jens-maus/yam

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src/tools/tz/zic.c

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/* Compile .zi time zone data into TZif binary files.  */

/*
** This file is in the public domain, so clarified as of
** 2006-07-17 by Arthur David Olson.
*/

#include "version.h"
#include "private.h"
#include "tzfile.h"

#include <fcntl.h>
#include <locale.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdio.h>

#define    ZIC_VERSION_PRE_2013 '2'
#define    ZIC_VERSION    '3'

typedef int_fast64_t    zic_t;
#define ZIC_MIN INT_FAST64_MIN
#define ZIC_MAX INT_FAST64_MAX
#define PRIdZIC PRIdFAST64
#define SCNdZIC SCNdFAST64

#ifndef ZIC_MAX_ABBR_LEN_WO_WARN
#define ZIC_MAX_ABBR_LEN_WO_WARN    6
#endif /* !defined ZIC_MAX_ABBR_LEN_WO_WARN */

#ifdef HAVE_DIRECT_H
# include <direct.h>
# include <io.h>
# undef mkdir
# define mkdir(name, mode) _mkdir(name)
#endif

#if HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#ifdef S_IRUSR
#define MKDIR_UMASK (S_IRUSR|S_IWUSR|S_IXUSR|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH)
#else
#define MKDIR_UMASK 0755
#endif
/* Port to native MS-Windows and to ancient UNIX.  */
#if !defined S_ISDIR && defined S_IFDIR && defined S_IFMT
# define S_ISDIR(mode) (((mode) & S_IFMT) == S_IFDIR)
#endif

#if HAVE_SYS_WAIT_H
#include <sys/wait.h>    /* for WIFEXITED and WEXITSTATUS */
#endif /* HAVE_SYS_WAIT_H */

#ifndef WIFEXITED
#define WIFEXITED(status)    (((status) & 0xff) == 0)
#endif /* !defined WIFEXITED */
#ifndef WEXITSTATUS
#define WEXITSTATUS(status)    (((status) >> 8) & 0xff)
#endif /* !defined WEXITSTATUS */

/* The maximum ptrdiff_t value, for pre-C99 platforms.  */
#ifndef PTRDIFF_MAX
static ptrdiff_t const PTRDIFF_MAX = MAXVAL(ptrdiff_t, TYPE_BIT(ptrdiff_t));
#endif

/* The minimum alignment of a type, for pre-C11 platforms.  */
#if __STDC_VERSION__ < 201112
# define _Alignof(type) offsetof(struct { char a; type b; }, b)
#endif

/* The type for line numbers.  Use PRIdMAX to format them; formerly
   there was also "#define PRIdLINENO PRIdMAX" and formats used
   PRIdLINENO, but xgettext cannot grok that.  */
typedef intmax_t lineno;

struct rule {
    const char *    r_filename;
    lineno        r_linenum;
    const char *    r_name;

    zic_t        r_loyear;    /* for example, 1986 */
    zic_t        r_hiyear;    /* for example, 1986 */
    const char *    r_yrtype;
    bool        r_lowasnum;
    bool        r_hiwasnum;

    int        r_month;    /* 0..11 */

    int        r_dycode;    /* see below */
    int        r_dayofmonth;
    int        r_wday;

    zic_t        r_tod;        /* time from midnight */
    bool        r_todisstd;    /* is r_tod standard time? */
    bool        r_todisut;    /* is r_tod UT? */
    bool        r_isdst;    /* is this daylight saving time? */
    zic_t        r_save;        /* offset from standard time */
    const char *    r_abbrvar;    /* variable part of abbreviation */

    bool        r_todo;        /* a rule to do (used in outzone) */
    zic_t        r_temp;        /* used in outzone */
};

/*
**    r_dycode        r_dayofmonth    r_wday
*/

#define DC_DOM        0    /* 1..31 */    /* unused */
#define DC_DOWGEQ    1    /* 1..31 */    /* 0..6 (Sun..Sat) */
#define DC_DOWLEQ    2    /* 1..31 */    /* 0..6 (Sun..Sat) */

struct zone {
    const char *    z_filename;
    lineno        z_linenum;

    const char *    z_name;
    zic_t        z_stdoff;
    char *        z_rule;
    const char *    z_format;
    char        z_format_specifier;

    bool        z_isdst;
    zic_t        z_save;

    struct rule *    z_rules;
    ptrdiff_t    z_nrules;

    struct rule    z_untilrule;
    zic_t        z_untiltime;
};

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

#if ! HAVE_LINK
# define link(from, to) (errno = ENOTSUP, -1)
#endif
#if ! HAVE_SYMLINK
# define readlink(file, buf, size) (errno = ENOTSUP, -1)
# define symlink(from, to) (errno = ENOTSUP, -1)
# define S_ISLNK(m) 0
#endif
#ifndef AT_SYMLINK_FOLLOW
# define linkat(fromdir, from, todir, to, flag) \
    (itssymlink(from) ? (errno = ENOTSUP, -1) : link(from, to))
#endif

static void    addtt(zic_t starttime, int type);
static int    addtype(zic_t, char const *, bool, bool, bool);
static void    leapadd(zic_t, bool, int, int);
static void    adjleap(void);
static void    associate(void);
static void    dolink(const char *, const char *, bool);
static char **    getfields(char * buf);
static zic_t    gethms(const char * string, const char * errstring);
static zic_t    getsave(char *, bool *);
static void    infile(const char * filename);
static void    inleap(char ** fields, int nfields);
static void    inlink(char ** fields, int nfields);
static void    inrule(char ** fields, int nfields);
static bool    inzcont(char ** fields, int nfields);
static bool    inzone(char ** fields, int nfields);
static bool    inzsub(char **, int, bool);
static bool    itsdir(char const *);
static bool    itssymlink(char const *);
static bool    is_alpha(char a);
static char    lowerit(char);
static void    mkdirs(char const *, bool);
static void    newabbr(const char * abbr);
static zic_t    oadd(zic_t t1, zic_t t2);
static void    outzone(const struct zone * zp, ptrdiff_t ntzones);
static zic_t    rpytime(const struct rule * rp, zic_t wantedy);
static void    rulesub(struct rule * rp,
            const char * loyearp, const char * hiyearp,
            const char * typep, const char * monthp,
            const char * dayp, const char * timep);
static zic_t    tadd(zic_t t1, zic_t t2);
static bool    yearistype(zic_t year, const char * type);

/* Bound on length of what %z can expand to.  */
enum { PERCENT_Z_LEN_BOUND = sizeof "+995959" - 1 };

/* If true, work around a bug in Qt 5.6.1 and earlier, which mishandles
   TZif files whose POSIX-TZ-style strings contain '<'; see
   QTBUG-53071 <https://bugreports.qt.io/browse/QTBUG-53071>.  This
   workaround will no longer be needed when Qt 5.6.1 and earlier are
   obsolete, say in the year 2021.  */
#ifndef WORK_AROUND_QTBUG_53071
enum { WORK_AROUND_QTBUG_53071 = true };
#endif

static int        charcnt;
static bool        errors;
static bool        warnings;
static const char *    filename;
static int        leapcnt;
static bool        leapseen;
static zic_t        leapminyear;
static zic_t        leapmaxyear;
static lineno        linenum;
static int        max_abbrvar_len = PERCENT_Z_LEN_BOUND;
static int        max_format_len;
static zic_t        max_year;
static zic_t        min_year;
static bool        noise;
static const char *    rfilename;
static lineno        rlinenum;
static const char *    progname;
static ptrdiff_t    timecnt;
static ptrdiff_t    timecnt_alloc;
static int        typecnt;

/*
** Line codes.
*/

#define LC_RULE        0
#define LC_ZONE        1
#define LC_LINK        2
#define LC_LEAP        3

/*
** Which fields are which on a Zone line.
*/

#define ZF_NAME        1
#define ZF_STDOFF    2
#define ZF_RULE        3
#define ZF_FORMAT    4
#define ZF_TILYEAR    5
#define ZF_TILMONTH    6
#define ZF_TILDAY    7
#define ZF_TILTIME    8
#define ZONE_MINFIELDS    5
#define ZONE_MAXFIELDS    9

/*
** Which fields are which on a Zone continuation line.
*/

#define ZFC_STDOFF    0
#define ZFC_RULE    1
#define ZFC_FORMAT    2
#define ZFC_TILYEAR    3
#define ZFC_TILMONTH    4
#define ZFC_TILDAY    5
#define ZFC_TILTIME    6
#define ZONEC_MINFIELDS    3
#define ZONEC_MAXFIELDS    7

/*
** Which files are which on a Rule line.
*/

#define RF_NAME        1
#define RF_LOYEAR    2
#define RF_HIYEAR    3
#define RF_COMMAND    4
#define RF_MONTH    5
#define RF_DAY        6
#define RF_TOD        7
#define RF_SAVE        8
#define RF_ABBRVAR    9
#define RULE_FIELDS    10

/*
** Which fields are which on a Link line.
*/

#define LF_FROM        1
#define LF_TO        2
#define LINK_FIELDS    3

/*
** Which fields are which on a Leap line.
*/

#define LP_YEAR        1
#define LP_MONTH    2
#define LP_DAY        3
#define LP_TIME        4
#define LP_CORR        5
#define LP_ROLL        6
#define LEAP_FIELDS    7

/*
** Year synonyms.
*/

#define YR_MINIMUM    0
#define YR_MAXIMUM    1
#define YR_ONLY        2

static struct rule *    rules;
static ptrdiff_t    nrules;    /* number of rules */
static ptrdiff_t    nrules_alloc;

static struct zone *    zones;
static ptrdiff_t    nzones;    /* number of zones */
static ptrdiff_t    nzones_alloc;

struct link {
    const char *    l_filename;
    lineno        l_linenum;
    const char *    l_from;
    const char *    l_to;
};

static struct link *    links;
static ptrdiff_t    nlinks;
static ptrdiff_t    nlinks_alloc;

struct lookup {
    const char *    l_word;
    const int    l_value;
};

static struct lookup const *    byword(const char * string,
                    const struct lookup * lp);

static struct lookup const zi_line_codes[] = {
    { "Rule",    LC_RULE },
    { "Zone",    LC_ZONE },
    { "Link",    LC_LINK },
    { NULL,        0 }
};
static struct lookup const leap_line_codes[] = {
    { "Leap",    LC_LEAP },
    { NULL,        0}
};

static struct lookup const    mon_names[] = {
    { "January",    TM_JANUARY },
    { "February",    TM_FEBRUARY },
    { "March",    TM_MARCH },
    { "April",    TM_APRIL },
    { "May",    TM_MAY },
    { "June",    TM_JUNE },
    { "July",    TM_JULY },
    { "August",    TM_AUGUST },
    { "September",    TM_SEPTEMBER },
    { "October",    TM_OCTOBER },
    { "November",    TM_NOVEMBER },
    { "December",    TM_DECEMBER },
    { NULL,        0 }
};

static struct lookup const    wday_names[] = {
    { "Sunday",    TM_SUNDAY },
    { "Monday",    TM_MONDAY },
    { "Tuesday",    TM_TUESDAY },
    { "Wednesday",    TM_WEDNESDAY },
    { "Thursday",    TM_THURSDAY },
    { "Friday",    TM_FRIDAY },
    { "Saturday",    TM_SATURDAY },
    { NULL,        0 }
};

static struct lookup const    lasts[] = {
    { "last-Sunday",    TM_SUNDAY },
    { "last-Monday",    TM_MONDAY },
    { "last-Tuesday",    TM_TUESDAY },
    { "last-Wednesday",    TM_WEDNESDAY },
    { "last-Thursday",    TM_THURSDAY },
    { "last-Friday",    TM_FRIDAY },
    { "last-Saturday",    TM_SATURDAY },
    { NULL,            0 }
};

static struct lookup const    begin_years[] = {
    { "minimum",    YR_MINIMUM },
    { "maximum",    YR_MAXIMUM },
    { NULL,        0 }
};

static struct lookup const    end_years[] = {
    { "minimum",    YR_MINIMUM },
    { "maximum",    YR_MAXIMUM },
    { "only",    YR_ONLY },
    { NULL,        0 }
};

static struct lookup const    leap_types[] = {
    { "Rolling",    true },
    { "Stationary",    false },
    { NULL,        0 }
};

static const int    len_months[2][MONSPERYEAR] = {
    { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },
    { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 }
};

static const int    len_years[2] = {
    DAYSPERNYEAR, DAYSPERLYEAR
};

static struct attype {
    zic_t        at;
    bool        dontmerge;
    unsigned char    type;
} *            attypes;
static zic_t        utoffs[TZ_MAX_TYPES];
static char        isdsts[TZ_MAX_TYPES];
static unsigned char    desigidx[TZ_MAX_TYPES];
static bool        ttisstds[TZ_MAX_TYPES];
static bool        ttisuts[TZ_MAX_TYPES];
static char        chars[TZ_MAX_CHARS];
static zic_t        trans[TZ_MAX_LEAPS];
static zic_t        corr[TZ_MAX_LEAPS];
static char        roll[TZ_MAX_LEAPS];

/*
** Memory allocation.
*/

static _Noreturn void
memory_exhausted(const char *msg)
{
    fprintf(stderr, _("%s: Memory exhausted: %s\n"), progname, msg);
    exit(EXIT_FAILURE);
}

static ATTRIBUTE_PURE size_t
size_product(size_t nitems, size_t itemsize)
{
    if (SIZE_MAX / itemsize < nitems)
        memory_exhausted(_("size overflow"));
    return nitems * itemsize;
}

static ATTRIBUTE_PURE size_t
align_to(size_t size, size_t alignment)
{
  size_t aligned_size = size + alignment - 1;
  aligned_size -= aligned_size % alignment;
  if (aligned_size < size)
    memory_exhausted(_("alignment overflow"));
  return aligned_size;
}

