Date: Sun, 24 Jan 1999 10:38:12 +0200 (IST)
From: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
X-Sender: eliz AT is
To: DJ Delorie <dj AT delorie DOT com>
cc: djgpp-workers AT delorie DOT com
Subject: Re: ctime.c problems
Message-ID: <Pine.SUN.3.91.990124103458.4501E-100000@is>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Reply-To: djgpp-workers AT delorie DOT com

Here's a test program I used to debug ctime.c.  It is derived from what 
Textutils uses as part of its configure script.

#include <stdlib.h>
#include <stdio.h>
/* Test program from Paul Eggert (eggert AT twinsun DOT com)
   and Tony Leneis (tony AT plaza DOT ds DOT adp DOT com).  */
# include <sys/time.h>
# include <time.h>
# include <unistd.h>

static time_t time_t_max;

/* Values we'll use to set the TZ environment variable.  */
static const char *const tz_strings[] = {
  (const 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]))

static void
fail (char *test, int status)
{
  if (status)
    fprintf (stderr, "%s test failed\n", test);
  exit (status);
}

/* Fail if mktime fails to convert a date in the spring-forward gap.
   Based on a problem report from Andreas Jaeger.  */
static void
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;
  if (mktime (&tm) == (time_t)-1)
    fail ("spring-forward gap", 1);
}

static void
mktime_test (now)
     time_t now;
{
  struct tm *lt;

  if ((lt = localtime (&now)) && mktime (lt) != now)
    exit (1);
  now = time_t_max - now;
  if ((lt = localtime (&now)) && mktime (lt) != now)
    fail ("mktime_test", 1);
}

static void
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);
  if (tm.tm_mon != 2 || tm.tm_mday != 31)
    fail ("Irix-6-4", 1);
}

static void
bigtime_test (j)
     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;
  /* This test makes some buggy mktime implementations loop.
     Give up after 10 seconds.  */
  alarm (10);
  now = mktime (&tm);
  alarm (0);
  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))))
	fail ("bigtime", 1);
    }
}

int
main ()
{
  time_t t, delta;
  int i, j;

  spring_forward_gap ();
  for (time_t_max = 1; 0 < time_t_max; time_t_max *= 2)
    continue;
  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)
	mktime_test (t);
      mktime_test ((time_t) 60 * 60);
      mktime_test ((time_t) 60 * 60 * 24);

      for (j = 1; 0 < j; j *= 2)
	bigtime_test (j);
      bigtime_test (j - 1);
    }
  irix_6_4_bug ();
  exit (0);
}