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bug#13860: 24.2; dir-locals-directory-cache unreliable in one rare case
From: |
Lars Ingebrigtsen |
Subject: |
bug#13860: 24.2; dir-locals-directory-cache unreliable in one rare case |
Date: |
Wed, 14 Aug 2019 23:18:44 -0700 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) |
Johan Claesson <johanclaesson@bredband.net> writes:
> Maybe i have misunderstood something but i find the cache
> mechanism for directory local variables unreliable in one rare
> case. If first .dir-locals.el is read and a binding say foo = 1 is
> inserted in the dir-locals-directory-cache. And then foo = 2 is
> written in the same second. Now next time the dir locals the old
> binding foo = 1 will be returned. The cache entry is considered
> valid when it should not.
>
> Of course it is unlikely that a user is typing so fast that they
> trigger this :). But it can be triggered from Lisp. I found out
> when playing with a ert test case that was tampering with a dir
> local.
(I'm going through old bug reports that have unfortunately gotten no
responses yet.)
> Here is a recipe for this:
>
> (defvar foo nil)
> (put 'foo 'safe-local-variable 'numberp)
> (let ((dir (make-temp-file "cache-test" t)))
> ;; Create .dir-locals.el with foo = 1.
> (with-temp-buffer
> (cd dir)
> (add-dir-local-variable nil 'foo 1)
> (save-buffer)
> (kill-buffer))
> ;; Read it into dir-locals-directory-cache
> ;; and save .dir-locals.el with foo = 2.
> (with-temp-buffer
> (cd dir)
> (make-local-variable 'foo)
> (hack-dir-local-variables-non-file-buffer)
> (add-dir-local-variable nil 'foo 2)
> (save-buffer)
> (kill-buffer))
> ;; Read it back again.
> ;; It should be 2 at this point but is 1 most of the times.
> ;; (At the rare occasion that seconds increase
> ;; between the two add-dir-local-variable it returns 1).
> (with-temp-buffer
> (cd dir)
> (make-local-variable 'foo)
> (hack-dir-local-variables-non-file-buffer)
> (delete-file dir-locals-file)
> (delete-directory dir)
> foo))
I'm unable to reproduce this problem in Emacs 27, but perhaps this could
be a problem if the file system doesn't have sub-second resolution? Are
there such file systems still in use (I mean, for something where'd you
store file with file-local variables)?
--
(domestic pets only, the antidote for overdose, milk.)
bloggy blog: http://lars.ingebrigtsen.no
- bug#13860: 24.2; dir-locals-directory-cache unreliable in one rare case,
Lars Ingebrigtsen <=