re PR libstdc++/78996 (<variant> uses macro as name)

2017-01-05  Tim Shen  <timshen@google.com>

	PR libstdc++/78996
	* include/std/variant (__gen_vtable_impl): rename __unused to
	__dimensions to avoid naming conflict.

From-SVN: r244092

libstdc++-v3/ChangeLog

+2017-01-05  Tim Shen  <timshen@google.com>
+
+	PR libstdc++/78996
+	* include/std/variant (__gen_vtable_impl): rename __unused to
+	__dimensions to avoid naming conflict.
+
 2017-01-04  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/78968

libstdc++-v3/include/std/variant

@@ -604,17 +604,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _Array_type, typename _Variant_tuple, typename _Index_seq>
     struct __gen_vtable_impl;
 
-  template<typename _Result_type, typename _Visitor, size_t... __unused,
+  template<typename _Result_type, typename _Visitor, size_t... __dimensions,
 	   typename... _Variants, size_t... __indices>
     struct __gen_vtable_impl<
-	_Multi_array<_Result_type (*)(_Visitor, _Variants...), __unused...>,
+	_Multi_array<_Result_type (*)(_Visitor, _Variants...), __dimensions...>,
 	tuple<_Variants...>, std::index_sequence<__indices...>>
     {
       using _Next =
 	  remove_reference_t<typename _Nth_type<sizeof...(__indices),
 			     _Variants...>::type>;
       using _Array_type =
-	  _Multi_array<_Result_type (*)(_Visitor, _Variants...), __unused...>;
+	  _Multi_array<_Result_type (*)(_Visitor, _Variants...),
+		       __dimensions...>;
 
       static constexpr _Array_type
       _S_apply()