It's not using heuristics. It's how the code is actually written. An implementation of std::list<T> is going to contain multiple objects of type __node<T>. __

It's not using heuristics. It's how the code is actually written. An implementation of std::list<T> is going to contain multiple objects of type __node<T>. __node<T> would be defined as: template <typename T> struct __node { __node *prev; __node *next; T value; }; (Note that this doesn't change what anyone else said though, T is a pointer in this particular case, so there's still another indirection)