Proposed GNU troff behavior change: require end-of-input macros to exit

[Douglas McIlroy]

> For historical reasons (and for compatibility with AT&T 'troff'),
> the end macro exits as soon as it causes a page break and
> no remaining data is in the partially collected line.

This isn't the only anomalous behavior at the end of a
document. Since day one, troff has occasionally emitted
a blank page at the end. I believe this is because a
new page is triggered when the previous page is filled
rather than when some output needs somewhere to
go. A document that exactly fills the last page thus
gets an extra page.

Before jumping for a special fix for .em, you might like
to consider the more general question of how a page
gets initiated and/or when a trap gets sprung (upon
reaching it or upon passing it?). Then .em might not
need so much special pleading.

In regard to the narrow issue of .em, what alternate
fixes have you considered? For example, instead of
exiting, .em might be required to do .rm em. Or the
removal could be done automatically when .em is
invoked. Under either regime, a user could even
arrange for .em to be reinstated to accomplish a
second coming--er, ending.

Doug