::insert(). It also provides convenient operator+() and
-    operator+=().
+    addition, it provides an insert() function that inserts but does
+    not overwrite any previous value if the key already exists,
+    and a replace() function that corresponds which does overwite
+    an existing value if they key is already in the map.
+    It also provides convenient operator+() and operator+=().
 
     Example:
     \snippet code/src_corelib_tools_qmap.cpp 25
@@ -1986,7 +1999,7 @@ void QMapDataBase::freeData(QMapDataBase *d)
     \sa replace()
 */
 
-/*! \fn template <class Key, class T> typename QMap<Key, T>::iterator QMultiMap<Key, T>::insert(typename QMap<Key, T>::const_iterator pos, const Key &key, const T &value)
+/*! \fn template <class Key, class T> typename QMultiMap<Key, T>::iterator QMultiMap<Key, T>::insert(typename QMultiMap<Key, T>::const_iterator pos, const Key &key, const T &value)
 
     \since 5.1
     Inserts a new item with the key \a key and value \a value and with hint \a pos
@@ -2095,4 +2108,31 @@ void QMapDataBase::freeData(QMapDataBase *d)
     \sa QMap::constFind()
 */
 
+/*! \fn template <class Key, class T> QList<T> QMultiMap<Key, T>::values(const Key &key) const
+
+    Returns a list containing all the values associated with key
+    \a key, from the most recently inserted to the least recently
+    inserted one.
+*/
+
+/*! \fn template <class Key, class T> int QMultiMap<Key, T>::count(const Key &key) const
+
+    Returns the number of items associated with key \a key.
+*/
+
+/*! \fn template <class Key, class T> QList<Key> QMultiMap<Key, T>::uniqueKeys() const
+    \since 4.2
+
+    Returns a list containing all the keys in the map in ascending
+    order. Keys that occur multiple times in the map occur only
+    once in the returned list.
+*/
+
+/*! \fn template <class Key, class T> QMultiMap<Key, T> &QMultiMap<Key, T>::unite(const QMultiMap<Key, T> &other)
+
+    Inserts all the items in the \a other map into this map. If a
+    key is common to both maps, the resulting map will contain the
+    key multiple times.
+*/
+
 QT_END_NAMESPACE
diff --git a/src/corelib/tools/qmap.h b/src/corelib/tools/qmap.h
index 18c681581f..281812b5e6 100644
--- a/src/corelib/tools/qmap.h
+++ b/src/corelib/tools/qmap.h
@@ -380,12 +380,15 @@ public:
     T &operator[](const Key &key);
     const T operator[](const Key &key) const;
 
-    QList<Key> uniqueKeys() const;
     QList<Key> keys() const;
     QList<Key> keys(const T &value) const;
     QList<T> values() const;
-    QList<T> values(const Key &key) const;
-    int count(const Key &key) const;
+#if QT_DEPRECATED_SINCE(5, 15)
+    QT_DEPRECATED_X("Use QMultiMap for maps storing multiple values with the same key.") QList<Key> uniqueKeys() const;
+    QT_DEPRECATED_X("Use QMultiMap for maps storing multiple values with the same key.") QList<T> values(const Key &key) const;
+    QT_DEPRECATED_X("Use QMultiMap for maps storing multiple values with the same key.") int count(const Key &key) const;
+#endif
+
 
     inline const Key &firstKey() const { Q_ASSERT(!isEmpty()); return constBegin().key(); }
     inline const Key &lastKey() const { Q_ASSERT(!isEmpty()); return (constEnd() - 1).key(); }
@@ -452,6 +455,7 @@ public:
             { return i != o.i; }
 #endif
         friend class QMap<Key, T>;
+        friend class QMultiMap<Key, T>;
     };
     friend class iterator;
 
@@ -514,6 +518,7 @@ public:
         inline bool operator!=(const iterator &o) const { return operator!=(const_iterator(o)); }
 #endif
         friend class QMap<Key, T>;
+        friend class QMultiMap<Key, T>;
     };
     friend class const_iterator;
 
@@ -578,9 +583,12 @@ public:
     const_iterator upperBound(const Key &key) const;
     iterator insert(const Key &key, const T &value);
     iterator insert(const_iterator pos, const Key &key, const T &value);
-    iterator insertMulti(const Key &key, const T &value);
-    iterator insertMulti(const_iterator pos, const Key &akey, const T &avalue);
-    QMap<Key, T> &unite(const QMap<Key, T> &other);
+    void insert(const QMap<Key, T> &map);
+#if QT_DEPRECATED_SINCE(5, 15)
+    QT_DEPRECATED_X("Use QMultiMap for maps storing multiple values with the same key.") iterator insertMulti(const Key &key, const T &value);
+    QT_DEPRECATED_X("Use QMultiMap for maps storing multiple values with the same key.") iterator insertMulti(const_iterator pos, const Key &akey, const T &avalue);
+    QT_DEPRECATED_X("Use QMultiMap for maps storing multiple values with the same key.") QMap<Key, T> &unite(const QMap<Key, T> &other);
+#endif
 
