Let QLoggingCategory::defaultCategory return a pointer

The pointer can be null. Going trough the reference invokes undefined
behavior here.

Change-Id: Ia84e4e732cdcbbaee0f5f0679765d18069ea8b2d
Reviewed-by: Kai Koehne <kai.koehne@digia.com>

3 files changed, 13 insertions, 6 deletions

diff --git a/src/corelib/global/qlogging.cpp b/src/corelib/global/qlogging.cpp
index 063e94069f..b9b5173881 100644
--- a/src/corelib/global/qlogging.cpp
+++ b/src/corelib/global/qlogging.cpp
@@ -927,7 +927,7 @@ static void qt_message_print(QtMsgType msgType, const QMessageLogContext &contex
 #ifndef QT_BOOTSTRAPPED
     // qDebug, qWarning, ... macros do not check whether category is enabled
     if (!context.category || (strcmp(context.category, "default") == 0)) {
-        if (QLoggingCategory *defaultCategory = &QLoggingCategory::defaultCategory()) {
+        if (QLoggingCategory *defaultCategory = QLoggingCategory::defaultCategory()) {
             if (!defaultCategory->isEnabled(msgType))
                 return;
         }
diff --git a/src/corelib/io/qloggingcategory.cpp b/src/corelib/io/qloggingcategory.cpp
index 6c5df1e8e7..2ef392c209 100644
--- a/src/corelib/io/qloggingcategory.cpp
+++ b/src/corelib/io/qloggingcategory.cpp
@@ -244,12 +244,19 @@ void QLoggingCategory::setEnabled(QtMsgType type, bool enable)
  */
 
 /*!
-    Returns the category \c "default" that is used e.g. by qDebug(), qWarning(),
-    qCritical(), qFatal().
+    Returns a pointer to the global category \c "default" that
+    is used e.g. by qDebug(), qWarning(), qCritical(), qFatal().
+
+    \note The returned pointer may be null during destruction of
+    static objects.
+
+    \note Ownership of the category is not transferred, do not
+    \c delete the returned pointer.
+
  */
-QLoggingCategory &QLoggingCategory::defaultCategory()
+QLoggingCategory *QLoggingCategory::defaultCategory()
 {
-    return *qtDefaultCategory();
+    return qtDefaultCategory();
 }
 
 /*!
diff --git a/src/corelib/io/qloggingcategory.h b/src/corelib/io/qloggingcategory.h
index 35da04c8f2..6009226127 100644
--- a/src/corelib/io/qloggingcategory.h
+++ b/src/corelib/io/qloggingcategory.h
@@ -72,7 +72,7 @@ public:
     // allows usage of both factory method and variable in qCX macros
     QLoggingCategory &operator()() { return *this; }
 
-    static QLoggingCategory &defaultCategory();
+    static QLoggingCategory *defaultCategory();
 
     typedef void (*CategoryFilter)(QLoggingCategory*);
     static CategoryFilter installFilter(CategoryFilter);