Ways to detect whether a C++ virtual function has been redefined in a derived class

Question

In brief: From a C++ base-class pointer which points to an instance of a derived class, how can one determine at run-time whether a non-pure virtual functio

Answer 1

And what if you didn't use virtual methods ?

At this point I am think of a template-base solution. It is possible (albeit not so easy) to use templates to detect whether a given class has a method with a certain signature, or not. Once identified, you can switch, at compile-time, between the lightweight scheme and the heavy scheme.

Note that I do not suggest that all the code be templated, the templated code will only cover the Template (Design Pattern) part of the solution, and the heavy-lifting can be done with regular functions to cut on dependencies.

Also, this can be completely transparent for the clients, providing you do not alter the signature of the methods.