Re: Double encoding in ~/Mail/active

[Katsumi Yamaoka <yamaoka@jpl.org>]

Adam Sjøgren wrote:
> On Tue, 03 Aug 2010 08:21:17 +0900, Katsumi wrote:
[...]
>>> Is this a GNU Emacs or an XEmacs bug? I guess it should be reported?
>> No, it's my fault. ;-p

> But isn't it inconsistent "in a bad way" that GNU Emacs won't double
> encode a string and XEmacs will? Wouldn't it be better if both emacsen
> behaved the same?

> I.e. your example:

>  (decode-coding-string
>   (encode-coding-string
>    (encode-coding-string "hyskenstræde" 'utf-8)
>    'utf-8)
>   'utf-8)

> ought to give either "hyskenstræde" or "hyskenstræde" on both emacsen?

First of all, I believe what is bad is a source code that does
the double encoding (I made ;-).

I don't know exactly how Emacs decides whether to encode an encoded
string but I guess the point is the multibyteness or other.  In
Emacs, an encoded string is always a unibyte string, that is not
worth encoding.  Though the double encoding happens in Emacs 21
and 22, and the following form returns the one that is the same
as that of XEmacs:

(decode-coding-string
 (encode-coding-string
  (string-make-multibyte
   (encode-coding-string "hyskenstræde" 'utf-8))
  'utf-8)
 'utf-8)

But as for Emacs 23 and greater (i.e. Unicode Emacsen), the double
encoding doesn't happen even for that form.  Those Emacsen may
examine what the data are.

OTOH, there is no concept of the multibyteness in XEmacs.  Making
XEmacs behave like the recent Emacsen may possibly mean making it
follow a long journey that Emacs trudged along.  And I think it
goes for nothing.  Again, the bad was me. ;-)