What happens if someone is sentenced to house arrest but they do not have a residence?

If you are sentenced to house arrest, typically you have to provide Pre-Trial Services, Probation Department or the court with a viable address to where you will be living and where they can contact you if need be. Not having a residence nullifies the purpose of "house arrest", thus the only alternatives would be 1) Jail time 2) Tether monitoring or 3) Probation.