bug#48563: move->fdes somewhat broken (EBADFD)

[Maxime Devos <maximedevos@telenet.be>]

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version: 3.0.5

Reproducer:

a.scm:
(define (test p)
  (let loop ((i 0))
    (when (< (pk 'i i) 40)
      (move->fdes p i)
      (loop (+ 1 i)))))

(test (car (pipe))

Run guile -l a.scm.
The result is non-deterministic.

Output (try #1--#2):

;;; (i 0)
[...]
;;; (i 9)
Backtrace:
In ice-9/boot-9.scm:
  1736:10  8 (with-exception-handler _ _ #:unwind? _ # _)
In unknown file:
           7 (apply-smob/0 #<thunk 7f7774266d60>)
In ice-9/boot-9.scm:
    718:2  6 (call-with-prompt ("prompt") #<procedure 7f7772d67e60 …> …)
In ice-9/eval.scm:
    619:8  5 (_ #(#(#<directory (guile-user) 7f7774260c80>)))
In ice-9/boot-9.scm:
   2806:4  4 (save-module-excursion #<procedure 7f7772d6a1e0 at ice-…>)
  4351:12  3 (_)
In /home/sylviidae/a.scm:
      4:6  2 (test #<input: #{read pipe}# 8>)
In ice-9/ports.scm:
    302:9  1 (move->fdes #<input: #{read pipe}# 8> _)
In unknown file:
           0 (primitive-move->fdes #<input: #{read pipe}# 8> 9)

ERROR: In procedure primitive-move->fdes:
In procedure primitive-move->fdes: Ongeldige bestandsdescriptor

Output (try #3): (this time no error)
;;; (i 0)
[...]
;;; (i 40)
GNU Guile 3.0.5
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Some more debugging.
scheme@(guile-user)> (getpid)
$1 = 23855
(Shell): ls /proc/23855/fd/
(Shell output) 0  1  10  11  12  13  14  2  3  4  5  6  7  8  9


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