From: Christopher Baines <mail@cbaines.net>
To: "Ludovic Courtès" <ludo@gnu.org>
Cc: 56218@debbugs.gnu.org
Subject: [bug#56218] [PATCH] guix: inferior: Fix the behaviour of open-inferior #:error-port.
Date: Mon, 27 Jun 2022 12:39:55 +0100 [thread overview]
Message-ID: <87fsjql3rw.fsf@cbaines.net> (raw)
In-Reply-To: <87v8snqvf2.fsf@gnu.org>
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Ludovic Courtès <ludo@gnu.org> writes:
> Hi Christopher,
>
> Christopher Baines <mail@cbaines.net> skribis:
>
>> This should be the error port used by the inferior process, but currently it's
>> either stderr if #:error-port is a file port, or /dev/null otherwise.
>
> That’s still the case with this patch, no?
>
> The patch does make a difference when (current-error-port) wraps a file
> descriptor other than 2 though.
Maybe this sentance is a little unclear.
What I'm trying to say is that passing a port as #:error-port doesn't
really work. There's no scenario where the output actually goes to the
port you provide, though it can have some effect.
>> +++ b/guix/inferior.scm
>> @@ -156,12 +156,14 @@ (define (open-bidirectional-pipe command . args)
>> (close-port parent)
>> (close-fdes 0)
>> (close-fdes 1)
>> + (close-fdes 2)
>> (dup2 (fileno child) 0)
>> (dup2 (fileno child) 1)
>> ;; Mimic 'open-pipe*'.
>> - (unless (file-port? (current-error-port))
>> - (close-fdes 2)
>> - (dup2 (open-fdes "/dev/null" O_WRONLY) 2))
>> + (dup2 (if (file-port? (current-error-port))
>> + (fileno (current-error-port))
>> + (open-fdes "/dev/null" O_WRONLY))
>> + 2)
>
> If (current-error-port) wraps FD 2 when the function is called, then, by
> the time we reach (dup2 … 2), the FD behind (current-error-port) has be
> closed; we end up doing (dup2 2 2), but FD 2 is closed, so we get EBADF.
>
> Or am I misunderstanding?
That sounds reasonable, I've only tested this change in the scenario
when the #:error-port isn't stderr, and I mostly adapted this from what
I thought open-pipe* did.
Maxime suggested using move->fdes, so maybe this would be an improved
version:
;; Mimic 'open-pipe*'.
(if (file-port? (current-error-port))
(unless (eq? (fileno (current-error-port)) 2)
(move-fdes (current-error-port) 2))
(move->fdes (open-file "/dev/null" O_WRONLY) 2))
> Perhaps we should add one test for each case (error port is a file port
> vs. error port is another kind of port) in ‘tests/inferior.scm’.
Yep, sounds good.
Thanks,
Chris
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next prev parent reply other threads:[~2022-06-27 11:56 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-25 17:18 [bug#56218] [PATCH] guix: inferior: Fix the behaviour of open-inferior #:error-port Christopher Baines
2022-06-25 17:50 ` Maxime Devos
2022-06-25 20:59 ` Maxime Devos
2022-06-27 11:37 ` Christopher Baines
2022-06-26 15:46 ` Ludovic Courtès
2022-06-27 11:39 ` Christopher Baines [this message]
2022-07-05 15:12 ` Ludovic Courtès
2022-07-08 12:54 ` bug#56218: " Christopher Baines
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