Mark H Weaver <mhw@netris.org> writes:

> Andy Wingo <wingo@pobox.com> writes:
>> Maybe if it is somehow confined to scm_peek_char and scm_fill_input it
>> could be doable.
>
> I think I now see a reasonable way to fix this.
>
> First of all, all interfaces that do something like 'peek' would, when
> returning an EOF, set a 'pending_eof' flag in the port structure.  Then
> 'scm_fill_input' would start by checking this flag; if it is set, then
> it would clear the flag and return EOF.
>
> We would also need to clear the 'pending_eof' flag in a few other
> places, most notably in 'scm_end_input'.  In theory, that might be
> enough, but to be on the safe side we should also clear the flag in any
> procedure that writes or seeks.

Upon further thought, I decided that we shouldn't clear it on writes.
If 'rw_random' is set, then 'scm_end_input' will be called anyway.  If
'rw_random' is not set, then we should *not* clear the flag on writes,
because it indicates that the read and write streams are independent,
e.g. a terminal or socket.

On the other hand, the 'pending_eof' flag should of course be cleared
when putting characters back (unget).

I've attached a proposed patch.  It depends on the three preliminary
patches posted here:

  http://lists.gnu.org/archive/html/guile-devel/2013-03/msg00221.html

Thoughts?

   Regards,
     Mark