继承自std :: exception，std :: exception的定义含糊不清

So I am a little confused, I have been looking around trying to determine an appropriate way of inheriting from std::exception for my own type. Now according to cplusplus.com (and i know this isn't necessarily the standard, thats why I'm asking), std::exception is a base class with no members. However, after looking at my implementation of the standard library (VS 2005), the class std::exception is quite clearly defined with two member variables:So I am a little confused, I have been looking