Could C++ have ARC?

Development C++ interoperability
1

Part of my codebase is C++ called from Swift and I've gotta do some refcounting myself.

Wouldn't it be great if C++ objects could be ARC'd like Swift and ObjC objects? Something like:

[[arc]] class MyCoolThing {
    ...
};

I wouldn't have to use smart pointers to manage the lifetime of MyCoolThing on the C++ side. Currently, I can't manage classes exposed to Swift using std::shared_ptr (right?) so I'd have to create my own smart pointer, or find some other intrusive reference counted smart pointer or just manually retain/release.

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2

I think mixing ARC in with all the existing facilities for memory management in C++ would further complicate the situation (there are already so many ways to manage lifetime in C++). If you really want this you can maybe use ObjC++.

How are you managing memory today? If you are using a smart pointer (including shared_ptr), it should come into Swift and be managed automatically. If you are using some intrusive reference counting, you can use Foreign Reference Types to import your C++ type as a Swift class with automatic reference counting.

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3

Right now I use SWIFT_SHARED_REFERENCE and I derive from an IntrusiveRefCounted just like the page you linked says. But it's not the most ergonomic solution if you're sharing ownership with other C++ objects.

I could embed a shared_ptr in some wrapper class and expose that to swift, but then I'd have to write wrapper functions.

Under the Shared Reference Types section, it says:

Other types that rely on std::shared_ptr for reference counting can still be used as value types in Swift.

What does that mean? Is that just referring to wrapping stuff in a class like this?

class MyCoolWrapper {
   std::shared_ptr<MyCoolThing> _ptr;
  public:
   void myCoolFunction() { _ptr->myCoolFunction(); }
}