#if !HAVE_STRDUP
static char *
strdup(char const *str)
{
  char *result = malloc(strlen(str) + 1);
  return result ? strcpy(result, str) : result;
}
#endif

static void *
memcheck(void *ptr)
{
    if (ptr == NULL)
        memory_exhausted(strerror(errno));
    return ptr;
}

static void * ATTRIBUTE_MALLOC
emalloc(size_t size)
{
  return memcheck(malloc(size));
}

static void *
erealloc(void *ptr, size_t size)
{
  return memcheck(realloc(ptr, size));
}

static char * ATTRIBUTE_MALLOC
ecpyalloc (char const *str)
{
  return memcheck(strdup(str));
}

static void *
growalloc(void *ptr, size_t itemsize, ptrdiff_t nitems, ptrdiff_t *nitems_alloc)
{
    if (nitems < *nitems_alloc)
        return ptr;
    else {
        ptrdiff_t nitems_max = PTRDIFF_MAX - WORK_AROUND_QTBUG_53071;
        ptrdiff_t amax = nitems_max < SIZE_MAX ? nitems_max : SIZE_MAX;
        if ((amax - 1) / 3 * 2 < *nitems_alloc)
            memory_exhausted(_("integer overflow"));
        *nitems_alloc += (*nitems_alloc >> 1) + 1;
        return erealloc(ptr, size_product(*nitems_alloc, itemsize));
    }
}

/*
** Error handling.
*/

static void
eats(char const *name, lineno num, char const *rname, lineno rnum)
{
    filename = name;
    linenum = num;
    rfilename = rname;
    rlinenum = rnum;
}

static void
eat(char const *name, lineno num)
{
    eats(name, num, NULL, -1);
}

static void ATTRIBUTE_FORMAT((printf, 1, 0))
verror(const char *const string, va_list args)
{
    /*
    ** Match the format of "cc" to allow sh users to
    **    zic ... 2>&1 | error -t "*" -v
    ** on BSD systems.
    */
    if (filename)
      fprintf(stderr, _("\"%s\", line %"PRIdMAX": "), filename, linenum);
    vfprintf(stderr, string, args);
    if (rfilename != NULL)
        fprintf(stderr, _(" (rule from \"%s\", line %"PRIdMAX")"),
            rfilename, rlinenum);
    fprintf(stderr, "\n");
}

static void ATTRIBUTE_FORMAT((printf, 1, 2))
error(const char *const string, ...)
{
    va_list args;
    va_start(args, string);
    verror(string, args);
    va_end(args);
    errors = true;
}

static void ATTRIBUTE_FORMAT((printf, 1, 2))
warning(const char *const string, ...)
{
    va_list args;
    fprintf(stderr, _("warning: "));
    va_start(args, string);
    verror(string, args);
    va_end(args);
    warnings = true;
}

static void
close_file(FILE *stream, char const *dir, char const *name)
{
  char const *e = (ferror(stream) ? _("I/O error")
           : fclose(stream) != 0 ? strerror(errno) : NULL);
  if (e) {
    fprintf(stderr, "%s: %s%s%s%s%s\n", progname,
        dir ? dir : "", dir ? "/" : "",
        name ? name : "", name ? ": " : "",
        e);
    exit(EXIT_FAILURE);
  }
}

static _Noreturn void
usage(FILE *stream, int status)
{
  fprintf(stream,
      _("%s: usage is %s [ --version ] [ --help ] [ -v ] \\\n"
        "\t[ -b {slim|fat} ] [ -d directory ] [ -l localtime ]"
        " [ -L leapseconds ] \\\n"
        "\t[ -p posixrules ] [ -r '[@lo][/@hi]' ] [ -t localtime-link ] \\\n"
        "\t[ filename ... ]\n\n"
        "Report bugs to %s.\n"),
      progname, progname, REPORT_BUGS_TO);
  if (status == EXIT_SUCCESS)
    close_file(stream, NULL, NULL);
  exit(status);
}

/* Change the working directory to DIR, possibly creating DIR and its
   ancestors.  After this is done, all files are accessed with names
   relative to DIR.  */
static void
change_directory (char const *dir)
{
  if (chdir(dir) != 0) {
    int chdir_errno = errno;
    if (chdir_errno == ENOENT) {
      mkdirs(dir, false);
      chdir_errno = chdir(dir) == 0 ? 0 : errno;
    }
    if (chdir_errno != 0) {
      fprintf(stderr, _("%s: Can't chdir to %s: %s\n"),
          progname, dir, strerror(chdir_errno));
      exit(EXIT_FAILURE);
    }
  }
}

#define TIME_T_BITS_IN_FILE 64

/* The minimum and maximum values representable in a TZif file.  */
static zic_t const min_time = MINVAL(zic_t, TIME_T_BITS_IN_FILE);
static zic_t const max_time = MAXVAL(zic_t, TIME_T_BITS_IN_FILE);

/* The minimum, and one less than the maximum, values specified by
   the -r option.  These default to MIN_TIME and MAX_TIME.  */
static zic_t lo_time = MINVAL(zic_t, TIME_T_BITS_IN_FILE);
static zic_t hi_time = MAXVAL(zic_t, TIME_T_BITS_IN_FILE);

/* Set the time range of the output to TIMERANGE.
   Return true if successful.  */
static bool
timerange_option(char *timerange)
{
  intmax_t lo = min_time, hi = max_time;
  char *lo_end = timerange, *hi_end;
  if (*timerange == '@') {
    errno = 0;
    lo = strtoimax (timerange + 1, &lo_end, 10);
    if (lo_end == timerange + 1 || (lo == INTMAX_MAX && errno == ERANGE))
      return false;
  }
  hi_end = lo_end;
  if (lo_end[0] == '/' && lo_end[1] == '@') {
    errno = 0;
    hi = strtoimax (lo_end + 2, &hi_end, 10);
    if (hi_end == lo_end + 2 || hi == INTMAX_MIN)
      return false;
    hi -= ! (hi == INTMAX_MAX && errno == ERANGE);
  }
  if (*hi_end || hi < lo || max_time < lo || hi < min_time)
    return false;
  lo_time = lo < min_time ? min_time : lo;
  hi_time = max_time < hi ? max_time : hi;
  return true;
}

static const char *    psxrules;
static const char *    lcltime;
static const char *    directory;
static const char *    leapsec;
static const char *    tzdefault;
static const char *    yitcommand;

/* -1 if the TZif output file should be slim, 0 if default, 1 if the
   output should be fat for backward compatibility.  Currently the
   default is fat, although this may change.  */
static int bloat;

static bool
want_bloat(void)
{
  return 0 <= bloat;
}

#ifndef ZIC_BLOAT_DEFAULT
# define ZIC_BLOAT_DEFAULT "fat"
#endif

int
main(int argc, char **argv)
{
    register int c, k;
    register ptrdiff_t i, j;
    bool timerange_given = false;

#ifdef S_IWGRP
    umask(umask(S_IWGRP | S_IWOTH) | (S_IWGRP | S_IWOTH));
#endif
#if HAVE_GETTEXT
    setlocale(LC_ALL, "");
#ifdef TZ_DOMAINDIR
    bindtextdomain(TZ_DOMAIN, TZ_DOMAINDIR);
#endif /* defined TEXTDOMAINDIR */
    textdomain(TZ_DOMAIN);
#endif /* HAVE_GETTEXT */
    progname = argv[0];
    if (TYPE_BIT(zic_t) < 64) {
        fprintf(stderr, "%s: %s\n", progname,
            _("wild compilation-time specification of zic_t"));
        return EXIT_FAILURE;
    }
    for (k = 1; k < argc; k++)
        if (strcmp(argv[k], "--version") == 0) {
            printf("zic %s%s\n", PKGVERSION, TZVERSION);
            close_file(stdout, NULL, NULL);
            return EXIT_SUCCESS;
        } else if (strcmp(argv[k], "--help") == 0) {
            usage(stdout, EXIT_SUCCESS);
        }
    while ((c = getopt(argc, argv, "b:d:l:L:p:r:st:vy:")) != EOF && c != -1)
        switch (c) {
            default:
                usage(stderr, EXIT_FAILURE);
            case 'b':
                if (strcmp(optarg, "slim") == 0) {
                  if (0 < bloat)
                    error(_("incompatible -b options"));
                  bloat = -1;
                } else if (strcmp(optarg, "fat") == 0) {
                  if (bloat < 0)
                    error(_("incompatible -b options"));
                  bloat = 1;
                } else
                  error(_("invalid option: -b '%s'"), optarg);
                break;
            case 'd':
                if (directory == NULL)
                    directory = optarg;
                else {
                    fprintf(stderr,
_("%s: More than one -d option specified\n"),
                        progname);
                    return EXIT_FAILURE;
                }
                break;
            case 'l':
                if (lcltime == NULL)
                    lcltime = optarg;
                else {
                    fprintf(stderr,
_("%s: More than one -l option specified\n"),
                        progname);
                    return EXIT_FAILURE;
                }
                break;
            case 'p':
                if (psxrules == NULL)
                    psxrules = optarg;
                else {
                    fprintf(stderr,
_("%s: More than one -p option specified\n"),
                        progname);
                    return EXIT_FAILURE;
                }
                break;
            case 't':
                if (tzdefault != NULL) {
                  fprintf(stderr,
                      _("%s: More than one -t option"
                        " specified\n"),
                      progname);
                  return EXIT_FAILURE;
                }
                tzdefault = optarg;
                break;
            case 'y':
                if (yitcommand == NULL) {
                    warning(_("-y is obsolescent"));
                    yitcommand = optarg;
                } else {
                    fprintf(stderr,
_("%s: More than one -y option specified\n"),
                        progname);
                    return EXIT_FAILURE;
                }
                break;
            case 'L':
                if (leapsec == NULL)
                    leapsec = optarg;
                else {
                    fprintf(stderr,
_("%s: More than one -L option specified\n"),
                        progname);
                    return EXIT_FAILURE;
                }
                break;
            case 'v':
                noise = true;
                break;
            case 'r':
                if (timerange_given) {
                  fprintf(stderr,
_("%s: More than one -r option specified\n"),
                      progname);
                  return EXIT_FAILURE;
                }
                if (! timerange_option(optarg)) {
                  fprintf(stderr,
_("%s: invalid time range: %s\n"),
                      progname, optarg);
                  return EXIT_FAILURE;
                }
                timerange_given = true;
                break;
            case 's':
                warning(_("-s ignored"));
                break;
        }
    if (optind == argc - 1 && strcmp(argv[optind], "=") == 0)
        usage(stderr, EXIT_FAILURE);    /* usage message by request */
    if (bloat == 0)
      bloat = strcmp(ZIC_BLOAT_DEFAULT, "slim") == 0 ? -1 : 1;
    if (directory == NULL)
        directory = TZDIR;
    if (tzdefault == NULL)
        tzdefault = TZDEFAULT;
    if (yitcommand == NULL)
        yitcommand = "yearistype";

    if (optind < argc && leapsec != NULL) {
        infile(leapsec);
        adjleap();
    }

    for (k = optind; k < argc; k++)
        infile(argv[k]);
    if (errors)
        return EXIT_FAILURE;
    associate();
    change_directory(directory);
    for (i = 0; i < nzones; i = j) {
        /*
        ** Find the next non-continuation zone entry.
        */
        for (j = i + 1; j < nzones && zones[j].z_name == NULL; ++j)
            continue;
        outzone(&zones[i], j - i);
    }
    /*
    ** Make links.
    */
    for (i = 0; i < nlinks; ++i) {
        eat(links[i].l_filename, links[i].l_linenum);
        dolink(links[i].l_from, links[i].l_to, false);
        if (noise)
            for (j = 0; j < nlinks; ++j)
                if (strcmp(links[i].l_to,
                    links[j].l_from) == 0)
                        warning(_("link to link"));
    }
    if (lcltime != NULL) {
        eat(_("command line"), 1);
        dolink(lcltime, tzdefault, true);
    }
    if (psxrules != NULL) {
        eat(_("command line"), 1);
        dolink(psxrules, TZDEFRULES, true);
    }
    if (warnings && (ferror(stderr) || fclose(stderr) != 0))
      return EXIT_FAILURE;
    return errors ? EXIT_FAILURE : EXIT_SUCCESS;
}

static bool
componentcheck(char const *name, char const *component,
           char const *component_end)
{
    enum { component_len_max = 14 };
    ptrdiff_t component_len = component_end - component;
    if (component_len == 0) {
      if (!*name)
        error (_("empty file name"));
      else
        error (_(component == name
             ? "file name '%s' begins with '/'"
             : *component_end
             ? "file name '%s' contains '//'"
             : "file name '%s' ends with '/'"),
           name);
      return false;
    }
    if (0 < component_len && component_len <= 2
        && component[0] == '.' && component_end[-1] == '.') {
      int len = component_len;
      error(_("file name '%s' contains '%.*s' component"),
        name, len, component);
      return false;
    }
    if (noise) {
      if (0 < component_len && component[0] == '-')
        warning(_("file name '%s' component contains leading '-'"),
            name);
      if (component_len_max < component_len)
        warning(_("file name '%s' contains overlength component"
              " '%.*s...'"),
            name, component_len_max, component);
    }
    return true;
}

static bool
namecheck(const char *name)
{
    register char const *cp;

