xref: /src/lib/libc/time/zdump.c

/*	$NetBSD: zdump.c,v 1.43.2.1 2016/11/04 14:48:53 pgoyette Exp $	*/
/*
** This file is in the public domain, so clarified as of
** 2009-05-17 by Arthur David Olson.
*/

#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: zdump.c,v 1.43.2.1 2016/11/04 14:48:53 pgoyette Exp $");
#endif /* !defined lint */

/*
** This code has been made independent of the rest of the time
** conversion package to increase confidence in the verification it provides.
** You can use this code to help in verifying other implementations.
**
** To do this, compile with -DUSE_LTZ=0 and link without the tz library.
*/

#ifndef NETBSD_INSPIRED
# define NETBSD_INSPIRED 1
#endif
#ifndef USE_LTZ
# define USE_LTZ 1
#endif

#if USE_LTZ
#include "private.h"
#endif

/* Enable tm_gmtoff and tm_zone on GNUish systems.  */
#define _GNU_SOURCE 1
/* Enable strtoimax on Solaris 10.  */
#define __EXTENSIONS__ 1

#include "stdio.h"	/* for stdout, stderr */
#include "string.h"	/* for strcpy */
#include "sys/types.h"	/* for time_t */
#include "time.h"	/* for struct tm */
#include "stdlib.h"	/* for exit, malloc, atoi */
#include "limits.h"	/* for CHAR_BIT, LLONG_MAX */
#include <errno.h>
#include <err.h>

/*
** Substitutes for pre-C99 compilers.
** Much of this section of code is stolen from private.h.
*/

#ifndef HAVE_STDINT_H
# define HAVE_STDINT_H \
    (199901 <= __STDC_VERSION__ \
     || 2 < __GLIBC__ + (1 <= __GLIBC_MINOR__)	\
     || __CYGWIN__ || INTMAX_MAX)
#endif
#if HAVE_STDINT_H
# include "stdint.h"
#endif
#ifndef HAVE_INTTYPES_H
# define HAVE_INTTYPES_H HAVE_STDINT_H
#endif
#if HAVE_INTTYPES_H
# include <inttypes.h>
#endif

#ifndef INT_FAST32_MAX
# if INT_MAX >> 31 == 0
typedef long int_fast32_t;
# else
typedef int int_fast32_t;
# endif
#endif

/* Pre-C99 GCC compilers define __LONG_LONG_MAX__ instead of LLONG_MAX.  */
#if !defined LLONG_MAX && defined __LONG_LONG_MAX__
# define LLONG_MAX __LONG_LONG_MAX__
#endif

#ifndef INTMAX_MAX
# ifdef LLONG_MAX
typedef long long intmax_t;
#  define strtoimax strtoll
#  define INTMAX_MAX LLONG_MAX
# else
typedef long intmax_t;
#  define strtoimax strtol
#  define INTMAX_MAX LONG_MAX
# endif
#endif

#ifndef PRIdMAX
# if INTMAX_MAX == LLONG_MAX
#  define PRIdMAX "lld"
# else
#  define PRIdMAX "ld"
# endif
#endif

/* Infer TM_ZONE on systems where this information is known, but suppress
   guessing if NO_TM_ZONE is defined.  Similarly for TM_GMTOFF.  */
#if (defined __GLIBC__ \
     || defined __FreeBSD__ || defined __NetBSD__ || defined __OpenBSD__ \
     || (defined __APPLE__ && defined __MACH__))
# if !defined TM_GMTOFF && !defined NO_TM_GMTOFF
#  define TM_GMTOFF tm_gmtoff
# endif
# if !defined TM_ZONE && !defined NO_TM_ZONE
#  define TM_ZONE tm_zone
# endif
#endif

#ifndef HAVE_LOCALTIME_R
# define HAVE_LOCALTIME_R 1
#endif

#ifndef HAVE_LOCALTIME_RZ
# ifdef TM_ZONE
#  define HAVE_LOCALTIME_RZ (NETBSD_INSPIRED && USE_LTZ)
# else
#  define HAVE_LOCALTIME_RZ 0
# endif
#endif

#ifndef HAVE_TZSET
# define HAVE_TZSET 1
#endif

#ifndef ZDUMP_LO_YEAR
#define ZDUMP_LO_YEAR	(-500)
#endif /* !defined ZDUMP_LO_YEAR */

#ifndef ZDUMP_HI_YEAR
#define ZDUMP_HI_YEAR	2500
#endif /* !defined ZDUMP_HI_YEAR */

#ifndef MAX_STRING_LENGTH
#define MAX_STRING_LENGTH	1024
#endif /* !defined MAX_STRING_LENGTH */

#if __STDC_VERSION__ < 199901
# define true 1
# define false 0
# define bool int
#else
# include <stdbool.h>
#endif

#ifndef TYPE_BIT
#define TYPE_BIT(type)	(sizeof (type) * CHAR_BIT)
#endif /* !defined TYPE_BIT */

#ifndef TYPE_SIGNED
#define TYPE_SIGNED(type) (((type) -1) < 0)
#endif /* !defined TYPE_SIGNED */

#ifndef INT_STRLEN_MAXIMUM
/*
** 302 / 1000 is log10(2.0) rounded up.
** Subtract one for the sign bit if the type is signed;
** add one for integer division truncation;
** add one more for a minus sign if the type is signed.
*/
#define INT_STRLEN_MAXIMUM(type) \
	((TYPE_BIT(type) - TYPE_SIGNED(type)) * 302 / 1000 + \
	1 + TYPE_SIGNED(type))
#endif /* !defined INT_STRLEN_MAXIMUM */

