Subject: bug#103: 23.0.60; Segmentation fault loading auto-lang.el

From: Kenichi Handa <[email-masked]>
Date: Tue, 08 Apr 2008 15:52:27 +0900

In article <[email-masked]>, Chong Yidong <[email-masked]> writes:

> > - download http://www.marquardt-home.de/auto-lang.el to ~/.elisp/
> > - run emacs -Q
> > - M-x load-file
> > - choose file ~/.elisp/auto-lang.el
> > => Emacs segfaults (same result with emacs -Q -nw)

> This is due to an infinite nesting depth in regexp-opt, which can be
> tracked down to the following problem:

> (let ((str (string-as-unibyte "ä")))
>   (string-match (char-to-string (string-to-char str)) str))

> evaluates to 0 in Emacs 22, and to nil in Emacs 23.  It turns out that
> this screws up the use of all-completions in regexp-opt-group.

> Anyone have any idea what's going on here?

(string-as-unibyte "ä") => "\303\244"
(string-to-char "\303\244") => 195 (because ?\303 == 195)
(char-to-string 195) => "Ã" (because 195==0xC3 U+00C3=='Ã')
(string-match "Ã" "ä") => nil (obvious)

Any Lisp program that depends on the result of
string-as-unibyte (thus Emacs' internal character
representation) won't work in Emacs 23.

---
Kenichi Handa
[email-masked]