-#elif defined _IOERR /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, mingw */
+# elif defined _IOERR /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, mingw, NonStop Kernel */
+# if defined __sun /* Solaris */
+ return (fp->_flag & _IOREAD) != 0 && (fp->_flag & _IOWRT) == 0;
+# else