GNU bug report logs - #75588
[PATCH] guix: utils: Delete temporary output files.

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Kierin Bell <fernseed <at> fernseed.me>
To: guix-patches <at> gnu.org
Subject: [PATCH] guix: utils: Delete temporary output files.
Date: Wed, 15 Jan 2025 11:51:50 -0500

* guix/build/utils.scm (call-with-temporary-output-file): Delete and
pass procedure the actual temporary file name, not the template name.

Change-Id: Id8e5da55444195fcee91517cf63ec8ebd20942e5
---

This change will trigger *many* rebuilds, I think because
'call-with-temporary-output-file' is used by 'download-to-store'.

This patch fixes a bug that causes: 1) the procedure passed to
'call-with-temporary-output-file' to always be called with the file name
template string "/guix-file.XXXXXX" rather than the name of the created
temporary file; and 2) the temporary file to persist rather than being
deleted.

Unless I'm missing something, Guix is creating temporary files without
deleting them and nobody is noticing.

Also, more importantly, it's a miracle that nothing has broken because
of issue #1. Apparently, in most applications in the Guix code base, the
procedures passed to this function discard their second argument (the
port) and only use the first argument (what should be the file name).
After a quick search, the only exceptions that I could find are some
unit tests and 'call-with-luks-key-file' in (gnu installer parted). I'm
not sure how this hasn't caused issues there.

I haven't had time to test this yet, because it triggers so many
rebuilds.

 guix/build/utils.scm | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/guix/build/utils.scm b/guix/build/utils.scm
index 94714bf397..dda8fb9d82 100644
--- a/guix/build/utils.scm
+++ b/guix/build/utils.scm
@@ -287,15 +287,16 @@ (define (call-with-temporary-output-file proc)
 call."
   (let* ((directory (or (getenv "TMPDIR") "/tmp"))
          (template  (string-append directory "/guix-file.XXXXXX"))
-         (out       (mkstemp! template)))
+         (out       (mkstemp! template))
+         (filename (port-filename out)))
     (dynamic-wind
       (lambda ()
         #t)
       (lambda ()
-        (proc template out))
+        (proc filename out))
       (lambda ()
         (false-if-exception (close out))
-        (false-if-exception (delete-file template))))))
+        (false-if-exception (delete-file filename))))))
 
 (define (call-with-ascii-input-file file proc)
   "Open FILE as an ASCII or binary file, and pass the resulting port to

base-commit: b696658ee8e0655b17f5d26e024956b5148e36d6
-- 
2.47.1

Message #8 received at 75588 <at> debbugs.gnu.org (full text, mbox):

From: Kierin Bell <fernseed <at> fernseed.me>
To: 75588 <at> debbugs.gnu.org
Subject: Re: bug#75588: Acknowledgement ([PATCH] guix: utils: Delete
 temporary output files.)
Date: Wed, 15 Jan 2025 14:40:48 -0500

help-debbugs <at> gnu.org (GNU bug Tracking System) writes:

So this bug should be canceled! It doesn't actually change the behavior
of the function in any way (though it may making it easier to read for
people not familiar with 'mkstemp!').

I did find a corner-case where temporary files created by
'call-with-temporary-output-file' are not deleted like I'd expect. It
involves using 'execl' to call a process from within
'call-with-temporary-output-file', where the temporary file is not
deleted, at least until after it the new process terminates. Though
confusing, this is probably the right behavior.

-- 
Kierin Bell

Message #13 received at 75588 <at> debbugs.gnu.org (full text, mbox):

From: Ludovic Courtès <ludo <at> gnu.org>
To: Kierin Bell <fernseed <at> fernseed.me>
Cc: 75588 <at> debbugs.gnu.org, Andreas Enge <andreas <at> enge.fr>,
 Janneke Nieuwenhuizen <janneke <at> gnu.org>
Subject: Re: [bug#75588] [PATCH] guix: utils: Delete temporary output files.
Date: Thu, 16 Jan 2025 09:52:01 +0100

Hello,

Kierin Bell <fernseed <at> fernseed.me> skribis:

> This patch fixes a bug that causes: 1) the procedure passed to
> 'call-with-temporary-output-file' to always be called with the file name
> template string "/guix-file.XXXXXX" rather than the name of the created
> temporary file; and 2) the temporary file to persist rather than being
> deleted.
>
> Unless I'm missing something, Guix is creating temporary files without
> deleting them and nobody is noticing.

[…]

> --- a/guix/build/utils.scm
> +++ b/guix/build/utils.scm
> @@ -287,15 +287,16 @@ (define (call-with-temporary-output-file proc)
>  call."
>    (let* ((directory (or (getenv "TMPDIR") "/tmp"))
>           (template  (string-append directory "/guix-file.XXXXXX"))
> -         (out       (mkstemp! template)))
> +         (out       (mkstemp! template))
> +         (filename (port-filename out)))
>      (dynamic-wind
>        (lambda ()
>          #t)
>        (lambda ()
> -        (proc template out))
> +        (proc filename out))
>        (lambda ()
>          (false-if-exception (close out))
> -        (false-if-exception (delete-file template))))))
> +        (false-if-exception (delete-file filename))))))

AFAICS the current code is fine because ‘template’ is modified by
‘mkstemp!’:

--8<---------------cut here---------------start------------->8---
scheme@(guile-user)> (define template (string-copy "/tmp/guix-example-XXXXXX"))
scheme@(guile-user)> (mkstemp! template)
$15 = #<input-output: /tmp/guix-example-uZ5z4s 13>
scheme@(guile-user)> template
$16 = "/tmp/guix-example-uZ5z4s"
--8<---------------cut here---------------end--------------->8---

All good?

Thanks,
Ludo’.

Message #16 received at 75588 <at> debbugs.gnu.org (full text, mbox):

From: Kierin Bell <fernseed <at> fernseed.me>
To: Ludovic Courtès <ludo <at> gnu.org>
Cc: 75588 <at> debbugs.gnu.org, Andreas Enge <andreas <at> enge.fr>,
 Janneke Nieuwenhuizen <janneke <at> gnu.org>
Subject: Re: [bug#75588] [PATCH] guix: utils: Delete temporary output files.
Date: Thu, 16 Jan 2025 10:02:17 -0500

Hi,

Ludovic Courtès <ludo <at> gnu.org> writes:

> AFAICS the current code is fine because ‘template’ is modified by
> ‘mkstemp!’:

Yes, the code is fine --- this was a misunderstanding on my part.

I was doing something unusual that was causing temporary files to
persist, and blamed it on 'call-with-temporary-output-file':

--8<---------------cut here---------------start------------->8---
(call-with-temporary-output-file (lambda (fn port) ... (execlp "swaymsg"
"swaymsg" "exec" "--" "touch" "foo")))
--8<---------------cut here---------------end--------------->8---

Sorry for the noise!

Thanks.

-- 
Kierin Bell

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