Resurrect data moves in QList

Use the data moves to readjust the free space in the QList,
which ultimately fixes the out-of-memory issues caused by
cases like:
forever {
  list.prepend(list.back());
  list.removeLast();
}

Task-number: QTBUG-91801
Task-number: QTBUG-91360
Task-number: QTBUG-93019
Change-Id: Iacff69cbf36b8b5b176bb2663df635ec972c875c
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
(cherry picked from commit a0253f5f0249024580050e4ec22d50cb139ef8d9)

2 files changed, 59 insertions, 16 deletions

diff --git a/tests/auto/corelib/tools/qarraydata/simplevector.h b/tests/auto/corelib/tools/qarraydata/simplevector.h
index 747af3d422..1fc5e9b8e1 100644
--- a/tests/auto/corelib/tools/qarraydata/simplevector.h
+++ b/tests/auto/corelib/tools/qarraydata/simplevector.h
@@ -209,22 +209,7 @@ public:
         d->insert(0, first, last - first);
     }
 
-    void append(const_iterator first, const_iterator last)
-    {
-        if (first == last)
-            return;
-
-        auto requiredSize = qsizetype(last - first);
-        if (d->needsDetach() || d.freeSpaceAtEnd() < requiredSize) {
-            DataPointer oldData;
-            d.reallocateAndGrow(QArrayData::GrowsAtEnd, requiredSize, &oldData);
-
-            d->copyAppend(first, last);
-            return;
-        }
-
-        d->copyAppend(first, last);
-    }
+    void append(const_iterator first, const_iterator last) { d->growAppend(first, last); }
 
     void insert(int position, const_iterator first, const_iterator last)
     {
diff --git a/tests/auto/corelib/tools/qlist/tst_qlist.cpp b/tests/auto/corelib/tools/qlist/tst_qlist.cpp
index 323c1f5136..34baf3baef 100644
--- a/tests/auto/corelib/tools/qlist/tst_qlist.cpp
+++ b/tests/auto/corelib/tools/qlist/tst_qlist.cpp
@@ -375,6 +375,12 @@ private slots:
     void emplaceWithElementFromTheSameContainer_data();
     void fromReadOnlyData() const;
     void reallocateCustomAlignedType_qtbug90359() const;
+    void reinsertToBeginInt_qtbug91360() const { reinsertToBegin<int>(); }
+    void reinsertToBeginMovable_qtbug91360() const { reinsertToBegin<Movable>(); }
+    void reinsertToBeginCustom_qtbug91360() const { reinsertToBegin<Custom>(); }
+    void reinsertToEndInt_qtbug91360() const { reinsertToEnd<int>(); }
+    void reinsertToEndMovable_qtbug91360() const { reinsertToEnd<Movable>(); }
+    void reinsertToEndCustom_qtbug91360() const { reinsertToEnd<Custom>(); }
 
 private:
     template<typename T> void copyConstructor() const;
@@ -405,6 +411,10 @@ private:
     template<typename T> void detachThreadSafety() const;
     template<typename T> void emplaceImpl() const;
     template<typename T> void emplaceConsistentWithStdVectorImpl() const;
+    template<typename T>
+    void reinsertToBegin() const;
+    template<typename T>
+    void reinsertToEnd() const;
 };
 
 
@@ -2844,5 +2854,53 @@ void tst_QList::reallocateCustomAlignedType_qtbug90359() const
     QCOMPARE(actual, expected);
 }
 
+template<typename T>
+void tst_QList::reinsertToBegin() const
+{
+    QList<T> list(1);
+    const auto reinsert = [](QList<T> &list) {
+        list.prepend(list.back());
+        list.removeLast();
+    };
+
+    // this constant is big enough for the QList to stop reallocating, after
+    // all, size is always less than 3
+    const int maxIters = 128;
+    for (int i = 0; i < maxIters; ++i) {
+        reinsert(list);
+    }
+
+    // if QList continues to grow, it's an error
+    qsizetype capacity = list.capacity();
+    for (int i = 0, enoughIters = int(capacity) * 2; i < enoughIters; ++i) {
+        reinsert(list);
+        QCOMPARE(capacity, list.capacity());
+    }
+}
+
+template<typename T>
+void tst_QList::reinsertToEnd() const
+{
+    QList<T> list(1);
+    const auto reinsert = [](QList<T> &list) {
+        list.append(list.front());
+        list.removeFirst();
+    };
+
+    // this constant is big enough for the QList to stop reallocating, after
+    // all, size is always less than 3
+    const int maxIters = 128;
+    for (int i = 0; i < maxIters; ++i) {
+        reinsert(list);
+    }
+
+    // if QList continues to grow, it's an error
+    qsizetype capacity = list.capacity();
+    for (int i = 0, enoughIters = int(capacity) * 2; i < enoughIters; ++i) {
+        reinsert(list);
+        QCOMPARE(capacity, list.capacity());
+    }
+}
+
 QTEST_MAIN(tst_QList)
 #include "tst_qlist.moc"