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diff --git a/gl/m4/mktime.m4 b/gl/m4/mktime.m4
--- /dev/null
+++ b/gl/m4/mktime.m4
@@ -0,0 +1,224 @@
+# serial 14
+dnl Copyright (C) 2002-2003, 2005-2007, 2009 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl From Jim Meyering.
+
+# Redefine AC_FUNC_MKTIME, to fix a bug in Autoconf 2.61a and earlier.
+# This redefinition can be removed once a new version of Autoconf is assumed.
+# The redefinition is taken from
+# <http://cvs.sv.gnu.org/viewcvs/*checkout*/autoconf/autoconf/lib/autoconf/functions.m4?rev=1.119>.
+# AC_FUNC_MKTIME
+# --------------
+AC_DEFUN([AC_FUNC_MKTIME],
+[AC_CHECK_HEADERS_ONCE([unistd.h])
+AC_CHECK_FUNCS_ONCE([alarm])
+AC_CACHE_CHECK([for working mktime], [ac_cv_func_working_mktime],
+[AC_RUN_IFELSE([AC_LANG_SOURCE(
+[[/* Test program from Paul Eggert and Tony Leneis. */
+#include <limits.h>
+#include <stdlib.h>
+#include <time.h>
+
+#ifdef HAVE_UNISTD_H
+# include <unistd.h>
+#endif
+
+#ifndef HAVE_ALARM
+# define alarm(X) /* empty */
+#endif
+
+/* Work around redefinition to rpl_putenv by other config tests. */
+#undef putenv
+
+static time_t time_t_max;
+static time_t time_t_min;
+
+/* Values we'll use to set the TZ environment variable. */
+static char *tz_strings[] = {
+ (char *) 0, "TZ=GMT0", "TZ=JST-9",
+ "TZ=EST+3EDT+2,M10.1.0/00:00:00,M2.3.0/00:00:00"
+};
+#define N_STRINGS (sizeof (tz_strings) / sizeof (tz_strings[0]))
+
+/* Return 0 if mktime fails to convert a date in the spring-forward gap.
+ Based on a problem report from Andreas Jaeger. */
+static int
+spring_forward_gap ()
+{
+ /* glibc (up to about 1998-10-07) failed this test. */
+ struct tm tm;
+
+ /* Use the portable POSIX.1 specification "TZ=PST8PDT,M4.1.0,M10.5.0"
+ instead of "TZ=America/Vancouver" in order to detect the bug even
+ on systems that don't support the Olson extension, or don't have the
+ full zoneinfo tables installed. */
+ putenv ("TZ=PST8PDT,M4.1.0,M10.5.0");
+
+ tm.tm_year = 98;
+ tm.tm_mon = 3;
+ tm.tm_mday = 5;
+ tm.tm_hour = 2;
+ tm.tm_min = 0;
+ tm.tm_sec = 0;
+ tm.tm_isdst = -1;
+ return mktime (&tm) != (time_t) -1;
+}
+
+static int
+mktime_test1 (time_t now)
+{
+ struct tm *lt;
+ return ! (lt = localtime (&now)) || mktime (lt) == now;
+}
+
+static int
+mktime_test (time_t now)
+{
+ return (mktime_test1 (now)
+ && mktime_test1 ((time_t) (time_t_max - now))
+ && mktime_test1 ((time_t) (time_t_min + now)));
+}
+
+static int
+irix_6_4_bug ()
+{
+ /* Based on code from Ariel Faigon. */
+ struct tm tm;
+ tm.tm_year = 96;
+ tm.tm_mon = 3;
+ tm.tm_mday = 0;
+ tm.tm_hour = 0;
+ tm.tm_min = 0;
+ tm.tm_sec = 0;
+ tm.tm_isdst = -1;
+ mktime (&tm);
+ return tm.tm_mon == 2 && tm.tm_mday == 31;
+}
+
+static int
+bigtime_test (int j)
+{
+ struct tm tm;
+ time_t now;
+ tm.tm_year = tm.tm_mon = tm.tm_mday = tm.tm_hour = tm.tm_min = tm.tm_sec = j;
+ now = mktime (&tm);
