XXX in a comment is usually a heads-up. It could be:
- Something that’s not implemented completely correctly.
- Something that should be fixed later on.
- Highlighting a possible problem spot.
- Something you’re not sure about, a question.
I’ve often preferred a more descriptive tag like FIXME or TODO or HACK. XXX is often used as a catch all for the above.
Searching for ‘XXX’ on the FreeBSD code cross reference is a good example of many of the uses. There are thousands…