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)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 58 insertions, 1 deletions

diff --git a/tests/auto/corelib/tools/qlist/tst_qlist.cpp b/tests/auto/corelib/tools/qlist/tst_qlist.cpp
index d977e1cb97..c4b338f0f2 100644
--- a/tests/auto/corelib/tools/qlist/tst_qlist.cpp
+++ b/tests/auto/corelib/tools/qlist/tst_qlist.cpp
@@ -347,8 +347,13 @@ private slots:
     void emplaceWithElementFromTheSameContainer_data();
 
     void fromReadOnlyData() const;
-
     void qtbug_90359() 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;
@@ -378,6 +383,10 @@ 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;
 };
 
 
@@ -3264,5 +3273,53 @@ void tst_QList::qtbug_90359() 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"