--- a/m4/check-decl.m4
+++ b/m4/check-decl.m4
@@ -1,10 +1,29 @@
-#serial 2
+#serial 3
 
 dnl This is just a wrapper function to encapsulate this kludge.
 dnl Putting it in a separate file like this helps share it between
 dnl different packages.
 AC_DEFUN(jm_CHECK_DECLS,
 [
+  headers='
+#include <stdio.h>
+#ifdef HAVE_STRING_H
+# if !STDC_HEADERS && HAVE_MEMORY_H
+#  include <memory.h>
+# endif
+# include <string.h>
+#else
+# ifdef HAVE_STRINGS_H
+#  include <strings.h>
+# endif
+#endif
+#ifdef HAVE_STDLIB_H
+# include <stdlib.h>
+#endif
+#ifdef HAVE_UNISTD_H
+# include <unistd.h>
+#endif
+'
   if test x = y; then
     dnl This code is deliberately never run via ./configure.
     dnl FIXME: this is a gross hack to make autoheader put entries
@@ -14,5 +33,44 @@
     AC_CHECK_FUNCS(DECL_FREE DECL_LSEEK DECL_MALLOC DECL_MEMCHR DECL_REALLOC \
 		   DECL_STPCPY DECL_STRSTR)
   fi
-  jm_CHECK_DECLARATIONS(free lseek malloc memchr realloc stpcpy strstr)
+  jm_CHECK_DECLARATIONS($headers, free lseek malloc \
+                        memchr realloc stpcpy strstr)
+
+  # Check for a declaration of localtime_r.
+  jm_CHECK_DECL_LOCALTIME_R
 ])
+
+dnl localtime_r is a special case...
+dnl Code that uses the result of this test must use the same cpp
+dnl directives as are used below.  Also include the following declaration
+dnl after the inclusion of time.h.
+dnl
+dnl #if ! defined HAVE_DECL_LOCALTIME_R
+dnl extern struct tm* localtime_r ();
+dnl #endif
+AC_DEFUN(jm_CHECK_DECL_LOCALTIME_R,
+[
+  if test x = y; then
+    dnl This code is deliberately never run via ./configure.
+    dnl FIXME: this is a gross hack to make autoheader put entries
+    dnl for each of these symbols in the config.h.in.
+    dnl Otherwise, I'd have to update acconfig.h every time I change
+    dnl this list of functions.
+    AC_CHECK_FUNCS(DECL_LOCALTIME_R)
+  fi
+
+  headers='
+/* Some systems need this in order to declare localtime_r properly.  */
+#ifndef __EXTENSIONS__
+# define __EXTENSIONS__ 1
+#endif
+
+#if HAVE_UNISTD_H
+# include <unistd.h>
+#endif
+
+#include <sys/types.h>
+#include <time.h>
+'
+  jm_CHECK_DECLARATIONS($headers, localtime_r)
+])