Could someone provide an example for using RtAudioErrorCallback in constructor?

[mjsmithers]

I'm trying to move from RtAudio 5 to 6 and I can't figure out how to use the constructor with RtAudioErrorCallback.
RtAudio( RtAudio::Api api=UNSPECIFIED, RtAudioErrorCallback&& errorCallback=0 );

In RtAudio 5, I have

RtAudio * p = new RtAudio(RtAudio::WINDOWS_ASIO);
catch (RtAudioError &error) {
// report error here
}

but in RtAudio 6 I keep getting compile errors trying to do something like

RtAudioErrorCallback errorCallback;
RtAudio * p = new RtAudio(RtAudio::MACOSX_CORE, errorCallback);

What should the code look like to use RtAudioErrorCallback?

Thanks,
Michael