+#if defined(__has_builtin)
+#define FOLLY_HAS_BUILTIN(...) __has_builtin(__VA_ARGS__)
+#else
+#define FOLLY_HAS_BUILTIN(...) 0
+#endif
+
+#if defined(__has_feature)
+#define FOLLY_HAS_FEATURE(...) __has_feature(__VA_ARGS__)
+#else
+#define FOLLY_HAS_FEATURE(...) 0
+#endif
+