#ifndef EXIT_SUCCESS
#define EXIT_SUCCESS	0
#endif /* !defined EXIT_SUCCESS */

#ifndef EXIT_FAILURE
#define EXIT_FAILURE	1
#endif /* !defined EXIT_FAILURE */

#ifndef SECSPERMIN
#define SECSPERMIN	60
#endif /* !defined SECSPERMIN */

#ifndef MINSPERHOUR
#define MINSPERHOUR	60
#endif /* !defined MINSPERHOUR */

#ifndef SECSPERHOUR
#define SECSPERHOUR	(SECSPERMIN * MINSPERHOUR)
#endif /* !defined SECSPERHOUR */

#ifndef HOURSPERDAY
#define HOURSPERDAY	24
#endif /* !defined HOURSPERDAY */

#ifndef EPOCH_YEAR
#define EPOCH_YEAR	1970
#endif /* !defined EPOCH_YEAR */

#ifndef TM_YEAR_BASE
#define TM_YEAR_BASE	1900
#endif /* !defined TM_YEAR_BASE */

#ifndef DAYSPERNYEAR
#define DAYSPERNYEAR	365
#endif /* !defined DAYSPERNYEAR */

#ifndef isleap
#define isleap(y) (((y) % 4) == 0 && (((y) % 100) != 0 || ((y) % 400) == 0))
#endif /* !defined isleap */

#ifndef isleap_sum
/*
** See tzfile.h for details on isleap_sum.
*/
#define isleap_sum(a, b)	isleap((a) % 400 + (b) % 400)
#endif /* !defined isleap_sum */

#define SECSPERDAY	((int_fast32_t) SECSPERHOUR * HOURSPERDAY)
#define SECSPERNYEAR	(SECSPERDAY * DAYSPERNYEAR)
#define SECSPERLYEAR	(SECSPERNYEAR + SECSPERDAY)
#define SECSPER400YEARS	(SECSPERNYEAR * (intmax_t) (300 + 3)	\
			 + SECSPERLYEAR * (intmax_t) (100 - 3))

/*
** True if SECSPER400YEARS is known to be representable as an
** intmax_t.  It's OK that SECSPER400YEARS_FITS can in theory be false
** even if SECSPER400YEARS is representable, because when that happens
** the code merely runs a bit more slowly, and this slowness doesn't
** occur on any practical platform.
*/
enum { SECSPER400YEARS_FITS = SECSPERLYEAR <= INTMAX_MAX / 400 };

#ifndef HAVE_GETTEXT
#define HAVE_GETTEXT 0
#endif
#if HAVE_GETTEXT
#include "locale.h"	/* for setlocale */
#include "libintl.h"
#endif /* HAVE_GETTEXT */

#ifndef ATTRIBUTE_PURE
#if 2 < __GNUC__ || (__GNUC__ == 2 && 96 <= __GNUC_MINOR__)
# define ATTRIBUTE_PURE __attribute__ ((ATTRIBUTE_PURE__))
#else
# define ATTRIBUTE_PURE /* empty */
#endif
#endif

#ifndef INITIALIZE
#if defined(__GNUC__) || defined(__lint__)
#define INITIALIZE(x)	((x) = 0)
#else /* !defined GNUC || lint */
#define INITIALIZE(x)
#endif /* !defined GNUC || lint */
#endif /* !defined INITIALIZE */

/*
** For the benefit of GNU folk...
** '_(MSGID)' uses the current locale's message library string for MSGID.
** The default is to use gettext if available, and use MSGID otherwise.
*/

#ifndef _
#if HAVE_GETTEXT
#define _(msgid) gettext(msgid)
#else /* !HAVE_GETTEXT */
#define _(msgid) msgid
#endif /* !HAVE_GETTEXT */
#endif /* !defined _ */

#if !defined TZ_DOMAIN && defined HAVE_GETTEXT
# define TZ_DOMAIN "tz"
#endif

#if ! HAVE_LOCALTIME_RZ
# undef  timezone_t
# define timezone_t char **
#endif

extern char **	environ;

#if !HAVE_POSIX_DECLS
extern int	getopt(int argc, char * const argv[],
			const char * options);
extern char *	optarg;
extern int	optind;
extern char *	tzname[];
#endif

/* The minimum and maximum finite time values.  */
enum { atime_shift = CHAR_BIT * sizeof (time_t) - 2 };
static time_t	absolute_min_time =
  ((time_t) -1 < 0
    ? (- ((time_t) ~ (time_t) 0 < 0)
       - (((time_t) 1 << atime_shift) - 1 + ((time_t) 1 << atime_shift)))
    : 0);
static time_t	absolute_max_time =
  ((time_t) -1 < 0
    ? (((time_t) 1 << atime_shift) - 1 + ((time_t) 1 << atime_shift))
   : -1);
static size_t	longest;
static char *	progname;
static bool	warned;
static bool	errout;

static char const *abbr(struct tm const *);
static intmax_t	delta(struct tm *, struct tm *) ATTRIBUTE_PURE;
static void dumptime(struct tm const *);
static time_t hunt(timezone_t, char *, time_t, time_t);
static void show(timezone_t, char *, time_t, bool);
static void showtrans(char const *, struct tm const *, time_t, char const *,
		      char const *);
static const char *tformat(void);
static time_t yeartot(intmax_t) ATTRIBUTE_PURE;