    /* Benign characters in a portable file name.  */
    static char const benign[] =
      "-/_"
      "abcdefghijklmnopqrstuvwxyz"
      "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    /* Non-control chars in the POSIX portable character set,
       excluding the benign characters.  */
    static char const printable_and_not_benign[] =
      " !\"#$%&'()*+,.0123456789:;<=>?@[\\]^`{|}~";

    register char const *component = name;
    for (cp = name; *cp; cp++) {
        unsigned char c = *cp;
        if (noise && !strchr(benign, c)) {
            warning((strchr(printable_and_not_benign, c)
                 ? _("file name '%s' contains byte '%c'")
                 : _("file name '%s' contains byte '\\%o'")),
                name, c);
        }
        if (c == '/') {
            if (!componentcheck(name, component, cp))
              return false;
            component = cp + 1;
        }
    }
    return componentcheck(name, component, cp);
}

/* Create symlink contents suitable for symlinking FROM to TO, as a
   freshly allocated string.  FROM should be a relative file name, and
   is relative to the global variable DIRECTORY.  TO can be either
   relative or absolute.  */
static char *
relname(char const *from, char const *to)
{
  size_t i, taillen, dotdotetcsize;
  size_t dir_len = 0, dotdots = 0, linksize = SIZE_MAX;
  char const *f = from;
  char *result = NULL;
  if (*to == '/') {
    /* Make F absolute too.  */
    size_t len = strlen(directory);
    bool needslash = len && directory[len - 1] != '/';
    linksize = len + needslash + strlen(from) + 1;
    f = result = emalloc(linksize);
    strcpy(result, directory);
    result[len] = '/';
    strcpy(result + len + needslash, from);
  }
  for (i = 0; f[i] && f[i] == to[i]; i++)
    if (f[i] == '/')
      dir_len = i + 1;
  for (; to[i]; i++)
    dotdots += to[i] == '/' && to[i - 1] != '/';
  taillen = strlen(f + dir_len);
  dotdotetcsize = 3 * dotdots + taillen + 1;
  if (dotdotetcsize <= linksize) {
    if (!result)
      result = emalloc(dotdotetcsize);
    for (i = 0; i < dotdots; i++)
      memcpy(result + 3 * i, "../", 3);
    memmove(result + 3 * dotdots, f + dir_len, taillen + 1);
  }
  return result;
}

/* Hard link FROM to TO, following any symbolic links.
   Return 0 if successful, an error number otherwise.  */
static int
hardlinkerr(char const *from, char const *to)
{
  int r = linkat(AT_FDCWD, from, AT_FDCWD, to, AT_SYMLINK_FOLLOW);
  return r == 0 ? 0 : errno;
}

static void
dolink(char const *fromfield, char const *tofield, bool staysymlink)
{
    bool todirs_made = false;
    int link_errno;

    /*
    ** We get to be careful here since
    ** there's a fair chance of root running us.
    */
    if (itsdir(fromfield)) {
        fprintf(stderr, _("%s: link from %s/%s failed: %s\n"),
            progname, directory, fromfield, strerror(EPERM));
        exit(EXIT_FAILURE);
    }
    if (staysymlink)
      staysymlink = itssymlink(tofield);
    if (remove(tofield) == 0)
      todirs_made = true;
    else if (errno != ENOENT) {
      char const *e = strerror(errno);
      fprintf(stderr, _("%s: Can't remove %s/%s: %s\n"),
          progname, directory, tofield, e);
      exit(EXIT_FAILURE);
    }
    link_errno = staysymlink ? ENOTSUP : hardlinkerr(fromfield, tofield);
    if (link_errno == ENOENT && !todirs_made) {
      mkdirs(tofield, true);
      todirs_made = true;
      link_errno = hardlinkerr(fromfield, tofield);
    }
    if (link_errno != 0) {
      bool absolute = *fromfield == '/';
      char *linkalloc = absolute ? NULL : relname(fromfield, tofield);
      char const *contents = absolute ? fromfield : linkalloc;
      int symlink_errno = symlink(contents, tofield) == 0 ? 0 : errno;
      if (!todirs_made
          && (symlink_errno == ENOENT || symlink_errno == ENOTSUP)) {
        mkdirs(tofield, true);
        if (symlink_errno == ENOENT)
          symlink_errno = symlink(contents, tofield) == 0 ? 0 : errno;
      }
      free(linkalloc);
      if (symlink_errno == 0) {
        if (link_errno != ENOTSUP)
          warning(_("symbolic link used because hard link failed: %s"),
              strerror(link_errno));
      } else {
        FILE *fp, *tp;
        int c;
        fp = fopen(fromfield, "rb");
        if (!fp) {
          char const *e = strerror(errno);
          fprintf(stderr, _("%s: Can't read %s/%s: %s\n"),
              progname, directory, fromfield, e);
          exit(EXIT_FAILURE);
        }
        tp = fopen(tofield, "wb");
        if (!tp) {
          char const *e = strerror(errno);
          fprintf(stderr, _("%s: Can't create %s/%s: %s\n"),
              progname, directory, tofield, e);
          exit(EXIT_FAILURE);
        }
        while ((c = getc(fp)) != EOF)
          putc(c, tp);
        close_file(fp, directory, fromfield);
        close_file(tp, directory, tofield);
        if (link_errno != ENOTSUP)
          warning(_("copy used because hard link failed: %s"),
              strerror(link_errno));
        else if (symlink_errno != ENOTSUP)
          warning(_("copy used because symbolic link failed: %s"),
              strerror(symlink_errno));
      }
    }
}

/* Return true if NAME is a directory.  */
static bool
itsdir(char const *name)
{
    struct stat st;
    int res = stat(name, &st);
#ifdef S_ISDIR
    if (res == 0)
        return S_ISDIR(st.st_mode) != 0;
#endif
    if (res == 0 || errno == EOVERFLOW) {
        size_t n = strlen(name);
        char *nameslashdot = emalloc(n + 3);
        bool dir;
        memcpy(nameslashdot, name, n);
        strcpy(&nameslashdot[n], &"/."[! (n && name[n - 1] != '/')]);
        dir = stat(nameslashdot, &st) == 0 || errno == EOVERFLOW;
        free(nameslashdot);
        return dir;
    }
    return false;
}

/* Return true if NAME is a symbolic link.  */
static bool
itssymlink(char const *name)
{
  char c;
  return 0 <= readlink(name, &c, 1);
}

/*
** Associate sets of rules with zones.
*/

/*
** Sort by rule name.
*/

static int
rcomp(const void *cp1, const void *cp2)
{
    return strcmp(((const struct rule *) cp1)->r_name,
        ((const struct rule *) cp2)->r_name);
}

static void
associate(void)
{
    register struct zone *    zp;
    register struct rule *    rp;
    register ptrdiff_t i, j, base, out;

    if (nrules != 0) {
        qsort(rules, nrules, sizeof *rules, rcomp);
        for (i = 0; i < nrules - 1; ++i) {
            if (strcmp(rules[i].r_name,
                rules[i + 1].r_name) != 0)
                    continue;
            if (strcmp(rules[i].r_filename,
                rules[i + 1].r_filename) == 0)
                    continue;
            eat(rules[i].r_filename, rules[i].r_linenum);
            warning(_("same rule name in multiple files"));
            eat(rules[i + 1].r_filename, rules[i + 1].r_linenum);
            warning(_("same rule name in multiple files"));
            for (j = i + 2; j < nrules; ++j) {
                if (strcmp(rules[i].r_name,
                    rules[j].r_name) != 0)
                        break;
                if (strcmp(rules[i].r_filename,
                    rules[j].r_filename) == 0)
                        continue;
                if (strcmp(rules[i + 1].r_filename,
                    rules[j].r_filename) == 0)
                        continue;
                break;
            }
            i = j - 1;
        }
    }
    for (i = 0; i < nzones; ++i) {
        zp = &zones[i];
        zp->z_rules = NULL;
        zp->z_nrules = 0;
    }
    for (base = 0; base < nrules; base = out) {
        rp = &rules[base];
        for (out = base + 1; out < nrules; ++out)
            if (strcmp(rp->r_name, rules[out].r_name) != 0)
                break;
        for (i = 0; i < nzones; ++i) {
            zp = &zones[i];
            if (strcmp(zp->z_rule, rp->r_name) != 0)
                continue;
            zp->z_rules = rp;
            zp->z_nrules = out - base;
        }
    }
    for (i = 0; i < nzones; ++i) {
        zp = &zones[i];
        if (zp->z_nrules == 0) {
            /*
            ** Maybe we have a local standard time offset.
            */
            eat(zp->z_filename, zp->z_linenum);
            zp->z_save = getsave(zp->z_rule, &zp->z_isdst);
            /*
            ** Note, though, that if there's no rule,
            ** a '%s' in the format is a bad thing.
            */
            if (zp->z_format_specifier == 's')
                error("%s", _("%s in ruleless zone"));
        }
    }
    if (errors)
        exit(EXIT_FAILURE);
}

static void
infile(const char *name)
{
    register FILE *            fp;
    register char **        fields;
    register char *            cp;
    register const struct lookup *    lp;
    register int            nfields;
    register bool            wantcont;
    register lineno            num;
    char                buf[BUFSIZ];

    if (strcmp(name, "-") == 0) {
        name = _("standard input");
        fp = stdin;
    } else if ((fp = fopen(name, "r")) == NULL) {
        const char *e = strerror(errno);

        fprintf(stderr, _("%s: Can't open %s: %s\n"),
            progname, name, e);
        exit(EXIT_FAILURE);
    }
    wantcont = false;
    for (num = 1; ; ++num) {
        eat(name, num);
        if (fgets(buf, sizeof buf, fp) != buf)
            break;
        cp = strchr(buf, '\n');
        if (cp == NULL) {
            error(_("line too long"));
            exit(EXIT_FAILURE);
        }
        *cp = '\0';
        fields = getfields(buf);
        nfields = 0;
        while (fields[nfields] != NULL) {
            static char    nada;

            if (strcmp(fields[nfields], "-") == 0)
                fields[nfields] = &nada;
            ++nfields;
        }
        if (nfields == 0) {
            /* nothing to do */
        } else if (wantcont) {
            wantcont = inzcont(fields, nfields);
        } else {
            struct lookup const *line_codes
              = name == leapsec ? leap_line_codes : zi_line_codes;
            lp = byword(fields[0], line_codes);
            if (lp == NULL)
                error(_("input line of unknown type"));
            else switch (lp->l_value) {
                case LC_RULE:
                    inrule(fields, nfields);
                    wantcont = false;
                    break;
                case LC_ZONE:
                    wantcont = inzone(fields, nfields);
                    break;
                case LC_LINK:
                    inlink(fields, nfields);
                    wantcont = false;
                    break;
                case LC_LEAP:
                    inleap(fields, nfields);
                    wantcont = false;
                    break;
                default:    /* "cannot happen" */
                    fprintf(stderr,
_("%s: panic: Invalid l_value %d\n"),
                        progname, lp->l_value);
                    exit(EXIT_FAILURE);
            }
        }
        free(fields);
    }
    close_file(fp, NULL, filename);
    if (wantcont)
        error(_("expected continuation line not found"));
}

/*
** Convert a string of one of the forms
**    h    -h    hh:mm    -hh:mm    hh:mm:ss    -hh:mm:ss
** into a number of seconds.
** A null string maps to zero.
** Call error with errstring and return zero on errors.
*/

static zic_t
gethms(char const *string, char const *errstring)
{
    zic_t    hh;
    int sign, mm = 0, ss = 0;
    char hhx, mmx, ssx, xr = '0', xs;
    int tenths = 0;
    bool ok = true;

    if (string == NULL || *string == '\0')
        return 0;
    if (*string == '-') {
        sign = -1;
        ++string;
    } else    sign = 1;
    switch (sscanf(string,
               "%"SCNdZIC"%c%d%c%d%c%1d%*[0]%c%*[0123456789]%c",
               &hh, &hhx, &mm, &mmx, &ss, &ssx, &tenths, &xr, &xs)) {
      default: ok = false; break;
      case 8:
        ok = '0' <= xr && xr <= '9';
        /* fallthrough */
      case 7:
        ok &= ssx == '.';
        if (ok && noise)
          warning(_("fractional seconds rejected by"
            " pre-2018 versions of zic"));
        /* fallthrough */
      case 5: ok &= mmx == ':'; /* fallthrough */
      case 3: ok &= hhx == ':'; /* fallthrough */
      case 1: break;
    }
    if (!ok) {
            error("%s", errstring);
            return 0;
    }
    if (hh < 0 ||
        mm < 0 || mm >= MINSPERHOUR ||
        ss < 0 || ss > SECSPERMIN) {
            error("%s", errstring);
            return 0;
    }
    if (ZIC_MAX / SECSPERHOUR < hh) {
        error(_("time overflow"));
        return 0;
    }
    ss += 5 + ((ss ^ 1) & (xr == '0')) <= tenths; /* Round to even.  */
    if (noise && (hh > HOURSPERDAY ||
        (hh == HOURSPERDAY && (mm != 0 || ss != 0))))
warning(_("values over 24 hours not handled by pre-2007 versions of zic"));
    return oadd(sign * hh * SECSPERHOUR,
            sign * (mm * SECSPERMIN + ss));
}

