Fix QSharedPointer crashing when it is used as a global static in an application.

If it's used as a static, then the order of destruction is
ill-defined. The QSharedPointer object may be destroyed after our
Q_GLOBAL_STATIC knownPointers has been deleted, thus causing a
null-pointer dereference.

Reviewed-by: Peter Hartmann <peter.hartmann@nokia.com>
Task-number: 246843

1 files changed, 13 insertions, 5 deletions

diff --git a/src/corelib/tools/qsharedpointer.cpp b/src/corelib/tools/qsharedpointer.cpp
index d8a9923..c3a989e 100644
--- a/src/corelib/tools/qsharedpointer.cpp
+++ b/src/corelib/tools/qsharedpointer.cpp
@@ -842,15 +842,19 @@ QT_BEGIN_NAMESPACE
 */
 void QtSharedPointer::internalSafetyCheckAdd(const volatile void *ptr)
 {
-    QMutexLocker lock(&knownPointers()->mutex);
+    KnownPointers *const kp = knownPointers();
+    if (!kp)
+        return;                 // end-game: the application is being destroyed already
+
+    QMutexLocker lock(&kp->mutex);
     void *actual = const_cast<void*>(ptr);
-    if (knownPointers()->values.contains(actual)) {
+    if (kp->values.contains(actual)) {
         printBacktrace(knownPointers()->values.value(actual));
         qFatal("QSharedPointerData: internal self-check failed: pointer %p was already tracked "
                "by another QSharedPointerData object", actual);
     }
 
-    knownPointers()->values.insert(actual, saveBacktrace());
+    kp->values.insert(actual, saveBacktrace());
 }
 
 /*!
@@ -858,9 +862,13 @@ void QtSharedPointer::internalSafetyCheckAdd(const volatile void *ptr)
 */
 void QtSharedPointer::internalSafetyCheckRemove(const volatile void *ptr)
 {
-    QMutexLocker lock(&knownPointers()->mutex);
+    KnownPointers *const kp = knownPointers();
+    if (!kp)
+        return;                 // end-game: the application is being destroyed already
+
+    QMutexLocker lock(&kp->mutex);
     void *actual = const_cast<void*>(ptr);
-    knownPointers()->values.remove(actual);
+    kp->values.remove(actual);
 }
 
 QT_END_NAMESPACE