Re: Coding system conversion error

["Jan D." <jan.h.d@swipnet.se>]

Stefan Monnier wrote:

> Well, maybe we can help, if you tell us what you know, ;-)


The mail you replied to was all I knew at the time.  But here is a 
distilled description of the problem (I've omitted the 1025 character 
string):

ELISP> (setq str (string-to-multibyte <1025 ASCII character string>))
...
ELISP> (multibyte-string-p str)
t
ELISP> (multibyte-string-p (encode-coding-string str
                                              
'compound-text-with-extensions))
t     <---- BUG, should be nil
ELISP> (multibyte-string-p (encode-coding-string str 'utf-8))
nil

Most applications don't ask for 'compound-text, so most of the time the 
xassert doesn't abort.


The compound-text case exits in the second return in 
encode_coding_string in coding.c in this code fragment (in the if (from 
== to_byte) cas near the bottom):

  if (! CODING_REQUIRE_ENCODING (coding))
    {
      coding->consumed = SBYTES (str);
      coding->consumed_char = SCHARS (str);
      if (STRING_MULTIBYTE (str))
       {
         str = Fstring_as_unibyte (str);
         nocopy = 1;
       }
      coding->produced = SBYTES (str);
      coding->produced_char = SCHARS (str);
      return (nocopy ? str : Fcopy_sequence (str));
    }

  if (coding->composing != COMPOSITION_DISABLED)
    coding_save_composition (coding, from, to, str);

  /* Try to skip the heading and tailing ASCIIs.  We can't skip them
     if we must run CCL program or there are compositions to
     encode.  */
  if (coding->type != coding_type_ccl
      && (! coding->cmp_data || coding->cmp_data->used == 0))
    {
      SHRINK_CONVERSION_REGION (&from, &to_byte, coding, SDATA (str),
                                1);
      if (from == to_byte)
       {
         coding_free_composition_data (coding);
         return (nocopy ? str : Fcopy_sequence (str));
       }
      shrinked_bytes = from + (SBYTES (str) - to_byte);
    }

So if str is mulitbyte when it enters this function, the return value is 
multibyte.  I suspect it is here Fstring_as_unibyte should be called, as 
it is in the previous early return.

    Jan D.