/* Unlike <ctype.h>'s isdigit, this also works if c < 0 | c > UCHAR_MAX. */
#define is_digit(c) ((unsigned)(c) - '0' <= 9)

/* Is A an alphabetic character in the C locale?  */
static bool
is_alpha(char a)
{
	switch (a) {
	  default:
		return false;
	  case 'A': case 'B': case 'C': case 'D': case 'E': case 'F': case 'G':
	  case 'H': case 'I': case 'J': case 'K': case 'L': case 'M': case 'N':
	  case 'O': case 'P': case 'Q': case 'R': case 'S': case 'T': case 'U':
	  case 'V': case 'W': case 'X': case 'Y': case 'Z':
	  case 'a': case 'b': case 'c': case 'd': case 'e': case 'f': case 'g':
	  case 'h': case 'i': case 'j': case 'k': case 'l': case 'm': case 'n':
	  case 'o': case 'p': case 'q': case 'r': case 's': case 't': case 'u':
	  case 'v': case 'w': case 'x': case 'y': case 'z':
	  	return true;
	}
}

/* Return A + B, exiting if the result would overflow.  */
static size_t
sumsize(size_t a, size_t b)
{
	size_t sum = a + b;
	if (sum < a)
		errx(EXIT_FAILURE, "size overflow");
	return sum;
}

/* Return a pointer to a newly allocated buffer of size SIZE, exiting
   on failure.  SIZE should be nonzero.  */
static void *
xmalloc(size_t size)
{
  void *p = malloc(size);
  if (!p) {
    perror(progname);
    exit(EXIT_FAILURE);
  }
  return p;
}

#if ! HAVE_TZSET
# undef tzset
# define tzset zdump_tzset
static void tzset(void) { }
#endif

/* Assume gmtime_r works if localtime_r does.
   A replacement localtime_r is defined below if needed.  */
#if ! HAVE_LOCALTIME_R

# undef gmtime_r
# define gmtime_r zdump_gmtime_r

static struct tm *
gmtime_r(time_t *tp, struct tm *tmp)
{
	struct tm *r = gmtime(tp);
	if (r) {
		*tmp = *r;
		r = tmp;
	}
	return r;
}

#endif

/* Platforms with TM_ZONE don't need tzname, so they can use the
   faster localtime_rz or localtime_r if available.  */

#if defined TM_ZONE && HAVE_LOCALTIME_RZ
# define USE_LOCALTIME_RZ true
#else
# define USE_LOCALTIME_RZ false
#endif

#if ! USE_LOCALTIME_RZ

# if !defined TM_ZONE || ! HAVE_LOCALTIME_R || ! HAVE_TZSET
#  undef localtime_r
#  define localtime_r zdump_localtime_r
static struct tm *
localtime_r(time_t *tp, struct tm *tmp)
{
	struct tm *r = localtime(tp);
	if (r) {
		*tmp = *r;
		r = tmp;
	}
	return r;
}
# endif

# undef localtime_rz
# define localtime_rz zdump_localtime_rz
static struct tm *
localtime_rz(timezone_t rz, time_t *tp, struct tm *tmp)
{
	return localtime_r(tp, tmp);
}

# ifdef TYPECHECK
#  undef mktime_z
#  define mktime_z zdump_mktime_z
static time_t
mktime_z(timezone_t tz, struct tm *tmp)
{
	return mktime(tmp);
}
# endif

# undef tzalloc
# undef tzfree
# define tzalloc zdump_tzalloc
# define tzfree zdump_tzfree

static timezone_t
tzalloc(char const *val)
{
	static char **fakeenv;
	char **env = fakeenv;
	char *env0;
	if (! env) {
		char **e = environ;
		int to;

		while (*e++)
			continue;
		env = xmalloc(sumsize(sizeof *environ,
		    (e - environ) * sizeof *environ));
		to = 1;
		for (e = environ; (env[to] = *e); e++)
			to += strncmp(*e, "TZ=", 3) != 0;
	}
	env0 = xmalloc(sumsize(sizeof "TZ=", strlen(val)));
	env[0] = strcat(strcpy(env0, "TZ="), val);
	environ = fakeenv = env;
	tzset();
	return env;
}

static void
tzfree(timezone_t env)
{
	environ = env + 1;
	free(env[0]);
}
#endif /* ! USE_LOCALTIME_RZ */

/* A UTC time zone, and its initializer.  */
static timezone_t gmtz;
static void
gmtzinit(void)
{
	if (USE_LOCALTIME_RZ) {
		static char const utc[] = "UTC0";
		gmtz = tzalloc(utc);
		if (!gmtz) {
		      err(EXIT_FAILURE, "Cannot create %s", utc);
		}
	}
}

/* Convert *TP to UTC, storing the broken-down time into *TMP.
   Return TMP if successful, NULL otherwise.  This is like gmtime_r(TP, TMP),
   except typically faster if USE_LOCALTIME_RZ.  */
static struct tm *
my_gmtime_r(time_t *tp, struct tm *tmp)
{
	return USE_LOCALTIME_RZ ?
	    localtime_rz(gmtz, tp, tmp) : gmtime_r(tp, tmp);
}

