attribute ((cleanup(f)): according to the documentation, this variable attribute would call the function f on the variable before exiting the current scope.
I was delighted.

How should you prefer to pass smart pointers, and why?

So what does this have to do with make_shared? An std::shared_ptr is a relatively complex beast that has to do atomic reference counting and efficient destruction dispatching and things like that. As such, a relatively large amount of code is instantiated for each std::shared_ptr<> type.