It can get truly bizarre with multiple threads. Some other thread hits some UB and suddenly your code has garbage register states. I've had someone UB the fp register stack in another thread so that when I tried to use it, I got their values for a bit, and then NaN when it ran out. Static analysis had caught their mistake, and then a group of my peers looked at it and said it was a false warning leaving me to find it long afterwards... I don't work with them anymore, and my new project is using rust, but it doesn't really matter if people sign off on code reviews that have unsafe{doHorribleStuff()}