Comment by neoteric

Absolutely, RAII is an abstraction (and a useful one), but it has a cost in that it prevents a form of useful optimization because cleanup is required at the destruction of the stack frame. You'd expect the same in C if you explicitly had to call a cleanup function on return from a call.

What C++ does with RAII is make this tradeoff not obvious. std::unique_ptr is a great example to show this: colloquially a std::unique_ptr is "just a pointer", but it isn't in this case because it's non-trivial destructor prevents TCO.