bug#9318: 23.3.50; The first call of encode-coding-region() returns wrong result

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 24 Aug 2011 18:37:24 +0900
> From: Kazuhiro Ito <kzhr@d1.dion.ne.jp>
> Cc: 9318@debbugs.gnu.org
> 
> > (progn
> >   (goto-char (point-min))
> >   (insert #x80)
> >   (insert (make-string 16 ?A))
> >   (encode-coding-region 1 18 'ctext-unix))
> > 
> > backtrace is below.  Please let me know if you need more information.
> > 
> > 
> > Program received signal SIGSEGV, Segmentation fault.
> > 0x0000000000557419 in mark_object (arg=4702111234474983745) at alloc.c:5473
> > 5473            if (STRING_MARKED_P (ptr))
> 
> I think relocation of buffer may cause the problem.
> 
> The comment for CODING_DECODE_CHAR macro in coding.c says as below.
> 
> > /* This wrapper macro is used to preserve validity of pointers into
> >    buffer text across calls to decode_char, which could cause
> >    relocation of buffers if it loads a charset map, because loading a
> >    charset map allocates large structures.  */
> 
> encode_coding_iso_2022() uses ENCODE_ISO_CHARACTER macro, which uses
> ENCODE_CHAR macro.  ENCODE_CHAR macro calls encode_char() and it may
> load a charset map.

But which pointer(s) in encode_coding_iso_2022 can be altered by
relocation?  Do you actually see any of the pointers used by this
function modified by relocation of some buffer?