     // STL compatibility
     typedef Key key_type;
@@ -609,6 +617,8 @@ private:
         return true;
 #endif
     }
+
+    friend class QMultiMap<Key, T>;
 };
 
 template <class Key, class T>
@@ -671,23 +681,6 @@ Q_INLINE_TEMPLATE T &QMap<Key, T>::operator[](const Key &akey)
 }
 
 template <class Key, class T>
-Q_INLINE_TEMPLATE int QMap<Key, T>::count(const Key &akey) const
-{
-    Node *firstNode;
-    Node *lastNode;
-    d->nodeRange(akey, &firstNode, &lastNode);
-
-    const_iterator ci_first(firstNode);
-    const const_iterator ci_last(lastNode);
-    int cnt = 0;
-    while (ci_first != ci_last) {
-        ++cnt;
-        ++ci_first;
-    }
-    return cnt;
-}
-
-template <class Key, class T>
 Q_INLINE_TEMPLATE bool QMap<Key, T>::contains(const Key &akey) const
 {
     return d->findNode(akey) != nullptr;
@@ -789,70 +782,44 @@ typename QMap<Key, T>::iterator QMap<Key, T>::insert(const_iterator pos, const K
 }
 
 template <class Key, class T>
-Q_INLINE_TEMPLATE typename QMap<Key, T>::iterator QMap<Key, T>::insertMulti(const Key &akey,
-                                                                            const T &avalue)
+Q_INLINE_TEMPLATE void QMap<Key, T>::insert(const QMap<Key, T> &map)
 {
-    detach();
-    Node* y = d->end();
-    Node* x = static_cast<Node *>(d->root());
-    bool left = true;
-    while (x != nullptr) {
-        left = !qMapLessThanKey(x->key, akey);
-        y = x;
-        x = left ? x->leftNode() : x->rightNode();
-    }
-    Node *z = d->createNode(akey, avalue, y, left);
-    return iterator(z);
-}
+    if (d == map.d)
+        return;
 
-template <class Key, class T>
-typename QMap<Key, T>::iterator QMap<Key, T>::insertMulti(const_iterator pos, const Key &akey, const T &avalue)
-{
-    if (d->ref.isShared())
-        return this->insertMulti(akey, avalue);
-
-    Q_ASSERT_X(isValidIterator(pos), "QMap::insertMulti", "The specified const_iterator argument 'pos' is invalid");
-
-    if (pos == constEnd()) {
-        // Hint is that the Node is larger than (or equal to) the largest value.
-        Node *n = static_cast<Node *>(pos.i->left);
-        if (n) {
-            while (n->right)
-                n = static_cast<Node *>(n->right);
+    detach();
 
-            if (!qMapLessThanKey(n->key, akey))
-                return this->insertMulti(akey, avalue); // ignore hint
-            Node *z = d->createNode(akey, avalue, n, false); // insert right most
-            return iterator(z);
+    Node *n = d->root();
+    auto it = map.cbegin();
+    const auto e = map.cend();
+    while (it != e) {
+        // Insertion here is based on insert(Key, T)
+        auto parent = d->end();
+        bool left = true;
+        Node *lastNode = nullptr;
+        while (n) {
+            parent = n;
+            if (!qMapLessThanKey(n->key, it.key())) {
+                lastNode = n;
+                n = n->leftNode();
+                left = true;
+            } else {
+                n = n->rightNode();
+                left = false;
+            }
         }
-        return this->insertMulti(akey, avalue);
-    } else {
-        // Hint indicates that the node should be less (or equal to) the hint given
-        // but larger than the previous value.
-        Node *next = const_cast<Node*>(pos.i);
-        if (qMapLessThanKey(next->key, akey))
-            return this->insertMulti(akey, avalue); // ignore hint
-
-        if (pos == constBegin()) {
-            // There is no previous value (insert left most)
-            Node *z = d->createNode(akey, avalue, begin().i, true);
-            return iterator(z);
+        if (lastNode && !qMapLessThanKey(it.key(), lastNode->key)) {
+            lastNode->value = it.value();
+            n = lastNode;
         } else {
-            Node *prev = const_cast<Node*>(pos.i->previousNode());
-            if (!qMapLessThanKey(prev->key, akey))
-                return this->insertMulti(akey, avalue); // ignore hint
-
-            // Hint is ok - do insert
-            if (prev->right == nullptr) {
-                Node *z = d->createNode(akey, avalue, prev, false);
-                return iterator(z);
-            }
-            if (next->left == nullptr) {
-                Node *z = d->createNode(akey, avalue, next, true);
-                return iterator(z);
-            }
-            Q_ASSERT(false); // We should have prev->right == nullptr or next->left == nullptr.
-            return this->insertMulti(akey, avalue);
+            n = d->createNode(it.key(), it.value(), parent, left);
+        }
+        ++it;
+        if (it != e) {
+            // Move back up the tree until we find the next branch or node which is
+            // relevant for the next key.
+            while (n != d->root() && qMapLessThanKey(n->key, it.key()))
+                n = static_cast<Node *>(n->parent());
         }
     }
 }
@@ -880,19 +847,6 @@ Q_INLINE_TEMPLATE typename QMap<Key, T>::iterator QMap<Key, T>::find(const Key &
 }
 
 template <class Key, class T>
-Q_INLINE_TEMPLATE QMap<Key, T> &QMap<Key, T>::unite(const QMap<Key, T> &other)
-{
-    QMap<Key, T> copy(other);
-    const_iterator it = copy.constEnd();
-    const const_iterator b = copy.constBegin();
-    while (it != b) {
-        --it;
-        insertMulti(it.key(), it.value());
-    }
-    return *this;
-}
-
-template <class Key, class T>
 QPair<typename QMap<Key, T>::iterator, typename QMap<Key, T>::iterator> QMap<Key, T>::equal_range(const Key &akey)
 {
     detach();
@@ -1008,26 +962,6 @@ Q_OUTOFLINE_TEMPLATE void QMap<Key, T>::detach_helper()
 }
 
 template <class Key, class T>
-Q_OUTOFLINE_TEMPLATE QList<Key> QMap<Key, T>::uniqueKeys() const
-{
-    QList<Key> res;
-    res.reserve(size()); // May be too much, but assume short lifetime
-    const_iterator i = begin();
-    if (i != end()) {
-        for (;;) {
-            const Key &aKey = i.key();
-            res.append(aKey);
-            do {
-                if (++i == end())
-                    goto break_out_of_outer_loop;
-            } while (!qMapLessThanKey(aKey, i.key()));   // loop while (key == i.key())
-        }
-    }
-break_out_of_outer_loop:
-    return res;
-}
-
-template <class Key, class T>
 Q_OUTOFLINE_TEMPLATE QList<Key> QMap<Key, T>::keys() const
 {
     QList<Key> res;
@@ -1080,21 +1014,6 @@ Q_OUTOFLINE_TEMPLATE QList<T> QMap<Key, T>::values() const
 }
 
