[glibc] intl: Treat C.UTF-8 locale like C locale (BZ# 16621)

[glibc] intl: Treat C.UTF-8 locale like C locale (BZ# 16621)

[Florian Weimer]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=2897b231a6b71ee17d47d3d63f1112b2641a476c

commit 2897b231a6b71ee17d47d3d63f1112b2641a476c
Author: Bruno Haible <bruno@clisp.org>
Date:   Mon Sep 4 15:31:36 2023 +0200

    intl: Treat C.UTF-8 locale like C locale (BZ# 16621)
    
    The wiki page https://sourceware.org/glibc/wiki/Proposals/C.UTF-8
    says that "Setting LC_ALL=C.UTF-8 will ignore LANGUAGE just like it
    does with LC_ALL=C." This patch implements it.
    
    * intl/dcigettext.c (guess_category_value): Treat C.<encoding> locale
    like the C locale.
    
    Reviewed-by: Florian Weimer <fweimer@redhat.com>

Diff:
---
 intl/dcigettext.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/intl/dcigettext.c b/intl/dcigettext.c
index 7886ac9545..27063886d2 100644
--- a/intl/dcigettext.c
+++ b/intl/dcigettext.c
@@ -1560,8 +1560,12 @@ guess_category_value (int category, const char *categoryname)
      2. The precise output of some programs in the "C" locale is specified
 	by POSIX and should not depend on environment variables like
 	"LANGUAGE" or system-dependent information.  We allow such programs
-        to use gettext().  */
-  if (strcmp (locale, "C") == 0)
+        to use gettext().
+     Ignore LANGUAGE and its system-dependent analogon also if the locale is
+     set to "C.UTF-8" or, more generally, to "C.<encoding>", because that's
+     the by-design behaviour for glibc, see
+     <https://sourceware.org/glibc/wiki/Proposals/C.UTF-8>.  */
+  if (locale[0] == 'C' && (locale[1] == '\0' || locale[1] == '.'))
     return locale;
 
   /* The highest priority value is the value of the 'LANGUAGE' environment