Replace qExchange calls with std::exchange

qExchange is one of the few remaining functionalities that have not been
moved out of qglobal. Given that std::exchange exists in the standard, we
can simply move to it everywhere...

...if it weren't for the fact that std::exchange is only constexpr in
C++20, and only has its noexceptness specified in (most likely) C++23.
Still, we want to move to the existing std functionality where
possible, to allow the removal of qglobal includes in lieu of something
more fine-grained in the future.
So leave any constexpr calls[1] alone for now (and observe that none of
our current usages cares about the conditional noexceptness), but
replace everything else.

[1] QScopedValueRollback' ctor and QExplicitlySharedDataPointerV2::take

Task-number: QTBUG-99313
Change-Id: I599cb9846cf319c7ffd3457130938347a75aad25
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/io/qdebug.h

@@ -72,7 +72,7 @@ public:
     explicit QDebug(QString *string) : stream(new Stream(string)) {}
     explicit QDebug(QtMsgType t) : stream(new Stream(t)) {}
     QDebug(const QDebug &o) : stream(o.stream) { ++stream->ref; }
-    QDebug(QDebug &&other) noexcept : stream{qExchange(other.stream, nullptr)} {}
+    QDebug(QDebug &&other) noexcept : stream{std::exchange(other.stream, nullptr)} {}
     inline QDebug &operator=(const QDebug &other);
     QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_MOVE_AND_SWAP(QDebug)
     ~QDebug();

src/corelib/itemmodels/qabstractitemmodel.h

@@ -184,7 +184,7 @@ public:
     { return !operator==(other); }
     QPersistentModelIndex &operator=(const QPersistentModelIndex &other);
     inline QPersistentModelIndex(QPersistentModelIndex &&other) noexcept
-        : d(qExchange(other.d, nullptr)) {}
+        : d(std::exchange(other.d, nullptr)) {}
     QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_PURE_SWAP(QPersistentModelIndex)
     void swap(QPersistentModelIndex &other) noexcept { qt_ptr_swap(d, other.d); }
     bool operator==(const QModelIndex &other) const;

src/corelib/kernel/qbasictimer.h

@@ -22,7 +22,7 @@ public:
     inline ~QBasicTimer() { if (id) stop(); }
 
     QBasicTimer(QBasicTimer &&other) noexcept
-        : id{qExchange(other.id, 0)}
+        : id{std::exchange(other.id, 0)}
     {}
 
     QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_MOVE_AND_SWAP(QBasicTimer)

src/corelib/kernel/qobjectdefs.h

@@ -600,7 +600,7 @@ public:
     operator RestrictedBool() const { return d_ptr && isConnected_helper() ? &Connection::d_ptr : nullptr; }
 #endif
 
-    Connection(Connection &&other) noexcept : d_ptr(qExchange(other.d_ptr, nullptr)) {}
+    Connection(Connection &&other) noexcept : d_ptr(std::exchange(other.d_ptr, nullptr)) {}
     QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_PURE_SWAP(Connection)
     void swap(Connection &other) noexcept { qt_ptr_swap(d_ptr, other.d_ptr); }
 };

src/corelib/kernel/qproperty.cpp

@@ -25,7 +25,7 @@ void QPropertyBindingPrivatePtr::reset(QtPrivate::RefCounted *ptr) noexcept
     if (ptr != d) {
         if (ptr)
             ptr->ref++;
-        auto *old = qExchange(d, ptr);
+        auto *old = std::exchange(d, ptr);
         if (old && (--old->ref == 0))
             QPropertyBindingPrivate::destroyAndFreeMemory(static_cast<QPropertyBindingPrivate *>(d));
     }

src/corelib/kernel/qpropertyprivate.h

@@ -82,7 +82,7 @@ public:
         reset(o);
         return *this;
     }
-    QPropertyBindingPrivatePtr(QPropertyBindingPrivatePtr &&o) noexcept : d(qExchange(o.d, nullptr)) {}
+    QPropertyBindingPrivatePtr(QPropertyBindingPrivatePtr &&o) noexcept : d(std::exchange(o.d, nullptr)) {}
     QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_MOVE_AND_SWAP(QPropertyBindingPrivatePtr)
 
     operator bool () const noexcept { return d != nullptr; }

src/corelib/plugin/qfactoryloader.cpp

@@ -319,7 +319,7 @@ void QFactoryLoader::setExtraSearchPath(const QString &path)
         return;             // nothing to do
 
