bug#46933: Possible bugs in filepos-to-bufferpos / bufferpos-to-filepos

[Eli Zaretskii]

> From: handa <handa@gnu.org>
> Cc: gregory@heytings.org, 46933@debbugs.gnu.org
> Date: Sun, 28 Mar 2021 23:29:41 +0900
> 
> > In any case, the problem is not with encoding, the problem is with
> > decoding.  Encoding doesn't have this problem because we always encode
> > more than enough (we use the value of BYTE as the count of
> > _characters_ to encode, so for ISO-2022 encoding it is usually much
> > more than needed).  By contrast, when decoding, we decode exactly
> > BYTE+1 bytes, which then hits the problem if that offset is inside a
> > shift sequence.
> 
> Then, that implementation should be changed.
> 
> Any coding system can have :post-read-conversion and
> :pre-write-conversion functions, it is not guaranteed that encoded byte
> length is greater than the number of characters.

Agreed, but AFAICT, ISO-2022-JP doesn't have any of these attributes,
right?