--- m4-1.4.16.orig/lib/freadahead.c	2011-03-01 17:39:27.000000000 +0100
+++ m4-1.4.16/lib/freadahead.c	2013-09-04 13:53:26.000000000 +0200
@@ -22,6 +22,7 @@
 #include <stdlib.h>
 #include "stdio-impl.h"
 
+#ifndef HAVE___FREADAHEAD
 size_t
 freadahead (FILE *fp)
 {
@@ -83,3 +84,4 @@ freadahead (FILE *fp)
  #error "Please port gnulib freadahead.c to your platform! Look at the definition of fflush, fread, ungetc on your system, then report this to bug-gnulib."
 #endif
 }
+#endif