QTBUG-27224 patch for 4.8.3

diff --git a/src/corelib/concurrent/qfutureinterface.cpp b/src/corelib/concurrent/qfutureinterface.cpp
index 17bd5e2..3e4ab66 100644
--- a/src/corelib/concurrent/qfutureinterface.cpp
+++ b/src/corelib/concurrent/qfutureinterface.cpp
@@ -419,6 +419,16 @@ bool QFutureInterfaceBase::referenceCountIsOne() const
     return d->refCount == 1;
 }

+bool QFutureInterfaceBase::refT() const
+{
+    return d->refCount.refT();
+}
+
+bool QFutureInterfaceBase::derefT() const
+{
+    return d->refCount.derefT();
+}
+
 QFutureInterfaceBasePrivate::QFutureInterfaceBasePrivate(QFutureInterfaceBase::State initialState)
     : refCount(1), m_progressValue(0), m_progressMinimum(0), m_progressMaximum(0),
       state(initialState), pendingResults(0),
diff --git a/src/corelib/concurrent/qfutureinterface.h b/src/corelib/concurrent/qfutureinterface.h
index a31bcf1..4c5a26f 100644
--- a/src/corelib/concurrent/qfutureinterface.h
+++ b/src/corelib/concurrent/qfutureinterface.h
@@ -132,6 +132,8 @@ public:

 protected:
     bool referenceCountIsOne() const;
+    bool refT() const;
+    bool derefT() const;
 public:

 #ifndef QFUTURE_TEST
@@ -150,13 +152,17 @@ class QFutureInterface : public QFutureInterfaceBase
 public:
     QFutureInterface(State initialState = NoState)
         : QFutureInterfaceBase(initialState)
-    { }
+    {
+        refT();
+    }
     QFutureInterface(const QFutureInterface &other)
         : QFutureInterfaceBase(other)
-    { }
+    {
+        refT();
+    }
     ~QFutureInterface()
     {
-        if (referenceCountIsOne())
+        if (!derefT())
             resultStore().clear();
     }

@@ -165,7 +171,8 @@ public:

     QFutureInterface &operator=(const QFutureInterface &other)
     {
-        if (referenceCountIsOne())
+        other.refT();
+        if (!derefT())
             resultStore().clear();
         QFutureInterfaceBase::operator=(other);
         return *this;
diff --git a/src/corelib/concurrent/qfutureinterface_p.h b/src/corelib/concurrent/qfutureinterface_p.h
index ea52621..3a34cda 100644
--- a/src/corelib/concurrent/qfutureinterface_p.h
+++ b/src/corelib/concurrent/qfutureinterface_p.h
@@ -129,7 +129,31 @@ class QFutureInterfaceBasePrivate
 public:
     QFutureInterfaceBasePrivate(QFutureInterfaceBase::State initialState);

-    QAtomicInt refCount;
+    // When the last QFuture<T> reference is removed, we need to make
+    // sure that data stored in the ResultStore is cleaned out.
+    // Since QFutureInterfaceBasePrivate can be shared between QFuture<T>
+    // and QFuture<void> objects, we use a separate ref. counter
+    // to keep track of QFuture<T> objects.
+    class RefCount
+    {
+    public:
+        inline RefCount(int r = 0, int rt = 0)
+            : m_refCount(r), m_refCountT(rt) {}
+        // Default ref counter for QFIBP
+        inline bool ref() { return m_refCount.ref(); }
+        inline bool deref() { return m_refCount.deref(); }
+        // Ref counter for type T
+        inline bool refT() { return m_refCountT.ref(); }
+        inline bool derefT() { return m_refCountT.deref(); }
+        inline operator int() const { return int(m_refCount); }
+        inline bool operator==(int value) const { return m_refCount == value; }
+
+    private:
+        QAtomicInt m_refCount;
+        QAtomicInt m_refCountT;
+    };
+
+    RefCount refCount;
     mutable QMutex m_mutex;
     QWaitCondition waitCondition;
     QList<QFutureCallOutInterface *> outputConnections;
diff --git a/src/corelib/concurrent/qtconcurrentresultstore.h b/src/corelib/concurrent/qtconcurrentresultstore.h
index fb5ef2f..81cd992 100644
--- a/src/corelib/concurrent/qtconcurrentresultstore.h
+++ b/src/corelib/concurrent/qtconcurrentresultstore.h
@@ -177,7 +177,10 @@ public:

     int addResults(int index, const QVector<T> *results, int totalCount)
     {
-        return ResultStoreBase::addResults(index, new QVector<T>(*results), results->count(), totalCount);
+        if (m_filterMode && totalCount && !results->count())
+            return ResultStoreBase::addResults(index, 0, 0, totalCount);
+        else
+            return ResultStoreBase::addResults(index, new QVector<T>(*results), results->count(), totalCount);
     }

     int addCanceledResult(int index)