Implement move-ctor and move-assignment-op for QScopedPointer

It makes sense for a QScopedPointer to be movable, for instance
for allowing instances to be returned from a function.
Ownwership of the managed pointer is still tied to one (and one only)
QScopedPointer instance.

Moreover, a move assignment operator makes sense as well, as it
implementing the equivalent of

  this->reset(other.take());

only when other is a rvalue and not a lvalue (so either it's a temporary
or it's getting explicitly moved in with std::move).

This makes QScopedPointer API's a bit closer to std::unique_ptr's one.

Task-number: QTBUG-29754
Change-Id: If1ac0c688327a67af4ad5b7ad45b439b022ed1c6
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/tools/qscopedpointer.cpp

@@ -130,6 +130,33 @@ QT_BEGIN_NAMESPACE
     Constructs this QScopedPointer instance and sets its pointer to \a p.
 */
 
+#ifndef Q_QDOC // QTBUG-32675, qdoc can't parse rvalue refs
+/*!
+    \fn QScopedPointer::QScopedPointer(QScopedPointer<T, Cleanup> &&other)
+
+    Move-constructs a QScopedPointer instance, making it point at the same
+    object that \a other was pointing to. \a other is reset to point to \c{NULL}.
+
+    \since 5.2
+*/
+
+/*!
+    \fn QScopedPointer<T, Cleanup> &operator=(QScopedPointer<T, Cleanup> &&other)
+
+    Move-assigns \a other to this QScopedPointer instance, transferring the
+    ownership of the managed pointer to this instance.
+
+    If \a other and this instance are actually the same object, this operator
+    does nothing.
+
+    Otherwise, this instance is set to point to the object \a other
+    is pointing to, and \a other is set to point to \c{NULL}.
+    If this instance was pointing to an object, that object is destroyed,
+
+    \since 5.2
+*/
+#endif
+
 /*!
     \fn QScopedPointer::~QScopedPointer()
 

src/corelib/tools/qscopedpointer.h

@@ -98,6 +98,19 @@ public:
         Cleanup::cleanup(oldD);
     }
 
+#ifdef Q_COMPILER_RVALUE_REFS
+    inline QScopedPointer(QScopedPointer<T, Cleanup> &&other)
+        : d(other.take())
+    {
+    }
+
+    inline QScopedPointer<T, Cleanup> &operator=(QScopedPointer<T, Cleanup> &&other)
+    {
+        reset(other.take());
+        return *this;
+    }
+#endif
+
     inline T &operator*() const
     {
         Q_ASSERT(d);

tests/auto/corelib/tools/qscopedpointer/qscopedpointer.pro

@@ -1,4 +1,5 @@
 CONFIG += testcase parallel_test
+contains(QT_CONFIG, c++11):CONFIG += c++11
 TARGET = tst_qscopedpointer
 QT = core testlib
 SOURCES = tst_qscopedpointer.cpp

tests/auto/corelib/tools/qscopedpointer/tst_qscopedpointer.cpp

@@ -42,6 +42,8 @@
 #include <QtTest/QtTest>
 #include <QtCore/QScopedPointer>
 
+#include <utility>
+
 /*!
  \class tst_QScopedPointer
  \internal
@@ -73,6 +75,7 @@ private Q_SLOTS:
     void objectSize();
     void comparison();
     void array();
+    void move();
     // TODO instanciate on const object
 };
 
@@ -458,6 +461,158 @@ void tst_QScopedPointer::array()
     QCOMPARE(instCount, RefCounted::instanceCount.load());
 }
 
