Index: __config
===================================================================
--- __config	(revision 191183)
+++ __config	(working copy)
@@ -79,6 +79,9 @@
 #  endif
 #  if defined(_MSC_VER) && !defined(__clang__)
 #    define _LIBCPP_MSVC // Using Microsoft Visual C++ compiler
+#    define _LIBCPP_TOSTRING2(x) #x
+#    define _LIBCPP_TOSTRING(x) _LIBCPP_TOSTRING2(x)
+#    define _LIBCPP_WARNING(x) __pragma(message(__FILE__ "(" _LIBCPP_TOSTRING(__LINE__) ") : warning note: " x))
 #  endif
 #  // If mingw not explicitly detected, assume using MS C runtime only.
 #  ifndef __MINGW32__
@@ -579,4 +582,16 @@
 #define _LIBCPP_EXPLICIT_AFTER_CXX11 explicit
 #endif
 
+// Try to find out if RTTI is disabled.
+// g++ and cl.exe have RTTI on by default and define a macro when it is.
+// g++ only defines the macro in 4.3.2 and onwards.
+#if !defined(_LIBCPP_NO_RTTI)
+#  if defined(__GNUG__) && (__GNUC__ >= 4 && \
+   (__GNUC_MINOR__ >= 3 || __GNUC_PATCHLEVEL__ >= 2)) && !defined(__GXX_RTTI)
+#    define _LIBCPP_NO_RTTI
+#  elif (defined(_MSC_VER) && !defined(__clang__)) && !defined(_CPPRTTI)
+#    define _LIBCPP_NO_RTTI
+#  endif
+#endif
+
 #endif  // _LIBCPP_CONFIG