On 3/13/25 15:43, Jennifier Burnett wrote:
> Could you elaborate on these? You've given some examples of move assignments, but I'm not sure how that would translate to move _construction_, since the examples here seem to be based around the fact that you're assigning to an already existing object rather than constructing a completely new one?
>
> Maybe an example of these translated to use trivial relocation would make it clearer?

AFAIUI, if a type is replaceable, then it's possible to, er, replace
move assignment with destruction + reconstruction. So if std::shared_ptr
is replaceable, it should be possible to rewrite the previous code as:

    template <class T>
    void replace (T& dest, T&& src) {
        dest.~T ();
        new (std::addressof (dest)) T (std::forward<T> (src));
    }

    struct X {
        std::shared_ptr<X> x;
    };

    int main () {
        std::shared_ptr<X> x = std::make_shared<X> ();

        x->x = std::make_shared<X> ();

        replace (x, std::move (x)); // (1)
        replace (x, std::move (x->x)); // (2)
    }

But since, in these cases, destroying `dest` causes the destruction of
`src` before reconstruction, that's obviously invalid.