commit 4af4a4a71827c0bc5e0ec67af23edef4f15cee8e
Author: Paul Eggert <address@hidden>
Date:   Mon Mar 5 10:56:29 2018 -0800

    fflush: adjust to glibc 2.28 libio.h removal
    (Only part of this commit was backported as needed.)

diff -Nrup a/lib/fseterr.c b/lib/fseterr.c
--- a/lib/fseterr.c	2015-01-04 11:43:50.000000000 -0500
+++ b/lib/fseterr.c	2018-08-06 01:27:29.869844228 -0400
@@ -29,7 +29,7 @@ fseterr (FILE *fp)
   /* Most systems provide FILE as a struct and the necessary bitmask in
      <stdio.h>, because they need it for implementing getc() and putc() as
      fast macros.  */
-#if defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Haiku, Linux libc5 */
+#if defined _IO_EOF_SEEN || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Haiku, Linux libc5 */
   fp->_flags |= _IO_ERR_SEEN;
 #elif defined __sferror || defined __DragonFly__ /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin */
   fp_->_flags |= __SERR;