codrive | Advanced driver-assistance system | Computer Vision library

If you want an optional argument for a function or ctor, either write two which differ in arity, or use a default-argument (= whatever directly after the optional parameter-name).
Neither option has anything to do with std::optional.

Anyway, when you use std::optional, be aware that all pointers can be null anyway. Or put another way, they are all instances of std::optional. So how does a null pointer differ from getting no pointer in your case?

_{As an aside, it's int main().}