From Hartwig Wiesmann, "in the files Image, Observer and TerrainTechnique unused parameters exist resulting in a couple of compiler warnings (depending on the compiler settings though).

The attached patches comment out the unused parameter names.
"

include/osg/Observer

@@ -64,7 +64,7 @@ class OSG_EXPORT ObserverSet : public osg::Referenced
     protected:
 
         ObserverSet(const ObserverSet& rhs): osg::Referenced(rhs) {}
-        ObserverSet& operator = (const ObserverSet& rhs) { return *this; }
+        ObserverSet& operator = (const ObserverSet& /*rhs*/) { return *this; }
         virtual ~ObserverSet();
 
         mutable OpenThreads::Mutex      _mutex;