Author here. Let's deconstruct your comment and see if it makes me dumber having read it.

P1: I'm sure the article is not the reason for you feeling dumber.

P2: It's a probability, something that as a programmer I'm sure you don't really understand so I can let it pass for now. Incidentally, your last sentence in that paragraph proves this.

P3: The safercopy does behave correctly on all the inputs, and these kinds of functions do exist. In fact I use them in the rest of the book and if you want to use them too there's libraries like bstring and safestring that do this. You could also just not use C.

P4: Wow, you flagged it....for being awful? Does that make you feel powerful today? You should go ask for a raise too. And demand kinky sex from your partner...assuming you have sex that is.