Yes, I agree especially for code intended to teach something else it's not a good idea to include GCCisms. I didn't find any section about compilation set-up (

Yes, I agree especially for code intended to teach something else it's not a good idea to include GCCisms. I didn't find any section about compilation set-up (compiler, warning levels, flags etc) at all in the OP, but didn't spend a lot of time looking. Perhaps it would be a good addition too to specify which dialect of C is used.