QHostInfo: add nothrow move constructor

QHostInfo isn't implicitly shared. The more important to optimize away
copies by providing a move constructor.

Port from QScopedPointer to Q_DECLARE_PRIVATE, as otherwise the move
ctor can't be inline, and we don't implement move ctors out-of-line in
Qt.

[ChangeLog][QtNetwork][QHostInfo] Added move contructor.

Change-Id: I6b63a04e36f63e299205830fdc590ff7e2af338b
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

src/network/kernel/qhostinfo.cpp

@@ -594,8 +594,9 @@ QHostInfo QHostInfoAgent::lookup(const QString &hostName)
     \sa lookupId()
 */
 QHostInfo::QHostInfo(int id)
-    : d(new QHostInfoPrivate)
+    : d_ptr(new QHostInfoPrivate)
 {
+    Q_D(QHostInfo);
     d->lookupId = id;
 }
 
@@ -603,17 +604,30 @@ QHostInfo::QHostInfo(int id)
     Constructs a copy of \a other.
 */
 QHostInfo::QHostInfo(const QHostInfo &other)
-    : d(new QHostInfoPrivate(*other.d.data()))
+    : d_ptr(new QHostInfoPrivate(*other.d_ptr))
 {
 }
 
+/*!
+    Move-constucts a new QHostInfo from \a other.
+
+    \note The moved-from object \a other is placed in a
+    partially-formed state, in which the only valid operations are
+    destruction and assignment of a new value.
+
+    \since 5.14
+*/
+
 /*!
     Assigns the data of the \a other object to this host info object,
     and returns a reference to it.
 */
 QHostInfo &QHostInfo::operator=(const QHostInfo &other)
 {
-    *d.data() = *other.d.data();
+    if (d_ptr)
+        *d_ptr = *other.d_ptr;
+    else
+        d_ptr = new QHostInfoPrivate(*other.d_ptr);
     return *this;
 }
 
@@ -622,6 +636,7 @@ QHostInfo &QHostInfo::operator=(const QHostInfo &other)
 */
 QHostInfo::~QHostInfo()
 {
+    delete d_ptr;
 }
 
 /*!
@@ -636,6 +651,7 @@ QHostInfo::~QHostInfo()
 */
 QList<QHostAddress> QHostInfo::addresses() const
 {
+    Q_D(const QHostInfo);
     return d->addrs;
 }
 
@@ -646,6 +662,7 @@ QList<QHostAddress> QHostInfo::addresses() const
 */
 void QHostInfo::setAddresses(const QList<QHostAddress> &addresses)
 {
+    Q_D(QHostInfo);
     d->addrs = addresses;
 }
 
@@ -656,6 +673,7 @@ void QHostInfo::setAddresses(const QList<QHostAddress> &addresses)
 */
 QString QHostInfo::hostName() const
 {
+    Q_D(const QHostInfo);
     return d->hostName;
 }
 
@@ -666,6 +684,7 @@ QString QHostInfo::hostName() const
 */
 void QHostInfo::setHostName(const QString &hostName)
 {
+    Q_D(QHostInfo);
     d->hostName = hostName;
 }
 
@@ -677,6 +696,7 @@ void QHostInfo::setHostName(const QString &hostName)
 */
 QHostInfo::HostInfoError QHostInfo::error() const
 {
+    Q_D(const QHostInfo);
     return d->err;
 }
 
@@ -687,6 +707,7 @@ QHostInfo::HostInfoError QHostInfo::error() const
 */
 void QHostInfo::setError(HostInfoError error)
 {
+    Q_D(QHostInfo);
     d->err = error;
 }
 
@@ -697,6 +718,7 @@ void QHostInfo::setError(HostInfoError error)
 */
 int QHostInfo::lookupId() const
 {
+    Q_D(const QHostInfo);
     return d->lookupId;
 }
 
@@ -707,6 +729,7 @@ int QHostInfo::lookupId() const
 */
 void QHostInfo::setLookupId(int id)
 {
+    Q_D(QHostInfo);
     d->lookupId = id;
 }
 
@@ -718,6 +741,7 @@ void QHostInfo::setLookupId(int id)
 */
 QString QHostInfo::errorString() const
 {
+    Q_D(const QHostInfo);
     return d->errorStr;
 }
 
@@ -729,6 +753,7 @@ QString QHostInfo::errorString() const
 */
 void QHostInfo::setErrorString(const QString &str)
 {
+    Q_D(QHostInfo);
     d->errorStr = str;
 }
 

src/network/kernel/qhostinfo.h

@@ -62,11 +62,12 @@ public:
 
     explicit QHostInfo(int lookupId = -1);
     QHostInfo(const QHostInfo &d);
+    QHostInfo(QHostInfo &&other) noexcept : d_ptr(qExchange(other.d_ptr, nullptr)) {}
     QHostInfo &operator=(const QHostInfo &d);
     QHostInfo &operator=(QHostInfo &&other) noexcept { swap(other); return *this; }
     ~QHostInfo();
 
-    void swap(QHostInfo &other) noexcept { qSwap(d, other.d); }
+    void swap(QHostInfo &other) noexcept { qSwap(d_ptr, other.d_ptr); }
 
     QString hostName() const;
     void setHostName(const QString &name);
@@ -147,7 +148,8 @@ public:
 #endif // Q_QDOC
 
 private:
-    QScopedPointer<QHostInfoPrivate> d;
+    QHostInfoPrivate *d_ptr;
+    Q_DECLARE_PRIVATE(QHostInfo)
 
     static int lookupHostImpl(const QString &name,
                               const QObject *receiver,