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Diffstat (limited to 'doc/guix.texi')
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diff --git a/doc/guix.texi b/doc/guix.texi index a23d8244ff..a164608b73 100644 --- a/doc/guix.texi +++ b/doc/guix.texi @@ -5562,6 +5562,11 @@ Library Reference Manual}). @xref{Locales}, for more information. The list of locale definitions to be compiled and that may be used at run time. @xref{Locales}. +@item @code{locale-libcs} (default: @code{(list @var{glibc})}) +The list of GNU@tie{}libc packages whose locale data and tools are used +to build the locale definitions. @xref{Locales}, for compatibility +considerations that justify this option. + @item @code{name-service-switch} (default: @var{%default-nss}) Configuration of libc's name service switch (NSS)---a @code{<name-service-switch>} object. @xref{Name Service Switch}, for @@ -6020,6 +6025,57 @@ instance it has @code{uk_UA.utf8} but @emph{not}, say, @code{uk_UA.UTF-8}. @end defvr +@subsubsection Locale Data Compatibility Considerations + +@cindex incompatibility, of locale data +@code{operating-system} declarations provide a @code{locale-libcs} field +to specify the GNU@tie{}libc packages that are used to compile locale +declarations (@pxref{operating-system Reference}). ``Why would I +care?'', you may ask. Well, it turns out that the binary format of +locale data is occasionally incompatible from one libc version to +another. + +@c See <https://sourceware.org/ml/libc-alpha/2015-09/msg00575.html> +@c and <https://lists.gnu.org/archive/html/guix-devel/2015-08/msg00737.html>. +For instance, a program linked against libc version 2.21 is unable to +read locale data produced with libc 2.22; worse, that program +@emph{aborts} instead of simply ignoring the incompatible locale +data@footnote{Versions 2.23 and later of GNU@tie{}libc will simply skip +the incompatible locale data, which is already an improvement.}. +Similarly, a program linked against libc 2.22 can read most, but not +all, the locale data from libc 2.21 (specifically, @code{LC_COLLATE} +data is incompatible); thus calls to @code{setlocale} may fail, but +programs will not abort. + +The ``problem'' in GuixSD is that users have a lot of freedom: They can +choose whether and when to upgrade software in their profiles, and might +be using a libc version different from the one the system administrator +used to build the system-wide locale data. + +Fortunately, unprivileged users can also install their own locale data +and define @var{GUIX_LOCPATH} accordingly (@pxref{locales-and-locpath, +@code{GUIX_LOCPATH} and locale packages}). + +Still, it is best if the system-wide locale data at +@file{/run/current-system/locale} is built for all the libc versions +actually in use on the system, so that all the programs can access +it---this is especially crucial on a multi-user system. To do that, the +administrator can specify several libc packages in the +@code{locale-libcs} field of @code{operating-system}: + +@example +(use-package-modules base) + +(operating-system + ;; @dots{} + (locale-libcs (list glibc-2.21 (canonical-package glibc)))) +@end example + +This example would lead to a system containing locale definitions for +both libc 2.21 and the current version of libc in +@file{/run/current-system/locale}. + + @node Services @subsection Services |