static zic_t
getsave(char *field, bool *isdst)
{
  int dst = -1;
  zic_t save;
  size_t fieldlen = strlen(field);
  if (fieldlen != 0) {
    char *ep = field + fieldlen - 1;
    switch (*ep) {
      case 'd': dst = 1; *ep = '\0'; break;
      case 's': dst = 0; *ep = '\0'; break;
    }
  }
  save = gethms(field, _("invalid saved time"));
  *isdst = dst < 0 ? save != 0 : dst;
  return save;
}

static void
inrule(char **fields, int nfields)
{
    static struct rule    r;

    if (nfields != RULE_FIELDS) {
        error(_("wrong number of fields on Rule line"));
        return;
    }
    switch (*fields[RF_NAME]) {
      case '\0':
      case ' ': case '\f': case '\n': case '\r': case '\t': case '\v':
      case '+': case '-':
      case '0': case '1': case '2': case '3': case '4':
      case '5': case '6': case '7': case '8': case '9':
        error(_("Invalid rule name \"%s\""), fields[RF_NAME]);
        return;
    }
    r.r_filename = filename;
    r.r_linenum = linenum;
    r.r_save = getsave(fields[RF_SAVE], &r.r_isdst);
    rulesub(&r, fields[RF_LOYEAR], fields[RF_HIYEAR], fields[RF_COMMAND],
        fields[RF_MONTH], fields[RF_DAY], fields[RF_TOD]);
    r.r_name = ecpyalloc(fields[RF_NAME]);
    r.r_abbrvar = ecpyalloc(fields[RF_ABBRVAR]);
    if (max_abbrvar_len < strlen(r.r_abbrvar))
        max_abbrvar_len = strlen(r.r_abbrvar);
    rules = growalloc(rules, sizeof *rules, nrules, &nrules_alloc);
    rules[nrules++] = r;
}

static bool
inzone(char **fields, int nfields)
{
    register ptrdiff_t i;

    if (nfields < ZONE_MINFIELDS || nfields > ZONE_MAXFIELDS) {
        error(_("wrong number of fields on Zone line"));
        return false;
    }
    if (lcltime != NULL && strcmp(fields[ZF_NAME], tzdefault) == 0) {
        error(
_("\"Zone %s\" line and -l option are mutually exclusive"),
            tzdefault);
        return false;
    }
    if (strcmp(fields[ZF_NAME], TZDEFRULES) == 0 && psxrules != NULL) {
        error(
_("\"Zone %s\" line and -p option are mutually exclusive"),
            TZDEFRULES);
        return false;
    }
    for (i = 0; i < nzones; ++i)
        if (zones[i].z_name != NULL &&
            strcmp(zones[i].z_name, fields[ZF_NAME]) == 0) {
                error(_("duplicate zone name %s"
                    " (file \"%s\", line %"PRIdMAX")"),
                    fields[ZF_NAME],
                    zones[i].z_filename,
                    zones[i].z_linenum);
                return false;
        }
    return inzsub(fields, nfields, false);
}

static bool
inzcont(char **fields, int nfields)
{
    if (nfields < ZONEC_MINFIELDS || nfields > ZONEC_MAXFIELDS) {
        error(_("wrong number of fields on Zone continuation line"));
        return false;
    }
    return inzsub(fields, nfields, true);
}

static bool
inzsub(char **fields, int nfields, bool iscont)
{
    register char *        cp;
    char *            cp1;
    static struct zone    z;
    register int        i_stdoff, i_rule, i_format;
    register int        i_untilyear, i_untilmonth;
    register int        i_untilday, i_untiltime;
    register bool        hasuntil;

    if (iscont) {
        i_stdoff = ZFC_STDOFF;
        i_rule = ZFC_RULE;
        i_format = ZFC_FORMAT;
        i_untilyear = ZFC_TILYEAR;
        i_untilmonth = ZFC_TILMONTH;
        i_untilday = ZFC_TILDAY;
        i_untiltime = ZFC_TILTIME;
        z.z_name = NULL;
    } else if (!namecheck(fields[ZF_NAME]))
        return false;
    else {
        i_stdoff = ZF_STDOFF;
        i_rule = ZF_RULE;
        i_format = ZF_FORMAT;
        i_untilyear = ZF_TILYEAR;
        i_untilmonth = ZF_TILMONTH;
        i_untilday = ZF_TILDAY;
        i_untiltime = ZF_TILTIME;
        z.z_name = ecpyalloc(fields[ZF_NAME]);
    }
    z.z_filename = filename;
    z.z_linenum = linenum;
    z.z_stdoff = gethms(fields[i_stdoff], _("invalid UT offset"));
    if ((cp = strchr(fields[i_format], '%')) != 0) {
        if ((*++cp != 's' && *cp != 'z') || strchr(cp, '%')
            || strchr(fields[i_format], '/')) {
            error(_("invalid abbreviation format"));
            return false;
        }
    }
    z.z_rule = ecpyalloc(fields[i_rule]);
    z.z_format = cp1 = ecpyalloc(fields[i_format]);
    z.z_format_specifier = cp ? *cp : '\0';
    if (z.z_format_specifier == 'z') {
      if (noise)
        warning(_("format '%s' not handled by pre-2015 versions of zic"),
            z.z_format);
      cp1[cp - fields[i_format]] = 's';
    }
    if (max_format_len < strlen(z.z_format))
        max_format_len = strlen(z.z_format);
    hasuntil = nfields > i_untilyear;
    if (hasuntil) {
        z.z_untilrule.r_filename = filename;
        z.z_untilrule.r_linenum = linenum;
        rulesub(&z.z_untilrule,
            fields[i_untilyear],
            "only",
            "",
            (nfields > i_untilmonth) ?
            fields[i_untilmonth] : "Jan",
            (nfields > i_untilday) ? fields[i_untilday] : "1",
            (nfields > i_untiltime) ? fields[i_untiltime] : "0");
        z.z_untiltime = rpytime(&z.z_untilrule,
            z.z_untilrule.r_loyear);
        if (iscont && nzones > 0 &&
            z.z_untiltime > min_time &&
            z.z_untiltime < max_time &&
            zones[nzones - 1].z_untiltime > min_time &&
            zones[nzones - 1].z_untiltime < max_time &&
            zones[nzones - 1].z_untiltime >= z.z_untiltime) {
                error(_(
"Zone continuation line end time is not after end time of previous line"
                    ));
                return false;
        }
    }
    zones = growalloc(zones, sizeof *zones, nzones, &nzones_alloc);
    zones[nzones++] = z;
    /*
    ** If there was an UNTIL field on this line,
    ** there's more information about the zone on the next line.
    */
    return hasuntil;
}

static void
inleap(char **fields, int nfields)
{
    register const char *        cp;
    register const struct lookup *    lp;
    register zic_t            i, j;
    zic_t                year;
    int                month, day;
    zic_t                dayoff, tod;
    zic_t                t;
    char xs;

    if (nfields != LEAP_FIELDS) {
        error(_("wrong number of fields on Leap line"));
        return;
    }
    dayoff = 0;
    cp = fields[LP_YEAR];
    if (sscanf(cp, "%"SCNdZIC"%c", &year, &xs) != 1) {
        /*
        ** Leapin' Lizards!
        */
        error(_("invalid leaping year"));
        return;
    }
    if (!leapseen || leapmaxyear < year)
        leapmaxyear = year;
    if (!leapseen || leapminyear > year)
        leapminyear = year;
    leapseen = true;
    j = EPOCH_YEAR;
    while (j != year) {
        if (year > j) {
            i = len_years[isleap(j)];
            ++j;
        } else {
            --j;
            i = -len_years[isleap(j)];
        }
        dayoff = oadd(dayoff, i);
    }
    if ((lp = byword(fields[LP_MONTH], mon_names)) == NULL) {
        error(_("invalid month name"));
        return;
    }
    month = lp->l_value;
    j = TM_JANUARY;
    while (j != month) {
        i = len_months[isleap(year)][j];
        dayoff = oadd(dayoff, i);
        ++j;
    }
    cp = fields[LP_DAY];
    if (sscanf(cp, "%d%c", &day, &xs) != 1 ||
        day <= 0 || day > len_months[isleap(year)][month]) {
            error(_("invalid day of month"));
            return;
    }
    dayoff = oadd(dayoff, day - 1);
    if (dayoff < min_time / SECSPERDAY) {
        error(_("time too small"));
        return;
    }
    if (dayoff > max_time / SECSPERDAY) {
        error(_("time too large"));
        return;
    }
    t = dayoff * SECSPERDAY;
    tod = gethms(fields[LP_TIME], _("invalid time of day"));
    cp = fields[LP_CORR];
    {
        register bool    positive;
        int        count;

        if (strcmp(cp, "") == 0) { /* infile() turns "-" into "" */
            positive = false;
            count = 1;
        } else if (strcmp(cp, "+") == 0) {
            positive = true;
            count = 1;
        } else {
            error(_("illegal CORRECTION field on Leap line"));
            return;
        }
        if ((lp = byword(fields[LP_ROLL], leap_types)) == NULL) {
            error(_(
                "illegal Rolling/Stationary field on Leap line"
                ));
            return;
        }
        t = tadd(t, tod);
        if (t < 0) {
            error(_("leap second precedes Epoch"));
            return;
        }
        leapadd(t, positive, lp->l_value, count);
    }
}

static void
inlink(char **fields, int nfields)
{
    struct link    l;

    if (nfields != LINK_FIELDS) {
        error(_("wrong number of fields on Link line"));
        return;
    }
    if (*fields[LF_FROM] == '\0') {
        error(_("blank FROM field on Link line"));
        return;
    }
    if (! namecheck(fields[LF_TO]))
      return;
    l.l_filename = filename;
    l.l_linenum = linenum;
    l.l_from = ecpyalloc(fields[LF_FROM]);
    l.l_to = ecpyalloc(fields[LF_TO]);
    links = growalloc(links, sizeof *links, nlinks, &nlinks_alloc);
    links[nlinks++] = l;
}

static void
rulesub(struct rule *rp, const char *loyearp, const char *hiyearp,
    const char *typep, const char *monthp, const char *dayp,
    const char *timep)
{
    register const struct lookup *    lp;
    register const char *        cp;
    register char *            dp;
    register char *            ep;
    char xs;

    if ((lp = byword(monthp, mon_names)) == NULL) {
        error(_("invalid month name"));
        return;
    }
    rp->r_month = lp->l_value;
    rp->r_todisstd = false;
    rp->r_todisut = false;
    dp = ecpyalloc(timep);
    if (*dp != '\0') {
        ep = dp + strlen(dp) - 1;
        switch (lowerit(*ep)) {
            case 's':    /* Standard */
                rp->r_todisstd = true;
                rp->r_todisut = false;
                *ep = '\0';
                break;
            case 'w':    /* Wall */
                rp->r_todisstd = false;
                rp->r_todisut = false;
                *ep = '\0';
                break;
            case 'g':    /* Greenwich */
            case 'u':    /* Universal */
            case 'z':    /* Zulu */
                rp->r_todisstd = true;
                rp->r_todisut = true;
                *ep = '\0';
                break;
        }
    }
    rp->r_tod = gethms(dp, _("invalid time of day"));
    free(dp);
    /*
    ** Year work.
    */
    cp = loyearp;
    lp = byword(cp, begin_years);
    rp->r_lowasnum = lp == NULL;
    if (!rp->r_lowasnum) switch (lp->l_value) {
        case YR_MINIMUM:
            rp->r_loyear = ZIC_MIN;
            break;
        case YR_MAXIMUM:
            rp->r_loyear = ZIC_MAX;
            break;
        default:    /* "cannot happen" */
            fprintf(stderr,
                _("%s: panic: Invalid l_value %d\n"),
                progname, lp->l_value);
            exit(EXIT_FAILURE);
    } else if (sscanf(cp, "%"SCNdZIC"%c", &rp->r_loyear, &xs) != 1) {
        error(_("invalid starting year"));
        return;
    }
    cp = hiyearp;
    lp = byword(cp, end_years);
    rp->r_hiwasnum = lp == NULL;
    if (!rp->r_hiwasnum) switch (lp->l_value) {
        case YR_MINIMUM:
            rp->r_hiyear = ZIC_MIN;
            break;
        case YR_MAXIMUM:
            rp->r_hiyear = ZIC_MAX;
            break;
        case YR_ONLY:
            rp->r_hiyear = rp->r_loyear;
            break;
        default:    /* "cannot happen" */
            fprintf(stderr,
                _("%s: panic: Invalid l_value %d\n"),
                progname, lp->l_value);
            exit(EXIT_FAILURE);
    } else if (sscanf(cp, "%"SCNdZIC"%c", &rp->r_hiyear, &xs) != 1) {
        error(_("invalid ending year"));
        return;
    }
    if (rp->r_loyear > rp->r_hiyear) {
        error(_("starting year greater than ending year"));
        return;
    }
    if (*typep == '\0')
        rp->r_yrtype = NULL;
    else {
        if (rp->r_loyear == rp->r_hiyear) {
            error(_("typed single year"));
            return;
        }
        warning(_("year type \"%s\" is obsolete; use \"-\" instead"),
            typep);
        rp->r_yrtype = ecpyalloc(typep);
    }
    /*
    ** Day work.
    ** Accept things such as:
    **    1
    **    lastSunday
    **    last-Sunday (undocumented; warn about this)
    **    Sun<=20
    **    Sun>=7
    */
    dp = ecpyalloc(dayp);
    if ((lp = byword(dp, lasts)) != NULL) {
        rp->r_dycode = DC_DOWLEQ;
        rp->r_wday = lp->l_value;
        rp->r_dayofmonth = len_months[1][rp->r_month];
    } else {
        if ((ep = strchr(dp, '<')) != 0)
            rp->r_dycode = DC_DOWLEQ;
        else if ((ep = strchr(dp, '>')) != 0)
            rp->r_dycode = DC_DOWGEQ;
        else {
            ep = dp;
            rp->r_dycode = DC_DOM;
        }
        if (rp->r_dycode != DC_DOM) {
            *ep++ = 0;
            if (*ep++ != '=') {
                error(_("invalid day of month"));
                free(dp);
                return;
            }
            if ((lp = byword(dp, wday_names)) == NULL) {
                error(_("invalid weekday name"));
                free(dp);
                return;
            }
            rp->r_wday = lp->l_value;
        }
        if (sscanf(ep, "%d%c", &rp->r_dayofmonth, &xs) != 1 ||
            rp->r_dayofmonth <= 0 ||
            (rp->r_dayofmonth > len_months[1][rp->r_month])) {
                error(_("invalid day of month"));
                free(dp);
                return;
        }
    }
    free(dp);
}