 template <class Key, class T>
-Q_OUTOFLINE_TEMPLATE QList<T> QMap<Key, T>::values(const Key &akey) const
-{
-    QList<T> res;
-    Node *n = d->findNode(akey);
-    if (n) {
-        const_iterator it(n);
-        do {
-            res.append(*it);
-            ++it;
-        } while (it != constEnd() && !qMapLessThanKey<Key>(akey, it.key()));
-    }
-    return res;
-}
-
-template <class Key, class T>
 Q_INLINE_TEMPLATE typename QMap<Key, T>::const_iterator QMap<Key, T>::lowerBound(const Key &akey) const
 {
     Node *lb = d->root() ? d->root()->lowerBound(akey) : nullptr;
@@ -1190,15 +1109,20 @@ public:
     QMultiMap(QMap<Key, T> &&other) noexcept : QMap<Key, T>(std::move(other)) {}
     void swap(QMultiMap<Key, T> &other) noexcept { QMap<Key, T>::swap(other); }
 
+    QList<Key> uniqueKeys() const;
+    QList<T> values(const Key &key) const;
+
+    using typename QMap<Key, T>::iterator;
+    using typename QMap<Key, T>::const_iterator;
+
     inline typename QMap<Key, T>::iterator replace(const Key &key, const T &value)
     { return QMap<Key, T>::insert(key, value); }
-    inline typename QMap<Key, T>::iterator insert(const Key &key, const T &value)
-    { return QMap<Key, T>::insertMulti(key, value); }
-    inline typename QMap<Key, T>::iterator insert(typename QMap<Key, T>::const_iterator pos, const Key &key, const T &value)
-    { return QMap<Key, T>::insertMulti(pos, key, value); }
+    iterator insert(const Key &key, const T &value);
+    iterator insert(const_iterator pos, const Key &key, const T &value);
 
+    QMultiMap &unite(const QMultiMap &other);
     inline QMultiMap &operator+=(const QMultiMap &other)
-    { this->unite(other); return *this; }
+    { return unite(other); }
     inline QMultiMap operator+(const QMultiMap &other) const
     { QMultiMap result = *this; result += other; return result; }
 
@@ -1207,11 +1131,18 @@ public:
     using QMap<Key, T>::count;
     using QMap<Key, T>::find;
     using QMap<Key, T>::constFind;
+    using QMap<Key, T>::values;
+    using QMap<Key, T>::size;
+    using QMap<Key, T>::detach;
+    using QMap<Key, T>::erase;
+    using QMap<Key, T>::isValidIterator;
+    using typename QMap<Key, T>::Node;
 
     bool contains(const Key &key, const T &value) const;
 
     int remove(const Key &key, const T &value);
 
+    int count(const Key &key) const;
     int count(const Key &key, const T &value) const;
 
     typename QMap<Key, T>::iterator find(const Key &key, const T &value) {
@@ -1242,6 +1173,123 @@ private:
 };
 
 template <class Key, class T>
+Q_OUTOFLINE_TEMPLATE QList<Key> QMultiMap<Key, T>::uniqueKeys() const
+{
+    QList<Key> res;
+    res.reserve(size()); // May be too much, but assume short lifetime
+    const_iterator i = this->begin();
+    if (i != this->end()) {
+        for (;;) {
+            const Key &aKey = i.key();
+            res.append(aKey);
+            do {
+                if (++i == this->end())
+                    goto break_out_of_outer_loop;
+            } while (!qMapLessThanKey(aKey, i.key()));   // loop while (key == i.key())
+        }
+    }
+break_out_of_outer_loop:
+    return res;
+}
+
+template <class Key, class T>
+Q_OUTOFLINE_TEMPLATE QList<T> QMultiMap<Key, T>::values(const Key &akey) const
+{
+    QList<T> res;
+    Node *n = this->d->findNode(akey);
+    if (n) {
+        const_iterator it(n);
+        do {
+            res.append(*it);
+            ++it;
+        } while (it != this->constEnd() && !qMapLessThanKey<Key>(akey, it.key()));
+    }
+    return res;
+}
+
+template <class Key, class T>
+Q_INLINE_TEMPLATE typename QMultiMap<Key, T>::iterator QMultiMap<Key, T>::insert(const Key &akey,
+                                                                                 const T &avalue)
+{
+    detach();
+    Node* y = this->d->end();
+    Node* x = static_cast<Node *>(this->d->root());
+    bool left = true;
+    while (x != nullptr) {
+        left = !qMapLessThanKey(x->key, akey);
+        y = x;
+        x = left ? x->leftNode() : x->rightNode();
+    }
+    Node *z = this->d->createNode(akey, avalue, y, left);
+    return iterator(z);
+}
+
+template <class Key, class T>
+typename QMultiMap<Key, T>::iterator QMultiMap<Key, T>::insert(const_iterator pos, const Key &akey, const T &avalue)
+{
+    if (this->d->ref.isShared())
+        return insert(akey, avalue);
+
+    Q_ASSERT_X(isValidIterator(pos), "QMap::insert", "The specified const_iterator argument 'pos' is invalid");
+
+    if (pos == this->constEnd()) {
+        // Hint is that the Node is larger than (or equal to) the largest value.
+        Node *n = static_cast<Node *>(pos.i->left);
+        if (n) {
+            while (n->right)
+                n = static_cast<Node *>(n->right);
+
+            if (!qMapLessThanKey(n->key, akey))
+                return insert(akey, avalue); // ignore hint
+            Node *z = this->d->createNode(akey, avalue, n, false); // insert right most
+            return iterator(z);
+        }
+        return insert(akey, avalue);
+    } else {
+        // Hint indicates that the node should be less (or equal to) the hint given
+        // but larger than the previous value.
+        Node *next = const_cast<Node*>(pos.i);
+        if (qMapLessThanKey(next->key, akey))
+            return insert(akey, avalue); // ignore hint
+
+        if (pos == this->constBegin()) {
+            // There is no previous value (insert left most)
+            Node *z = this->d->createNode(akey, avalue, this->begin().i, true);
+            return iterator(z);
+        } else {
+            Node *prev = const_cast<Node*>(pos.i->previousNode());
+            if (!qMapLessThanKey(prev->key, akey))
+                return insert(akey, avalue); // ignore hint
+
+            // Hint is ok - do insert
+            if (prev->right == nullptr) {
+                Node *z = this->d->createNode(akey, avalue, prev, false);
+                return iterator(z);
+            }
+            if (next->left == nullptr) {
+                Node *z = this->d->createNode(akey, avalue, next, true);
+                return iterator(z);
+            }
+            Q_ASSERT(false); // We should have prev->right == nullptr or next->left == nullptr.
+            return insert(akey, avalue);
+        }
+    }
+}
+
+template <class Key, class T>
+Q_INLINE_TEMPLATE QMultiMap<Key, T> &QMultiMap<Key, T>::unite(const QMultiMap<Key, T> &other)
+{
+    QMultiMap<Key, T> copy(other);
+    const_iterator it = copy.constEnd();
+    const const_iterator b = copy.constBegin();
+    while (it != b) {
+        --it;
+        insert(it.key(), it.value());
+    }
+    return *this;
+}
+
+template <class Key, class T>
 Q_INLINE_TEMPLATE bool QMultiMap<Key, T>::contains(const Key &key, const T &value) const
 {
     return constFind(key, value) != QMap<Key, T>::constEnd();
@@ -1255,7 +1303,7 @@ Q_INLINE_TEMPLATE int QMultiMap<Key, T>::remove(const Key &key, const T &value)
     typename QMap<Key, T>::iterator end(QMap<Key, T>::end());
     while (i != end && !qMapLessThanKey<Key>(key, i.key())) {
         if (i.value() == value) {
-            i = this->erase(i);
+            i = erase(i);
             ++n;
         } else {
             ++i;
@@ -1265,6 +1313,23 @@ Q_INLINE_TEMPLATE int QMultiMap<Key, T>::remove(const Key &key, const T &value)
 }
 
