3 files changed, 44 insertions, 25 deletions

diff --git a/src/corelib/tools/qsharedpointer.cpp b/src/corelib/tools/qsharedpointer.cpp
index ee0aee2399..77c3d1e2cb 100644
--- a/src/corelib/tools/qsharedpointer.cpp
+++ b/src/corelib/tools/qsharedpointer.cpp
@@ -1226,24 +1226,22 @@ QT_BEGIN_NAMESPACE
 /*!
     \internal
     This function is called for a just-created QObject \a obj, to enable
-    the use of QSharedPointer and QWeakPointer.
+    the use of QSharedPointer and QWeakPointer in the future.
+ */
+void QtSharedPointer::ExternalRefCountData::setQObjectShared(const QObject *, bool)
+{}
 
-    When QSharedPointer is active in a QObject, the object must not be deleted
-    directly: the lifetime is managed by the QSharedPointer object. In that case,
-    the deleteLater() and parent-child relationship in QObject only decrease
-    the strong reference count, instead of deleting the object.
+/*!
+    \internal
+    This function is called when a QSharedPointer is created from a QWeakPointer
+
+    We check that the QWeakPointer was really created from a QSharedPointer, and
+    not from a QObject.
 */
-void QtSharedPointer::ExternalRefCountData::setQObjectShared(const QObject *obj, bool)
+void QtSharedPointer::ExternalRefCountData::checkQObjectShared(const QObject *)
 {
-    Q_ASSERT(obj);
-    QObjectPrivate *d = QObjectPrivate::get(const_cast<QObject *>(obj));
-
-    if (d->sharedRefcount.load() != 0)
-        qFatal("QSharedPointer: pointer %p already has reference counting", obj);
-    d->sharedRefcount.store(this);
-
-    // QObject decreases the refcount too, so increase it up
-    weakref.ref();
+    if (strongref.load() < 0)
+        qWarning("QSharedPointer: cannot create a QSharedPointer from a QObject-tracking QWeakPointer");
 }
 
 QtSharedPointer::ExternalRefCountData *QtSharedPointer::ExternalRefCountData::getAndRef(const QObject *obj)
diff --git a/src/corelib/tools/qsharedpointer_impl.h b/src/corelib/tools/qsharedpointer_impl.h
index ebab027196..58010dd8d9 100644
--- a/src/corelib/tools/qsharedpointer_impl.h
+++ b/src/corelib/tools/qsharedpointer_impl.h
@@ -192,7 +192,9 @@ namespace QtSharedPointer {
 #ifndef QT_NO_QOBJECT
         Q_CORE_EXPORT static ExternalRefCountData *getAndRef(const QObject *);
         Q_CORE_EXPORT void setQObjectShared(const QObject *, bool enable);
+        Q_CORE_EXPORT void checkQObjectShared(const QObject *);
 #endif
+        inline void checkQObjectShared(...) { }
         inline void setQObjectShared(...) { }
     };
     // sizeof(ExternalRefCount) = 12 (32-bit) / 16 (64-bit)
@@ -432,10 +434,12 @@ namespace QtSharedPointer {
                     tmp = o->strongref.load();  // failed, try again
                 }
 
-                if (tmp > 0)
+                if (tmp > 0) {
                     o->weakref.ref();
-                else
+                } else {
+                    o->checkQObjectShared(actual);
                     o = 0;
+                }
             }
 
             qSwap(d, o);
diff --git a/tests/auto/corelib/tools/qsharedpointer/tst_qsharedpointer.cpp b/tests/auto/corelib/tools/qsharedpointer/tst_qsharedpointer.cpp
index 2bae52a622..6dae58a006 100644
--- a/tests/auto/corelib/tools/qsharedpointer/tst_qsharedpointer.cpp
+++ b/tests/auto/corelib/tools/qsharedpointer/tst_qsharedpointer.cpp
@@ -76,6 +76,7 @@ private slots:
     void upCast();
     void qobjectWeakManagement();
     void noSharedPointerFromWeakQObject();
+    void sharedPointerFromQObjectWithWeak();
     void weakQObjectFromSharedPointer();
     void objectCast();
     void differentPointers();
@@ -692,12 +693,34 @@ void tst_QSharedPointer::noSharedPointerFromWeakQObject()
     QObject obj;
     QWeakPointer<QObject> weak(&obj);
 
-    QSharedPointer<QObject> strong = weak.toStrongRef();
-    QVERIFY(strong.isNull());
+    {
+        QTest::ignoreMessage(QtWarningMsg ,  "QSharedPointer: cannot create a QSharedPointer from a QObject-tracking QWeakPointer");
+        QSharedPointer<QObject> strong = weak.toStrongRef();
+        QVERIFY(strong.isNull());
+    }
+    {
+        QTest::ignoreMessage(QtWarningMsg ,  "QSharedPointer: cannot create a QSharedPointer from a QObject-tracking QWeakPointer");
+        QSharedPointer<QObject> strong = weak;
+        QVERIFY(strong.isNull());
+    }
 
+    QCOMPARE(weak.data(), &obj);
     // if something went wrong, we'll probably crash here
 }
 
+void tst_QSharedPointer::sharedPointerFromQObjectWithWeak()
+{
+    QObject *ptr = new QObject;
+    QWeakPointer<QObject> weak = ptr;
+    {
+        QSharedPointer<QObject> shared(ptr);
+        QVERIFY(!weak.isNull());
+        QCOMPARE(shared.data(), ptr);
+        QCOMPARE(weak.data(), ptr);
+    }
+    QVERIFY(weak.isNull());
+}
+
 void tst_QSharedPointer::weakQObjectFromSharedPointer()
 {
     // this is the inverse of the above: you're allowed to create a QWeakPointer
@@ -1767,12 +1790,6 @@ void tst_QSharedPointer::invalidConstructs_data()
         << "Data *ptr = 0;\n"
            "QWeakPointer<Data> weakptr(ptr);\n";
 
-    QTest::newRow("shared-pointer-from-unmanaged-qobject")
-        << &QTest::QExternalTest::tryRunFail
-        << "QObject *ptr = new QObject;\n"
-           "QWeakPointer<QObject> weak = ptr;\n"    // this makes the object unmanaged
-           "QSharedPointer<QObject> shared(ptr);\n";
-
     QTest::newRow("shared-pointer-implicit-from-uninitialized")
         << &QTest::QExternalTest::tryCompileFail
         << "Data *ptr = 0;\n"