bug#14434: 24.3; lisp mode's comment start seems bad

[Stefan Monnier]

> After fixing bug#14303, we can observe the following bug:
> 1. Emacs -q
> 2. insert in a emacs lisp mode buffer:
>    (
>      ;;
>    )
> 3. Move point to be end of ;;
> 4. M-j

> You should see:

>    (
>      ;;
>      ;
>    )

> This seems to be due to bad comment-start-skip.

That's one way to see it.  Another is that it's a regression introduced
by the fix to bug#14303.  It probably affects more than
emacs-lisp-mode.  So it'd be better to fix it by improving your fix to
bug#14303.  E.g. after the new while loop which finds the comment start, do
a looking-at to make sure the match-data extends as far as possible.

Tho maybe, we should take a new look at bug#14303 to see why it failed,
since after all the old comment-search-backward did already pay
attention to comment-use-global-state (via comment-search-forward), so
maybe bug#14303 was really due to a bug in comment-search-forward.


        Stefan