guile-launcher: Avoid the “C” locale and try “C.UTF-8”.

This is a followup to ed0cd12a82b429bc5058f693a0f75f2ba0ee47c4, which
adds the C.UTF-8 locale to the glibc package, and
ee4e79f871bc2f848ce4b4a176bb725ab71e3cd6, which changed the default to
“C.UTF-8” for ‘guix’ commands.

Fixes a bug whereby starting ‘guix’ in an environment where the LC_*
variables are unset would start it in the “C” locale:

  echo '(pk (setlocale LC_ALL))' | guix shell -CW coreutils -- guix repl

This would lead to breakage for commands such as ‘guix substitute’ that
need to run in a UTF-8 locale.

* gnu/packages/aux-files/guile-launcher.c (main): Try “C.UTF-8” before
“en_US.UTF-8”.  Do that also when the current locale is “C”.
* guix/ui.scm (install-locale): Likewise.

Change-Id: I36da4db8f898f1083b33760e1ab46c3a257de811

1 files changed, 11 insertions, 5 deletions

diff --git a/gnu/packages/aux-files/guile-launcher.c b/gnu/packages/aux-files/guile-launcher.c
index c205477f64..44f7e1f432 100644
--- a/gnu/packages/aux-files/guile-launcher.c
+++ b/gnu/packages/aux-files/guile-launcher.c
@@ -84,11 +84,17 @@ int
 main (int argc, char **argv)
 {
   /* Try to install the current locale; remain silent if it fails.  */
-  if (setlocale (LC_ALL, "") == NULL)
-    /* The 'guix pull'-provided 'guix' includes at least en_US.utf8 so use
-       that.  That gives us UTF-8 support for 'scm_to_locale_string', etc.,
-       which is always preferable over the C locale.  */
-    setlocale (LC_ALL, "en_US.utf8");
+  char *locale = setlocale (LC_ALL, "");
+  if (locale == NULL || strcmp (locale, "C") == 0)
+    {
+      /* The 'guix pull'-provided 'guix' includes at least C.UTF-8 (which is
+	 baked into glibc, except when cross-compiling) so use that, and fall
+	 back to en_US.UTF-8.  That gives us UTF-8 support for
+	 'scm_to_locale_string', etc., which is always preferable over the C
+	 locale.  */
+      if (setlocale (LC_ALL, "C.UTF-8") == NULL)
+	setlocale (LC_ALL, "en_US.utf8");
+    }
 
   const char *str;
   str = getenv ("GUILE_LOAD_PATH");