--- a/libcxx/include/cstdint	Mon May 25 11:55:54 2020 +0900
+++ b/libcxx/include/cstdint	Tue Jun 08 06:07:14 2021 +0900
@@ -149,42 +149,42 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-using::int8_t;
-using::int16_t;
-using::int32_t;
-using::int64_t;
+using ::int8_t _LIBCPP_USING_IF_EXISTS;
+using ::int16_t _LIBCPP_USING_IF_EXISTS;
+using ::int32_t _LIBCPP_USING_IF_EXISTS;
+using ::int64_t _LIBCPP_USING_IF_EXISTS;
 
-using::uint8_t;
-using::uint16_t;
-using::uint32_t;
-using::uint64_t;
+using ::uint8_t _LIBCPP_USING_IF_EXISTS;
+using ::uint16_t _LIBCPP_USING_IF_EXISTS;
+using ::uint32_t _LIBCPP_USING_IF_EXISTS;
+using ::uint64_t _LIBCPP_USING_IF_EXISTS;
 
-using::int_least8_t;
-using::int_least16_t;
-using::int_least32_t;
-using::int_least64_t;
+using ::int_least8_t _LIBCPP_USING_IF_EXISTS;
+using ::int_least16_t _LIBCPP_USING_IF_EXISTS;
+using ::int_least32_t _LIBCPP_USING_IF_EXISTS;
+using ::int_least64_t _LIBCPP_USING_IF_EXISTS;
 
-using::uint_least8_t;
-using::uint_least16_t;
-using::uint_least32_t;
-using::uint_least64_t;
+using ::uint_least8_t _LIBCPP_USING_IF_EXISTS;
+using ::uint_least16_t _LIBCPP_USING_IF_EXISTS;
+using ::uint_least32_t _LIBCPP_USING_IF_EXISTS;
+using ::uint_least64_t _LIBCPP_USING_IF_EXISTS;
 
-using::int_fast8_t;
-using::int_fast16_t;
-using::int_fast32_t;
-using::int_fast64_t;
+using ::int_fast8_t _LIBCPP_USING_IF_EXISTS;
+using ::int_fast16_t _LIBCPP_USING_IF_EXISTS;
+using ::int_fast32_t _LIBCPP_USING_IF_EXISTS;
+using ::int_fast64_t _LIBCPP_USING_IF_EXISTS;
 
-using::uint_fast8_t;
-using::uint_fast16_t;
-using::uint_fast32_t;
-using::uint_fast64_t;
+using ::uint_fast8_t _LIBCPP_USING_IF_EXISTS;
+using ::uint_fast16_t _LIBCPP_USING_IF_EXISTS;
+using ::uint_fast32_t _LIBCPP_USING_IF_EXISTS;
+using ::uint_fast64_t _LIBCPP_USING_IF_EXISTS;
 
-using::intptr_t;
-using::uintptr_t;
+using ::intptr_t _LIBCPP_USING_IF_EXISTS;
+using ::uintptr_t _LIBCPP_USING_IF_EXISTS;
 
-using::intmax_t;
-using::uintmax_t;
+using ::intmax_t _LIBCPP_USING_IF_EXISTS;
+using ::uintmax_t _LIBCPP_USING_IF_EXISTS;
 
 _LIBCPP_END_NAMESPACE_STD
 
-#endif  // _LIBCPP_CSTDINT
+#endif // _LIBCPP_CSTDINT