&gt; So what do you do when an index into an array is out of bounds at run-time. You can&#x27;t perform a check every time because that would go against the C&#x27;s principle, and at the same time it would degrade performance, making it less useful compared to newer languages.<p>Bounds checks are not really a problem <i>if</i> you get rid of for loops in favor of constructions that eliminate bounds checks by construction (e.g. iterators). Of course, they&#x27;re still problems in languages that continue the tradition of C-style for loops.<p>This is a classic example of how just defining away undefined behavior can make <i>C</i> unacceptably slow, but does not necessarily make other languages unacceptably slow.