Re: [musl] nl_langinfo(CODESET) does not match locale

[Rich Felker <dalias@libc.org>]

On Sat, May 11, 2024 at 07:58:09PM +0200, Petr Pisar wrote:
> When debugging test failures in libisds on Gentoo with musl
> <https://bugs.gentoo.org/show_bug.cgi?id=928107>, I found that
> nl_langinfo(CODESET) does not match current locale.
> 
> A reproducer:
> 
> #include <locale.h>
> #include <stdio.h>
> #include <langinfo.h>
> 
> int main(void) {
>     char *old_locale = setlocale(LC_ALL, "cs_CZ.ISO8859-2");
>     if (old_locale == NULL) {
>         perror("setlocale() set failed");
>         return 1;
>     }
>     old_locale = setlocale(LC_ALL, NULL);
>     if (old_locale == NULL) {
>         perror("setlocale() query failed");
>         return 1;
>     }
>     printf("Current LC_ALL=%s\n", old_locale);
>     printf("CODESET=%s\n", nl_langinfo(CODESET));
>     return 0;
> }
> 
> # gcc test.c && ./a.out
> Current LC_ALL=cs_CZ.ISO8859-2
> CODESET=UTF-8
> 
> While on glibc:
> 
> $ gcc test.c && ./a.out
> Current LC_ALL=cs_CZ.ISO8859-2
> CODESET=ISO-8859-2

Yes it does match. The encoding on musl is *always* UTF-8. The only
weirdness here is that, presently, all locale names exist, and in the
absence of a translation file, are just aliases for C.UTF-8.

> I can see that for cs_CZ.UTF8 locale, it nl_langinfo() correctly reports UTF-8,
> as well for C reports ASCII. However, for any other character set it always
> returns UTF-8.
> 
> I found a notice <https://wiki.gentoo.org/wiki/Musl_usage_guide#Locales> that
> musl does not implements non-UTF-8 locales. If that is true, then selocale() for
> "cs_CZ.ISO8859-2" should fail, instead of accepting the locale.

It's an open issue that users/applications would like to be able to
know "no such locale is installed" when attempting to set an explicit
locale by name, and it will probably be resolved by making
setlocale(...,"explicit_name.bad_encoding") fail (and likewise, any
explicit name not matching a file fail) but setlocale(...,"") where
the environment contains a bad locale name succeed and produce a
default UTF-8 locale. This part of the big pending locale-overhaul
project.

Rich