#ifndef TYPECHECK
#define my_localtime_rz	localtime_rz
#else /* !defined TYPECHECK */
static struct tm *
my_localtime_rz(timezone_t tz, const time_t *tp, struct tm *tmp)
{
	tmp = localtime_rz(tz, tp, tmp);
	if (tmp) {
		struct tm	tm;
		time_t	t;

		tm = *tmp;
		t = mktime_z(tz, &tm);
		if (t != *tp) {
			(void) fflush(stdout);
			(void) fprintf(stderr, "\n%s: ", progname);
			(void) fprintf(stderr, tformat(), *tp);
			(void) fprintf(stderr, " ->");
			(void) fprintf(stderr, " year=%d", tmp->tm_year);
			(void) fprintf(stderr, " mon=%d", tmp->tm_mon);
			(void) fprintf(stderr, " mday=%d", tmp->tm_mday);
			(void) fprintf(stderr, " hour=%d", tmp->tm_hour);
			(void) fprintf(stderr, " min=%d", tmp->tm_min);
			(void) fprintf(stderr, " sec=%d", tmp->tm_sec);
			(void) fprintf(stderr, " isdst=%d", tmp->tm_isdst);
			(void) fprintf(stderr, " -> ");
			(void) fprintf(stderr, tformat(), t);
			(void) fprintf(stderr, "\n");
			errout = true;
		}
	}
	return tmp;
}
#endif /* !defined TYPECHECK */

static void
abbrok(const char *const abbrp, const char *const zone)
{
	const char *cp;
	const char *wp;

	if (warned)
		return;
	cp = abbrp;
	while (is_alpha(*cp) || is_digit(*cp) || *cp == '-' || *cp == '+')
		++cp;
	if (cp - abbrp < 3)
		wp = _("has fewer than 3 characters");
	else if (cp - abbrp > 6)
		wp = _("has more than 6 characters");
	else if (*cp)
		wp = _("has characters other than ASCII alphanumerics, '-' or '+'");
	else
		return;
	(void) fflush(stdout);
	(void) fprintf(stderr,
		_("%s: warning: zone \"%s\" abbreviation \"%s\" %s\n"),
		progname, zone, abbrp, wp);
	warned = errout = true;
}

/* Return a time zone abbreviation.  If the abbreviation needs to be
   saved, use *BUF (of size *BUFALLOC) to save it, and return the
   abbreviation in the possibly-reallocated *BUF.  Otherwise, just
   return the abbreviation.  Get the abbreviation from TMP.
   Exit on memory allocation failure.  */
static char const *
saveabbr(char **buf, size_t *bufalloc, struct tm const *tmp)
{
	char const *ab = abbr(tmp);
	if (HAVE_LOCALTIME_RZ)
		return ab;
	else {
		size_t ablen = strlen(ab);
		if (*bufalloc <= ablen) {
			free(*buf);

			/* Make the new buffer at least twice as long as the
			   old, to avoid O(N**2) behavior on repeated calls.  */
			*bufalloc = sumsize(*bufalloc, ablen + 1);
			*buf = xmalloc(*bufalloc);
		}
		return strcpy(*buf, ab);
	}
}

static void
close_file(FILE *stream)
{
	char const *e = (ferror(stream) ? _("I/O error")
	    : fclose(stream) != 0 ? strerror(errno) : NULL);
	if (e) {
		errx(EXIT_FAILURE, "%s", e);
	}
}

__dead static void
usage(FILE *const stream, const int status)
{
	(void) fprintf(stream,
_("%s: usage: %s OPTIONS ZONENAME ...\n"
  "Options include:\n"
  "  -c [L,]U   Start at year L (default -500), end before year U (default 2500)\n"
  "  -t [L,]U   Start at time L, end before time U (in seconds since 1970)\n"
  "  -i         List transitions briefly (format is experimental)\n" \
  "  -v         List transitions verbosely\n"
  "  -V         List transitions a bit less verbosely\n"
  "  --help     Output this help\n"
  "  --version  Output version info\n"
  "\n"
  "Report bugs to %s.\n"),
	   progname, progname, REPORT_BUGS_TO);
	if (status == EXIT_SUCCESS)
		close_file(stream);
	exit(status);
}

int
main(int argc, char *argv[])
{
	/* These are static so that they're initially zero.  */
	static char *		abbrev;
	static size_t		abbrevsize;

	int		i;
	bool		vflag;
	bool		Vflag;
	char *		cutarg;
	char *		cuttimes;
	time_t		cutlotime;
	time_t		cuthitime;
	time_t		now;
	bool iflag = false;

	cutlotime = absolute_min_time;
	cuthitime = absolute_max_time;
#if HAVE_GETTEXT
	(void) setlocale(LC_ALL, "");
#ifdef TZ_DOMAINDIR
	(void) bindtextdomain(TZ_DOMAIN, TZ_DOMAINDIR);
#endif /* defined TEXTDOMAINDIR */
	(void) textdomain(TZ_DOMAIN);
#endif /* HAVE_GETTEXT */
	progname = argv[0];
	for (i = 1; i < argc; ++i)
		if (strcmp(argv[i], "--version") == 0) {
			(void) printf("zdump %s%s\n", PKGVERSION, TZVERSION);
			return EXIT_SUCCESS;
		} else if (strcmp(argv[i], "--help") == 0) {
			usage(stdout, EXIT_SUCCESS);
		}
	vflag = Vflag = false;
	cutarg = cuttimes = NULL;
	for (;;)
	  switch (getopt(argc, argv, "c:it:vV")) {
	  case 'c': cutarg = optarg; break;
	  case 't': cuttimes = optarg; break;
	  case 'i': iflag = true; break;
	  case 'v': vflag = true; break;
	  case 'V': Vflag = true; break;
	  case -1:
	    if (! (optind == argc - 1 && strcmp(argv[optind], "=") == 0))
	      goto arg_processing_done;
	    /* Fall through.  */
	  default:
	    usage(stderr, EXIT_FAILURE);
	  }
 arg_processing_done:;

