[PATCH] intl: Treat C.UTF-8 locale like C locale, part 2 (BZ# 16621)

[Florian Weimer]

* Bruno Haible:

> The previous commit was incomplete: gettext() still returns a translation
> if the file /usr/share/locale/C/LC_MESSAGES/<domain>.mo exists. This patch
> prohibits the translation also in this case.
>
> * gettext-runtime/intl/dcigettext.c (DCIGETTEXT): Treat C.<encoding> locale
> like the C locale.
> ---
>  intl/dcigettext.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/intl/dcigettext.c b/intl/dcigettext.c
> index 27063886d2..fb69bbf94b 100644
> --- a/intl/dcigettext.c
> +++ b/intl/dcigettext.c
> @@ -691,9 +691,10 @@ DCIGETTEXT (const char *domainname, const char *msgid1, const char *msgid2,
>  	    continue;
>  	}
>  
> -      /* If the current locale value is C (or POSIX) we don't load a
> -	 domain.  Return the MSGID.  */
> -      if (strcmp (single_locale, "C") == 0
> +      /* If the current locale value is "C" or "C.<encoding>" or "POSIX",
> +	 we don't load a domain.  Return the MSGID.  */
> +      if ((single_locale[0] == 'C'
> +	   && (single_locale[1] == '\0' || single_locale[1] == '.'))
>  	  || strcmp (single_locale, "POSIX") == 0)
>  	break;

These arguments:

> * The wiki page https://sourceware.org/glibc/wiki/Proposals/C.UTF-8 states
>   "It shall be the C locale but with UTF-8 encodings."
>   and
>   "These will be the same as C... LC_MESSAGES"
> 
>   The C locale has the property that gettext() returns the msgid in all cases,
>   regardless of what files are on disk and regardless of the values of any
>   environment variables.
> 
>   If the C.UTF-8 has the property that gettext() returns msgid only if there
>   is no translation catalog at /usr/share/locale/C/LC_MESSAGES/<domain>.mo,
>   it is *not* the same as "the C locale but with UTF-8 encodings".
> 
> * We have this rule, that gettext() returns the msgid when the locale is the
>   "C" locale, because
>      - the POSIX standard specifies the precise output of some programs (e.g.
>        'diff') in the C locale, and
>      - we wanted, from the beginning in 1995, that gettext() can be used in
>        the source code of these programs, without an explicit check for the
>        locale.
>   It is possible that, in the long run, POSIX adopts the C.UTF-8 locale,
>   since several platforms already have it: glibc, musl libc, FreeBSD, NetBSD,
>   OpenBSD, Cygwin, Android.
>   When this happens, we want that the maintainers of 'diff' etc. can continue
>   to use gettext(), without introducing an explicit check for the locale.

<https://inbox.sourceware.org/libc-alpha/10272749.85pcf5A44T@nimes/>

convined me, so:

Reviewed-by: Florian Weimer <fweimer@redhat.com>

I'll push it for you.

Thanks,
Florian