+#if !defined (HOST_WIN32)
+
+/*
+ * OS X doesn't define MAP_ANONYMOUS, but it does define MAP_ANON.
+ * Alias them to fix: https://bugzilla.xamarin.com/show_bug.cgi?id=3419
+ */
+#ifdef HOST_DARWIN
+#ifndef MAP_ANONYMOUS
+#define MAP_ANONYMOUS MAP_ANON
+#endif /* ndef MAP_ANONYMOUS */
+#endif /* ndef HOST_DARWIN */
+
+/*
+ * XATTR_AUTO is a synonym for 0 within XattrFlags, but most systems don't
+ * define it. map.c doesn't know that, though, so we ensure that it's defined
+ * so that the value 0 round-trips through MonoPosixHelper.
+ */
+
+#ifndef XATTR_AUTO
+#define XATTR_AUTO 0
+#endif /* ndef XATTR_AUTO */
+
+#endif /* ndef HOST_WIN32 */