GNU bug report logs - #73275
‘with-imported-modules’ fails to cope with dangling symlinks

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Ludovic Courtès <ludo <at> gnu.org>
Subject: bug#73275: closed (Re: bug#73275: ‘with-imported-modules’
 fails to cope with dangling symlinks)
Date: Sun, 15 Sep 2024 22:27:02 +0000

[Message part 1 (text/plain, inline)]

Your bug report

#73275: ‘with-imported-modules’ fails to cope with dangling symlinks

which was filed against the guix package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 73275 <at> debbugs.gnu.org.

-- 
73275: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=73275
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

[Message part 2 (message/rfc822, inline)]

From: Ludovic Courtès <ludo <at> gnu.org>
To: 73275-done <at> debbugs.gnu.org
Subject: Re: bug#73275: ‘with-imported-modules’
 fails to cope with dangling symlinks
Date: Mon, 16 Sep 2024 00:26:05 +0200

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

> $ guix shell -CWP guile guix -- guile imported-modules-dangling-symlink.scm
> ;;; note: auto-compilation is enabled, set GUILE_AUTO_COMPILE=0
> ;;;       or pass the --no-auto-compile argument to disable.
> ;;; compiling /home/ludo/src/guix-debugging/imported-modules-dangling-symlink.scm
> ;;; compiled /home/ludo/.cache/guile/ccache/3.0-LE-8-4.7/home/ludo/src/guix-debugging/imported-modules-dangling-symlink.scm.go
>
> ;;; (symlink)
>
> ;;; (drv #<derivation /gnu/store/8r2vh6x599i82gf9rphfxldaiyr67glq-bar.scm.drv => /gnu/store/a1sz94kb0h1n0k238w49bw4zdrrhml6h-bar.scm 7fce7f287640>)
> building path(s) `/gnu/store/qmxv9mavj48jmqb3x4ayq2a2q948kd40-module-import-compiled'
> [ 1/ 4] Loading './foo.scm'...
> Backtrace:
>            6 (primitive-load "/gnu/store/9c5vjhqsjxkg5fvaxhxz14w6ms3?")
> In ice-9/eval.scm:
>     619:8  5 (_ #f)
> In srfi/srfi-1.scm:
>    460:18  4 (fold #<procedure 7ffff5f2a9a0 at ice-9/eval.scm:336:1?> ?)
>    460:18  3 (fold #<procedure 7ffff5f41c60 at ice-9/eval.scm:336:1?> ?)
> In ice-9/eval.scm:
>    245:16  2 (_ #(#(#<directory (guix build utils) 7ffff7746320>) # ?))
> In ice-9/boot-9.scm:
>   1982:24  1 (_ _)
> In unknown file:
>            0 (stat "./guix/base16.scm" #<undefined>)
>
> ERROR: In procedure stat:
> In procedure stat: No such file or directory: "./guix/base16.scm"
> builder for `/gnu/store/f3w43lq1wfq35dym2r48sav22x4l88dh-module-import-compiled.drv' failed with exit code 1

Fixed in a7bb45b39d7d698e0868c2b3ac9097b70ef9d401.

The trick is that ‘imported-files/derivation’ should copy files instead
of symlinking them.  As noted in the commit log, I believe this was the
original intent but due to a typo it did not work that way.

Ludo’.

[Message part 3 (message/rfc822, inline)]

From: Ludovic Courtès <ludo <at> gnu.org>
To: bug-guix <at> gnu.org
Subject: ‘with-imported-modules’ fails to cope
 with dangling symlinks
Date: Sun, 15 Sep 2024 12:49:30 +0200

Consider this code, which uses ‘with-imported-modules’ with a computed
module ‘foo’ (thereby leading to the creation of a “module-import”
derivation, via ‘imported-files/derivation’):

--8<---------------cut here---------------start------------->8---
(use-modules (guix))

(pk (stat:type (lstat (search-path %load-path "guix/base16.scm"))))

(let* ((foo (scheme-file "foo.scm" #~(define-module (foo))))
       (bar (scheme-file "bar.scm"
                         (with-imported-modules `((guix base16)
                                                  ((foo) => ,foo))
                           #~(begin
                               (use-modules (guix base16) (foo))
                               (pk 'hi!))))))
  (with-store store
    (run-with-store store
      (mlet %store-monad ((drv (lower-object bar)))
        (built-derivations (list (pk 'drv drv)))))))
--8<---------------cut here---------------end--------------->8---

It works fine in “normal” conditions:

--8<---------------cut here---------------start------------->8---
$ guile imported-modules-dangling-symlink.scm

;;; (regular)

;;; (drv #<derivation /gnu/store/8lzl8p1rjwxnhdyvjiwa4w35pclm1a37-bar.scm.drv => /gnu/store/px8b5453gspxbjixi33x96hjm558s6gk-bar.scm 7f6f88c84f50>)
--8<---------------cut here---------------end--------------->8---

But it fails when running from a profile:

--8<---------------cut here---------------start------------->8---
$ guix shell -CWP guile guix -- guile imported-modules-dangling-symlink.scm
;;; note: auto-compilation is enabled, set GUILE_AUTO_COMPILE=0
;;;       or pass the --no-auto-compile argument to disable.
;;; compiling /home/ludo/src/guix-debugging/imported-modules-dangling-symlink.scm
;;; compiled /home/ludo/.cache/guile/ccache/3.0-LE-8-4.7/home/ludo/src/guix-debugging/imported-modules-dangling-symlink.scm.go

;;; (symlink)

