If your patch enforcing that a function tagged with noreturn does not return (so core.stdc.stdlib.exit must be tagged with noreturn)?
It isn't currently compulsory. Any noreturn function will still compile without the attribute. If adopted, it would of course be prudent to make stdlib.exit noreturn (though I haven't bothered with it, as I haven't used stdlib.exit yet)
A more general comment: in few years I have seen lot of wasted work done on D/DMD. So I suggest first to discuss a feature, to find some kind of (partial) consensus that it's an acceptable idea, and only then, try to implement it. Otherwise I think time is better spent fixing bugs, implementing popular (well voted) enhancement requests of Bugzilla, or even better helping the review of already written patches and applying them: at the moment creating more pull requests is not the top priority because currently there are about 115 open pull requests for DMD.
That's understandable, however I didn't add these because I wanted to improve D. I made them because my project called for them, and modifying the compiler felt cleaner than hacking the project.
