関連ワード:  cpp unique_ptr vs shared_ptr    c++ unique_ptr vs shared_ptr performance    cpp unique pointer vs shared pointer    c++ unique_ptr or shared_ptr    c++ return unique_ptr or shared_ptr    cpp unique_ptr to shared_ptr    c++ when to use unique_ptr vs shared_ptr    c++ unique_ptr shared_ptr 区别    difference between unique_ptr and shared_ptr in c++    c++ shared_ptr vs unique_ptr vs weak_ptr