c++ – Keep boost asio io_service

There is never a copy of io_service (or the more recent io_context that replaces the deprecated io_service). That’s because it’s not copyable.

If you don’t maintain the lifetime while async operations have not completed, the behaviour is indeed undefined. However, it’s not too hard to make sure no async operations/completions happen by stopping the service forcibly gracefully awaiting for it to complete any pending operations.

I suggest the latter approach for production quality code.