Why does the insertion of user defined destructor require an user defined copy constructor

Question

The following code compiles:

#include 
#include 
#include 

using namespace std;

class container
{
public:
    conta         


        

Answer 1

The idea is that, if the compiler-generated destructor is not good enough for your class, then chances are the copy constructor and copy assignment operator are also not good enough, so the compiler may delete the implicit implementations of those copy operations. Technically, the compiler may still give you implicit copy operations even if you have a user-defined destructor, but that behavior is deprecated in c++11.

See Rule of Three

AFAIK, you still need a copy constructor because buildShip() returns by value.

(However, it's interesting that you are able to compile the versions that use an implicit copy constructor. You shouldn't be able to do that because of the unique_ptr member...)