What are defaulted destructors used for?

Question

I can understand defaulted constructors, since user defined constructors will disable the compiler generated ones making the object non trivially copyable etc.

In the destructor case, apart from changing access category, what use is there to define a defaulted destructor considering that no user defined member function can disable them (you can't overload destructors anyway) ?

// Which version should I choose ? 
struct Example 
{
    //1. ~Example() = default; 
    //2. ~Example() {}
    //3. 
}; 

Even in the case of virtual destructors, defaulting them would not make them trivial so what good is it doing it?

Answer 1

The exception for trivial destructors omission has to do with the derived class' destructor, not the base one. So virtual ~Foo() = default; is a useful construct to keep the default destructor, but virtualize it.

Answer 2

One use is making the destructor protected or private while potentially keeping the class trivial: just list it after the desired access specifier.

Another: when writing classes, some programmers like to order the class's functions: e.g. constructors, then the destructor, then the non-const "mutating" members, then the const "accessor" members, then static functions. By being able to explicitly = default the destructor, you can list it in the expected order and the reader looking there knows there can't be another misplaced version of it. In large classes, that may have some documentary/safety value.

It also gives you something concrete around which to add comments, which can help some documentation tools realise the comments relate to destruction.