bug#18520: string ports should not have an encoding

[ludo@gnu.org (Ludovic Courtès)]

David Kastrup <dak@gnu.org> skribis:

> I'm currently migrating LilyPond over to GUILE 2.0.  LilyPond has its
> own UTF-8 verification, error flagging, processing and indexing.

Do I understand correctly that LilyPond expects Guile strings to be byte
vectors, which it can feed with UTF-8 byte sequences that it built by
itself?

> If you take a look at
> <URL:http://git.savannah.gnu.org/cgit/lilypond.git/tree/scm/parser-ly-from-scheme.scm>,
> ftell on a string port is here used for correlating the positions of
> parsed subexpressions with the original data.  Reencoding strings in
> utf-8 is not going to make this work with string indexing since ftell
> does not bear a useful relation to string positions.

AIUI the result of ‘ftell’ is used in only one place, while ‘port-line’
and ‘port-column’ are used in other places.  The latter seems more
appropriate to me when it comes to tracking source location.

How is the result of ‘ftell’ used by callers of ‘read-lily-expression’?

> I have more than enough crashes and obscure errors to contend with as
> it stands,

Could you open a separate bug with the backtrace of such crashes, if you
think it may be Guile’s fault?

Thanks,
Ludo’.