Index: include/__config
===================================================================
--- include/__config	(revision 181689)
+++ include/__config	(working copy)
@@ -278,10 +278,20 @@
 #define _LIBCPP_HAS_NO_CONSTEXPR
 #endif
 
-#if ( defined(__FreeBSD__) || defined(__linux__) ) && (__ISO_C_VISIBLE >= 2011 || __cplusplus >= 201103L)
+#if __ISO_C_VISIBLE >= 2011 || __cplusplus >= 201103L
+#if defined(__FreeBSD__)
 #define _LIBCPP_HAS_QUICK_EXIT
 #define _LIBCPP_HAS_C11_FEATURES
+#elif defined(__linux__)
+#include <features.h>
+#if __GLIBC_PREREQ(2, 15)
+#define _LIBCPP_HAS_QUICK_EXIT
 #endif
+#if __GLIBC_PREREQ(2, 17)
+#define _LIBCPP_HAS_C11_FEATURES
+#endif
+#endif
+#endif
 
 #if (__has_feature(cxx_noexcept))
 #  define _NOEXCEPT noexcept