Ensure that the C++ compiler used for testing actually works on a

simple test program; if not, skip the C++-related tests.

m4/cxx.m4

@@ -0,0 +1,46 @@
+# -*- Autoconf -*-
+# Sanity-test a C++ compiler.
+#
+# Copyright (C) 2004 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 2 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, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+# 02111-1307  USA
+
+# Written by Paul Eggert <eggert@cs.ucla.edu>.
+
+AC_DEFUN([BISON_TEST_FOR_WORKING_CXX_COMPILER],
+[
+ AC_CACHE_CHECK([whether $CXX builds executables that work],
+   bison_cv_cxx_works,
+   [AC_LANG_PUSH([C++])
+    AC_RUN_IFELSE(
+      [AC_LANG_PROGRAM(
+	 [#include <iostream>
+	  using namespace std;],
+         [cout << "";])],
+      [bison_cv_cxx_works=yes],
+      [bison_cv_cxx_works=no],
+      [bison_cv_cxx_works=cross])
+    AC_LANG_POP([C++])])
+
+ case $bison_cv_cxx_works in
+ yes)
+    BISON_CXX_WORKS=':';;
+ no | cross)
+    BISON_CXX_WORKS='exit 77';;
+ esac
+
+ AC_SUBST([BISON_CXX_WORKS])
+])