Ensure that unmatched arity fails in C++

ext/-test-/cxxanyargs/extconf.rb

@@ -22,5 +22,18 @@ begin
 end
 
 if ok
-  create_makefile("-test-/cxxanyargs")
+  $srcs = %w[cxxanyargs.cpp]
+  $cleanfiles << "failure.failed"
+  create_makefile("-test-/cxxanyargs") do |mk|
+    mk << <<MK
+
+cxxanyargs.#$OBJEXT: failure.failed
+
+failure.failed: failure.cpp
+\t$(Q)$(RUBY) -rfileutils \\
+\t  -e "err = IO.popen(%[$(MAKE) failure.#$OBJEXT], err:[:child, :out], &:read)" \\
+\t  -e "abort err unless /rb_define_method/ =~ err" \\
+\t  -e "FileUtils.touch(*ARGV)" $@
+MK
+  end
 end

ext/-test-/cxxanyargs/failure.cpp

@@ -0,0 +1,13 @@
+#include <ruby/ruby.h>
+
+static VALUE
+func_arg1(VALUE self, VALUE arg1)
+{
+    return arg1;
+}
+
+extern "C" void
+Init_failure(void)
+{
+    rb_define_method(rb_cObject, "arg1", func_arg1, 0);
+}