diff -up m4-1.4.18/lib/fflush.c.orig m4-1.4.18/lib/fflush.c

--- m4-1.4.18/lib/fflush.c.orig	2018-05-02 12:35:59.536851666 +0200

+++ m4-1.4.18/lib/fflush.c	2018-05-02 12:37:02.768958606 +0200

@@ -33,7 +33,7 @@

 #undef fflush

-#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 */

 /* Clear the stream's ungetc buffer, preserving the value of ftello (fp).  */

 static void

@@ -72,7 +72,7 @@ clear_ungetc_buffer (FILE *fp)

 #endif

-#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 */)

 # if (defined __sferror || defined __DragonFly__ || defined __ANDROID__) && defined __SNPT

 /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Android */

@@ -148,7 +148,7 @@ rpl_fflush (FILE *stream)

   if (stream == NULL || ! freading (stream))

     return fflush (stream);

-#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 */

   clear_ungetc_buffer_preserving_position (stream);

diff -up m4-1.4.18/lib/fpending.c.orig m4-1.4.18/lib/fpending.c

--- m4-1.4.18/lib/fpending.c.orig	2018-05-02 12:35:32.305806774 +0200

+++ m4-1.4.18/lib/fpending.c	2018-05-02 12:35:44.944827347 +0200

@@ -32,7 +32,7 @@ __fpending (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 */

   return fp->_IO_write_ptr - fp->_IO_write_base;

 #elif defined __sferror || defined __DragonFly__ || defined __ANDROID__

   /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin, Android */

diff -up m4-1.4.18/lib/fpurge.c.orig m4-1.4.18/lib/fpurge.c

--- m4-1.4.18/lib/fpurge.c.orig	2018-05-02 12:38:13.586078669 +0200

+++ m4-1.4.18/lib/fpurge.c	2018-05-02 12:38:38.785121867 +0200

@@ -62,7 +62,7 @@ fpurge (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->_IO_read_end = fp->_IO_read_ptr;

   fp->_IO_write_ptr = fp->_IO_write_base;

   /* Avoid memory leak when there is an active ungetc buffer.  */

diff -up m4-1.4.18/lib/freadahead.c.orig m4-1.4.18/lib/freadahead.c

--- m4-1.4.18/lib/freadahead.c.orig	2016-12-31 14:54:41.000000000 +0100

+++ m4-1.4.18/lib/freadahead.c	2018-05-02 11:43:19.570336724 +0200

@@ -25,7 +25,7 @@

 size_t

 freadahead (FILE *fp)

 {

-#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 */

   if (fp->_IO_write_ptr > fp->_IO_write_base)

     return 0;

   return (fp->_IO_read_end - fp->_IO_read_ptr)

diff -up m4-1.4.18/lib/freading.c.orig m4-1.4.18/lib/freading.c

--- m4-1.4.18/lib/freading.c.orig	2018-05-02 12:37:33.970011368 +0200

+++ m4-1.4.18/lib/freading.c	2018-05-02 12:37:59.393054359 +0200

@@ -31,7 +31,7 @@ freading (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 */

   return ((fp->_flags & _IO_NO_WRITES) != 0

           || ((fp->_flags & (_IO_NO_READS | _IO_CURRENTLY_PUTTING)) == 0

               && fp->_IO_read_base != NULL));

diff -up m4-1.4.18/lib/fseeko.c.orig m4-1.4.18/lib/fseeko.c

--- m4-1.4.18/lib/fseeko.c.orig	2018-05-02 11:44:17.947460233 +0200

+++ m4-1.4.18/lib/fseeko.c	2018-05-02 12:39:49.537216897 +0200

@@ -47,7 +47,7 @@ fseeko (FILE *fp, off_t offset, int when

 #endif

   /* These tests are based on fpurge.c.  */

-#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 */

   if (fp->_IO_read_end == fp->_IO_read_ptr

       && fp->_IO_write_ptr == fp->_IO_write_base

       && fp->_IO_save_base == NULL)

@@ -123,7 +123,7 @@ fseeko (FILE *fp, off_t offset, int when

           return -1;

         }

-#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_EOF_SEEN;

       fp->_offset = pos;

 #elif defined __sferror || defined __DragonFly__ || defined __ANDROID__

diff -up m4-1.4.18/lib/stdio-impl.h.orig m4-1.4.18/lib/stdio-impl.h

--- m4-1.4.18/lib/stdio-impl.h.orig	2016-12-31 14:54:42.000000000 +0100

+++ m4-1.4.18/lib/stdio-impl.h	2018-05-02 11:43:19.570336724 +0200

@@ -18,6 +18,12 @@

    the same implementation of stdio extension API, except that some fields

    have different naming conventions, or their access requires some casts.  */

+/* Glibc 2.28 made _IO_IN_BACKUP private.  For now, work around this

+   problem by defining it ourselves.  FIXME: Do not rely on glibc

+   internals.  */

+#if !defined _IO_IN_BACKUP && defined _IO_EOF_SEEN

+# define _IO_IN_BACKUP 0x100

+#endif

 /* BSD stdio derived implementations.  */