QtConcurrent: Fix for leak in QFuture

To avoid leaking when converting a QFuture<T> to a QFuture<void> we need
to have a separate ref. counter for QFuture<T>. When the last QFuture<T>
goes out of scope, we need to clean out the result data.

backported from qt/qtbase commit 731ba8ed08f80644b403556638c7f6229e678ebe
Original commit by Christian Strømme

Task-number: QTBUG-27224
Change-Id: I0c6b525cf241b5c559a1bab4e0066cd4de556ea8
Reviewed-by: Christian Stromme <christian.stromme@digia.com>

1 files changed, 22 insertions, 8 deletions

diff --git a/tests/auto/qfuture/tst_qfuture.cpp b/tests/auto/qfuture/tst_qfuture.cpp
index f6ed5a9..0f1836c 100644
--- a/tests/auto/qfuture/tst_qfuture.cpp
+++ b/tests/auto/qfuture/tst_qfuture.cpp
@@ -1282,18 +1282,32 @@ void tst_QFuture::throttling()
 
 void tst_QFuture::voidConversions()
 {
-    QFutureInterface<int> iface;
-    iface.reportStarted();
+    {
+        QFutureInterface<int> iface;
+        iface.reportStarted();
 
-    QFuture<int> intFuture(&iface);
+        QFuture<int> intFuture(&iface);
+        int value = 10;
+        iface.reportFinished(&value);
 
-    int value = 10;
-    iface.reportFinished(&value);
+        QFuture<void> voidFuture(intFuture);
+        voidFuture = intFuture;
+
+        QVERIFY(voidFuture == intFuture);
+    }
 
-    QFuture<void> voidFuture(intFuture);
-    voidFuture = intFuture;
+    {
+        QFuture<void> voidFuture;
+        {
+            QFutureInterface<QList<int> > iface;
+            iface.reportStarted();
 
-    QVERIFY(voidFuture == intFuture);
+            QFuture<QList<int> > listFuture(&iface);
+            iface.reportResult(QList<int>() << 1 << 2 << 3);
+            voidFuture = listFuture;
+        }
+        QCOMPARE(voidFuture.resultCount(), 0);
+    }
 }