I think people are misunderstanding this; it's pedagogical. From the link: 'I want to use it as an exercise for you in finding hacks, attacks, defects, and bug

I think people are misunderstanding this; it's pedagogical. From the link: 'I want to use it as an exercise for you in finding hacks, attacks, defects, and bugs by going through "K&R C" to break all the code...When you are done doing this, you will have a finely honed eye for defect.' He's trying to train his readers to think about places code can break.