How does returning std::make_unique work?

Question

I have a base class and its subclass:

class Base {
    public:
    virtual void hi() {
        cout << \"hi\" << endl;
    } 
};

class Derived : pub         


        

Answer 1

You will find that std::unique_ptr can move from derived's to base's, if you look into its definition. Basically is_convertible here check this situation.

   /** @brief Converting constructor from another type
   *
   * Requires that the pointer owned by @p __u is convertible to the
   * type of pointer owned by this object, @p __u does not own an array,
   * and @p __u has a compatible deleter type.
   */
  template,
       typename conditional::value,
                is_same<_Ep, _Dp>,
                is_convertible<_Ep, _Dp>>::type>>
unique_ptr(unique_ptr<_Up, _Ep>&& __u) noexcept
: _M_t(__u.release(), std::forward<_Ep>(__u.get_deleter()))
{ }