Memory write errors (some times induced by UB) in one place of the program can easily propagate and later fail in a very different location of the program, with

Memory write errors (some times induced by UB) in one place of the program can easily propagate and later fail in a very different location of the program, with absolutely zero diagnostics of why your variable suddenly had a value out of possible range. This is why valgrind, asan and friends exist. They move the error diagnostic to the place where error actually happened.