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

[Jeff Norden]

> 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.

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.

Also, it's good that you and Alan are getting segfaults instead of the
really horrible behavior that I found.  Maybe some change since 27.1 has
helped with that.

Regards,
-Jeff