Fix access to uninitialized values in QtXmlPatterns

Fixes valgrind warning like below when executing tst_QXmlQuery::copyConstructor()
  Conditional jump or move depends on uninitialised value(s)
    at: QPatternist::NodeIndexStorage::operator!=(QPatternist::NodeIndexStorage const&) const (q
    by: QXmlItem::operator=(QXmlItem const&) (qabstractxmlnodemodel.cpp:1228)

Reason for the warning is that QPatternist::NodeIndexStorage::operator!=
accesses all fields of NodeIndexStorage, which are all not intialized in
every execution path of QXmlItem::QXmlItem(const QVariant &) and class
QPatternist::Item constructors.

Fixed by adding NodeIndexStorage::reset() function that resets all fields
and put a call to that function where NodeIndexStorage objects were
previously incompletely initialized. Note that unfortunately class
NodeIndexStorage cannot have a default constructor, because it is used as
a union field.

Change-Id: I686433ba552f025658f7e583226e77346db82159
(cherry picked from commit f42f82f435d738339ad85c1380d1167338517247)
(cherry picked from commit 65d2458408ccda1b37e1069fd13791a60fa0c672)
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>

2 files changed, 10 insertions, 12 deletions

diff --git a/src/xmlpatterns/api/qabstractxmlnodemodel.cpp b/src/xmlpatterns/api/qabstractxmlnodemodel.cpp
index 81c6473..e0a04f7 100644
--- a/src/xmlpatterns/api/qabstractxmlnodemodel.cpp
+++ b/src/xmlpatterns/api/qabstractxmlnodemodel.cpp
@@ -1138,9 +1138,7 @@ bool QAbstractXmlNodeModel::isDeepEqual(const QXmlNodeModelIndex &n1,
  */
 QXmlItem::QXmlItem()
 {
-    m_node.model = 0;
-    m_node.data = 0;
-    m_node.additionalData = 0;
+    m_node.reset();
 }
 
 bool QXmlItem::internalIsAtomicValue() const
@@ -1164,12 +1162,10 @@ QXmlItem::QXmlItem(const QXmlItem &other) : m_node(other.m_node)
  */
 QXmlItem::QXmlItem(const QVariant &atomicValue)
 {
+    m_node.reset();
     if(atomicValue.isNull())
     {
         /* Then we behave just like the default constructor. */
-        m_node.model = 0;
-        m_node.data = 0;
-        m_node.additionalData = 0;
         return;
     }
 
@@ -1188,10 +1184,7 @@ QXmlItem::QXmlItem(const QVariant &atomicValue)
     else
     {
         m_atomicValue = 0;
-        m_node.model = 0;
     }
-
-    m_node.additionalData = 0;
 }
 
 /*!
diff --git a/src/xmlpatterns/api/qabstractxmlnodemodel.h b/src/xmlpatterns/api/qabstractxmlnodemodel.h
index f8663ed..8c2f7ec 100644
--- a/src/xmlpatterns/api/qabstractxmlnodemodel.h
+++ b/src/xmlpatterns/api/qabstractxmlnodemodel.h
@@ -105,6 +105,13 @@ namespace QPatternist
 
         /* Implementation is in qabstractxmlnodemodel.cpp. */
         inline bool operator!=(const NodeIndexStorage &other) const;
+
+        void reset()
+        {
+            data = 0;
+            additionalData = 0;
+            model = 0;
+        }
     };
 }
 
@@ -217,9 +224,7 @@ public:
 
     inline void reset()
     {
-        m_storage.data = 0;
-        m_storage.additionalData = 0;
-        m_storage.model = 0;
+        m_storage.reset();
     }
 
 private: