--- a/lib/strnlen.c
+++ b/lib/strnlen.c
@@ -21,21 +21,7 @@
 #endif
 #undef strnlen
 
-#if HAVE_STRING_H
-# if !STDC_HEADERS && HAVE_MEMORY_H
-#  include <memory.h>
-# endif
-# include <string.h>
-#else
-# include <strings.h>
-#endif
-
-#ifndef HAVE_DECL_MEMCHR
-"this configure-time declaration test was not run"
-#endif
-#if !HAVE_DECL_MEMCHR
-char *memchr ();
-#endif
+#include <string.h>
 
 #undef __strnlen
 #undef strnlen

--- a/m4/strnlen.m4
+++ b/m4/strnlen.m4
@@ -1,4 +1,4 @@
-# strnlen.m4 serial 2
+# strnlen.m4 serial 3
 dnl Copyright (C) 2002-2003 Free Software Foundation, Inc.
 dnl This file is free software, distributed under the terms of the GNU
 dnl General Public License.  As a special exception to the GNU General
@@ -24,9 +24,4 @@
 ])
 
 # Prerequisites of lib/strnlen.c.
-AC_DEFUN([gl_PREREQ_STRNLEN], [
-  AC_REQUIRE([AC_HEADER_STDC])
-  AC_CHECK_HEADERS_ONCE(memory.h string.h)
-  AC_CHECK_DECLS(memchr)
-])
-
+AC_DEFUN([gl_PREREQ_STRNLEN], [:])