Index: libcxx/src/include/config_elast.h
===================================================================
--- libcxx/src/include/config_elast.h
+++ libcxx/src/include/config_elast.h
@@ -39,6 +39,8 @@
 #define _LIBCPP_ELAST 1160
 #elif defined(_LIBCPP_MSVCRT_LIKE)
 #define _LIBCPP_ELAST (_sys_nerr - 1)
+#elif defined(_AIX)
+#define _LIBCPP_ELAST 127
 #else
 // Warn here so that the person doing the libcxx port has an easier time:
 #warning ELAST for this platform not yet implemented