Restore symmetry between QSharedPointer and QWeakPointer on QObjects.

With the previous commit, you could create a QWeakPointer from any
QObject-derived object. It's possible because QObject now has a
pointer to the QWeakPointer's d-pointer.

However, if you did:
    QSharedPointer<QObject> obj(new QObject);
    QWeakPointer<QObject> weak1(obj);
    QWeakPointer<QObject> weak2(obj.data());

Then weak1 would shared d-pointers with QSharedPointer, but weak2
wouldn't. Also, weak1.toStrongRef() would work, but
weak2.toStrongRef() wouldn't.

This change makes QObject know where the d-pointer created by
QSharedPointer is, so weak2 would get the same d-pointer.

As a nice side-effect, you can check if a given QObject is shared by
trying to promote its QWeakPointer to QSharedPointer.

Reviewed-by: Bradley T. Hughes

1 files changed, 3 insertions, 0 deletions

diff --git a/src/corelib/tools/qsharedpointer_impl.h b/src/corelib/tools/qsharedpointer_impl.h
index 421db34..8a34362 100644
--- a/src/corelib/tools/qsharedpointer_impl.h
+++ b/src/corelib/tools/qsharedpointer_impl.h
@@ -165,7 +165,9 @@ namespace QtSharedPointer {
 
 #ifndef QT_NO_QOBJECT
         Q_CORE_EXPORT static ExternalRefCountData *getAndRef(const QObject *);
+        Q_CORE_EXPORT void setQObjectShared(const QObject *, bool enable);
 #endif
+        inline void setQObjectShared(...) { }
     };
     // sizeof(ExternalRefCount) = 12 (32-bit) / 16 (64-bit)
 
@@ -328,6 +330,7 @@ namespace QtSharedPointer {
         inline void internalFinishConstruction(T *ptr)
         {
             Basic<T>::internalConstruct(ptr);
+            if (ptr) d->setQObjectShared(ptr, true);
 #ifdef QT_SHAREDPOINTER_TRACK_POINTERS
             if (ptr) internalSafetyCheckAdd2(d, ptr);
 #endif