diff --git a/libcxx/include/__config b/libcxx/include/__config
--- a/libcxx/include/__config
+++ b/libcxx/include/__config
@@ -394,8 +394,7 @@
 #  ifndef _LIBCPP_CXX03_LANG
 
 #    define _LIBCPP_ALIGNOF(_Tp) alignof(_Tp)
-#    define _ALIGNAS_TYPE(x) alignas(x)
-#    define _ALIGNAS(x) alignas(x)
+#    define _ALIGNAS(...) alignas(__VA_ARGS__)
 #    define _LIBCPP_NORETURN [[noreturn]]
 #    define _NOEXCEPT noexcept
 #    define _NOEXCEPT_(x) noexcept(x)
@@ -403,8 +402,7 @@
 #  else
 
 #    define _LIBCPP_ALIGNOF(_Tp) _Alignof(_Tp)
-#    define _ALIGNAS_TYPE(x) __attribute__((__aligned__(_LIBCPP_ALIGNOF(x))))
-#    define _ALIGNAS(x) __attribute__((__aligned__(x)))
+#    define _ALIGNAS(...) _Alignas(__VA_ARGS__)
 #    define _LIBCPP_NORETURN __attribute__((noreturn))
 #    define _LIBCPP_HAS_NO_NOEXCEPT
 #    define nullptr __nullptr
diff --git a/libcxx/include/__memory/shared_ptr.h b/libcxx/include/__memory/shared_ptr.h
--- a/libcxx/include/__memory/shared_ptr.h
+++ b/libcxx/include/__memory/shared_ptr.h
@@ -330,7 +330,7 @@
     // we now use a properly aligned char buffer while making sure that we maintain
     // the same layout that we had when we used a compressed pair.
     using _CompressedPair = __compressed_pair<_Alloc, _Tp>;
-    struct _ALIGNAS_TYPE(_CompressedPair) _Storage {
+    struct _ALIGNAS(_CompressedPair) _Storage {
         char __blob_[sizeof(_CompressedPair)];
 
         _LIBCPP_HIDE_FROM_ABI explicit _Storage(_Alloc&& __a) {
diff --git a/libcxx/include/array b/libcxx/include/array
--- a/libcxx/include/array
+++ b/libcxx/include/array
@@ -272,7 +272,7 @@
                                 char>::type _CharType;
 
     struct  _ArrayInStructT { _Tp __data_[1]; };
-    _ALIGNAS_TYPE(_ArrayInStructT) _CharType __elems_[sizeof(_ArrayInStructT)];
+    _ALIGNAS(_ArrayInStructT) _CharType __elems_[sizeof(_ArrayInStructT)];
 
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
     value_type* data() _NOEXCEPT {return nullptr;}
diff --git a/libcxx/test/support/test_macros.h b/libcxx/test/support/test_macros.h
--- a/libcxx/test/support/test_macros.h
+++ b/libcxx/test/support/test_macros.h
@@ -127,7 +127,7 @@
 #   else
 #    define TEST_ALIGNOF(...) __alignof(__VA_ARGS__)
 #   endif
-# define TEST_ALIGNAS(...) __attribute__((__aligned__(__VA_ARGS__)))
+# define TEST_ALIGNAS(...) _Alignas(__VA_ARGS__)
 # define TEST_CONSTEXPR
 # define TEST_NOEXCEPT throw()
 # define TEST_NOEXCEPT_FALSE