A strictly compliant compiler must behave exactly as specified in this document and in Andrew Appel's book, and as demonstrated by the samples exhibited in this document, and in the “Reports” document.
Nevertheless, you are entirely free to extend your compiler as you wish, as long as this extension is enabled by a non standard option. Extensions include:
isatty
, as the correction program will not appreciate.
In any case, if you don't implement an extension that was suggested (such as --hir-use-ix, then you must not accept the option. If the compiler accepts an option, then the effect of this option will be checked. For instance, if your compiler accepts --hir-use-ix but does not implement it, then be sure to get 0 on these tests.