	if (iflag | vflag | Vflag) {
		intmax_t	lo;
		intmax_t	hi;
		char *loend, *hiend;
		intmax_t cutloyear = ZDUMP_LO_YEAR;
		intmax_t cuthiyear = ZDUMP_HI_YEAR;
		if (cutarg != NULL) {
			lo = strtoimax(cutarg, &loend, 10);
			if (cutarg != loend && !*loend) {
				hi = lo;
				cuthiyear = hi;
			} else if (cutarg != loend && *loend == ','
				   && (hi = strtoimax(loend + 1, &hiend, 10),
				       loend + 1 != hiend && !*hiend)) {
				cutloyear = lo;
				cuthiyear = hi;
			} else {
				fprintf(stderr, _("%s: wild -c argument %s\n"),
					progname, cutarg);
				return EXIT_FAILURE;
			}
		}
		if (cutarg != NULL || cuttimes == NULL) {
			cutlotime = yeartot(cutloyear);
			cuthitime = yeartot(cuthiyear);
		}
		if (cuttimes != NULL) {
			lo = strtoimax(cuttimes, &loend, 10);
			if (cuttimes != loend && !*loend) {
				hi = lo;
				if (hi < cuthitime) {
					if (hi < absolute_min_time)
						hi = absolute_min_time;
					cuthitime = hi;
				}
			} else if (cuttimes != loend && *loend == ','
				   && (hi = strtoimax(loend + 1, &hiend, 10),
				       loend + 1 != hiend && !*hiend)) {
				if (cutlotime < lo) {
					if (absolute_max_time < lo)
						lo = absolute_max_time;
					cutlotime = lo;
				}
				if (hi < cuthitime) {
					if (hi < absolute_min_time)
						hi = absolute_min_time;
					cuthitime = hi;
				}
			} else {
				(void) fprintf(stderr,
					_("%s: wild -t argument %s\n"),
					progname, cuttimes);
				return EXIT_FAILURE;
			}
		}
	}
	gmtzinit();
	INITIALIZE (now);
	if (! (iflag | vflag | Vflag))
	  now = time(NULL);
	longest = 0;
	for (i = optind; i < argc; i++) {
		size_t arglen = strlen(argv[i]);
		if (longest < arglen)
			longest = arglen < INT_MAX ? arglen : INT_MAX;
	}

	for (i = optind; i < argc; ++i) {
		timezone_t tz = tzalloc(argv[i]);
		char const *ab;
		time_t t;
		struct tm tm, newtm;
		bool tm_ok;

		if (!tz) {
			errx(EXIT_FAILURE, "%s", argv[i]);
		}
		if (! (iflag | vflag | Vflag)) {
			show(tz, argv[i], now, false);
			tzfree(tz);
			continue;
		}
		warned = false;
		t = absolute_min_time;
		if (! (iflag | Vflag)) {
			show(tz, argv[i], t, true);
			t += SECSPERDAY;
			show(tz, argv[i], t, true);
		}
		if (t < cutlotime)
			t = cutlotime;
		tm_ok = my_localtime_rz(tz, &t, &tm) != NULL;
		if (tm_ok) {
			ab = saveabbr(&abbrev, &abbrevsize, &tm);
			if (iflag) {
				showtrans("\nTZ=%f", &tm, t, ab, argv[i]);
				showtrans("-\t-\t%Q", &tm, t, ab, argv[i]);
			}
		} else
			ab = NULL;
		while (t < cuthitime) {
			time_t newt = ((t < absolute_max_time - SECSPERDAY / 2
			    && t + SECSPERDAY / 2 < cuthitime)
			    ? t + SECSPERDAY / 2 : cuthitime);
			struct tm *newtmp = localtime_rz(tz, &newt, &newtm);
			bool newtm_ok = newtmp != NULL;
			if (! (tm_ok & newtm_ok
			    ? (delta(&newtm, &tm) == newt - t
			    && newtm.tm_isdst == tm.tm_isdst
			    && strcmp(abbr(&newtm), ab) == 0)
			    : tm_ok == newtm_ok)) {
				newt = hunt(tz, argv[i], t, newt);
				newtmp = localtime_rz(tz, &newt, &newtm);
				newtm_ok = newtmp != NULL;
				if (iflag)
					showtrans("%Y-%m-%d\t%L\t%Q",
					    newtmp, newt, newtm_ok ?
					    abbr(&newtm) : NULL, argv[i]);
				else {
					show(tz, argv[i], newt - 1, true);
					show(tz, argv[i], newt, true);
				}
			}
			t = newt;
			tm_ok = newtm_ok;
			if (newtm_ok) {
				ab = saveabbr(&abbrev, &abbrevsize, &newtm);
				tm = newtm;
			}
		}
		if (! (iflag | Vflag)) {
			t = absolute_max_time;
			t -= SECSPERDAY;
			show(tz, argv[i], t, true);
			t += SECSPERDAY;
			show(tz, argv[i], t, true);
		}
		tzfree(tz);
	}
	close_file(stdout);
	if (errout && (ferror(stderr) || fclose(stderr) != 0))
		return EXIT_FAILURE;
	return EXIT_SUCCESS;
}

