[PATCH] localename: Port to cygwin 2.6.

[Eric Blake]

Cygwin 2.6 introduced uselocale() and thread-local locales in general,
but lacks any way to get at the name of each portion of a locale_t
object short of peeking behind an opaque object.  I'm proposing a
patch to add NL_LOCALE_NAME() to Cygwin patterned after glibc's
extension of the same name, but we might as well work around it
in the meantime.

* lib/localename.c (gl_locale_name_thread_unsafe): Add clause for
Cygwin.

Signed-off-by: Eric Blake <address@hidden>
---

I won't actually push this to gnulib until I've sent the corresponding
newlib/Cygwin patch to add NL_LOCALE_NAME, and tweaked the commit
messages of both patches to refer to the appropriate mailing list
threads.  But this was enough to get test-localename passing on
Cygwin again.

 ChangeLog        |  6 ++++++
 lib/localename.c | 13 +++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index e4339fc..f0e23a1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2017-01-19  Eric Blake  <address@hidden>
+
+       localename: Port to cygwin 2.6.
+       * lib/localename.c (gl_locale_name_thread_unsafe): Add clause for
+       Cygwin.
+
 2017-01-17  Pádraig Brady  <address@hidden>

        parse-datetime: fix dependence on AC_PROG_SED
diff --git a/lib/localename.c b/lib/localename.c
index 33879e9..89ce889 100644
--- a/lib/localename.c
+++ b/lib/localename.c
@@ -2734,6 +2734,19 @@ gl_locale_name_thread_unsafe (int category, const char 
*categoryname)
 #  elif defined __sun && HAVE_GETLOCALENAME_L
         /* Solaris >= 12.  */
         return getlocalename_l (category, thread_locale);
+#  elif defined __CYGWIN__
+        /* Cygwin < 2.6 lacks uselocale and thread-local locales altogether.
+           Cygwin <= 2.6.1 lacks NL_LOCALE_NAME, requiring peeking inside
+           an opaque struct.  */
+#   ifdef NL_LOCALE_NAME
+        return nl_langinfo_l (NL_LOCALE_NAME (category), thread_locale);
+#   else
+        /* FIXME: Remove when we can assume new-enough Cygwin.  */
+        struct __locale_t {
+          char categories[7][32];
+        };
+        return ((struct __locale_t *) thread_locale)->categories[category];
+#   endif
 #  elif defined __ANDROID__
         return MB_CUR_MAX == 4 ? "C.UTF-8" : "C";
 #  endif
-- 
2.9.3