Eric Blake wrote on 2017-01-19:
> > * lib/localename.c (gl_locale_name_thread_unsafe): Add clause for
> > Cygwin.
It relies on the NL_LOCALE_NAME macro, which is defined in <langinfo.h>.
Better than to hope that it gets included by chance, include it explicitly.
2017-05-18 Bruno Haible <br...@clisp.org>
localename: Include necessary header files on Cygwin.
* lib/localename.c [__CYGWIN__]: Include <langinfo.h>, since this is
where NL_LOCALE_NAME is defined.
diff --git a/lib/localename.c b/lib/localename.c
index 3ba9d08..eb0755c 100644
--- a/lib/localename.c
+++ b/lib/localename.c
@@ -40,7 +40,7 @@
# if defined __APPLE__ && defined __MACH__
# include <xlocale.h>
# endif
-# if __GLIBC__ >= 2 && !defined __UCLIBC__
+# if (__GLIBC__ >= 2 && !defined __UCLIBC__) || defined __CYGWIN__
# include <langinfo.h>
# endif
# if !defined IN_LIBINTL