 template <class Key, class T>
+Q_INLINE_TEMPLATE int QMultiMap<Key, T>::count(const Key &akey) const
+{
+    QMultiMap::Node *firstNode;
+    QMultiMap::Node *lastNode;
+    this->d->nodeRange(akey, &firstNode, &lastNode);
+
+    const_iterator ci_first(firstNode);
+    const const_iterator ci_last(lastNode);
+    int cnt = 0;
+    while (ci_first != ci_last) {
+        ++cnt;
+        ++ci_first;
+    }
+    return cnt;
+}
+
+template <class Key, class T>
 Q_INLINE_TEMPLATE int QMultiMap<Key, T>::count(const Key &key, const T &value) const
 {
     int n = 0;
@@ -1278,6 +1343,44 @@ Q_INLINE_TEMPLATE int QMultiMap<Key, T>::count(const Key &key, const T &value) c
     return n;
 }
 
+#if QT_DEPRECATED_SINCE(5, 15)
+template<class Key, class T>
+QList<Key> QMap<Key, T>::uniqueKeys() const
+{
+    return static_cast<const QMultiMap<Key, T> *>(this)->uniqueKeys();
+}
+
+template<class Key, class T>
+QList<T> QMap<Key, T>::values(const Key &key) const
+{
+    return static_cast<const QMultiMap<Key, T> *>(this)->values(key);
+}
+
+template<class Key, class T>
+int QMap<Key, T>::count(const Key &key) const
+{
+    return static_cast<const QMultiMap<Key, T> *>(this)->count(key);
+}
+
+template<class Key, class T>
+typename QMap<Key, T>::iterator QMap<Key, T>::insertMulti(const Key &key, const T &value)
+{
+    return static_cast<QMultiMap<Key, T> *>(this)->insert(key, value);
+}
+
+template<class Key, class T>
+typename QMap<Key, T>::iterator QMap<Key, T>::insertMulti(const_iterator pos, const Key &akey, const T &avalue)
+{
+    return static_cast<QMultiMap<Key, T> *>(this)->insert(pos, akey, avalue);
+}
+
+template<class Key, class T>
+QMap<Key, T> &QMap<Key, T>::unite(const QMap<Key, T> &other)
+{
+    return static_cast<QMultiMap<Key, T> *>(this)->unite(other);
+}
+#endif
+
 Q_DECLARE_ASSOCIATIVE_ITERATOR(Map)
 Q_DECLARE_MUTABLE_ASSOCIATIVE_ITERATOR(Map)
 
diff --git a/src/corelib/tools/qscopedvaluerollback.h b/src/corelib/tools/qscopedvaluerollback.h
index f904b8dfcb..b8ceff6665 100644
--- a/src/corelib/tools/qscopedvaluerollback.h
+++ b/src/corelib/tools/qscopedvaluerollback.h
@@ -45,7 +45,11 @@
 QT_BEGIN_NAMESPACE
 
 template <typename T>
-class QScopedValueRollback
+class
+#if QT_HAS_CPP_ATTRIBUTE(nodiscard) && __cplusplus >= 201703L
+[[nodiscard]]
+#endif
+QScopedValueRollback
 {
 public:
     explicit QScopedValueRollback(T &var)
diff --git a/src/corelib/tools/qscopeguard.h b/src/corelib/tools/qscopeguard.h
index 40d2747b1d..6a5bc6cc61 100644
--- a/src/corelib/tools/qscopeguard.h
+++ b/src/corelib/tools/qscopeguard.h
@@ -1,6 +1,7 @@
 /****************************************************************************
 **
 ** Copyright (C) 2018 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Sérgio Martins <sergio.martins@kdab.com>
+** Copyright (C) 2019 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -42,13 +43,11 @@
 
