What modern interpretation? As long as C has been standardized, undefined behaviour has meant nasal demons.<p>There&#x27;s an argument to be had that some undefined behaviour should rather be unspecified or implementation-defined, but compilers making use of it for aggressive optimization? That&#x27;s by design.<p>Quoting another article by John Regehr:<p><i>My view is that exploiting undefined behavior can sometimes be OK if a good debugging tool is available to find the undefined behavior.</i><p>Thus -fsanitize=undefined.