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utils: Make switch-symlinks robust against interruption.

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* guix/build/utils.scm (switch-symlinks): Delete pivot link if it already
exists.

Co-authored-by: Maxime Devos <maximedevos@telenet.be>
This commit is contained in:
Arun Isaac 2022-06-13 17:03:06 +05:30
parent 2c05a6112b
commit 8452fdaccf
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1 changed files with 15 additions and 3 deletions
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18
guix/build/utils.scm
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@ -3,11 +3,11 @@
;;; Copyright © 2013 Andreas Enge <andreas@enge.fr>
;;; Copyright © 2013 Nikita Karetnikov <nikita@karetnikov.org>
;;; Copyright © 2015, 2018, 2021 Mark H Weaver <mhw@netris.org>
;;; Copyright © 2018 Arun Isaac <arunisaac@systemreboot.net>
;;; Copyright © 2018, 2022 Arun Isaac <arunisaac@systemreboot.net>
;;; Copyright © 2018, 2019 Ricardo Wurmus <rekado@elephly.net>
;;; Copyright © 2020 Efraim Flashner <efraim@flashner.co.il>
;;; Copyright © 2020, 2021 Maxim Cournoyer <maxim.cournoyer@gmail.com>
;;; Copyright © 2021 Maxime Devos <maximedevos@telenet.be>
;;; Copyright © 2021, 2022 Maxime Devos <maximedevos@telenet.be>
;;; Copyright © 2021 Brendan Tildesley <mail@brendan.scot>
;;;
;;; This file is part of GNU Guix.
@ -245,7 +245,19 @@ introduce the version part."
"Atomically switch LINK, a symbolic link, to point to TARGET. Works
both when LINK already exists and when it does not."
(let ((pivot (string-append link ".new")))
(symlink target pivot)
;; Create pivot link, deleting it if it already exists. This can
;; happen if a previous switch-symlinks was interrupted.
(let symlink/remove-old ()
(catch 'system-error
(lambda ()
(symlink target pivot))
(lambda args
(if (= (system-error-errno args) EEXIST)
(begin
;; Remove old link and retry.
(delete-file pivot)
(symlink/remove-old))
(apply throw args)))))
(rename-file pivot link)))
(define (call-with-temporary-output-file proc)