Fix std::tuples EBO when targeting the MSVC ABI.
MSVC/clang-cl doesn't do a full EBO unless __declspec(empty_bases)
is applied to the derived type. This causes certain tuple tests
to fail.
This patch adds the empty_bases attribute to __tuple_impl in order
for tuple to fully provide the EBO.
llvm-svn: 292159
diff --git a/libcxx/include/tuple b/libcxx/include/tuple
index cddb709..a17ea01 100644
--- a/libcxx/include/tuple
+++ b/libcxx/include/tuple
@@ -366,7 +366,7 @@
template<class _Indx, class ..._Tp> struct __tuple_impl;
template<size_t ..._Indx, class ..._Tp>
-struct __tuple_impl<__tuple_indices<_Indx...>, _Tp...>
+struct _LIBCPP_DECLSPEC_EMPTY_BASES __tuple_impl<__tuple_indices<_Indx...>, _Tp...>
: public __tuple_leaf<_Indx, _Tp>...
{
_LIBCPP_INLINE_VISIBILITY