static void
convert(const int_fast32_t val, char *const buf)
{
    register int    i;
    register int    shift;
    unsigned char *const b = (unsigned char *) buf;

    for (i = 0, shift = 24; i < 4; ++i, shift -= 8)
        b[i] = val >> shift;
}

static void
convert64(const zic_t val, char *const buf)
{
    register int    i;
    register int    shift;
    unsigned char *const b = (unsigned char *) buf;

    for (i = 0, shift = 56; i < 8; ++i, shift -= 8)
        b[i] = val >> shift;
}

static void
puttzcode(const int_fast32_t val, FILE *const fp)
{
    char    buf[4];

    convert(val, buf);
    fwrite(buf, sizeof buf, 1, fp);
}

static void
puttzcodepass(zic_t val, FILE *fp, int pass)
{
  if (pass == 1)
    puttzcode(val, fp);
  else {
    char    buf[8];

    convert64(val, buf);
    fwrite(buf, sizeof buf, 1, fp);
  }
}

static int
atcomp(const void *avp, const void *bvp)
{
    const zic_t    a = ((const struct attype *) avp)->at;
    const zic_t    b = ((const struct attype *) bvp)->at;

    return (a < b) ? -1 : (a > b);
}

struct timerange {
  int defaulttype;
  ptrdiff_t base, count;
  int leapbase, leapcount;
};

static struct timerange
limitrange(struct timerange r, zic_t lo, zic_t hi,
       zic_t const *ats, unsigned char const *types)
{
  while (0 < r.count && ats[r.base] < lo) {
    r.defaulttype = types[r.base];
    r.count--;
    r.base++;
  }
  while (0 < r.leapcount && trans[r.leapbase] < lo) {
    r.leapcount--;
    r.leapbase++;
  }

  if (hi < ZIC_MAX) {
    while (0 < r.count && hi + 1 < ats[r.base + r.count - 1])
      r.count--;
    while (0 < r.leapcount && hi + 1 < trans[r.leapbase + r.leapcount - 1])
      r.leapcount--;
  }

  return r;
}

static void
writezone(const char *const name, const char *const string, char version,
      int defaulttype)
{
    register FILE *            fp;
    register ptrdiff_t        i, j;
    register int            pass;
    static const struct tzhead    tzh0;
    static struct tzhead        tzh;
    bool dir_checked = false;
    zic_t one = 1;
    zic_t y2038_boundary = one << 31;
    ptrdiff_t nats = timecnt + WORK_AROUND_QTBUG_53071;

    /* Allocate the ATS and TYPES arrays via a single malloc,
       as this is a bit faster.  */
    zic_t *ats = emalloc(align_to(size_product(nats, sizeof *ats + 1),
                      _Alignof(zic_t)));
    void *typesptr = ats + nats;
    unsigned char *types = typesptr;
    struct timerange rangeall, range32, range64;

    /*
    ** Sort.
    */
    if (timecnt > 1)
        qsort(attypes, timecnt, sizeof *attypes, atcomp);
    /*
    ** Optimize.
    */
    {
        ptrdiff_t fromi, toi;

        toi = 0;
        fromi = 0;
        for ( ; fromi < timecnt; ++fromi) {
            if (toi != 0
                && ((attypes[fromi].at
                 + utoffs[attypes[toi - 1].type])
                <= (attypes[toi - 1].at
                    + utoffs[toi == 1 ? 0
                         : attypes[toi - 2].type]))) {
                    attypes[toi - 1].type =
                        attypes[fromi].type;
                    continue;
            }
            if (toi == 0
                || attypes[fromi].dontmerge
                || (utoffs[attypes[toi - 1].type]
                != utoffs[attypes[fromi].type])
                || (isdsts[attypes[toi - 1].type]
                != isdsts[attypes[fromi].type])
                || (desigidx[attypes[toi - 1].type]
                != desigidx[attypes[fromi].type]))
                    attypes[toi++] = attypes[fromi];
        }
        timecnt = toi;
    }

    if (noise && timecnt > 1200) {
      if (timecnt > TZ_MAX_TIMES)
        warning(_("reference clients mishandle"
              " more than %d transition times"),
            TZ_MAX_TIMES);
      else
        warning(_("pre-2014 clients may mishandle"
              " more than 1200 transition times"));
    }
    /*
    ** Transfer.
    */
    for (i = 0; i < timecnt; ++i) {
        ats[i] = attypes[i].at;
        types[i] = attypes[i].type;
    }

    /*
    ** Correct for leap seconds.
    */
    for (i = 0; i < timecnt; ++i) {
        j = leapcnt;
        while (--j >= 0)
            if (ats[i] > trans[j] - corr[j]) {
                ats[i] = tadd(ats[i], corr[j]);
                break;
            }
    }

    /* Work around QTBUG-53071 for timestamps less than y2038_boundary - 1,
       by inserting a no-op transition at time y2038_boundary - 1.
       This works only for timestamps before the boundary, which
       should be good enough in practice as QTBUG-53071 should be
       long-dead by 2038.  Do this after correcting for leap
       seconds, as the idea is to insert a transition just before
       32-bit time_t rolls around, and this occurs at a slightly
       different moment if transitions are leap-second corrected.  */
    if (WORK_AROUND_QTBUG_53071 && timecnt != 0 && want_bloat()
        && ats[timecnt - 1] < y2038_boundary - 1 && strchr(string, '<')) {
      ats[timecnt] = y2038_boundary - 1;
      types[timecnt] = types[timecnt - 1];
      timecnt++;
    }

    rangeall.defaulttype = defaulttype;
    rangeall.base = rangeall.leapbase = 0;
    rangeall.count = timecnt;
    rangeall.leapcount = leapcnt;
    range64 = limitrange(rangeall, lo_time, hi_time, ats, types);
    range32 = limitrange(range64, INT32_MIN, INT32_MAX, ats, types);

    /*
    ** Remove old file, if any, to snap links.
    */
    if (remove(name) == 0)
        dir_checked = true;
    else if (errno != ENOENT) {
        const char *e = strerror(errno);

        fprintf(stderr, _("%s: Can't remove %s/%s: %s\n"),
            progname, directory, name, e);
        exit(EXIT_FAILURE);
    }
    fp = fopen(name, "wb");
    if (!fp) {
      int fopen_errno = errno;
      if (fopen_errno == ENOENT && !dir_checked) {
        mkdirs(name, true);
        fp = fopen(name, "wb");
        fopen_errno = errno;
      }
      if (!fp) {
        fprintf(stderr, _("%s: Can't create %s/%s: %s\n"),
            progname, directory, name, strerror(fopen_errno));
        exit(EXIT_FAILURE);
      }
    }
    for (pass = 1; pass <= 2; ++pass) {
        register ptrdiff_t thistimei, thistimecnt, thistimelim;
        register int    thisleapi, thisleapcnt, thisleaplim;
        int currenttype, thisdefaulttype;
        bool locut, hicut;
        zic_t lo;
        int old0;
        char        omittype[TZ_MAX_TYPES];
        int        typemap[TZ_MAX_TYPES];
        int        thistypecnt, stdcnt, utcnt;
        char        thischars[TZ_MAX_CHARS];
        int        thischarcnt;
        bool        toomanytimes;
        int        indmap[TZ_MAX_CHARS];

        if (pass == 1) {
            /* Arguably the default time type in the 32-bit data
               should be range32.defaulttype, which is suited for
               timestamps just before INT32_MIN.  However, zic
               traditionally used the time type of the indefinite
               past instead.  Internet RFC 8532 says readers should
               ignore 32-bit data, so this discrepancy matters only
               to obsolete readers where the traditional type might
               be more appropriate even if it's "wrong".  So, use
               the historical zic value, unless -r specifies a low
               cutoff that excludes some 32-bit timestamps.  */
            thisdefaulttype = (lo_time <= INT32_MIN
                       ? range64.defaulttype
                       : range32.defaulttype);

            thistimei = range32.base;
            thistimecnt = range32.count;
            toomanytimes = thistimecnt >> 31 >> 1 != 0;
            thisleapi = range32.leapbase;
            thisleapcnt = range32.leapcount;
            locut = INT32_MIN < lo_time;
            hicut = hi_time < INT32_MAX;
        } else {
            thisdefaulttype = range64.defaulttype;
            thistimei = range64.base;
            thistimecnt = range64.count;
            toomanytimes = thistimecnt >> 31 >> 31 >> 2 != 0;
            thisleapi = range64.leapbase;
            thisleapcnt = range64.leapcount;
            locut = min_time < lo_time;
            hicut = hi_time < max_time;
        }
        if (toomanytimes)
          error(_("too many transition times"));

        /* Keep the last too-low transition if no transition is
           exactly at LO.  The kept transition will be output as
           a LO "transition"; see "Output a LO_TIME transition"
           below.  This is needed when the output is truncated at
           the start, and is also useful when catering to buggy
           32-bit clients that do not use time type 0 for
           timestamps before the first transition.  */
        if (0 < thistimei && ats[thistimei] != lo_time) {
          thistimei--;
          thistimecnt++;
          locut = false;
        }

        thistimelim = thistimei + thistimecnt;
        thisleaplim = thisleapi + thisleapcnt;
        if (thistimecnt != 0) {
          if (ats[thistimei] == lo_time)
            locut = false;
          if (hi_time < ZIC_MAX && ats[thistimelim - 1] == hi_time + 1)
            hicut = false;
        }
        memset(omittype, true, typecnt);
        omittype[thisdefaulttype] = false;
        for (i = thistimei; i < thistimelim; i++)
          omittype[types[i]] = false;

        /* Reorder types to make THISDEFAULTTYPE type 0.
           Use TYPEMAP to swap OLD0 and THISDEFAULTTYPE so that
           THISDEFAULTTYPE appears as type 0 in the output instead
           of OLD0.  TYPEMAP also omits unused types.  */
        old0 = strlen(omittype);

#ifndef LEAVE_SOME_PRE_2011_SYSTEMS_IN_THE_LURCH
        /*
        ** For some pre-2011 systems: if the last-to-be-written
        ** standard (or daylight) type has an offset different from the
        ** most recently used offset,
        ** append an (unused) copy of the most recently used type
        ** (to help get global "altzone" and "timezone" variables
        ** set correctly).
        */
        if (want_bloat()) {
            register int    mrudst, mrustd, hidst, histd, type;

            hidst = histd = mrudst = mrustd = -1;
            for (i = thistimei; i < thistimelim; ++i)
                if (isdsts[types[i]])
                    mrudst = types[i];
                else    mrustd = types[i];
            for (i = old0; i < typecnt; i++) {
              int h = (i == old0 ? thisdefaulttype
                   : i == thisdefaulttype ? old0 : i);
              if (!omittype[h]) {
                if (isdsts[h])
                  hidst = i;
                else
                  histd = i;
              }
            }
            if (hidst >= 0 && mrudst >= 0 && hidst != mrudst &&
                utoffs[hidst] != utoffs[mrudst]) {
                    isdsts[mrudst] = -1;
                    type = addtype(utoffs[mrudst],
                        &chars[desigidx[mrudst]],
                        true,
                        ttisstds[mrudst],
                        ttisuts[mrudst]);
                    isdsts[mrudst] = 1;
                    omittype[type] = false;
            }
            if (histd >= 0 && mrustd >= 0 && histd != mrustd &&
                utoffs[histd] != utoffs[mrustd]) {
                    isdsts[mrustd] = -1;
                    type = addtype(utoffs[mrustd],
                        &chars[desigidx[mrustd]],
                        false,
                        ttisstds[mrustd],
                        ttisuts[mrustd]);
                    isdsts[mrustd] = 0;
                    omittype[type] = false;
            }
        }
#endif /* !defined LEAVE_SOME_PRE_2011_SYSTEMS_IN_THE_LURCH */
        thistypecnt = 0;
        for (i = old0; i < typecnt; i++)
          if (!omittype[i])
            typemap[i == old0 ? thisdefaulttype
                : i == thisdefaulttype ? old0 : i]
              = thistypecnt++;

        for (i = 0; i < sizeof indmap / sizeof indmap[0]; ++i)
            indmap[i] = -1;
        thischarcnt = stdcnt = utcnt = 0;
        for (i = old0; i < typecnt; i++) {
            register char *    thisabbr;

            if (omittype[i])
                continue;
            if (ttisstds[i])
              stdcnt = thistypecnt;
            if (ttisuts[i])
              utcnt = thistypecnt;
            if (indmap[desigidx[i]] >= 0)
                continue;
            thisabbr = &chars[desigidx[i]];
            for (j = 0; j < thischarcnt; ++j)
                if (strcmp(&thischars[j], thisabbr) == 0)
                    break;
            if (j == thischarcnt) {
                strcpy(&thischars[thischarcnt], thisabbr);
                thischarcnt += strlen(thisabbr) + 1;
            }
            indmap[desigidx[i]] = j;
        }
        if (pass == 1 && !want_bloat()) {
          utcnt = stdcnt = thisleapcnt = 0;
          thistimecnt = - (locut + hicut);
          thistypecnt = thischarcnt = 1;
          thistimelim = thistimei;
        }
#define DO(field)    fwrite(tzh.field, sizeof tzh.field, 1, fp)
        tzh = tzh0;
        memcpy(tzh.tzh_magic, TZ_MAGIC, sizeof tzh.tzh_magic);
        tzh.tzh_version[0] = version;
        convert(utcnt, tzh.tzh_ttisutcnt);
        convert(stdcnt, tzh.tzh_ttisstdcnt);
        convert(thisleapcnt, tzh.tzh_leapcnt);
        convert(locut + thistimecnt + hicut, tzh.tzh_timecnt);
        convert(thistypecnt, tzh.tzh_typecnt);
        convert(thischarcnt, tzh.tzh_charcnt);
        DO(tzh_magic);
        DO(tzh_version);
        DO(tzh_reserved);
        DO(tzh_ttisutcnt);
        DO(tzh_ttisstdcnt);
        DO(tzh_leapcnt);
        DO(tzh_timecnt);
        DO(tzh_typecnt);
        DO(tzh_charcnt);
#undef DO
        if (pass == 1 && !want_bloat()) {
          /* Output a minimal data block with just one time type.  */
          puttzcode(0, fp);    /* utoff */
          putc(0, fp);        /* dst */
          putc(0, fp);        /* index of abbreviation */
          putc(0, fp);        /* empty-string abbreviation */
          continue;
        }

