That'd only be the case if you're not using things like unique_ptr / shared_ptr. Or if you have a really funky entangled ownership model such that a split-copy

That'd only be the case if you're not using things like unique_ptr / shared_ptr. Or if you have a really funky entangled ownership model such that a split-copy ends up leaving you in a confused ownership model such that the destructor doesn't do the right thing. And you didn't catch the exception to patch that up before propagating it. That seems like a bit of a stretch to come up with hitting such a scenario, and if you do it doesn't seem like a copy & swap idiom is really the solution.