limit_reference: Make constructor explicit.

murraycu · murraycu · commit 32f583948824 · 2016-04-22T10:08:04.000+02:00
diff --git a/sigc++/limit_reference.h b/sigc++/limit_reference.h
@@ -56,7 +56,7 @@ class limit_reference
   /** Constructor.
    * @param target The reference to limit.
    */
-  limit_reference(reference_type& target) : visited(target) {}
+  explicit limit_reference(reference_type& target) : visited(target) {}
 
   /** Retrieve the entity to visit for visit_each().
    * Depending on the template specialization, this is either a derived reference, or
