bug#19610: Unbuffered custom binary input ports crash

[ludo@gnu.org (Ludovic Courtès)]

This is a followup to <http://bugs.gnu.org/19610>.

ludo@gnu.org (Ludovic Courtès) skribis:

> However, I tested it live, and it aborts like this (this is with Guile
> 2.0.11.109-e1d29 on x86_64-linux-gnu):
>
> retrieving 1 files from 'wildebeest.jxself.org'...
> importing file or directory '/gnu/store/prrwzx5v33miiz5fh8653m1izl5f8d4k-brasero-3.8.0'...
>
> ;;; (sigport #f #<input: r6rs-custom-binary-input-port 1eee0d0>)
> guile: ../../libguile/ports.c:2527: scm_i_port_iconv_descriptors: Assertion `pti->encoding_mode == SCM_PORT_ENCODING_MODE_ICONV' failed.
> builder for `/gnu/store/izjx4wllhcy66nsn9pxbkghaq2cy06qv-brasero-3.8.0.drv' failed due to signal 6 (Aborted)

Here’s a way to reproduce the assertion failure above (with Guile
2.0.11+):

--8<---------------cut here---------------start------------->8---
(use-modules (rnrs io ports))

(define port
  (let ((input (open-input-string (make-string 1000 #\a))))
    (make-custom-binary-input-port "foo"
                                   (lambda (bv index count)
                                     (let ((n (get-bytevector-n! input bv index
                                                                 count)))
                                       (if (eof-object? n)
                                           0
                                           n)))
                                   #f #f
                                   (lambda ()
                                     (close-port input)))))

(setvbuf port _IONBF)
(pk 'e (port-encoding port))
(get-string-all port)
--8<---------------cut here---------------end--------------->8---

Ludo’.