Hi Andreas,
And welcome back! :-)
Andreas Rottmann <m...@r0tty.org> skribis:
> Andreas Rottmann <m...@r0tty.org> writes:
>
>> [...] I isolated the cause; the following snippet hangs on Guile 2.2
>> and 3.0, while it worked as expected on 2.0:
>>
>> ;; ------------------
>> (import (rnrs))
>>
>> (let* ((p (pipe))
>> (in (car p))
>> (out (transcoded-port (cdr p) (make-transcoder (utf-8-codec)))))
>> (put-datum out "foo")
>> (flush-output-port out)
>> (display "Should have written to pipe by now, attempting reading a byte\n")
>> (display "Got")
>> (display (get-u8 in))
>> (newline))
>> ;; -------------------
>>
>> It seems the underlying port is no longer flushed to the OS, so the
>> `get-u8` now hangs waiting for input, starting with Guile 2.2.
>>
> I'd like to add that this is indeed not passing data to the OS, as
> verified by strace. Also, I have now figured out the commit introducing
> the regression, namely 8399e7af5 ("Generic port facility provides
> buffering uniformly"); the commit before (e8eeeeb1d) still runs the
> above code to completion.
Actually I think the code above behaves as expected. ‘pipe’ returns
buffered ports by default. When flushing the transcoded port,
‘transcoded_port_write’ is called, but then bytes written to the pipe
are buffered.
The fix is to add:
(setvbuf (cdr p) 'none)
Does that make sense?
Thanks,
Ludo’.