+ if (now != (time_t) -1)
+ {
+ struct tm *lt = localtime (&now);
+ if (! (lt
+ && lt->tm_year == tm.tm_year
+ && lt->tm_mon == tm.tm_mon
+ && lt->tm_mday == tm.tm_mday
+ && lt->tm_hour == tm.tm_hour
+ && lt->tm_min == tm.tm_min
+ && lt->tm_sec == tm.tm_sec
+ && lt->tm_yday == tm.tm_yday
+ && lt->tm_wday == tm.tm_wday
+ && ((lt->tm_isdst < 0 ? -1 : 0 < lt->tm_isdst)
+ == (tm.tm_isdst < 0 ? -1 : 0 < tm.tm_isdst))))
+ return 0;
+ }
+ return 1;
+}
+
+static int
+year_2050_test ()
+{
+ /* The correct answer for 2050-02-01 00:00:00 in Pacific time,
+ ignoring leap seconds. */
+ unsigned long int answer = 2527315200UL;
+
+ struct tm tm;
+ time_t t;
+ tm.tm_year = 2050 - 1900;
+ tm.tm_mon = 2 - 1;
+ tm.tm_mday = 1;
+ tm.tm_hour = tm.tm_min = tm.tm_sec = 0;
+ tm.tm_isdst = -1;
+
+ /* Use the portable POSIX.1 specification "TZ=PST8PDT,M4.1.0,M10.5.0"
+ instead of "TZ=America/Vancouver" in order to detect the bug even
+ on systems that don't support the Olson extension, or don't have the
+ full zoneinfo tables installed. */
+ putenv ("TZ=PST8PDT,M4.1.0,M10.5.0");
+
+ t = mktime (&tm);
+
+ /* Check that the result is either a failure, or close enough
+ to the correct answer that we can assume the discrepancy is
+ due to leap seconds. */
+ return (t == (time_t) -1
+ || (0 < t && answer - 120 <= t && t <= answer + 120));
+}
+
+int
+main ()
+{
+ time_t t, delta;
+ int i, j;
+
+ /* This test makes some buggy mktime implementations loop.
+ Give up after 60 seconds; a mktime slower than that
+ isn't worth using anyway. */
+ alarm (60);
+
+ for (;;)
+ {
+ t = (time_t_max << 1) + 1;
+ if (t <= time_t_max)
+ break;
+ time_t_max = t;
+ }
+ time_t_min = - ((time_t) ~ (time_t) 0 == (time_t) -1) - time_t_max;
+
+ delta = time_t_max / 997; /* a suitable prime number */
+ for (i = 0; i < N_STRINGS; i++)
+ {
+ if (tz_strings[i])
+ putenv (tz_strings[i]);
+
+ for (t = 0; t <= time_t_max - delta; t += delta)
+ if (! mktime_test (t))
+ return 1;
+ if (! (mktime_test ((time_t) 1)
+ && mktime_test ((time_t) (60 * 60))
+ && mktime_test ((time_t) (60 * 60 * 24))))
+ return 1;
+
+ for (j = 1; ; j <<= 1)
+ if (! bigtime_test (j))
+ return 1;
+ else if (INT_MAX / 2 < j)
+ break;
+ if (! bigtime_test (INT_MAX))
+ return 1;
+ }
+ return ! (irix_6_4_bug () && spring_forward_gap () && year_2050_test ());
+}]])],
+ [ac_cv_func_working_mktime=yes],
+ [ac_cv_func_working_mktime=no],
+ [ac_cv_func_working_mktime=no])])
+if test $ac_cv_func_working_mktime = no; then
+ AC_LIBOBJ([mktime])
+fi
+])# AC_FUNC_MKTIME
+
+AC_DEFUN([gl_FUNC_MKTIME],
+[
+ AC_FUNC_MKTIME
+ dnl Note: AC_FUNC_MKTIME does AC_LIBOBJ([mktime]).
+ if test $ac_cv_func_working_mktime = no; then
+ AC_DEFINE([mktime], [rpl_mktime],
+ [Define to rpl_mktime if the replacement function should be used.])
+ gl_PREREQ_MKTIME
+ fi
+])
+
+# Prerequisites of lib/mktime.c.
+AC_DEFUN([gl_PREREQ_MKTIME],
+[
+ AC_REQUIRE([AC_C_INLINE])
+])