--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,13 @@
 2010-03-07  Bruno Haible  <bruno@clisp.org>
 
+	Tests of module 'langinfo' in C++ mode.
+	* tests/test-langinfo-c++.cc: New file.
+	* modules/langinfo-tests (Files): Add it and tests/signature.h.
+	(Depends-on): Add ansi-c++-opt.
+	(Makefile.am): Arrange to compile and run test-langinfo-c++.
+	* m4/langinfo_h.m4 (gl_LANGINFO_MODULE_INDICATOR): Invoke
+	gl_MODULE_INDICATOR.
+
 	Tests of module 'iconv-h' in C++ mode.
 	* tests/test-iconv-h-c++.cc: New file.
 	* modules/iconv-h-tests (Files): Add it and tests/signature.h.

--- a/m4/langinfo_h.m4
+++ b/m4/langinfo_h.m4
@@ -1,4 +1,4 @@
-# langinfo_h.m4 serial 3
+# langinfo_h.m4 serial 4
 dnl Copyright (C) 2009, 2010 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -63,6 +63,8 @@
   dnl Use AC_REQUIRE here, so that the default settings are expanded once only.
   AC_REQUIRE([gl_LANGINFO_H_DEFAULTS])
   GNULIB_[]m4_translit([$1],[abcdefghijklmnopqrstuvwxyz./-],[ABCDEFGHIJKLMNOPQRSTUVWXYZ___])=1
+  dnl Define it also as a C macro, for the benefit of the unit tests.
+  gl_MODULE_INDICATOR([$1])
 ])
 
 AC_DEFUN([gl_LANGINFO_H_DEFAULTS],

--- a/modules/langinfo-tests
+++ b/modules/langinfo-tests
@@ -1,10 +1,18 @@
 Files:
 tests/test-langinfo.c
+tests/test-langinfo-c++.cc
+tests/signature.h
 
 Depends-on:
+ansi-c++-opt
 
 configure.ac:
 
 Makefile.am:
 TESTS += test-langinfo
 check_PROGRAMS += test-langinfo
+if ANSICXX
+TESTS += test-langinfo-c++
+check_PROGRAMS += test-langinfo-c++
+test_langinfo_c___SOURCES = test-langinfo-c++.cc
+endif

new file mode 100644
--- /dev/null
+++ b/tests/test-langinfo-c++.cc
@@ -0,0 +1,35 @@
+/* Test of <langinfo.h> substitute in C++ mode.
+   Copyright (C) 2010 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program 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 General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+/* Written by Bruno Haible <bruno@clisp.org>, 2010.  */
+
+#define GNULIB_NAMESPACE gnulib
+#include <config.h>
+
+#include <langinfo.h>
+
+#include "signature.h"
+
+
+#if GNULIB_NL_LANGINFO
+SIGNATURE_CHECK (GNULIB_NAMESPACE::nl_langinfo, char *, (nl_item));
+#endif
+
+
+int
+main ()
+{
+}