+#ifdef Q_COMPILER_RVALUE_REFS
+struct CountedInteger
+{
+    CountedInteger(int i) : i(i)
+    {
+        ++instanceCount;
+    }
+    ~CountedInteger()
+    {
+        --instanceCount;
+    }
+    CountedInteger(const CountedInteger &c)
+        : i(c.i)
+    {
+        ++instanceCount;
+    }
+
+    static int instanceCount;
+    int i;
+};
+
+int CountedInteger::instanceCount = 0;
+
+QScopedPointer<CountedInteger> returnScopedPointer(int i)
+{
+    return QScopedPointer<CountedInteger>(new CountedInteger(i));
+}
+#endif
+
+void tst_QScopedPointer::move()
+{
+#ifndef Q_COMPILER_RVALUE_REFS
+    QSKIP("This test requires rvalues refs");
+#else
+    QCOMPARE(CountedInteger::instanceCount, 0);
+
+    {
+        QScopedPointer<CountedInteger> p = returnScopedPointer(42);
+        QVERIFY(!p.isNull());
+        QCOMPARE(p->i, 42);
+        QCOMPARE(CountedInteger::instanceCount, 1);
+
+        QScopedPointer<CountedInteger> q = returnScopedPointer(51);
+        QVERIFY(!q.isNull());
+        QCOMPARE(q->i, 51);
+        QCOMPARE(CountedInteger::instanceCount, 2);
+
+        q = returnScopedPointer(123);
+        QVERIFY(!q.isNull());
+        QCOMPARE(q->i, 123);
+        QCOMPARE(CountedInteger::instanceCount, 2);
+
+        p = std::move(q);
+        QVERIFY(!p.isNull());
+        QCOMPARE(p->i, 123);
+        QVERIFY(q.isNull());
+        QCOMPARE(CountedInteger::instanceCount, 1);
+
+        p = std::move(q);
+        QVERIFY(p.isNull());
+        QVERIFY(q.isNull());
+        QCOMPARE(CountedInteger::instanceCount, 0);
+    }
+
+    QCOMPARE(CountedInteger::instanceCount, 0);
+
+    {
+        QScopedPointer<CountedInteger> p = returnScopedPointer(1024);
+        QVERIFY(!p.isNull());
+        QCOMPARE(p->i, 1024);
+        QCOMPARE(CountedInteger::instanceCount, 1);
+
+        p.reset();
+        QVERIFY(p.isNull());
+        QCOMPARE(CountedInteger::instanceCount, 0);
+
+        p = returnScopedPointer(1024);
+        const CountedInteger * const rawPtr = p.data();
+        p = std::move(p);
+        // now p is in a "valid, but unspecified state". so the test must not crash.
+        // we do actually know that this move should've been a noop.
+        QVERIFY(!p.isNull());
+        QCOMPARE(p.data(), rawPtr);
+        QCOMPARE(p->i, 1024);
+        QCOMPARE(CountedInteger::instanceCount, 1);
+
+        p.reset();
+        QVERIFY(p.isNull());
+        QCOMPARE(CountedInteger::instanceCount, 0);
+    }
+
+    QCOMPARE(CountedInteger::instanceCount, 0);
+
+    {
+        QScopedPointer<CountedInteger> p = returnScopedPointer(-1);
+        QVERIFY(!p.isNull());
+        QCOMPARE(p->i, -1);
+        QCOMPARE(CountedInteger::instanceCount, 1);
+    }
+
+    QCOMPARE(CountedInteger::instanceCount, 0);
+
+    {
+        QScopedPointer<CountedInteger> p = returnScopedPointer(0);
+        QVERIFY(!p.isNull());
+        QCOMPARE(p->i, 0);
+        QCOMPARE(CountedInteger::instanceCount, 1);
+
+        QScopedPointer<CountedInteger> q;
+        QVERIFY(q.isNull());
+
+        p = std::move(q);
+        QVERIFY(p.isNull());
+        QVERIFY(q.isNull());
+        QCOMPARE(CountedInteger::instanceCount, 0);
+    }
+
+    QCOMPARE(CountedInteger::instanceCount, 0);
+
+    {
+        QScopedPointer<CountedInteger> p;
+        QVERIFY(p.isNull());
+        QCOMPARE(CountedInteger::instanceCount, 0);
+
+        QScopedPointer<CountedInteger> q = returnScopedPointer(123);
+        QVERIFY(!q.isNull());
+        QCOMPARE(q->i, 123);
+        QCOMPARE(CountedInteger::instanceCount, 1);
+
+        p = std::move(q);
+        QVERIFY(!p.isNull());
+        QCOMPARE(p->i, 123);
+        QVERIFY(q.isNull());
+        QCOMPARE(CountedInteger::instanceCount, 1);
+    }
+
+    QCOMPARE(CountedInteger::instanceCount, 0);
+
+    {
+        QScopedPointer<CountedInteger> p;
+        QVERIFY(p.isNull());
+        QCOMPARE(CountedInteger::instanceCount, 0);
+
+        p = returnScopedPointer(2001);
+        QVERIFY(!p.isNull());
+        QCOMPARE(p->i, 2001);
+        QCOMPARE(CountedInteger::instanceCount, 1);
+    }
+
+    QCOMPARE(CountedInteger::instanceCount, 0);
+#endif
+}
 
 QTEST_MAIN(tst_QScopedPointer)
 #include "tst_qscopedpointer.moc"