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, 5 insertions, 0 deletions

diff --git a/src/corelib/kernel/qobject.cpp b/src/corelib/kernel/qobject.cpp
index 3417232..e37b6d3 100644
--- a/src/corelib/kernel/qobject.cpp
+++ b/src/corelib/kernel/qobject.cpp
@@ -770,6 +770,11 @@ QObject::~QObject()
     }
 
     if (d->sharedRefcount) {
+        if (d->sharedRefcount->strongref > 0) {
+            qWarning("QObject: shared QObject was deleted directly. The program is malformed and may crash.");
+            // but continue deleting, it's too late to stop anyway
+        }
+
         // indicate to all QWeakPointers that this QObject has now been deleted
         d->sharedRefcount->strongref = 0;
         if (!d->sharedRefcount->weakref.deref())