Comment by fc417fc802

It's subtly wrong, just like most of the rest of the commentary in this comment section. Yes, crypt is specified to return NULL on failure but if you read the rest of that page it is only permitted to fail with ENOSYS. The spec does not allow for failure for any other reason.

So if you're strictly adhering to the spec in this case then unfortunately NULL is not an acceptable way to signal a generic error condition. Hence all the seemingly bizarre special values. (In a strange turn of events all those experts doing things that looked weird turned out to know what they were doing. Go figure.)