Fastest `finally` for C++ [closed]

Answer 1

You can implement Finally without type erasure and overhead of std::function:

template 
class Finally {
    F f;
public:
    template 
    Finally(Func&& func) : f(std::forward(func)) {}
    ~Finally() { f(); }

    Finally(const Finally&) = delete;
    Finally(Finally&&) = delete;
    Finally& operator =(const Finally&) = delete;
    Finally& operator =(Finally&&) = delete;
};

template 
Finally make_finally(F&& f)
{
    return { std::forward(f) };
}

And use it like:

auto&& doFinally = make_finally([&] { var++; });

Demo