        /* Output a LO_TIME transition if needed; see limitrange.
           But do not go below the minimum representable value
           for this pass.  */
        lo = pass == 1 && lo_time < INT32_MIN ? INT32_MIN : lo_time;

        if (locut)
          puttzcodepass(lo, fp, pass);
        for (i = thistimei; i < thistimelim; ++i) {
          zic_t at = ats[i] < lo ? lo : ats[i];
          puttzcodepass(at, fp, pass);
        }
        if (hicut)
          puttzcodepass(hi_time + 1, fp, pass);
        currenttype = 0;
        if (locut)
          putc(currenttype, fp);
        for (i = thistimei; i < thistimelim; ++i) {
          currenttype = typemap[types[i]];
          putc(currenttype, fp);
        }
        if (hicut)
          putc(currenttype, fp);

        for (i = old0; i < typecnt; i++) {
          int h = (i == old0 ? thisdefaulttype
               : i == thisdefaulttype ? old0 : i);
          if (!omittype[h]) {
            puttzcode(utoffs[h], fp);
            putc(isdsts[h], fp);
            putc(indmap[desigidx[h]], fp);
          }
        }
        if (thischarcnt != 0)
            fwrite(thischars, sizeof thischars[0],
                      thischarcnt, fp);
        for (i = thisleapi; i < thisleaplim; ++i) {
            register zic_t    todo;

            if (roll[i]) {
                if (timecnt == 0 || trans[i] < ats[0]) {
                    j = 0;
                    while (isdsts[j])
                        if (++j >= typecnt) {
                            j = 0;
                            break;
                        }
                } else {
                    j = 1;
                    while (j < timecnt &&
                        trans[i] >= ats[j])
                            ++j;
                    j = types[j - 1];
                }
                todo = tadd(trans[i], -utoffs[j]);
            } else    todo = trans[i];
            puttzcodepass(todo, fp, pass);
            puttzcode(corr[i], fp);
        }
        if (stdcnt != 0)
          for (i = old0; i < typecnt; i++)
            if (!omittype[i])
                putc(ttisstds[i], fp);
        if (utcnt != 0)
          for (i = old0; i < typecnt; i++)
            if (!omittype[i])
                putc(ttisuts[i], fp);
    }
    fprintf(fp, "\n%s\n", string);
    close_file(fp, directory, name);
    free(ats);
}

static char const *
abbroffset(char *buf, zic_t offset)
{
  char sign = '+';
  int seconds, minutes;

  if (offset < 0) {
    offset = -offset;
    sign = '-';
  }

  seconds = offset % SECSPERMIN;
  offset /= SECSPERMIN;
  minutes = offset % MINSPERHOUR;
  offset /= MINSPERHOUR;
  if (100 <= offset) {
    error(_("%%z UT offset magnitude exceeds 99:59:59"));
    return "%z";
  } else {
    char *p = buf;
    *p++ = sign;
    *p++ = '0' + offset / 10;
    *p++ = '0' + offset % 10;
    if (minutes | seconds) {
      *p++ = '0' + minutes / 10;
      *p++ = '0' + minutes % 10;
      if (seconds) {
    *p++ = '0' + seconds / 10;
    *p++ = '0' + seconds % 10;
      }
    }
    *p = '\0';
    return buf;
  }
}

static size_t
doabbr(char *abbr, struct zone const *zp, char const *letters,
       bool isdst, zic_t save, bool doquotes)
{
    register char *    cp;
    register char *    slashp;
    register size_t    len;
    char const *format = zp->z_format;

    slashp = strchr(format, '/');
    if (slashp == NULL) {
      char letterbuf[PERCENT_Z_LEN_BOUND + 1];
      if (zp->z_format_specifier == 'z')
        letters = abbroffset(letterbuf, zp->z_stdoff + save);
      else if (!letters)
        letters = "%s";
      sprintf(abbr, format, letters);
    } else if (isdst) {
        strcpy(abbr, slashp + 1);
    } else {
        memcpy(abbr, format, slashp - format);
        abbr[slashp - format] = '\0';
    }
    len = strlen(abbr);
    if (!doquotes)
        return len;
    for (cp = abbr; is_alpha(*cp); cp++)
        continue;
    if (len > 0 && *cp == '\0')
        return len;
    abbr[len + 2] = '\0';
    abbr[len + 1] = '>';
    memmove(abbr + 1, abbr, len);
    abbr[0] = '<';
    return len + 2;
}

static void
updateminmax(const zic_t x)
{
    if (min_year > x)
        min_year = x;
    if (max_year < x)
        max_year = x;
}

static int
stringoffset(char *result, zic_t offset)
{
    register int    hours;
    register int    minutes;
    register int    seconds;
    bool negative = offset < 0;
    int len = negative;

    if (negative) {
        offset = -offset;
        result[0] = '-';
    }
    seconds = offset % SECSPERMIN;
    offset /= SECSPERMIN;
    minutes = offset % MINSPERHOUR;
    offset /= MINSPERHOUR;
    hours = offset;
    if (hours >= HOURSPERDAY * DAYSPERWEEK) {
        result[0] = '\0';
        return 0;
    }
    len += sprintf(result + len, "%d", hours);
    if (minutes != 0 || seconds != 0) {
        len += sprintf(result + len, ":%02d", minutes);
        if (seconds != 0)
            len += sprintf(result + len, ":%02d", seconds);
    }
    return len;
}

static int
stringrule(char *result, struct rule *const rp, zic_t save, zic_t stdoff)
{
    register zic_t    tod = rp->r_tod;
    register int    compat = 0;

    if (rp->r_dycode == DC_DOM) {
        register int    month, total;

        if (rp->r_dayofmonth == 29 && rp->r_month == TM_FEBRUARY)
            return -1;
        total = 0;
        for (month = 0; month < rp->r_month; ++month)
            total += len_months[0][month];
        /* Omit the "J" in Jan and Feb, as that's shorter.  */
        if (rp->r_month <= 1)
          result += sprintf(result, "%d", total + rp->r_dayofmonth - 1);
        else
          result += sprintf(result, "J%d", total + rp->r_dayofmonth);
    } else {
        register int    week;
        register int    wday = rp->r_wday;
        register int    wdayoff;

        if (rp->r_dycode == DC_DOWGEQ) {
            wdayoff = (rp->r_dayofmonth - 1) % DAYSPERWEEK;
            if (wdayoff)
                compat = 2013;
            wday -= wdayoff;
            tod += wdayoff * SECSPERDAY;
            week = 1 + (rp->r_dayofmonth - 1) / DAYSPERWEEK;
        } else if (rp->r_dycode == DC_DOWLEQ) {
            if (rp->r_dayofmonth == len_months[1][rp->r_month])
                week = 5;
            else {
                wdayoff = rp->r_dayofmonth % DAYSPERWEEK;
                if (wdayoff)
                    compat = 2013;
                wday -= wdayoff;
                tod += wdayoff * SECSPERDAY;
                week = rp->r_dayofmonth / DAYSPERWEEK;
            }
        } else    return -1;    /* "cannot happen" */
        if (wday < 0)
            wday += DAYSPERWEEK;
        result += sprintf(result, "M%d.%d.%d",
                  rp->r_month + 1, week, wday);
    }
    if (rp->r_todisut)
      tod += stdoff;
    if (rp->r_todisstd && !rp->r_isdst)
      tod += save;
    if (tod != 2 * SECSPERMIN * MINSPERHOUR) {
        *result++ = '/';
        if (! stringoffset(result, tod))
            return -1;
        if (tod < 0) {
            if (compat < 2013)
                compat = 2013;
        } else if (SECSPERDAY <= tod) {
            if (compat < 1994)
                compat = 1994;
        }
    }
    return compat;
}

static int
rule_cmp(struct rule const *a, struct rule const *b)
{
    if (!a)
        return -!!b;
    if (!b)
        return 1;
    if (a->r_hiyear != b->r_hiyear)
        return a->r_hiyear < b->r_hiyear ? -1 : 1;
    if (a->r_month - b->r_month != 0)
        return a->r_month - b->r_month;
    return a->r_dayofmonth - b->r_dayofmonth;
}

static int
stringzone(char *result, struct zone const *zpfirst, ptrdiff_t zonecount)
{
    register const struct zone *    zp;
    register struct rule *        rp;
    register struct rule *        stdrp;
    register struct rule *        dstrp;
    register ptrdiff_t        i;
    register const char *        abbrvar;
    register int            compat = 0;
    register int            c;
    size_t                len;
    int                offsetlen;
    struct rule            stdr, dstr;

    result[0] = '\0';

    /* Internet RFC 8536 section 5.1 says to use an empty TZ string if
       future timestamps are truncated.  */
    if (hi_time < max_time)
      return -1;

    zp = zpfirst + zonecount - 1;
    stdrp = dstrp = NULL;
    for (i = 0; i < zp->z_nrules; ++i) {
        rp = &zp->z_rules[i];
        if (rp->r_hiwasnum || rp->r_hiyear != ZIC_MAX)
            continue;
        if (rp->r_yrtype != NULL)
            continue;
        if (!rp->r_isdst) {
            if (stdrp == NULL)
                stdrp = rp;
            else    return -1;
        } else {
            if (dstrp == NULL)
                dstrp = rp;
            else    return -1;
        }
    }
    if (stdrp == NULL && dstrp == NULL) {
        /*
        ** There are no rules running through "max".
        ** Find the latest std rule in stdabbrrp
        ** and latest rule of any type in stdrp.
        */
        register struct rule *stdabbrrp = NULL;
        for (i = 0; i < zp->z_nrules; ++i) {
            rp = &zp->z_rules[i];
            if (!rp->r_isdst && rule_cmp(stdabbrrp, rp) < 0)
                stdabbrrp = rp;
            if (rule_cmp(stdrp, rp) < 0)
                stdrp = rp;
        }
        if (stdrp != NULL && stdrp->r_isdst) {
            /* Perpetual DST.  */
            dstr.r_month = TM_JANUARY;
            dstr.r_dycode = DC_DOM;
            dstr.r_dayofmonth = 1;
            dstr.r_tod = 0;
            dstr.r_todisstd = dstr.r_todisut = false;
            dstr.r_isdst = stdrp->r_isdst;
            dstr.r_save = stdrp->r_save;
            dstr.r_abbrvar = stdrp->r_abbrvar;
            stdr.r_month = TM_DECEMBER;
            stdr.r_dycode = DC_DOM;
            stdr.r_dayofmonth = 31;
            stdr.r_tod = SECSPERDAY + stdrp->r_save;
            stdr.r_todisstd = stdr.r_todisut = false;
            stdr.r_isdst = false;
            stdr.r_save = 0;
            stdr.r_abbrvar
              = (stdabbrrp ? stdabbrrp->r_abbrvar : "");
            dstrp = &dstr;
            stdrp = &stdr;
        }
    }
    if (stdrp == NULL && (zp->z_nrules != 0 || zp->z_isdst))
        return -1;
    abbrvar = (stdrp == NULL) ? "" : stdrp->r_abbrvar;
    len = doabbr(result, zp, abbrvar, false, 0, true);
    offsetlen = stringoffset(result + len, - zp->z_stdoff);
    if (! offsetlen) {
        result[0] = '\0';
        return -1;
    }
    len += offsetlen;
    if (dstrp == NULL)
        return compat;
    len += doabbr(result + len, zp, dstrp->r_abbrvar,
              dstrp->r_isdst, dstrp->r_save, true);
    if (dstrp->r_save != SECSPERMIN * MINSPERHOUR) {
      offsetlen = stringoffset(result + len,
                   - (zp->z_stdoff + dstrp->r_save));
      if (! offsetlen) {
        result[0] = '\0';
        return -1;
      }
      len += offsetlen;
    }
    result[len++] = ',';
    c = stringrule(result + len, dstrp, dstrp->r_save, zp->z_stdoff);
    if (c < 0) {
        result[0] = '\0';
        return -1;
    }
    if (compat < c)
        compat = c;
    len += strlen(result + len);
    result[len++] = ',';
    c = stringrule(result + len, stdrp, dstrp->r_save, zp->z_stdoff);
    if (c < 0) {
        result[0] = '\0';
        return -1;
    }
    if (compat < c)
        compat = c;
    return compat;
}

