>Assertions MUST NOT be the only thing between misbehavior and input data, including data returned from other APIs (e.g. fopen calls, i.e. auto x = fopen ("foo"); assert (foo != NULL); is invalid). Anything dealing with foreign data must not assume anything about the state or contents of the data, and as such, cannot ever assert, as it doesn’t have an assertion to make. If you take away only one thing from this article, let it be this: assertions do not verify arbitrary inputs.

The author seems overconfident in this point. Like, what if the "input data" is from another software system I control?

Triggering an assert failure on bad user input is a little sloppy, but if there's no way to recover at that point anyways, I don't see why it matters.

Can someone enlighten me?