     QMutexLocker locker(&qt_factoryloader_global->mutex);
-    QString oldPath = qExchange(d->extraSearchPath, path);
+    QString oldPath = std::exchange(d->extraSearchPath, path);
     if (oldPath.isEmpty()) {
         // easy case, just update this directory
         d->updateSinglePath(d->extraSearchPath);

src/corelib/serialization/qcborvalue.h

@@ -141,7 +141,7 @@ public:
 
     QCborValue(const QCborValue &other) noexcept;
     QCborValue(QCborValue &&other) noexcept
-        : n(other.n), container(qExchange(other.container, nullptr)), t(qExchange(other.t, Undefined))
+        : n(other.n), container(std::exchange(other.container, nullptr)), t(std::exchange(other.t, Undefined))
     {
     }
     QCborValue &operator=(const QCborValue &other) noexcept;

src/corelib/text/qregularexpression.cpp

@@ -2671,7 +2671,7 @@ QRegularExpressionMatch QRegularExpressionMatchIterator::next()
     }
 
     d.detach();
-    return qExchange(d->next, d->next.d.constData()->nextMatch());
+    return std::exchange(d->next, d->next.d.constData()->nextMatch());
 }
 
 /*!

src/corelib/thread/qsemaphore.h

@@ -82,7 +82,7 @@ public:
 
     QSemaphore *cancel() noexcept
     {
-        return qExchange(m_sem, nullptr);
+        return std::exchange(m_sem, nullptr);
     }
 
 private:

src/corelib/tools/qhash.h

@@ -172,7 +172,7 @@ struct MultiNode
 
     MultiNode(MultiNode &&other)
         : key(other.key),
-          value(qExchange(other.value, nullptr))
+          value(std::exchange(other.value, nullptr))
     {
     }
 
@@ -203,7 +203,7 @@ struct MultiNode
     void insertMulti(Args &&... args)
     {
         Chain *e = new Chain{ T(std::forward<Args>(args)...), nullptr };
-        e->next = qExchange(value, e);
+        e->next = std::exchange(value, e);
     }
     template<typename ...Args>
     void emplaceValue(Args &&... args)
@@ -1412,8 +1412,8 @@ public:
         return *this;
     }
     QMultiHash(QMultiHash &&other) noexcept
-        : d(qExchange(other.d, nullptr)),
+        : d(std::exchange(other.d, nullptr)),
-          m_size(qExchange(other.m_size, 0))
+          m_size(std::exchange(other.m_size, 0))
     {
     }
     QMultiHash &operator=(QMultiHash &&other) noexcept(std::is_nothrow_destructible<Node>::value)

src/corelib/tools/qscopedpointer.h

@@ -120,7 +120,7 @@ public:
     {
         if (d == other)
             return;
-        T *oldD = qExchange(d, other);
+        T *oldD = std::exchange(d, other);
         Cleanup::cleanup(oldD);
     }
 
@@ -128,7 +128,7 @@ public:
     QT_DEPRECATED_VERSION_X_6_1("Use std::unique_ptr instead, and call release().")
     T *take() noexcept
     {
-        T *oldD = qExchange(d, nullptr);
+        T *oldD = std::exchange(d, nullptr);
         return oldD;
     }
 #endif

src/corelib/tools/qscopeguard.h

@@ -28,7 +28,7 @@ public:
 
