Implement the infrastructure for feature-test macros. Very few actual feature test macros, though. Reviewed as: https://reviews.llvm.org/D51955
git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@342073 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/atomic b/include/atomic
index 809f78a..d37e7b4 100644
--- a/include/atomic
+++ b/include/atomic
@@ -544,6 +544,7 @@
#include <cstddef>
#include <cstdint>
#include <type_traits>
+#include <version>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#pragma GCC system_header
@@ -559,10 +560,6 @@
#error C++ standard library is incompatible with <stdatomic.h>
#endif
-#if _LIBCPP_STD_VER > 14
-# define __cpp_lib_atomic_is_always_lock_free 201603L
-#endif
-
#define _LIBCPP_CHECK_STORE_MEMORY_ORDER(__m) \
_LIBCPP_DIAGNOSE_WARNING(__m == memory_order_consume || \
__m == memory_order_acquire || \