 #include <QtCore/qglobal.h>
 
+#include <type_traits>
+#include <utility>
 
 QT_BEGIN_NAMESPACE
 
-
-template <typename F> class QScopeGuard;
-template <typename F> QScopeGuard<F> qScopeGuard(F f);
-
 template <typename F>
 class
 #if __has_cpp_attribute(nodiscard)
@@ -59,13 +58,23 @@ Q_REQUIRED_RESULT
 QScopeGuard
 {
 public:
+    explicit QScopeGuard(F &&f) noexcept
+        : m_func(std::move(f))
+    {
+    }
+
+    explicit QScopeGuard(const F &f) noexcept
+        : m_func(f)
+    {
+    }
+
     QScopeGuard(QScopeGuard &&other) noexcept
         : m_func(std::move(other.m_func))
         , m_invoke(qExchange(other.m_invoke, false))
     {
     }
 
-    ~QScopeGuard()
+    ~QScopeGuard() noexcept
     {
         if (m_invoke)
             m_func();
@@ -77,26 +86,23 @@ public:
     }
 
 private:
-    explicit QScopeGuard(F &&f) noexcept
-        : m_func(std::move(f))
-    {
-    }
-
     Q_DISABLE_COPY(QScopeGuard)
 
     F m_func;
     bool m_invoke = true;
-    friend QScopeGuard qScopeGuard<F>(F);
 };
 
+#ifdef __cpp_deduction_guides
+template <typename F> QScopeGuard(F(&)()) -> QScopeGuard<F(*)()>;
+#endif
 
 template <typename F>
 #if __has_cpp_attribute(nodiscard)
 Q_REQUIRED_RESULT
 #endif
-QScopeGuard<F> qScopeGuard(F f)
+QScopeGuard<typename std::decay<F>::type> qScopeGuard(F &&f)
 {
-    return QScopeGuard<F>(std::move(f));
+    return QScopeGuard<typename std::decay<F>::type>(std::forward<F>(f));
 }
 
 QT_END_NAMESPACE
diff --git a/src/corelib/tools/qscopeguard.qdoc b/src/corelib/tools/qscopeguard.qdoc
index 6b3c942e84..572934d890 100644
--- a/src/corelib/tools/qscopeguard.qdoc
+++ b/src/corelib/tools/qscopeguard.qdoc
@@ -1,6 +1,7 @@
 /****************************************************************************
 **
 ** Copyright (C) 2018 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Sérgio Martins <sergio.martins@kdab.com>
+** Copyright (C) 2019 The Qt Company Ltd.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the documentation of the Qt Toolkit.
@@ -35,6 +36,30 @@ QT_BEGIN_NAMESPACE
     \inmodule QtCore
     \brief Provides a scope guard for calling a function at the end of
            a scope.
+
+    QScopeGuard<F> is a class of which the sole purpose is to run the function
+    \a f in its destructor. This is useful for guaranteeing
+    your cleanup code is executed, whether the function is exited normally,
+    exited early by a return statement, or exited by an exception.
+
+    \note Exceptions are not supported. The callable shouldn't throw when
+          executed, copied or moved.
+
+    \sa QScopedValueRollback
+*/
+
+/*!
+    \fn template <typename F> QScopeGuard<F>::QScopeGuard(F &&f)
+    \fn template <typename F> QScopeGuard<F>::QScopeGuard(const F &f)
+
+    Create a scope guard that will execute \a f at the end of the scope.
+
+    If \e F is a lambda, its type cannot be written. In that case you need to
+    either rely on class template argument deduction (C++17 feature) and leave
+    the template parameter out completely or use the helper function
+    qScopeGuard() instead of this constructor.
+
+    \since 5.15
 */
 
 /*! \fn template <typename F> void QScopeGuard<F>::dismiss()
@@ -51,23 +76,17 @@ QT_BEGIN_NAMESPACE
            of the scope.
     \ingroup misc
 
-    QScopeGuard<F> is a class of which the sole purpose is to run the function
-    \a f in its destructor. This is useful for guaranteeing
-    your cleanup code is executed, whether the function is exited normally,
-    exited early by a return statement, or exited by an exception.
+    Create a scope guard that will execute \a f at the end of the scope.
 
-    If \e F is a lambda then you cannot instantiate the template directly,
-    therefore the qScopeGuard() helper is provided and QScopeGuard<F> is made a
-    private implementation detail.
+    This helper function is provided so that you can easily construct a
+    QScopeGuard without having to name the template parameter for the type of
+    the callable. If \e F is a lambda then you cannot write its type and relying
+    on this helper or class template argument deduction is necessary.
 
     Example usage is as follows:
 
     \snippet code/src_corelib_tools_qscopeguard.cpp 0
 
-    \note Exceptions are not supported. The callable shouldn't throw when
-          executed, copied or moved.
-
-    \sa QScopedValueRollback
 */
 