     QScopeGuard(QScopeGuard &&other) noexcept
         : m_func(std::move(other.m_func))
-        , m_invoke(qExchange(other.m_invoke, false))
+        , m_invoke(std::exchange(other.m_invoke, false))
     {
     }
 

src/corelib/tools/qshareddata.h

@@ -66,7 +66,7 @@ public:
         if (ptr != d) {
             if (ptr)
                 ptr->ref.ref();
-            T *old = qExchange(d, ptr);
+            T *old = std::exchange(d, ptr);
             if (old && !old->ref.deref())
                 delete old;
         }
@@ -82,7 +82,7 @@ public:
         reset(o);
         return *this;
     }
-    QSharedDataPointer(QSharedDataPointer &&o) noexcept : d(qExchange(o.d, nullptr)) {}
+    QSharedDataPointer(QSharedDataPointer &&o) noexcept : d(std::exchange(o.d, nullptr)) {}
     QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_MOVE_AND_SWAP(QSharedDataPointer)
 
     operator bool () const noexcept { return d != nullptr; }
@@ -135,7 +135,7 @@ public:
     T *data() const noexcept { return d; }
     T *get() const noexcept { return d; }
     const T *constData() const noexcept { return d; }
-    T *take() noexcept { return qExchange(d, nullptr); }
+    T *take() noexcept { return std::exchange(d, nullptr); }
 
     void detach() { if (d && d->ref.loadRelaxed() != 1) detach_helper(); }
 
@@ -163,7 +163,7 @@ public:
         if (ptr != d) {
             if (ptr)
                 ptr->ref.ref();
-            T *old = qExchange(d, ptr);
+            T *old = std::exchange(d, ptr);
             if (old && !old->ref.deref())
                 delete old;
         }
@@ -179,7 +179,7 @@ public:
         reset(o);
         return *this;
     }
-    QExplicitlySharedDataPointer(QExplicitlySharedDataPointer &&o) noexcept : d(qExchange(o.d, nullptr)) {}
+    QExplicitlySharedDataPointer(QExplicitlySharedDataPointer &&o) noexcept : d(std::exchange(o.d, nullptr)) {}
     QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_MOVE_AND_SWAP(QExplicitlySharedDataPointer)
 
     operator bool () const noexcept { return d != nullptr; }

src/corelib/tools/qshareddata_impl.h

@@ -51,7 +51,7 @@ public:
     }
 
     QExplicitlySharedDataPointerV2(QExplicitlySharedDataPointerV2 &&other) noexcept
-        : d(qExchange(other.d, nullptr))
+        : d(std::exchange(other.d, nullptr))
     {
     }
 

src/gui/image/qicon.h

@@ -26,7 +26,7 @@ public:
     QIcon(const QPixmap &pixmap);
     QIcon(const QIcon &other);
     QIcon(QIcon &&other) noexcept
-        : d(qExchange(other.d, nullptr))
+        : d(std::exchange(other.d, nullptr))
     {}
     explicit QIcon(const QString &fileName); // file or resource name
     explicit QIcon(QIconEngine *engine);

src/gui/image/qimage.h

@@ -96,7 +96,7 @@ public:
 
     QImage(const QImage &);
     QImage(QImage &&other) noexcept
-        : QPaintDevice(), d(qExchange(other.d, nullptr))
+        : QPaintDevice(), d(std::exchange(other.d, nullptr))
     {}
     ~QImage();
 

src/gui/kernel/qcursor.h

@@ -51,7 +51,7 @@ public:
     QCursor(const QCursor &cursor);
     ~QCursor();
     QCursor &operator=(const QCursor &cursor);
-    QCursor(QCursor &&other) noexcept : d(qExchange(other.d, nullptr)) {}
+    QCursor(QCursor &&other) noexcept : d(std::exchange(other.d, nullptr)) {}
     QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_MOVE_AND_SWAP(QCursor)
 
     void swap(QCursor &other) noexcept { qt_ptr_swap(d, other.d); }

src/gui/kernel/qpalette.h

@@ -32,7 +32,7 @@ public:
     ~QPalette();
     QPalette &operator=(const QPalette &palette);
     QPalette(QPalette &&other) noexcept
-        : d(qExchange(other.d, nullptr)), currentGroup(other.currentGroup)
+        : d(std::exchange(other.d, nullptr)), currentGroup(other.currentGroup)
     {}
     QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_PURE_SWAP(QPalette)
 

src/gui/painting/qpen.h

@@ -35,7 +35,7 @@ public:
 