static time_t
yeartot(intmax_t y)
{
	intmax_t	myy, seconds, years;
	time_t		t;

	myy = EPOCH_YEAR;
	t = 0;
	while (myy < y) {
		if (SECSPER400YEARS_FITS && 400 <= y - myy) {
			intmax_t diff400 = (y - myy) / 400;
			if (INTMAX_MAX / SECSPER400YEARS < diff400)
				return absolute_max_time;
			seconds = diff400 * SECSPER400YEARS;
			years = diff400 * 400;
                } else {
			seconds = isleap(myy) ? SECSPERLYEAR : SECSPERNYEAR;
			years = 1;
		}
		myy += years;
		if (t > absolute_max_time - seconds)
			return absolute_max_time;
		t += seconds;
	}
	while (y < myy) {
		if (SECSPER400YEARS_FITS && y + 400 <= myy && myy < 0) {
			intmax_t diff400 = (myy - y) / 400;
			if (INTMAX_MAX / SECSPER400YEARS < diff400)
				return absolute_min_time;
			seconds = diff400 * SECSPER400YEARS;
			years = diff400 * 400;
		} else {
			seconds = isleap(myy - 1) ? SECSPERLYEAR : SECSPERNYEAR;
			years = 1;
		}
		myy -= years;
		if (t < absolute_min_time + seconds)
			return absolute_min_time;
		t -= seconds;
	}
	return t;
}

static time_t
hunt(timezone_t tz, char *name, time_t lot, time_t hit)
{
	static char *		loab;
	static size_t		loabsize;
	char const *		ab;
	time_t			t;
	struct tm		lotm;
	struct tm		tm;
	bool lotm_ok = my_localtime_rz(tz, &lot, &lotm) != NULL;
	bool tm_ok;

	if (lotm_ok)
		ab = saveabbr(&loab, &loabsize, &lotm);
	else
		ab = NULL;
	for ( ; ; ) {
		time_t diff = hit - lot;
		if (diff < 2)
			break;
		t = lot;
		t += diff / 2;
		if (t <= lot)
			++t;
		else if (t >= hit)
			--t;
		tm_ok = my_localtime_rz(tz, &t, &tm) != NULL;
		if (lotm_ok & tm_ok
		    ? (delta(&tm, &lotm) == t - lot
		       && tm.tm_isdst == lotm.tm_isdst
		       && strcmp(abbr(&tm), ab) == 0)
		    : lotm_ok == tm_ok) {
		  lot = t;
		  if (tm_ok)
		    lotm = tm;
		} else	hit = t;
	}
	return hit;
}

/*
** Thanks to Paul Eggert for logic used in delta.
*/

static intmax_t
delta(struct tm *newp, struct tm *oldp)
{
	intmax_t	result;
	int		tmy;

	if (newp->tm_year < oldp->tm_year)
		return -delta(oldp, newp);
	result = 0;
	for (tmy = oldp->tm_year; tmy < newp->tm_year; ++tmy)
		result += DAYSPERNYEAR + isleap_sum(tmy, TM_YEAR_BASE);
	result += newp->tm_yday - oldp->tm_yday;
	result *= HOURSPERDAY;
	result += newp->tm_hour - oldp->tm_hour;
	result *= MINSPERHOUR;
	result += newp->tm_min - oldp->tm_min;
	result *= SECSPERMIN;
	result += newp->tm_sec - oldp->tm_sec;
	return result;
}

#ifndef TM_GMTOFF
/* Return A->tm_yday, adjusted to compare it fairly to B->tm_yday.
   Assume A and B differ by at most one year.  */
static int
adjusted_yday(struct tm const *a, struct tm const *b)
{
	int yday = a->tm_yday;
	if (b->tm_year < a->tm_year)
		yday += 365 + isleap_sum(b->tm_year, TM_YEAR_BASE);
	return yday;
}
#endif

/* If A is the broken-down local time and B the broken-down UTC for
   the same instant, return A's UTC offset in seconds, where positive
   offsets are east of Greenwich.  On failure, return LONG_MIN.

   If T is nonnull, *T is the time stamp that corresponds to A; call
   my_gmtime_r and use its result instead of B.  Otherwise, B is the
   possibly nonnull result of an earlier call to my_gmtime_r.  */
static long
gmtoff(struct tm const *a, time_t *t, struct tm const *b)
{
#ifdef TM_GMTOFF
	return a->TM_GMTOFF;
#else
	struct tm tm;
	if (t)
		b = my_gmtime_r(t, &tm);
	if (! b)
		return LONG_MIN;
	else {
		int ayday = adjusted_yday(a, b);
		int byday = adjusted_yday(b, a);
		int days = ayday - byday;
		long hours = a->tm_hour - b->tm_hour + 24 * days;
		long minutes = a->tm_min - b->tm_min + 60 * hours;
		long seconds = a->tm_sec - b->tm_sec + 60 * minutes;
		return seconds;
	}
#endif
}

static void
show(timezone_t tz, char *zone, time_t t, bool v)
{
	struct tm *	tmp;
	struct tm *	gmtmp;
	struct tm tm, gmtm;

