The C++ virtual method call is faster on the Uno than both the switch-case and the function pointer versions. The additional function call and switch-case case processing took a toll for the Uno.

I have read in several books (including a book on using QT toolkit) warning about using C++'s virtual function because of performance penalty.But they are quite vague on why this is so. Can ...

Nevertheless, I'd be surprised if the proper behavior for your example code above were standardized; any C++ gurus know for sure?