移动构造函数

class HasPtrMem 
{
public:
    HasPtrMem() : d(new int(3)) 
    {
        cout << "Construct: " << ++n_cstr << endl;
    }

    HasPtrMem(const HasPtrMem & h) : d(new int(*h.d)) 
    {
        cout << "Copy construct: " << ++n_cptr << endl;
    }

    HasPtrMem(HasPtrMem && h) : d(h.d)    // 移动构造函数
    { 
        h.d = nullptr;                  // 将临时值的指针成员置空
        cout << "Move construct: " << ++n_mvtr << endl;
    }

    ~HasPtrMem() 
    {
        delete d;
        cout << "Destruct: " << ++n_dstr << endl;
    }

    int * d;
    static int n_cstr;
    static int n_dstr;
    static int n_cptr;
    static int n_mvtr;
};