 QT_END_NAMESPACE
diff --git a/src/corelib/tools/qset.h b/src/corelib/tools/qset.h
index 2e72832185..879e2176f2 100644
--- a/src/corelib/tools/qset.h
+++ b/src/corelib/tools/qset.h
@@ -108,7 +108,11 @@ public:
         friend class QSet<T>;
 
     public:
+#if QT_DEPRECATED_SINCE(5, 15)
         typedef std::bidirectional_iterator_tag iterator_category;
+#else
+        typedef std::forward_iterator_tag iterator_category;
+#endif
         typedef qptrdiff difference_type;
         typedef T value_type;
         typedef const T *pointer;
@@ -128,13 +132,15 @@ public:
             { return i != o.i; }
         inline iterator &operator++() { ++i; return *this; }
         inline iterator operator++(int) { iterator r = *this; ++i; return r; }
-        inline iterator &operator--() { --i; return *this; }
-        inline iterator operator--(int) { iterator r = *this; --i; return r; }
-        inline iterator operator+(int j) const { return i + j; }
-        inline iterator operator-(int j) const { return i - j; }
-        friend inline iterator operator+(int j, iterator k) { return k + j; }
-        inline iterator &operator+=(int j) { i += j; return *this; }
-        inline iterator &operator-=(int j) { i -= j; return *this; }
+#if QT_DEPRECATED_SINCE(5, 15)
+        inline QT_DEPRECATED iterator &operator--() { --i; return *this; }
+        inline QT_DEPRECATED iterator operator--(int) { iterator r = *this; --i; return r; }
+        inline QT_DEPRECATED iterator operator+(int j) const { return i + j; }
+        inline QT_DEPRECATED iterator operator-(int j) const { return i - j; }
+        friend inline QT_DEPRECATED iterator operator+(int j, iterator k) { return k + j; }
+        inline QT_DEPRECATED iterator &operator+=(int j) { i += j; return *this; }
+        inline QT_DEPRECATED iterator &operator-=(int j) { i -= j; return *this; }
+#endif
     };
 
     class const_iterator
@@ -145,7 +151,11 @@ public:
         friend class QSet<T>;
 
     public:
+#if QT_DEPRECATED_SINCE(5, 15)
         typedef std::bidirectional_iterator_tag iterator_category;
+#else
+        typedef std::forward_iterator_tag iterator_category;
+#endif
         typedef qptrdiff difference_type;
         typedef T value_type;
         typedef const T *pointer;
@@ -163,19 +173,18 @@ public:
         inline bool operator!=(const const_iterator &o) const { return i != o.i; }
         inline const_iterator &operator++() { ++i; return *this; }
         inline const_iterator operator++(int) { const_iterator r = *this; ++i; return r; }
-        inline const_iterator &operator--() { --i; return *this; }
-        inline const_iterator operator--(int) { const_iterator r = *this; --i; return r; }
-        inline const_iterator operator+(int j) const { return i + j; }
-        inline const_iterator operator-(int j) const { return i - j; }
-        friend inline const_iterator operator+(int j, const_iterator k) { return k + j; }
-        inline const_iterator &operator+=(int j) { i += j; return *this; }
-        inline const_iterator &operator-=(int j) { i -= j; return *this; }
+#if QT_DEPRECATED_SINCE(5, 15)
+        inline QT_DEPRECATED const_iterator &operator--() { --i; return *this; }
+        inline QT_DEPRECATED const_iterator operator--(int) { const_iterator r = *this; --i; return r; }
+        inline QT_DEPRECATED const_iterator operator+(int j) const { return i + j; }
+        inline QT_DEPRECATED const_iterator operator-(int j) const { return i - j; }
+        friend inline QT_DEPRECATED const_iterator operator+(int j, const_iterator k) { return k + j; }
+        inline QT_DEPRECATED const_iterator &operator+=(int j) { i += j; return *this; }
+        inline QT_DEPRECATED const_iterator &operator-=(int j) { i -= j; return *this; }
+#endif
     };
 
     // STL style
-    typedef std::reverse_iterator<iterator> reverse_iterator;
-    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
-
     inline iterator begin() { return q_hash.begin(); }
     inline const_iterator begin() const noexcept { return q_hash.begin(); }
     inline const_iterator cbegin() const noexcept { return q_hash.begin(); }
@@ -185,12 +194,17 @@ public:
     inline const_iterator cend() const noexcept { return q_hash.end(); }
     inline const_iterator constEnd() const noexcept { return q_hash.constEnd(); }
 
-    reverse_iterator rbegin() { return reverse_iterator(end()); }
-    reverse_iterator rend() { return reverse_iterator(begin()); }
-    const_reverse_iterator rbegin() const noexcept { return const_reverse_iterator(end()); }
-    const_reverse_iterator rend() const noexcept { return const_reverse_iterator(begin()); }
-    const_reverse_iterator crbegin() const noexcept { return const_reverse_iterator(end()); }
-    const_reverse_iterator crend() const noexcept { return const_reverse_iterator(begin()); }
+#if QT_DEPRECATED_SINCE(5, 15)
+    typedef std::reverse_iterator<iterator> reverse_iterator;
+    typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
+
+    reverse_iterator QT_DEPRECATED rbegin() { return reverse_iterator(end()); }
+    reverse_iterator QT_DEPRECATED rend() { return reverse_iterator(begin()); }
+    const_reverse_iterator QT_DEPRECATED rbegin() const noexcept { return const_reverse_iterator(end()); }
+    const_reverse_iterator QT_DEPRECATED rend() const noexcept { return const_reverse_iterator(begin()); }
+    const_reverse_iterator QT_DEPRECATED crbegin() const noexcept { return const_reverse_iterator(end()); }
+    const_reverse_iterator QT_DEPRECATED crend() const noexcept { return const_reverse_iterator(begin()); }
+#endif
 
     iterator erase(iterator i)
     { return erase(m2c(i)); }
@@ -429,17 +443,19 @@ public:
     inline bool hasNext() const { return c->constEnd() != i; }
     inline const T &next() { n = i++; return *n; }
     inline const T &peekNext() const { return *i; }
-    inline bool hasPrevious() const { return c->constBegin() != i; }
-    inline const T &previous() { n = --i; return *n; }
-    inline const T &peekPrevious() const { iterator p = i; return *--p; }
     inline void remove()
     { if (c->constEnd() != n) { i = c->erase(n); n = c->end(); } }
     inline const T &value() const { Q_ASSERT(item_exists()); return *n; }
     inline bool findNext(const T &t)
     { while (c->constEnd() != (n = i)) if (*i++ == t) return true; return false; }
-    inline bool findPrevious(const T &t)
+#if QT_DEPRECATED_SINCE(5, 15)
+    inline QT_DEPRECATED bool hasPrevious() const { return c->constBegin() != i; }
+    inline QT_DEPRECATED const T &previous() { n = --i; return *n; }
+    inline QT_DEPRECATED const T &peekPrevious() const { iterator p = i; return *--p; }
+    inline QT_DEPRECATED bool findPrevious(const T &t)
     { while (c->constBegin() != i) if (*(n = --i) == t) return true;
       n = c->end(); return false;  }
+#endif
 };
 #endif // QT_NO_JAVA_STYLE_ITERATORS
 