     QPen &operator=(const QPen &pen) noexcept;
     QPen(QPen &&other) noexcept
-        : d(qExchange(other.d, nullptr)) {}
+        : d(std::exchange(other.d, nullptr)) {}
     QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_PURE_SWAP(QPen)
     void swap(QPen &other) noexcept { qt_ptr_swap(d, other.d); }
 

src/gui/painting/qregion.h

@@ -34,7 +34,7 @@ public:
     QRegion(const QPolygon &pa, Qt::FillRule fillRule = Qt::OddEvenFill);
     QRegion(const QRegion &region);
     QRegion(QRegion &&other) noexcept
-        : d(qExchange(other.d, const_cast<QRegionData*>(&shared_empty))) {}
+        : d(std::exchange(other.d, const_cast<QRegionData*>(&shared_empty))) {}
     QRegion(const QBitmap &bitmap);
     ~QRegion();
     QRegion &operator=(const QRegion &);

src/gui/text/qfontengine_p.h

@@ -277,8 +277,8 @@ public:
         explicit Holder(void *p, qt_destroy_func_t d) : ptr(p), destroy_func(d) {}
         ~Holder() { if (ptr && destroy_func) destroy_func(ptr); }
         Holder(Holder &&other) noexcept
-            : ptr(qExchange(other.ptr, nullptr)),
+            : ptr(std::exchange(other.ptr, nullptr)),
-              destroy_func(qExchange(other.destroy_func, nullptr))
+              destroy_func(std::exchange(other.destroy_func, nullptr))
         {
         }
         QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_PURE_SWAP(Holder)

src/network/access/qhttpprotocolhandler.cpp

@@ -298,7 +298,7 @@ bool QHttpProtocolHandler::sendRequest()
             sendRequest(); //recurse
         } else {
             // no data to send: just send the HTTP headers
-            m_socket->write(qExchange(m_header, {}));
+            m_socket->write(std::exchange(m_header, {}));
             QMetaObject::invokeMethod(m_reply, "requestSent", Qt::QueuedConnection);
             m_channel->state = QHttpNetworkConnectionChannel::WaitingState; // now wait for response
             sendRequest(); //recurse
@@ -314,7 +314,7 @@ bool QHttpProtocolHandler::sendRequest()
             // the upload device might have no data to send, but we still have to send the headers,
             // do it now.
             if (!m_header.isEmpty())
-                m_socket->write(qExchange(m_header, {}));
+                m_socket->write(std::exchange(m_header, {}));
             if (uploadByteDevice)
                 emit m_reply->dataSendProgress(m_channel->written, m_channel->bytesTotal);
             m_channel->state = QHttpNetworkConnectionChannel::WaitingState; // now wait for response
@@ -371,7 +371,7 @@ bool QHttpProtocolHandler::sendRequest()
                     // assemble header and data and send them together
                     const qint64 headerSize = m_header.size();
                     m_header.append(readPointer, currentReadSize);
-                    currentWriteSize = m_socket->write(qExchange(m_header, {}));
+                    currentWriteSize = m_socket->write(std::exchange(m_header, {}));
                     if (currentWriteSize != -1)
                         currentWriteSize -= headerSize;
                     QMetaObject::invokeMethod(m_reply, "requestSent", Qt::QueuedConnection);

src/network/access/qnetworkreplyimpl.cpp

@@ -281,7 +281,7 @@ void QNetworkReplyImplPrivate::handleNotifications()
     if (notificationHandlingPaused)
         return;
 
-     for (InternalNotifications notification : qExchange(pendingNotifications, {})) {
+     for (InternalNotifications notification : std::exchange(pendingNotifications, {})) {
         if (state != Working)
             return;
         switch (notification) {

src/network/kernel/qhostinfo.h

@@ -26,7 +26,7 @@ public:
 
     explicit QHostInfo(int lookupId = -1);
     QHostInfo(const QHostInfo &d);
-    QHostInfo(QHostInfo &&other) noexcept : d_ptr(qExchange(other.d_ptr, nullptr)) {}
+    QHostInfo(QHostInfo &&other) noexcept : d_ptr(std::exchange(other.d_ptr, nullptr)) {}
     QHostInfo &operator=(const QHostInfo &d);
     QHostInfo &operator=(QHostInfo &&other) noexcept { swap(other); return *this; }
     ~QHostInfo();