refs #495 Workaround lack of atomic operations on std::shared_ptr in GCC 4.9.

src/blackmisc/lockfree.cpp

@@ -0,0 +1,23 @@
+/* Copyright (C) 2015
+* swift project Community / Contributors
+*
+* This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+* directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+* including this file, may be copied, modified, propagated, or distributed except according to the terms
+* contained in the LICENSE file.
+*/
+
+#include "lockfree.h"
+
+namespace BlackMisc
+{
+    namespace Private
+    {
+        // this is only needed for GCC <= 4.9, but we define it for all compilers to avoid warning about empty cpp file
+        QMutex *atomicSharedPtrMutex()
+        {
+            static QMutex mutex(QMutex::Recursive);
+            return &mutex;
+        }
+    }
+};