static void
outzone(const struct zone *zpfirst, ptrdiff_t zonecount)
{
    register const struct zone *    zp;
    register struct rule *        rp;
    register ptrdiff_t        i, j;
    register bool            usestart, useuntil;
    register zic_t            starttime, untiltime;
    register zic_t            stdoff;
    register zic_t            save;
    register zic_t            year;
    register zic_t            startoff;
    register bool            startttisstd;
    register bool            startttisut;
    register int            type;
    register char *            startbuf;
    register char *            ab;
    register char *            envvar;
    register int            max_abbr_len;
    register int            max_envvar_len;
    register bool            prodstic; /* all rules are min to max */
    register int            compat;
    register bool            do_extend;
    register char            version;
    ptrdiff_t lastatmax = -1;
    zic_t one = 1;
    zic_t y2038_boundary = one << 31;
    zic_t max_year0;
    int defaulttype = -1;

    max_abbr_len = 2 + max_format_len + max_abbrvar_len;
    max_envvar_len = 2 * max_abbr_len + 5 * 9;
    startbuf = emalloc(max_abbr_len + 1);
    ab = emalloc(max_abbr_len + 1);
    envvar = emalloc(max_envvar_len + 1);
    INITIALIZE(untiltime);
    INITIALIZE(starttime);
    /*
    ** Now. . .finally. . .generate some useful data!
    */
    timecnt = 0;
    typecnt = 0;
    charcnt = 0;
    prodstic = zonecount == 1;
    /*
    ** Thanks to Earl Chew
    ** for noting the need to unconditionally initialize startttisstd.
    */
    startttisstd = false;
    startttisut = false;
    min_year = max_year = EPOCH_YEAR;
    if (leapseen) {
        updateminmax(leapminyear);
        updateminmax(leapmaxyear + (leapmaxyear < ZIC_MAX));
    }
    for (i = 0; i < zonecount; ++i) {
        zp = &zpfirst[i];
        if (i < zonecount - 1)
            updateminmax(zp->z_untilrule.r_loyear);
        for (j = 0; j < zp->z_nrules; ++j) {
            rp = &zp->z_rules[j];
            if (rp->r_lowasnum)
                updateminmax(rp->r_loyear);
            if (rp->r_hiwasnum)
                updateminmax(rp->r_hiyear);
            if (rp->r_lowasnum || rp->r_hiwasnum)
                prodstic = false;
        }
    }
    /*
    ** Generate lots of data if a rule can't cover all future times.
    */
    compat = stringzone(envvar, zpfirst, zonecount);
    version = compat < 2013 ? ZIC_VERSION_PRE_2013 : ZIC_VERSION;
    do_extend = compat < 0;
    if (noise) {
        if (!*envvar)
            warning("%s %s",
                _("no POSIX environment variable for zone"),
                zpfirst->z_name);
        else if (compat != 0) {
            /* Circa-COMPAT clients, and earlier clients, might
               not work for this zone when given dates before
               1970 or after 2038.  */
            warning(_("%s: pre-%d clients may mishandle"
                  " distant timestamps"),
                zpfirst->z_name, compat);
        }
    }
    if (do_extend) {
        /*
        ** Search through a couple of extra years past the obvious
        ** 400, to avoid edge cases.  For example, suppose a non-POSIX
        ** rule applies from 2012 onwards and has transitions in March
        ** and September, plus some one-off transitions in November
        ** 2013.  If zic looked only at the last 400 years, it would
        ** set max_year=2413, with the intent that the 400 years 2014
        ** through 2413 will be repeated.  The last transition listed
        ** in the tzfile would be in 2413-09, less than 400 years
        ** after the last one-off transition in 2013-11.  Two years
        ** might be overkill, but with the kind of edge cases
        ** available we're not sure that one year would suffice.
        */
        enum { years_of_observations = YEARSPERREPEAT + 2 };

        if (min_year >= ZIC_MIN + years_of_observations)
            min_year -= years_of_observations;
        else    min_year = ZIC_MIN;
        if (max_year <= ZIC_MAX - years_of_observations)
            max_year += years_of_observations;
        else    max_year = ZIC_MAX;
        /*
        ** Regardless of any of the above,
        ** for a "proDSTic" zone which specifies that its rules
        ** always have and always will be in effect,
        ** we only need one cycle to define the zone.
        */
        if (prodstic) {
            min_year = 1900;
            max_year = min_year + years_of_observations;
        }
    }
    max_year0 = max_year;
    if (want_bloat()) {
      /* For the benefit of older systems,
         generate data from 1900 through 2038.  */
      if (min_year > 1900)
        min_year = 1900;
      if (max_year < 2038)
        max_year = 2038;
    }

    for (i = 0; i < zonecount; ++i) {
        struct rule *prevrp = NULL;
        /*
        ** A guess that may well be corrected later.
        */
        save = 0;
        zp = &zpfirst[i];
        usestart = i > 0 && (zp - 1)->z_untiltime > min_time;
        useuntil = i < (zonecount - 1);
        if (useuntil && zp->z_untiltime <= min_time)
            continue;
        stdoff = zp->z_stdoff;
        eat(zp->z_filename, zp->z_linenum);
        *startbuf = '\0';
        startoff = zp->z_stdoff;
        if (zp->z_nrules == 0) {
            save = zp->z_save;
            doabbr(startbuf, zp, NULL, zp->z_isdst, save, false);
            type = addtype(oadd(zp->z_stdoff, save),
                startbuf, zp->z_isdst, startttisstd,
                startttisut);
            if (usestart) {
                addtt(starttime, type);
                usestart = false;
            } else
                defaulttype = type;
        } else for (year = min_year; year <= max_year; ++year) {
            if (useuntil && year > zp->z_untilrule.r_hiyear)
                break;
            /*
            ** Mark which rules to do in the current year.
            ** For those to do, calculate rpytime(rp, year);
            */
            for (j = 0; j < zp->z_nrules; ++j) {
                rp = &zp->z_rules[j];
                eats(zp->z_filename, zp->z_linenum,
                    rp->r_filename, rp->r_linenum);
                rp->r_todo = year >= rp->r_loyear &&
                        year <= rp->r_hiyear &&
                        yearistype(year, rp->r_yrtype);
                if (rp->r_todo) {
                    rp->r_temp = rpytime(rp, year);
                    rp->r_todo
                      = (rp->r_temp < y2038_boundary
                         || year <= max_year0);
                }
            }
            for ( ; ; ) {
                register ptrdiff_t k;
                register zic_t    jtime, ktime;
                register zic_t    offset;

                INITIALIZE(ktime);
                if (useuntil) {
                    /*
                    ** Turn untiltime into UT
                    ** assuming the current stdoff and
                    ** save values.
                    */
                    untiltime = zp->z_untiltime;
                    if (!zp->z_untilrule.r_todisut)
                        untiltime = tadd(untiltime,
                                 -stdoff);
                    if (!zp->z_untilrule.r_todisstd)
                        untiltime = tadd(untiltime,
                                 -save);
                }
                /*
                ** Find the rule (of those to do, if any)
                ** that takes effect earliest in the year.
                */
                k = -1;
                for (j = 0; j < zp->z_nrules; ++j) {
                    rp = &zp->z_rules[j];
                    if (!rp->r_todo)
                        continue;
                    eats(zp->z_filename, zp->z_linenum,
                        rp->r_filename, rp->r_linenum);
                    offset = rp->r_todisut ? 0 : stdoff;
                    if (!rp->r_todisstd)
                        offset = oadd(offset, save);
                    jtime = rp->r_temp;
                    if (jtime == min_time ||
                        jtime == max_time)
                            continue;
                    jtime = tadd(jtime, -offset);
                    if (k < 0 || jtime < ktime) {
                        k = j;
                        ktime = jtime;
                    } else if (jtime == ktime) {
                      char const *dup_rules_msg =
                        _("two rules for same instant");
                      eats(zp->z_filename, zp->z_linenum,
                           rp->r_filename, rp->r_linenum);
                      warning("%s", dup_rules_msg);
                      rp = &zp->z_rules[k];
                      eats(zp->z_filename, zp->z_linenum,
                           rp->r_filename, rp->r_linenum);
                      error("%s", dup_rules_msg);
                    }
                }
                if (k < 0)
                    break;    /* go on to next year */
                rp = &zp->z_rules[k];
                rp->r_todo = false;
                if (useuntil && ktime >= untiltime)
                    break;
                save = rp->r_save;
                if (usestart && ktime == starttime)
                    usestart = false;
                if (usestart) {
                    if (ktime < starttime) {
                        startoff = oadd(zp->z_stdoff,
                                save);
                        doabbr(startbuf, zp,
                            rp->r_abbrvar,
                            rp->r_isdst,
                            rp->r_save,
                            false);
                        continue;
                    }
                    if (*startbuf == '\0'
                        && startoff == oadd(zp->z_stdoff,
                                save)) {
                            doabbr(startbuf,
                                zp,
                                rp->r_abbrvar,
                                rp->r_isdst,
                                rp->r_save,
                                false);
                    }
                }
                eats(zp->z_filename, zp->z_linenum,
                    rp->r_filename, rp->r_linenum);
                doabbr(ab, zp, rp->r_abbrvar,
                       rp->r_isdst, rp->r_save, false);
                offset = oadd(zp->z_stdoff, rp->r_save);
                if (!want_bloat() && !useuntil && !do_extend
                    && prevrp
                    && rp->r_hiyear == ZIC_MAX
                    && prevrp->r_hiyear == ZIC_MAX)
                  break;
                type = addtype(offset, ab, rp->r_isdst,
                    rp->r_todisstd, rp->r_todisut);
                if (defaulttype < 0 && !rp->r_isdst)
                  defaulttype = type;
                if (rp->r_hiyear == ZIC_MAX
                    && ! (0 <= lastatmax
                      && ktime < attypes[lastatmax].at))
                  lastatmax = timecnt;
                addtt(ktime, type);
                prevrp = rp;
            }
        }
        if (usestart) {
            if (*startbuf == '\0' &&
                zp->z_format != NULL &&
                strchr(zp->z_format, '%') == NULL &&
                strchr(zp->z_format, '/') == NULL)
                    strcpy(startbuf, zp->z_format);
            eat(zp->z_filename, zp->z_linenum);
            if (*startbuf == '\0')
error(_("can't determine time zone abbreviation to use just after until time"));
            else {
              bool isdst = startoff != zp->z_stdoff;
              type = addtype(startoff, startbuf, isdst,
                     startttisstd, startttisut);
              if (defaulttype < 0 && !isdst)
                defaulttype = type;
              addtt(starttime, type);
            }
        }
        /*
        ** Now we may get to set starttime for the next zone line.
        */
        if (useuntil) {
            startttisstd = zp->z_untilrule.r_todisstd;
            startttisut = zp->z_untilrule.r_todisut;
            starttime = zp->z_untiltime;
            if (!startttisstd)
              starttime = tadd(starttime, -save);
            if (!startttisut)
              starttime = tadd(starttime, -stdoff);
        }
    }
    if (defaulttype < 0)
      defaulttype = 0;
    if (0 <= lastatmax)
      attypes[lastatmax].dontmerge = true;
    if (do_extend) {
        /*
        ** If we're extending the explicitly listed observations
        ** for 400 years because we can't fill the POSIX-TZ field,
        ** check whether we actually ended up explicitly listing
        ** observations through that period.  If there aren't any
        ** near the end of the 400-year period, add a redundant
        ** one at the end of the final year, to make it clear
        ** that we are claiming to have definite knowledge of
        ** the lack of transitions up to that point.
        */
        struct rule xr;
        struct attype *lastat;
        xr.r_month = TM_JANUARY;
        xr.r_dycode = DC_DOM;
        xr.r_dayofmonth = 1;
        xr.r_tod = 0;
        for (lastat = attypes, i = 1; i < timecnt; i++)
            if (attypes[i].at > lastat->at)
                lastat = &attypes[i];
        if (!lastat || lastat->at < rpytime(&xr, max_year - 1)) {
            addtt(rpytime(&xr, max_year + 1),
                  lastat ? lastat->type : defaulttype);
            attypes[timecnt - 1].dontmerge = true;
        }
    }
    writezone(zpfirst->z_name, envvar, version, defaulttype);
    free(startbuf);
    free(ab);
    free(envvar);
}

static void
addtt(zic_t starttime, int type)
{
    attypes = growalloc(attypes, sizeof *attypes, timecnt, &timecnt_alloc);
    attypes[timecnt].at = starttime;
    attypes[timecnt].dontmerge = false;
    attypes[timecnt].type = type;
    ++timecnt;
}

static int
addtype(zic_t utoff, char const *abbr, bool isdst, bool ttisstd, bool ttisut)
{
    register int    i, j;

    if (! (-1L - 2147483647L <= utoff && utoff <= 2147483647L)) {
        error(_("UT offset out of range"));
        exit(EXIT_FAILURE);
    }
    if (!want_bloat())
      ttisstd = ttisut = false;

    for (j = 0; j < charcnt; ++j)
        if (strcmp(&chars[j], abbr) == 0)
            break;
    if (j == charcnt)
        newabbr(abbr);
    else {
      /* If there's already an entry, return its index.  */
      for (i = 0; i < typecnt; i++)
        if (utoff == utoffs[i] && isdst == isdsts[i] && j == desigidx[i]
        && ttisstd == ttisstds[i] && ttisut == ttisuts[i])
          return i;
    }
    /*
    ** There isn't one; add a new one, unless there are already too
    ** many.
    */
    if (typecnt >= TZ_MAX_TYPES) {
        error(_("too many local time types"));
        exit(EXIT_FAILURE);
    }
    i = typecnt++;
    utoffs[i] = utoff;
    isdsts[i] = isdst;
    ttisstds[i] = ttisstd;
    ttisuts[i] = ttisut;
    desigidx[i] = j;
    return i;
}

static void
leapadd(zic_t t, bool positive, int rolling, int count)
{
    register int    i, j;

    if (leapcnt + (positive ? count : 1) > TZ_MAX_LEAPS) {
        error(_("too many leap seconds"));
        exit(EXIT_FAILURE);
    }
    for (i = 0; i < leapcnt; ++i)
        if (t <= trans[i])
            break;
    do {
        for (j = leapcnt; j > i; --j) {
            trans[j] = trans[j - 1];
            corr[j] = corr[j - 1];
            roll[j] = roll[j - 1];
        }
        trans[i] = t;
        corr[i] = positive ? 1 : -count;
        roll[i] = rolling;
        ++leapcnt;
    } while (positive && --count != 0);
}

static void
adjleap(void)
{
    register int    i;
    register zic_t    last = 0;
    register zic_t    prevtrans = 0;

