bug#43499: 27.1; It is possible for (forward-comment -1) to crash emacs

[Eli Zaretskii <eliz@gnu.org>]

> From: Jeff Norden <jnorden@tntech.edu>
> Cc: 43499@debbugs.gnu.org
> Date: Sat, 19 Sep 2020 11:24:23 -0500
> 
> > Thanks.  I propose a slightly different change below.  I think it's
> > somewhat better, because it does the comparison only once, and the
> > while loop can then run at full speed without testing on each
> > iteration.  (It looks like a large change, but almost all of it is
> > just whitespace changes due to re-indentation of the loop.)  Do you
> > agree?
> 
> I think either change will work fine.  It doesn't seem to me that either
> one would be faster, unless I'm missing something.  My suggestion was to
> move the test from the body of the loop (where from == stop is checked
> each iteration) to the clause of the while statement (as from > stop
> instead).  But, maybe a test before the loop starts makes the code more
> clear - that is entirely your call.

Thanks, I installed my changes.

> Perhaps I should have included my patch in the body of the email,
> instead of as an attachment, which might have made my suggestion more
> clear.

It was clear to me, FWIW.