The Importance of Contract Violation Handlers in C++

I'm perplexed about the premise that just writing while true after user do you want to quit if the user says yes break is undefined behavior right now in C++. How did the program interrupt was there some sort of signal and the external button being pressed or something? Yeah, I think it was interrupt based. It was a long time ago. So infinite loop is a UB. Maybe if the compiler can demonstrate that in no case that if becomes true and then in no case the program will break, then there is a problem. But otherwise, I Think it shouldn't be fine.