Re: emacs crash when open some newsgroups with gnus

[S.P.Tseng <deftsp@gmail.com>]

Kenichi Handa <handa@m17n.org> writes:

> In article <853ak09tr5.fsf@modprobe.cn>, "S.P.Tseng" <deftsp@gmail.com> writes:
>
>>>> "(define-coding-system-alias 'gbk 'gb2312)" for emacs22 tricked me.
>> >
>> > Do you mean that you had the above code in your .emacs, and
>> > after deleting it, Emacs 23 doesn't crash anymore?
>> >
>
>> Yes.
>
> I put that line in my .emacs, run Emacs 23, and visited
> gmain.emacs.devel by Gnus, but couldn't reproduce the crash.
>
> Please run Emacs under gdb and find at which point Emacs
> crashes in your case.

I think I have found the reason.

After execute '(define-coding-system-alias 'gbk 'gb2312)', charset gbk will be
treated as charset gb2312. Emacs22 do not have the charset gbk, so that will be
fine. But Emacs23 support both. You know the charset gbk is bigger than gb2312,
when some char belong to charset gbk but be treated as gb2312 it will cause
overflow.

So, visited gmane.emacs.devel will or will not reproduce the crash.
But visited "cn.bbs.comp.emacs" from "new.cn99.com" can reproduce the crash.

How about when execute (define-coding-system-alias A B), if charset A is bigger than B,
give some warning or refuse?