4 files changed, 60 insertions, 5 deletions

diff --git a/src/corelib/kernel/qobject.cpp b/src/corelib/kernel/qobject.cpp
index 7e7dcaf..3417232 100644
--- a/src/corelib/kernel/qobject.cpp
+++ b/src/corelib/kernel/qobject.cpp
@@ -56,6 +56,7 @@
 #include <qvarlengtharray.h>
 #include <qset.h>
 #include <qsemaphore.h>
+#include <qsharedpointer.h>
 
 #include <private/qorderedmutexlocker_p.h>
 #include <private/qmutexpool_p.h>
@@ -768,6 +769,13 @@ QObject::~QObject()
         QObjectPrivate::clearGuards(this);
     }
 
+    if (d->sharedRefcount) {
+        // indicate to all QWeakPointers that this QObject has now been deleted
+        d->sharedRefcount->strongref = 0;
+        if (!d->sharedRefcount->weakref.deref())
+            delete d->sharedRefcount;
+    }
+
     emit destroyed(this);
     if (d->declarativeData)
         d->declarativeData->destroyed(this);
diff --git a/src/corelib/kernel/qobject_p.h b/src/corelib/kernel/qobject_p.h
index e58ee6c..056dee3 100644
--- a/src/corelib/kernel/qobject_p.h
+++ b/src/corelib/kernel/qobject_p.h
@@ -67,6 +67,7 @@ QT_BEGIN_NAMESPACE
 class QVariant;
 class QThreadData;
 class QObjectConnectionListVector;
+namespace QtSharedPointer { class ExternalRefCountData; }
 
 /* mirrored in QtTestLib, DON'T CHANGE without prior warning */
 struct QSignalSpyCallbackSet
@@ -187,6 +188,7 @@ public:
     // plus QPointer, which keeps a separate list
     QDeclarativeData *declarativeData;
     QGuard<QObject> *objectGuards;
+    QAtomicPointer<QtSharedPointer::ExternalRefCountData> sharedRefcount;
     int *deleteWatch;
 };
 
diff --git a/src/corelib/tools/qsharedpointer.cpp b/src/corelib/tools/qsharedpointer.cpp
index ef4dfac..e2c5e95 100644
--- a/src/corelib/tools/qsharedpointer.cpp
+++ b/src/corelib/tools/qsharedpointer.cpp
@@ -864,6 +864,33 @@
 #include <qset.h>
 #include <qmutex.h>
 
+#if !defined(QT_NO_QOBJECT)
+#include "../kernel/qobject_p.h"
+
+QtSharedPointer::ExternalRefCountData *QtSharedPointer::ExternalRefCountData::getAndRef(const QObject *obj)
+{
+    Q_ASSERT(obj);
+    QObjectPrivate *d = QObjectPrivate::get(const_cast<QObject *>(obj));
+    ExternalRefCountData *that = d->sharedRefcount;
+    if (that) {
+        that->weakref.ref();
+        return that;
+    }
+
+    // we can create the refcount data because it doesn't exist
+    ExternalRefCountData *x = new ExternalRefCountData(Qt::Uninitialized);
+    x->strongref = -1;
+    x->weakref = 2;  // the QWeakPointer that called us plus the QObject itself
+    if (!d->sharedRefcount.testAndSetRelease(0, x)) {
+        delete x;
+        d->sharedRefcount->weakref.ref();
+    }
+    return d->sharedRefcount;
+}
+#endif
+
+
+
 #if !defined(QT_NO_MEMBER_TEMPLATES)
 
 //#  define QT_SHARED_POINTER_BACKTRACE_SUPPORT
diff --git a/src/corelib/tools/qsharedpointer_impl.h b/src/corelib/tools/qsharedpointer_impl.h
index 3ee407c..1fed024 100644
--- a/src/corelib/tools/qsharedpointer_impl.h
+++ b/src/corelib/tools/qsharedpointer_impl.h
@@ -162,13 +162,22 @@ namespace QtSharedPointer {
 
     struct ExternalRefCountData
     {
-        QAtomicInt weakref;
-        QAtomicInt strongref;
+        QBasicAtomicInt weakref;
+        QBasicAtomicInt strongref;
 
-        inline ExternalRefCountData() : weakref(1), strongref(1) { }
-        virtual inline ~ExternalRefCountData() { Q_ASSERT(!weakref); Q_ASSERT(!strongref); }
+        inline ExternalRefCountData()
+        {
+            QBasicAtomicInt proto = Q_BASIC_ATOMIC_INITIALIZER(1);
+            weakref = strongref = proto;
+        }
+        inline ExternalRefCountData(Qt::Initialization) { }
+        virtual inline ~ExternalRefCountData() { Q_ASSERT(!weakref); Q_ASSERT(strongref <= 0); }
 
         virtual inline bool destroy() { return false; }
+
+#ifndef QT_NO_QOBJECT
+        Q_CORE_EXPORT static ExternalRefCountData *getAndRef(const QObject *);
+#endif
     };
     // sizeof(ExternalRefCount) = 12 (32-bit) / 16 (64-bit)
 
@@ -376,7 +385,7 @@ namespace QtSharedPointer {
                     tmp = o->strongref;  // failed, try again
                 }
 
-                if (tmp)
+                if (tmp > 0)
                     o->weakref.ref();
                 else
                     o = 0;
@@ -495,6 +504,15 @@ public:
 
     inline QWeakPointer() : d(0), value(0) { }
     inline ~QWeakPointer() { if (d && !d->weakref.deref()) delete d; }
+
+    // special constructor that is enabled only if X derives from QObject
+    template <class X>
+    inline QWeakPointer(X *ptr) : d(ptr ? d->getAndRef(ptr) : 0), value(ptr)
+    { }
+    template <class X>
+    inline QWeakPointer &operator=(X *ptr)
+    { return *this = QWeakPointer(ptr); }
+
     inline QWeakPointer(const QWeakPointer<T> &o) : d(o.d), value(o.value)
     { if (d) d->weakref.ref(); }
     inline QWeakPointer<T> &operator=(const QWeakPointer<T> &o)