Why explicitly declare classes special functions as "default" [duplicate]

Question

What is the difference between explicitly declaring classes special functions default.

class Myclass
{
public:

    Myclass() = default;
    virtual ~Myclass() = default;

    Myclass(MyClass&&) = default;
    Myclass& operator=(MyClass&&) = default;

    Myclass(const MyClass&) = default;
    Myclass& operator=(const MyClass&) = default;
};

MyClass{};

What is the difference between this 2 declarations? Why explicitly specify the default behavioral functions as default??

Answer 1

Because under certain conditions the compiler might not add the constructors, destructor or operators even though you may want the compiler-generated defaults. Then by using the explicit default designator the compiler will do that anyway.

You can find out more in e.g. this class reference.