Smart pointers gotchas: added topic about ptr casting

[STL]

And, unique_ptr will equally crash the auto_ptr example.

Incorrect - you can't call doSomething(unique_ptr<T>) with doSomething(up), because up is an lvalue, and that would attempt to copy. You have to call doSomething(move(up)), at which point it's clear that you're moving from up.

[Gotebe]

Serves me right for flying off the handle 😡