Like using std::shared_ptr<T> in C++ or Rc<T> (or Arc<T>, which in that case stands for atomic, not automatic) in Rust. That is, you as a programmer choose for

Like using std::shared_ptr<T> in C++ or Rc<T> (or Arc<T>, which in that case stands for atomic, not automatic) in Rust. That is, you as a programmer choose for which variables to use reference counting.