	(void) printf("%-*s  ", (int) longest, zone);
	if (v) {
		gmtmp = my_gmtime_r(&t, &gmtm);
		if (gmtmp == NULL) {
			printf(tformat(), t);
		} else {
			dumptime(gmtmp);
			(void) printf(" UT");
		}
		(void) printf(" = ");
	}
	tmp = my_localtime_rz(tz, &t, &tm);
	dumptime(tmp);
	if (tmp != NULL) {
		if (*abbr(tmp) != '\0')
			(void) printf(" %s", abbr(tmp));
		if (v) {
			long off = gmtoff(tmp, NULL,  gmtmp);
			(void) printf(" isdst=%d", tmp->tm_isdst);
			if (off != LONG_MIN)
				(void) printf(" gmtoff=%ld", off);
		}
	}
	(void) printf("\n");
	if (tmp != NULL && *abbr(tmp) != '\0')
		abbrok(abbr(tmp), zone);
}

/* Store into BUF, of size SIZE, a formatted local time taken from *TM.
   Use ISO 8601 format +HH:MM:SS.  Omit :SS if SS is zero, and omit
   :MM too if MM is also zero.

   Return the length of the resulting string.  If the string does not
   fit, return the length that the string would have been if it had
   fit; do not overrun the output buffer.  */
static int
format_local_time(char *buf, size_t size, struct tm const *tm)
{
  int ss = tm->tm_sec, mm = tm->tm_min, hh = tm->tm_hour;
  return (ss
	  ? snprintf(buf, size, "%02d:%02d:%02d", hh, mm, ss)
	  : mm
	  ? snprintf(buf, size, "%02d:%02d", hh, mm)
	  : snprintf(buf, size, "%02d", hh));
}

/* Store into BUF, of size SIZE, a formatted UTC offset for the
   localtime *TM corresponding to time T.  Use ISO 8601 format
   +HH:MM:SS, or -HH:MM:SS for time stamps west of Greenwich.  Omit
   :SS if :SS is zero, and omit :MM too if :MM is also zero.  If the
   time stamp represents an unknown UTC offset, use the format -00.

   Return the length of the resulting string, or -1 if the result is
   not representable as a string.  If the string does not fit, return
   the length that the string would have been if it had fit; do not
   overrun the output buffer.  */
static int
format_utc_offset(char *buf, size_t size, struct tm const *tm, time_t t)
{
  long off = gmtoff(tm, &t, NULL);
  char sign = ((off < 0
		|| (off == 0
		    && (*abbr(tm) == '-' || strcmp(abbr(tm), "zzz") == 0)))
	       ? '-' : '+');
  long hh;
  int mm, ss;
  if (off < 0)
    {
      if (off == LONG_MIN)
	return -1;
      off = -off;
    }
  ss = off % 60;
  mm = off / 60 % 60;
  hh = off / 60 / 60;
  return (ss
	  ? snprintf(buf, size, "%c%02ld:%02d:%02d", sign, hh, mm, ss)
	  : mm
	  ? snprintf(buf, size, "%c%02ld:%02d", sign, hh, mm)
	  : snprintf(buf, size, "%c%02ld", sign, hh));
}

/* Store into BUF (of size SIZE) a quoted string representation of P.
   If the representation's length is less than SIZE, return the
   length; the representation is not null terminated.  Otherwise
   return SIZE, to indicate that BUF is too small.  */
static size_t
format_quoted_string(char *buf, size_t size, char const *p)
{
  char *b = buf;
  size_t s = size;
  if (!s)
    return size;
  *b++ = '"', s--;
  for (;;) {
    char c = *p++;
    if (s <= 1)
      return size;
    switch (c) {
    default: *b++ = c, s--; continue;
    case '\0': *b++ = '"', s--; return size - s;
    case '"': case '\\': break;
    case ' ': c = 's'; break;
    case '\f': c = 'f'; break;
    case '\n': c = 'n'; break;
    case '\r': c = 'r'; break;
    case '\t': c = 't'; break;
    case '\v': c = 'v'; break;
    }
    *b++ = '\\', *b++ = c, s -= 2;
  }
}

/* Store into BUF (of size SIZE) a time stamp formatted by TIME_FMT.
   TM is the broken-down time, T the seconds count, AB the time zone
   abbreviation, and ZONE_NAME the zone name.  Return true if
   successful, false if the output would require more than SIZE bytes.
   TIME_FMT uses the same format that strftime uses, with these
   additions:

   %f zone name
   %L local time as per format_local_time
   %Q like "U\t%Z\tD" where U is the UTC offset as for format_utc_offset
      and D is the isdst flag; except omit D if it is zero, omit %Z if
      it equals U, quote and escape %Z if it contains nonalphabetics,
      and omit any trailing tabs.  */

static bool
istrftime(char *buf, size_t size, char const *time_fmt,
	  struct tm const *tm, time_t t, char const *ab, char const *zone_name)
{
  char *b = buf;
  size_t s = size;
  char const *f = time_fmt, *p;

