#endif
-#ifndef HAS_LONG_DOUBLE /* XXX What to do about long doubles? */
+#ifdef HAS_LONG_DOUBLE
+# if LONG_DOUBLESIZE > DOUBLESIZE
+# undef HAS_LONG_DOUBLE /* XXX until we figure out how to use them */
+# endif
+#endif
+
+#ifndef HAS_LONG_DOUBLE
#ifdef LDBL_MAX
#undef LDBL_MAX
#endif