;;; (drv #<derivation /gnu/store/8r2vh6x599i82gf9rphfxldaiyr67glq-bar.scm.drv => /gnu/store/a1sz94kb0h1n0k238w49bw4zdrrhml6h-bar.scm 7fce7f287640>)
building path(s) `/gnu/store/qmxv9mavj48jmqb3x4ayq2a2q948kd40-module-import-compiled'
[ 1/ 4] Loading './foo.scm'...
Backtrace:
           6 (primitive-load "/gnu/store/9c5vjhqsjxkg5fvaxhxz14w6ms3?")
In ice-9/eval.scm:
    619:8  5 (_ #f)
In srfi/srfi-1.scm:
   460:18  4 (fold #<procedure 7ffff5f2a9a0 at ice-9/eval.scm:336:1?> ?)
   460:18  3 (fold #<procedure 7ffff5f41c60 at ice-9/eval.scm:336:1?> ?)
In ice-9/eval.scm:
   245:16  2 (_ #(#(#<directory (guix build utils) 7ffff7746320>) # ?))
In ice-9/boot-9.scm:
  1982:24  1 (_ _)
In unknown file:
           0 (stat "./guix/base16.scm" #<undefined>)

ERROR: In procedure stat:
In procedure stat: No such file or directory: "./guix/base16.scm"
builder for `/gnu/store/f3w43lq1wfq35dym2r48sav22x4l88dh-module-import-compiled.drv' failed with exit code 1
cannot build derivation `/gnu/store/8r2vh6x599i82gf9rphfxldaiyr67glq-bar.scm.drv': 1 dependencies couldn't be built
Backtrace:
In ice-9/boot-9.scm:
  1755:12 11 (with-exception-handler _ _ #:unwind? _ # _)
In unknown file:
          10 (apply-smob/0 #<thunk 7fce95112300>)
In ice-9/boot-9.scm:
    724:2  9 (call-with-prompt _ _ #<procedure default-prompt-handle?>)
In ice-9/eval.scm:
    619:8  8 (_ #(#(#<directory (guile-user) 7fce95115c80>)))
In ice-9/boot-9.scm:
   2858:4  7 (save-module-excursion _)
  4408:12  6 (_)
  1755:12  5 (with-exception-handler _ _ #:unwind? _ # _)
In guix/store.scm:
   689:37  4 (thunk)
  2210:25  3 (run-with-store #<store-connection 256.100 7fce90c59a50> ?)
  2082:38  2 (_ #<store-connection 256.100 7fce7f2875a0>)
  1449:15  1 (_ #<store-connection 256.100 7fce7f2875a0> _ _)
In ice-9/boot-9.scm:
  1676:22  0 (raise-exception _ #:continuable? _)

ice-9/boot-9.scm:1676:22: In procedure raise-exception:
ERROR:
  1. &store-protocol-error:
      message: "build of `/gnu/store/8r2vh6x599i82gf9rphfxldaiyr67glq-bar.scm.drv' failed"
      status: 100
--8<---------------cut here---------------end--------------->8---

The key difference is that, in the profile, ‘guix/base16.scm’ is a
symlink and the import machinery ends up inserting a dangling symlink in
the store:

--8<---------------cut here---------------start------------->8---
$ guix gc --references /gnu/store/f3w43lq1wfq35dym2r48sav22x4l88dh-module-import-compiled.drv
/gnu/store/3w29f4qjbap3awsi7yngnp2l1zvb5gbc-module-import.drv
/gnu/store/4ah6s53jjfmcqnly3mdgh8zpkk0jyz28-guile-3.0.9.drv
/gnu/store/9c5vjhqsjxkg5fvaxhxz14w6ms317wsg-compile-modules
/gnu/store/c1qxdflcdb2hv4rjglap3qb5jfqhs72r-build-utils.scm
$ guix gc --references /gnu/store/3w29f4qjbap3awsi7yngnp2l1zvb5gbc-module-import.drv
/gnu/store/4ah6s53jjfmcqnly3mdgh8zpkk0jyz28-guile-3.0.9.drv
/gnu/store/c1qxdflcdb2hv4rjglap3qb5jfqhs72r-build-utils.scm
/gnu/store/g0660kdr7n20927cxx2pmmr9dyj4l4q4-foo.scm.drv
/gnu/store/mg756z8cykpz9szdk71c5zchyymyl2br-module-import-builder
/gnu/store/nkz7k36n9i7qwvwk7ayyd9sq4ssdghxh-base16.scm
$ ls -l /gnu/store/nkz7k36n9i7qwvwk7ayyd9sq4ssdghxh-base16.scm
lrwxrwxrwx 1 root root 102 Jan  1  1970 /gnu/store/nkz7k36n9i7qwvwk7ayyd9sq4ssdghxh-base16.scm -> /gnu/store/jk9pi1qk158zdmnh4q3nzp3l53cvzhnk-guix-1.4.0-24.9a2ddcc/share/guile/site/3.0/guix/base16.scm
$ guix gc --references /gnu/store/nkz7k36n9i7qwvwk7ayyd9sq4ssdghxh-base16.scm | grep base16
$ echo $?
1
--8<---------------cut here---------------end--------------->8---

Note that the symlink is valid when you have a full view of the store,
but it’s dangling inside the build environment because that
/gnu/store/nkz7k36n9i7qwvwk7ayyd9sq4ssdghxh-base16.scm item doesn’t have
a reference to its target file, as shown by ‘guix gc --references’.

There’s no such problem on regular imports as created by
‘imported-files’.

This is sorta similar to the issue discussed in
<https://issues.guix.gnu.org/72867>.

Ludo’.

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