Andy Piper <andy(a)xemacs.org&gt; writes: Basically every package that attempts to use a new feature that we advertise. Also, every package that attempts to use functionality that used to crash, but is now fixed. Of course, this excludes packages that try to be compatible with multiple XEmacs versions, but there is code that just tries to support the latest XEmacs, whose authors don't feel like supporting everything (some of them might not have access to old XEmacs versions). If we implement that, I think the decision should be in the hands of the actual maintainer.