    /*
    ** propagate leap seconds forward
    */
    for (i = 0; i < leapcnt; ++i) {
        if (trans[i] - prevtrans < 28 * SECSPERDAY) {
          error(_("Leap seconds too close together"));
          exit(EXIT_FAILURE);
        }
        prevtrans = trans[i];
        trans[i] = tadd(trans[i], last);
        last = corr[i] += last;
    }
}

static char *
shellquote(char *b, char const *s)
{
  *b++ = '\'';
  while (*s) {
    if (*s == '\'')
      *b++ = '\'', *b++ = '\\', *b++ = '\'';
    *b++ = *s++;
  }
  *b++ = '\'';
  return b;
}

static bool
yearistype(zic_t year, const char *type)
{
    char *buf;
    char *b;
    int result;

    if (type == NULL || *type == '\0')
        return true;
    buf = emalloc(1 + 4 * strlen(yitcommand) + 2
              + INT_STRLEN_MAXIMUM(zic_t) + 2 + 4 * strlen(type) + 2);
    b = shellquote(buf, yitcommand);
    *b++ = ' ';
    b += sprintf(b, "%"PRIdZIC, year);
    *b++ = ' ';
    b = shellquote(b, type);
    *b = '\0';
    result = system(buf);
    if (WIFEXITED(result)) {
      int status = WEXITSTATUS(result);
      if (status <= 1) {
        free(buf);
        return status == 0;
      }
    }
    error(_("Wild result from command execution"));
    fprintf(stderr, _("%s: command was '%s', result was %d\n"),
        progname, buf, result);
    exit(EXIT_FAILURE);
}

/* Is A a space character in the C locale?  */
static bool
is_space(char a)
{
    switch (a) {
      default:
        return false;
      case ' ': case '\f': case '\n': case '\r': case '\t': case '\v':
        return true;
    }
}

/* 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;
    }
}

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

/* case-insensitive equality */
static ATTRIBUTE_PURE bool
ciequal(register const char *ap, register const char *bp)
{
    while (lowerit(*ap) == lowerit(*bp++))
        if (*ap++ == '\0')
            return true;
    return false;
}

static ATTRIBUTE_PURE bool
itsabbr(register const char *abbr, register const char *word)
{
    if (lowerit(*abbr) != lowerit(*word))
        return false;
    ++word;
    while (*++abbr != '\0')
        do {
            if (*word == '\0')
                return false;
        } while (lowerit(*word++) != lowerit(*abbr));
    return true;
}

/* Return true if ABBR is an initial prefix of WORD, ignoring ASCII case.  */

static ATTRIBUTE_PURE bool
ciprefix(char const *abbr, char const *word)
{
  do
    if (!*abbr)
      return true;
  while (lowerit(*abbr++) == lowerit(*word++));

  return false;
}

static const struct lookup *
byword(const char *word, const struct lookup *table)
{
    register const struct lookup *    foundlp;
    register const struct lookup *    lp;

    if (word == NULL || table == NULL)
        return NULL;

    /* If TABLE is LASTS and the word starts with "last" followed
       by a non-'-', skip the "last" and look in WDAY_NAMES instead.
       Warn about any usage of the undocumented prefix "last-".  */
    if (table == lasts && ciprefix("last", word) && word[4]) {
      if (word[4] == '-')
        warning(_("\"%s\" is undocumented; use \"last%s\" instead"),
            word, word + 5);
      else {
        word += 4;
        table = wday_names;
      }
    }

    /*
    ** Look for exact match.
    */
    for (lp = table; lp->l_word != NULL; ++lp)
        if (ciequal(word, lp->l_word))
            return lp;
    /*
    ** Look for inexact match.
    */
    foundlp = NULL;
    for (lp = table; lp->l_word != NULL; ++lp)
        if (ciprefix(word, lp->l_word)) {
            if (foundlp == NULL)
                foundlp = lp;
            else    return NULL;    /* multiple inexact matches */
        }

    if (foundlp && noise) {
      /* Warn about any backward-compatibility issue with pre-2017c zic.  */
      bool pre_2017c_match = false;
      for (lp = table; lp->l_word; lp++)
        if (itsabbr(word, lp->l_word)) {
          if (pre_2017c_match) {
        warning(_("\"%s\" is ambiguous in pre-2017c zic"), word);
        break;
          }
          pre_2017c_match = true;
        }
    }

    return foundlp;
}

static char **
getfields(register char *cp)
{
    register char *        dp;
    register char **    array;
    register int        nsubs;

    if (cp == NULL)
        return NULL;
    array = emalloc(size_product(strlen(cp) + 1, sizeof *array));
    nsubs = 0;
    for ( ; ; ) {
        while (is_space(*cp))
                ++cp;
        if (*cp == '\0' || *cp == '#')
            break;
        array[nsubs++] = dp = cp;
        do {
            if ((*dp = *cp++) != '"')
                ++dp;
            else while ((*dp = *cp++) != '"')
                if (*dp != '\0')
                    ++dp;
                else {
                  error(_("Odd number of quotation marks"));
                  exit(EXIT_FAILURE);
                }
        } while (*cp && *cp != '#' && !is_space(*cp));
        if (is_space(*cp))
            ++cp;
        *dp = '\0';
    }
    array[nsubs] = NULL;
    return array;
}

static _Noreturn void
time_overflow(void)
{
  error(_("time overflow"));
  exit(EXIT_FAILURE);
}

static ATTRIBUTE_PURE zic_t
oadd(zic_t t1, zic_t t2)
{
    if (t1 < 0 ? t2 < ZIC_MIN - t1 : ZIC_MAX - t1 < t2)
      time_overflow();
    return t1 + t2;
}

static ATTRIBUTE_PURE zic_t
tadd(zic_t t1, zic_t t2)
{
  if (t1 < 0) {
    if (t2 < min_time - t1) {
      if (t1 != min_time)
    time_overflow();
      return min_time;
    }
  } else {
    if (max_time - t1 < t2) {
      if (t1 != max_time)
    time_overflow();
      return max_time;
    }
  }
  return t1 + t2;
}

/*
** Given a rule, and a year, compute the date (in seconds since January 1,
** 1970, 00:00 LOCAL time) in that year that the rule refers to.
*/

static zic_t
rpytime(const struct rule *rp, zic_t wantedy)
{
    register int    m, i;
    register zic_t    dayoff;            /* with a nod to Margaret O. */
    register zic_t    t, y;

    if (wantedy == ZIC_MIN)
        return min_time;
    if (wantedy == ZIC_MAX)
        return max_time;
    dayoff = 0;
    m = TM_JANUARY;
    y = EPOCH_YEAR;
    if (y < wantedy) {
      wantedy -= y;
      dayoff = (wantedy / YEARSPERREPEAT) * (SECSPERREPEAT / SECSPERDAY);
      wantedy %= YEARSPERREPEAT;
      wantedy += y;
    } else if (wantedy < 0) {
      dayoff = (wantedy / YEARSPERREPEAT) * (SECSPERREPEAT / SECSPERDAY);
      wantedy %= YEARSPERREPEAT;
    }
    while (wantedy != y) {
        if (wantedy > y) {
            i = len_years[isleap(y)];
            ++y;
        } else {
            --y;
            i = -len_years[isleap(y)];
        }
        dayoff = oadd(dayoff, i);
    }
    while (m != rp->r_month) {
        i = len_months[isleap(y)][m];
        dayoff = oadd(dayoff, i);
        ++m;
    }
    i = rp->r_dayofmonth;
    if (m == TM_FEBRUARY && i == 29 && !isleap(y)) {
        if (rp->r_dycode == DC_DOWLEQ)
            --i;
        else {
            error(_("use of 2/29 in non leap-year"));
            exit(EXIT_FAILURE);
        }
    }
    --i;
    dayoff = oadd(dayoff, i);
    if (rp->r_dycode == DC_DOWGEQ || rp->r_dycode == DC_DOWLEQ) {
        register zic_t    wday;

#define LDAYSPERWEEK    ((zic_t) DAYSPERWEEK)
        wday = EPOCH_WDAY;
        /*
        ** Don't trust mod of negative numbers.
        */
        if (dayoff >= 0)
            wday = (wday + dayoff) % LDAYSPERWEEK;
        else {
            wday -= ((-dayoff) % LDAYSPERWEEK);
            if (wday < 0)
                wday += LDAYSPERWEEK;
        }
        while (wday != rp->r_wday)
            if (rp->r_dycode == DC_DOWGEQ) {
                dayoff = oadd(dayoff, 1);
                if (++wday >= LDAYSPERWEEK)
                    wday = 0;
                ++i;
            } else {
                dayoff = oadd(dayoff, -1);
                if (--wday < 0)
                    wday = LDAYSPERWEEK - 1;
                --i;
            }
        if (i < 0 || i >= len_months[isleap(y)][m]) {
            if (noise)
                warning(_("rule goes past start/end of month; \
will not work with pre-2004 versions of zic"));
        }
    }
    if (dayoff < min_time / SECSPERDAY)
        return min_time;
    if (dayoff > max_time / SECSPERDAY)
        return max_time;
    t = (zic_t) dayoff * SECSPERDAY;
    return tadd(t, rp->r_tod);
}

static void
newabbr(const char *string)
{
    register int    i;

    if (strcmp(string, GRANDPARENTED) != 0) {
        register const char *    cp;
        const char *        mp;

        cp = string;
        mp = NULL;
        while (is_alpha(*cp) || ('0' <= *cp && *cp <= '9')
               || *cp == '-' || *cp == '+')
                ++cp;
        if (noise && cp - string < 3)
          mp = _("time zone abbreviation has fewer than 3 characters");
        if (cp - string > ZIC_MAX_ABBR_LEN_WO_WARN)
          mp = _("time zone abbreviation has too many characters");
        if (*cp != '\0')
mp = _("time zone abbreviation differs from POSIX standard");
        if (mp != NULL)
            warning("%s (%s)", mp, string);
    }
    i = strlen(string) + 1;
    if (charcnt + i > TZ_MAX_CHARS) {
        error(_("too many, or too long, time zone abbreviations"));
        exit(EXIT_FAILURE);
    }
    strcpy(&chars[charcnt], string);
    charcnt += i;
}

/* Ensure that the directories of ARGNAME exist, by making any missing
   ones.  If ANCESTORS, do this only for ARGNAME's ancestors; otherwise,
   do it for ARGNAME too.  Exit with failure if there is trouble.
   Do not consider an existing non-directory to be trouble.  */
static void
mkdirs(char const *argname, bool ancestors)
{
    register char *    name;
    register char *    cp;

    cp = name = ecpyalloc(argname);

    /* On MS-Windows systems, do not worry about drive letters or
       backslashes, as this should suffice in practice.  Time zone
       names do not use drive letters and backslashes.  If the -d
       option of zic does not name an already-existing directory,
       it can use slashes to separate the already-existing
       ancestor prefix from the to-be-created subdirectories.  */

    /* Do not mkdir a root directory, as it must exist.  */
    while (*cp == '/')
      cp++;

    while (cp && ((cp = strchr(cp, '/')) || !ancestors)) {
        if (cp)
          *cp = '\0';
        /*
        ** Try to create it.  It's OK if creation fails because
        ** the directory already exists, perhaps because some
        ** other process just created it.  For simplicity do
        ** not check first whether it already exists, as that
        ** is checked anyway if the mkdir fails.
        */
        if (mkdir(name, MKDIR_UMASK) != 0) {
            /* For speed, skip itsdir if errno == EEXIST.  Since
               mkdirs is called only after open fails with ENOENT
               on a subfile, EEXIST implies itsdir here.  */
            int err = errno;
            if (err != EEXIST && !itsdir(name)) {
                error(_("%s: Can't create directory %s: %s"),
                      progname, name, strerror(err));
                exit(EXIT_FAILURE);
            }
        }
        if (cp)
          *cp++ = '/';
    }
    free(name);
}