Don't crash by modifying read-only shared_null

Functions that modify the d-pointer must detach or otherwise take
measures to not modify the const, read-only shared_null.

The setSharable(bool) function takes care to detach when setting
sharable to false, but should avoid setting the sharable data member
unless d is not the shared null.

Similarly, QMap<Key, T>::setInsertInOrder() needs to detach if it is
shared with the shared_null (the logic has been updated to be the same
as setSharable()).

Change-Id: Ida5cb9818b86695f1b9f0264418b955c56424898
Reviewed-on: http://codereview.qt-project.org/5929
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Bradley T. Hughes <bradley.hughes@nokia.com>
Reviewed-by: Jan-Arve Sæther <jan-arve.saether@nokia.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/tests/auto/corelib/tools/qlist/tst_qlist.cpp b/tests/auto/corelib/tools/qlist/tst_qlist.cpp
index 3901b6ffe8..3d062919da 100644
--- a/tests/auto/corelib/tools/qlist/tst_qlist.cpp
+++ b/tests/auto/corelib/tools/qlist/tst_qlist.cpp
@@ -91,6 +91,8 @@ private slots:
     void testOperators() const;
 
     void initializeList() const;
+
+    void const_shared_null() const;
 };
 
 void tst_QList::length() const
@@ -688,5 +690,16 @@ void tst_QList::initializeList() const
 #endif
 }
 
+void tst_QList::const_shared_null() const
+{
+    QList<int> list1;
+    list1.setSharable(false);
+    QVERIFY(list1.isDetached());
+
+    QList<int> list2;
+    list2.setSharable(true);
+    QVERIFY(!list2.isDetached());
+}
+
 QTEST_APPLESS_MAIN(tst_QList)
 #include "tst_qlist.moc"