1 files changed, 47 insertions, 0 deletions
diff --git a/lib/hard-locale.c b/lib/hard-locale.c
new file mode 100644
index 0000000..c01fce5
--- /dev/null
+++ b/lib/hard-locale.c
@@ -0,0 +1,47 @@
+/* hard-locale.c -- Determine whether a locale is hard.
+
+   Copyright (C) 1997-1999, 2002-2004, 2006-2007, 2009-2023 Free Software
+   Foundation, Inc.
+
+   This file is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
+
+   This file is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+#include "hard-locale.h"
+
+#include <locale.h>
+#include <stdlib.h>
+#include <string.h>
+
+bool
+hard_locale (int category)
+{
+  char locale[SETLOCALE_NULL_MAX];
+
+  if (setlocale_null_r (category, locale, sizeof (locale)))
+    return false;
+
+  if (!(strcmp (locale, "C") == 0 || strcmp (locale, "POSIX") == 0))
+    return true;
+
+#if defined __ANDROID__
+  /* On Android 5.0 or newer, it is possible to set a locale that has the same
+     name as the "C" locale but in fact uses UTF-8 encoding.  Cf. test case 2 in
+     <https://lists.gnu.org/archive/html/bug-gnulib/2023-01/msg00141.html>.  */
+  if (MB_CUR_MAX > 1)
+    return true;
+#endif
+
+  return false;
+}