Index: include/__config
===================================================================
--- include/__config
+++ include/__config
@@ -714,10 +714,12 @@
 #define _LIBCPP_LOCALE__L_EXTENSIONS 1
 #endif
 
-#if !defined(_WIN32) && !defined(__ANDROID__) && !defined(_NEWLIB_VERSION) && \
-    !defined(__CloudABI__)
+#if defined(__unix__) || (defined(__APPLE__) && defined(__MACH__))
+// Most unix variants have catopen.  These are the specific ones that don't.
+#if !defined(_WIN32) && !defined(__ANDROID__) && !defined(_NEWLIB_VERSION)
 #define _LIBCPP_HAS_CATOPEN 1
 #endif
+#endif
 
 #ifdef __FreeBSD__
 #define _DECLARE_C99_LDBL_MATH 1