  for (p = f; ; p++)
    if (*p == '%' && p[1] == '%')
      p++;
    else if (!*p
	     || (*p == '%'
		 && (p[1] == 'f' || p[1] == 'L' || p[1] == 'Q'))) {
      size_t formatted_len;
      size_t f_prefix_len = p - f;
      size_t f_prefix_copy_size = p - f + 2;
      char fbuf[100];
      bool oversized = sizeof fbuf <= f_prefix_copy_size;
      char *f_prefix_copy = oversized ? xmalloc(f_prefix_copy_size) : fbuf;
      memcpy(f_prefix_copy, f, f_prefix_len);
      strcpy(f_prefix_copy + f_prefix_len, "X");
      formatted_len = strftime(b, s, f_prefix_copy, tm);
      if (oversized)
	free(f_prefix_copy);
      if (formatted_len == 0)
	return false;
      formatted_len--;
      b += formatted_len, s -= formatted_len;
      if (!*p++)
	break;
      switch (*p) {
      case 'f':
	formatted_len = format_quoted_string(b, s, zone_name);
	break;
      case 'L':
	formatted_len = format_local_time(b, s, tm);
	break;
      case 'Q':
	{
	  bool show_abbr;
	  int offlen = format_utc_offset(b, s, tm, t);
	  if (! (0 <= offlen && (size_t)offlen < s))
	    return false;
	  show_abbr = strcmp(b, ab) != 0;
	  b += offlen, s -= offlen;
	  if (show_abbr) {
	    char const *abp;
	    size_t len;
	    if (s <= 1)
	      return false;
	    *b++ = '\t', s--;
	    for (abp = ab; is_alpha(*abp); abp++)
	      continue;
	    len = (!*abp && *ab
		   ? (size_t)snprintf(b, s, "%s", ab)
		   : format_quoted_string(b, s, ab));
	    if (s <= len)
	      return false;
	    b += len, s -= len;
	  }
	  formatted_len = (tm->tm_isdst
			   ? snprintf(b, s, &"\t\t%d"[show_abbr], tm->tm_isdst)
			   : 0);
	}
	break;
      }
      if (! (formatted_len < s))
	return false;
      b += formatted_len, s -= formatted_len;
      f = p + 1;
    }
  *b = '\0';
  return true;
}

/* Show a time transition.  */
static void
showtrans(char const *time_fmt, struct tm const *tm, time_t t, char const *ab,
	  char const *zone_name)
{
  if (!tm) {
    printf(tformat(), t);
    putchar('\n');
  } else {
    char stackbuf[1000];
    size_t size = sizeof stackbuf;
    char *buf = stackbuf;
    char *bufalloc = NULL;
    while (! istrftime(buf, size, time_fmt, tm, t, ab, zone_name)) {
      size = sumsize(size, size);
      free(bufalloc);
      buf = bufalloc = xmalloc(size);
    }
    puts(buf);
    free(bufalloc);
  }
}

static const char *
abbr(struct tm const *tmp)
{
#ifdef TM_ZONE
	return tmp->TM_ZONE;
#else
	return (0 <= tmp->tm_isdst && tzname[0 < tmp->tm_isdst]
		? tzname[0 < tmp->tm_isdst]
		: "");
#endif
}

/*
** The code below can fail on certain theoretical systems;
** it works on all known real-world systems as of 2004-12-30.
*/

static const char *
tformat(void)
{
	if (0 > (time_t) -1) {		/* signed */
		if (sizeof (time_t) == sizeof (intmax_t))
			return "%"PRIdMAX;
		if (sizeof (time_t) > sizeof (long))
			return "%lld";
		if (sizeof (time_t) > sizeof (int))
			return "%ld";
		return "%d";
	}
#ifdef PRIuMAX
	if (sizeof (time_t) == sizeof (uintmax_t))
		return "%"PRIuMAX;
#endif
	if (sizeof (time_t) > sizeof (unsigned long))
		return "%llu";
	if (sizeof (time_t) > sizeof (unsigned int))
		return "%lu";
	return "%u";
}

static void
dumptime(const struct tm *timeptr)
{
	static const char	wday_name[][3] = {
		"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
	};
	static const char	mon_name[][3] = {
		"Jan", "Feb", "Mar", "Apr", "May", "Jun",
		"Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
	};
	const char *	wn;
	const char *	mn;
	int		lead;
	int		trail;

	if (timeptr == NULL) {
		printf("NULL");
		return;
	}
	/*
	** The packaged localtime_rz and gmtime_r never put out-of-range
	** values in tm_wday or tm_mon, but since this code might be compiled
	** with other (perhaps experimental) versions, paranoia is in order.
	*/
	if (timeptr->tm_wday < 0 || timeptr->tm_wday >=
		(int) (sizeof wday_name / sizeof wday_name[0]))
			wn = "???";
	else		wn = wday_name[timeptr->tm_wday];
	if (timeptr->tm_mon < 0 || timeptr->tm_mon >=
		(int) (sizeof mon_name / sizeof mon_name[0]))
			mn = "???";
	else		mn = mon_name[timeptr->tm_mon];
	printf("%.3s %.3s%3d %.2d:%.2d:%.2d ",
		wn, mn,
		timeptr->tm_mday, timeptr->tm_hour,
		timeptr->tm_min, timeptr->tm_sec);
#define DIVISOR	10
	trail = timeptr->tm_year % DIVISOR + TM_YEAR_BASE % DIVISOR;
	lead = timeptr->tm_year / DIVISOR + TM_YEAR_BASE / DIVISOR +
		trail / DIVISOR;
	trail %= DIVISOR;
	if (trail < 0 && lead > 0) {
		trail += DIVISOR;
		--lead;
	} else if (lead < 0 && trail > 0) {
		trail -= DIVISOR;
		++lead;
	}
	if (lead == 0)
		printf("%d", trail);
	else	printf("%d%d", lead, ((trail < 0) ? -trail : trail));
}