diff --git a/src/corelib/tools/qset.qdoc b/src/corelib/tools/qset.qdoc
index 78854be0de..33a0697e12 100644
--- a/src/corelib/tools/qset.qdoc
+++ b/src/corelib/tools/qset.qdoc
@@ -906,8 +906,6 @@
 
     Calling this function on QSet<T>::constEnd() leads to
     undefined results.
-
-    \sa operator--()
 */
 
 /*!
@@ -924,6 +922,7 @@
 /*!
     \fn template <class T> QSet<T>::iterator &QSet<T>::iterator::operator--()
     \fn template <class T> QSet<T>::const_iterator &QSet<T>::const_iterator::operator--()
+    \obsolete
 
     The prefix -- operator (\c{--it}) makes the preceding item
     current and returns an iterator to the new current item.
@@ -937,6 +936,7 @@
 /*!
     \fn template <class T> QSet<T>::iterator QSet<T>::iterator::operator--(int)
     \fn template <class T> QSet<T>::const_iterator QSet<T>::const_iterator::operator--(int)
+    \obsolete
 
     \overload
 
@@ -947,6 +947,7 @@
 /*!
     \fn template <class T> QSet<T>::iterator QSet<T>::iterator::operator+(int j) const
     \fn template <class T> QSet<T>::const_iterator QSet<T>::const_iterator::operator+(int j) const
+    \obsolete
 
     Returns an iterator to the item at \a j positions forward from
     this iterator. (If \a j is negative, the iterator goes backward.)
@@ -959,6 +960,7 @@
 /*!
     \fn template <class T> QSet<T>::iterator QSet<T>::iterator::operator-(int j) const
     \fn template <class T> QSet<T>::const_iterator QSet<T>::const_iterator::operator-(int j) const
+    \obsolete
 
     Returns an iterator to the item at \a j positions backward from
     this iterator. (If \a j is negative, the iterator goes forward.)
@@ -971,6 +973,7 @@
 /*!
     \fn template <class T> QSet<T>::iterator &QSet<T>::iterator::operator+=(int j)
     \fn template <class T> QSet<T>::const_iterator &QSet<T>::const_iterator::operator+=(int j)
+    \obsolete
 
     Advances the iterator by \a j items. (If \a j is negative, the
     iterator goes backward.)
@@ -983,6 +986,7 @@
 /*!
     \fn template <class T> QSet<T>::iterator &QSet<T>::iterator::operator-=(int j)
     \fn template <class T> QSet<T>::const_iterator &QSet<T>::const_iterator::operator-=(int j)
+    \obsolete
 
     Makes the iterator go back by \a j items. (If \a j is negative,
     the iterator goes forward.)
diff --git a/src/corelib/tools/qsimd.cpp b/src/corelib/tools/qsimd.cpp
index fb9b5996f6..75c380ee8a 100644
--- a/src/corelib/tools/qsimd.cpp
+++ b/src/corelib/tools/qsimd.cpp
@@ -1,7 +1,7 @@
 /****************************************************************************
 **
 ** Copyright (C) 2016 The Qt Company Ltd.
-** Copyright (C) 2018 Intel Corporation.
+** Copyright (C) 2019 Intel Corporation.
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -188,6 +188,8 @@ static inline quint64 detectProcessorFeatures()
 # define PICreg "%%rbx"
 #endif
 
+static bool checkRdrndWorks() noexcept;
+
 static int maxBasicCpuidSupported()
 {
 #if defined(Q_CC_EMSCRIPTEN)
@@ -376,37 +378,8 @@ static quint64 detectProcessorFeatures()
         features &= ~AllAVX512;
     }
 
-#if defined(Q_PROCESSOR_X86) && QT_COMPILER_SUPPORTS_HERE(RDRND)
-    /**
-     * Some AMD CPUs (e.g. AMD A4-6250J and AMD Ryzen 3000-series) have a
-     * failing random generation instruction, which always returns
-     * 0xffffffff, even when generation was "successful".
-     *
-     * This code checks if hardware random generator generates four consecutive
-     * equal numbers. If it does, then we probably have a failing one and
-     * should disable it completely.
-     *
-     * https://bugreports.qt.io/browse/QTBUG-69423
-     */
-    if (features & CpuFeatureRDRND) {
-        const qsizetype testBufferSize = 4;
-        unsigned testBuffer[4] = {};
-
-        const qsizetype generated = qRandomCpu(testBuffer, testBufferSize);
-
-        if (Q_UNLIKELY(generated == testBufferSize &&
-            testBuffer[0] == testBuffer[1] &&
-            testBuffer[1] == testBuffer[2] &&
-            testBuffer[2] == testBuffer[3])) {
-
-            fprintf(stderr, "WARNING: CPU random generator seem to be failing, disable hardware random number generation\n");
-            fprintf(stderr, "WARNING: RDRND generated: 0x%x 0x%x 0x%x 0x%x\n",
-                    testBuffer[0], testBuffer[1], testBuffer[2], testBuffer[3]);
-
-            features &= ~CpuFeatureRDRND;
-        }
-    }
-#endif
+    if (features & CpuFeatureRDRND && !checkRdrndWorks())
+        features &= ~(CpuFeatureRDRND | CpuFeatureRDSEED);
 
     return features;
 }
@@ -626,16 +599,45 @@ void qDumpCPUFeatures()
 
