Merge branch 'clang.AthenaMonitoring-20170911' into 'master'

AthenaMonitoring: Fix compilation with clang 4.0.1.

See merge request !4585

Control/AthenaMonitoring/AthenaMonitoring/MonitoredCollection.h

@@ -119,8 +119,11 @@ namespace Monitored {
             using value_type = typename detail::get_value_type<T>::value_type;
 
             /// @brief .     \if empty doc string required due to doxygen bug 787131 \endif
-            friend MonitoredObjectsCollection<T> declare<T>(std::string name, const T& collection, 
-                                                            std::function<double(const value_type&)> converterToDouble);
+            // With a non-template friend declaration, clang 4.0.1
+            // fails to match the friend.
+            template <class U>
+            friend MonitoredObjectsCollection<U> declare(std::string name, const U& collection, 
+                                                         std::function<double(const typename MonitoredObjectsCollection<U>::value_type&)> converterToDouble);
             
             MonitoredObjectsCollection(MonitoredObjectsCollection&&) = default;
             

Control/AthenaMonitoring/AthenaMonitoring/MonitoredScalar.h

@@ -40,6 +40,12 @@ namespace Monitored {
 	    
             operator T() const { return m_value; }
             operator T&() { return m_value; }
+
+            // Needed to work around an apparent bug in clang 4.0.1.
+            // Without these declarations, clang rejects `--SCALAR'
+            // (but ++SCALAR, SCALAR++, and SCALAR-- are all accepted!).
+            T operator--() { return --m_value; }
+            T operator--(int) { return m_value--; }
             
             const std::vector<double> getVectorRepresentation() const override { return { double(m_value) }; }
         private: