+#elif HAVE___FLBF && HAVE___FBUFSIZE /* musl libc */
+ if (__flbf (fp))
+ return _IOLBF;
+ return (__fbufsize (fp) > 0 ? _IOFBF : _IONBF);
+#elif defined EPLAN9 /* Plan9 */
+ if (fp->flags & 2 /* LINEBUF */)
+ return _IOLBF;
+ if (fp->bufl)
+ return _IOFBF;
+ return _IONBF;