Problem: Programs linked against libc < 2.22 abort when trying to load
libc 2.22-or-later locale data:

  https://lists.gnu.org/archive/html/guix-devel/2015-08/msg00737.html

Programs linked against libc 2.22 do not abort when trying to load 2.21
locale data, but they fail to load data for the LC_COLLATE category (in
which case ‘setlocale’ returns ENOENT and the program prints a warning)
due to the addition of the _NL_COLLATE_ENCODING_TYPE element.

In all situations, as a last resort, one can always run:

  export LC_ALL=C

to sidestep the incompatibility issues.

Since ‘core-updates’ will soon be merged, bringing libc 2.22, here’s a
preview of the problems you may encounter and possible solutions.

Consequences on GuixSD:

  • If programs in user profile use libc 2.22 but
    /run/current-system/locale provides libc 2.21 locales: no hard
    problem, but the LC_COLLATE problem.

  • If LOCPATH points to 2.22 locales but /run/current-system/profile
    contains 2.21 programs (Coreutils, sed, grep, etc.), these will
    abort.  Solution: unset LOCPATH so that programs use the 2.21 locale
    data from /run/current-system/locale.

  • If /run/current-system is upgraded to 2.22 but user profiles contain
    2.21 programs, these will abort.  Solution: upgrade user profiles,
    or install glibc-utf8-locale-2.21 in user profile (preferably before
    upgrading GuixSD to libc 2.22.)

Consequences for Guix on foreign distros:

  • If the host distro provides binaries that use libc < 2.22 and you
    use a mixture of Guix-provided and distro-provided programs, this is
    pretty bad.

    Solution: unset LOCPATH and say goodbye to locales for Guix-provided
    packages (setting LOCPATH=$HOME/.guix-profile/lib/locale would break
    all the distro-provided programs), or use exclusively Guix-provided
    programs, or use the “C” locale.

Lesson learned:

  • On GuixSD, we should use a versioned directory,
    /run/current-system/locale/X.Y, as the default locale directory,
    which would avoid problems.

  • The attached patches allow GuixSD users to choose a different libc
    than the current one to build the locales that go to
    /run/current-system/locale.  However this isn’t really satisfying.

Comments welcome!

Ludo’.