Re: Error with fill-paragraph in my own major mode

[Stefan Monnier <monnier@iro.umontreal.ca>]

> Today it has been brought to my attention that there is an error when
> one tries to fill a paragraph (M-q) using that major mode in Gnu Emacs
> 22.  Back then I wrote that mode in XEmacs, today I seem to be a Gnu
> Emacs user so I'd like to fix that issue.

> Hitting M-q leads to an error
> Args out of range: "", -1, 0

> Using debug-on-error and edebug I could track that error down to the
> following code in function fill-comment-paragraph in fill.el:

>   (if (string-match comment-start-skip (concat "\0" commark "a"))
>       (concat "[ \t]*" (regexp-quote commark)
>               ;; Make sure we only match comments that
>               ;; use the exact same comment marker.
>               "[^" (substring commark -1) "]")
>                    ^^^^^^^^^^^^^^^^^^^^^^

The problem is the setting of comment-start-skip.
This regexp should match a "comment-start marker" (plus some optional
whitespace), where you set it to "".


        Stefan