 #  ifdef Q_PROCESSOR_X86_64
 #    define _rdrandXX_step _rdrand64_step
+#    define _rdseedXX_step _rdseed64_step
 #  else
 #    define _rdrandXX_step _rdrand32_step
+#    define _rdseedXX_step _rdseed32_step
 #  endif
 
-QT_FUNCTION_TARGET(RDRND) qsizetype qRandomCpu(void *buffer, qsizetype count) noexcept
+#  if QT_COMPILER_SUPPORTS_HERE(RDSEED)
+static QT_FUNCTION_TARGET(RDSEED) unsigned *qt_random_rdseed(unsigned *ptr, unsigned *end) noexcept
 {
-    unsigned *ptr = reinterpret_cast<unsigned *>(buffer);
-    unsigned *end = ptr + count;
-    int retries = 10;
+    // Unlike for the RDRAND code below, the Intel whitepaper describing the
+    // use of the RDSEED instruction indicates we should not retry in a loop.
+    // If the independent bit generator used by RDSEED is out of entropy, it
+    // may take time to replenish.
+    // https://software.intel.com/en-us/articles/intel-digital-random-number-generator-drng-software-implementation-guide
+    while (ptr + sizeof(qregisteruint)/sizeof(*ptr) <= end) {
+        if (_rdseedXX_step(reinterpret_cast<qregisteruint *>(ptr)) == 0)
+            goto out;
+        ptr += sizeof(qregisteruint)/sizeof(*ptr);
+    }
+
+    if (sizeof(*ptr) != sizeof(qregisteruint) && ptr != end) {
+        if (_rdseed32_step(ptr) == 0)
+            goto out;
+        ++ptr;
+    }
+
+out:
+    return ptr;
+}
+#  else
+static unsigned *qt_random_rdseed(unsigned *ptr, unsigned *)
+{
+    return ptr;
+}
+#  endif
 
+static QT_FUNCTION_TARGET(RDRND) unsigned *qt_random_rdrnd(unsigned *ptr, unsigned *end) noexcept
+{
+    int retries = 10;
     while (ptr + sizeof(qregisteruint)/sizeof(*ptr) <= end) {
         if (_rdrandXX_step(reinterpret_cast<qregisteruint *>(ptr)))
             ptr += sizeof(qregisteruint)/sizeof(*ptr);
@@ -653,9 +655,64 @@ QT_FUNCTION_TARGET(RDRND) qsizetype qRandomCpu(void *buffer, qsizetype count) no
     }
 
 out:
-    return ptr - reinterpret_cast<unsigned *>(buffer);
+    return ptr;
+}
+
+static QT_FUNCTION_TARGET(RDRND) Q_DECL_COLD_FUNCTION bool checkRdrndWorks() noexcept
+{
+    /*
+     * Some AMD CPUs (e.g. AMD A4-6250J and AMD Ryzen 3000-series) have a
+     * failing random generation instruction, which always returns
+     * 0xffffffff, even when generation was "successful".
+     *
+     * This code checks if hardware random generator generates four consecutive
+     * equal numbers. If it does, then we probably have a failing one and
+     * should disable it completely.
+     *
+     * https://bugreports.qt.io/browse/QTBUG-69423
+     */
+    constexpr qsizetype TestBufferSize = 4;
+    unsigned testBuffer[TestBufferSize] = {};
+
+    unsigned *end = qt_random_rdrnd(testBuffer, testBuffer + TestBufferSize);
+    if (end < testBuffer + 3) {
+        // Random generation didn't produce enough data for us to make a
+        // determination whether it's working or not. Assume it isn't, but
+        // don't print a warning.
+        return false;
+    }
+
+    // Check the results for equality
+    if (testBuffer[0] == testBuffer[1]
+        && testBuffer[0] == testBuffer[2]
+        && (end < testBuffer + TestBufferSize || testBuffer[0] == testBuffer[3])) {
+        fprintf(stderr, "WARNING: CPU random generator seem to be failing, "
+                        "disabling hardware random number generation\n"
+                        "WARNING: RDRND generated:");
+        for (unsigned *ptr = testBuffer; ptr < end; ++ptr)
+            fprintf(stderr, " 0x%x", *ptr);
+        fprintf(stderr, "\n");
+        return false;
+    }
+
+    // We're good
+    return true;
 }
-#endif
 
+QT_FUNCTION_TARGET(RDRND) qsizetype qRandomCpu(void *buffer, qsizetype count) noexcept
+{
+    unsigned *ptr = reinterpret_cast<unsigned *>(buffer);
+    unsigned *end = ptr + count;
+
+    if (qCpuHasFeature(RDSEED))
+        ptr = qt_random_rdseed(ptr, end);
+
+    // fill the buffer with RDRND if RDSEED didn't
+    ptr = qt_random_rdrnd(ptr, end);
+    return ptr - reinterpret_cast<unsigned *>(buffer);
+}
+#elif defined(Q_PROCESSOR_X86) && !defined(Q_OS_NACL) && !defined(Q_PROCESSOR_ARM)
+static bool checkRdrndWorks() noexcept { return false; }
+#endif // Q_PROCESSOR_X86 && RDRND
 
 QT_END_NAMESPACE
diff --git a/src/corelib/tools/tools.pri b/src/corelib/tools/tools.pri
index 40c84157cd..e078ab4409 100644
--- a/src/corelib/tools/tools.pri
+++ b/src/corelib/tools/tools.pri
@@ -12,6 +12,7 @@ HEADERS +=  \
         tools/qcontainerfwd.h \
         tools/qcontainertools_impl.h \
         tools/qcryptographichash.h \
+        tools/qduplicatetracker_p.h \
         tools/qfreelist_p.h \
         tools/qhash.h \
         tools/qhashfunctions.h \