Adding upstream version 15.4.upstream/15.4upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1777 insertions, 0 deletions

diff --git a/src/bin/initdb/findtimezone.c b/src/bin/initdb/findtimezone.c
new file mode 100644
index 0000000..ddb65e6
--- /dev/null
+++ b/src/bin/initdb/findtimezone.c
@@ -0,0 +1,1777 @@
+/*-------------------------------------------------------------------------
+ *
+ * findtimezone.c
+ *	  Functions for determining the default timezone to use.
+ *
+ * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/bin/initdb/findtimezone.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres_fe.h"
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "pgtz.h"
+
+/* Ideally this would be in a .h file, but it hardly seems worth the trouble */
+extern const char *select_default_timezone(const char *share_path);
+
+
+#ifndef SYSTEMTZDIR
+static char tzdirpath[MAXPGPATH];
+#endif
+
+
+/*
+ * Return full pathname of timezone data directory
+ *
+ * In this file, tzdirpath is assumed to be set up by select_default_timezone.
+ */
+static const char *
+pg_TZDIR(void)
+{
+#ifndef SYSTEMTZDIR
+	/* normal case: timezone stuff is under our share dir */
+	return tzdirpath;
+#else
+	/* we're configured to use system's timezone database */
+	return SYSTEMTZDIR;
+#endif
+}
+
+
+/*
+ * Given a timezone name, open() the timezone data file.  Return the
+ * file descriptor if successful, -1 if not.
+ *
+ * This is simpler than the backend function of the same name because
+ * we assume that the input string has the correct case already, so there
+ * is no need for case-folding.  (This is obviously true if we got the file
+ * name from the filesystem to start with.  The only other place it can come
+ * from is the environment variable TZ, and there seems no need to allow
+ * case variation in that; other programs aren't likely to.)
+ *
+ * If "canonname" is not NULL, then on success the canonical spelling of the
+ * given name is stored there (the buffer must be > TZ_STRLEN_MAX bytes!).
+ * This is redundant but kept for compatibility with the backend code.
+ */
+int
+pg_open_tzfile(const char *name, char *canonname)
+{
+	char		fullname[MAXPGPATH];
+
+	if (canonname)
+		strlcpy(canonname, name, TZ_STRLEN_MAX + 1);
+
+	strlcpy(fullname, pg_TZDIR(), sizeof(fullname));
+	if (strlen(fullname) + 1 + strlen(name) >= MAXPGPATH)
+		return -1;				/* not gonna fit */
+	strcat(fullname, "/");
+	strcat(fullname, name);
+
+	return open(fullname, O_RDONLY | PG_BINARY, 0);
+}
+
+
+
+/*
+ * Load a timezone definition.
+ * Does not verify that the timezone is acceptable!
+ *
+ * This corresponds to the backend's pg_tzset(), except that we only support
+ * one loaded timezone at a time.
+ */
+static pg_tz *
+pg_load_tz(const char *name)
+{
+	static pg_tz tz;
+
+	if (strlen(name) > TZ_STRLEN_MAX)
+		return NULL;			/* not going to fit */
+
+	/*
+	 * "GMT" is always sent to tzparse(); see comments for pg_tzset().
+	 */
+	if (strcmp(name, "GMT") == 0)
+	{
+		if (!tzparse(name, &tz.state, true))
+		{
+			/* This really, really should not happen ... */
+			return NULL;
+		}
+	}
+	else if (tzload(name, NULL, &tz.state, true) != 0)
+	{
+		if (name[0] == ':' || !tzparse(name, &tz.state, false))
+		{
+			return NULL;		/* unknown timezone */
+		}
+	}
+
+	strcpy(tz.TZname, name);
+
+	return &tz;
+}
+
+
+/*
+ * The following block of code attempts to determine which timezone in our
+ * timezone database is the best match for the active system timezone.
+ *
+ * On most systems, we rely on trying to match the observable behavior of
+ * the C library's localtime() function.  The database zone that matches
+ * furthest into the past is the one to use.  Often there will be several
+ * zones with identical rankings (since the IANA database assigns multiple
+ * names to many zones).  We break ties by first checking for "preferred"
+ * names (such as "UTC"), and then arbitrarily by preferring shorter, then
+ * alphabetically earlier zone names.  (If we did not explicitly prefer
+ * "UTC", we would get the alias name "UCT" instead due to alphabetic
+ * ordering.)
+ *
+ * Many modern systems use the IANA database, so if we can determine the
+ * system's idea of which zone it is using and its behavior matches our zone
+ * of the same name, we can skip the rather-expensive search through all the
+ * zones in our database.  This short-circuit path also ensures that we spell
+ * the zone name the same way the system setting does, even in the presence
+ * of multiple aliases for the same zone.
+ *
+ * Win32's native knowledge about timezones appears to be too incomplete
+ * and too different from the IANA database for the above matching strategy
+ * to be of any use. But there is just a limited number of timezones
+ * available, so we can rely on a handmade mapping table instead.
+ */
+
+#ifndef WIN32
+
+#define T_DAY	((time_t) (60*60*24))
+#define T_WEEK	((time_t) (60*60*24*7))
+#define T_MONTH ((time_t) (60*60*24*31))
+
+#define MAX_TEST_TIMES (52*100) /* 100 years */
+
+struct tztry
+{
+	int			n_test_times;
+	time_t		test_times[MAX_TEST_TIMES];
+};
+
+static bool check_system_link_file(const char *linkname, struct tztry *tt,
+								   char *bestzonename);
+static void scan_available_timezones(char *tzdir, char *tzdirsub,
+									 struct tztry *tt,
+									 int *bestscore, char *bestzonename);
+
+
+/*
+ * Get GMT offset from a system struct tm
+ */
+static int
+get_timezone_offset(struct tm *tm)
+{
+#if defined(HAVE_STRUCT_TM_TM_ZONE)
+	return tm->tm_gmtoff;
+#elif defined(HAVE_INT_TIMEZONE)
+	return -TIMEZONE_GLOBAL;
+#else
+#error No way to determine TZ? Can this happen?
+#endif
+}
+
+/*
+ * Convenience subroutine to convert y/m/d to time_t (NOT pg_time_t)
+ */
+static time_t
+build_time_t(int year, int month, int day)
+{
+	struct tm	tm;
+
+	memset(&tm, 0, sizeof(tm));
+	tm.tm_mday = day;
+	tm.tm_mon = month - 1;
+	tm.tm_year = year - 1900;
+	tm.tm_isdst = -1;
+
+	return mktime(&tm);
+}
+
+/*
+ * Does a system tm value match one we computed ourselves?
+ */
+static bool
+compare_tm(struct tm *s, struct pg_tm *p)
+{
+	if (s->tm_sec != p->tm_sec ||
+		s->tm_min != p->tm_min ||
+		s->tm_hour != p->tm_hour ||
+		s->tm_mday != p->tm_mday ||
+		s->tm_mon != p->tm_mon ||
+		s->tm_year != p->tm_year ||
+		s->tm_wday != p->tm_wday ||
+		s->tm_yday != p->tm_yday ||
+		s->tm_isdst != p->tm_isdst)
+		return false;
+	return true;
+}
+
+/*
+ * See how well a specific timezone setting matches the system behavior
+ *
+ * We score a timezone setting according to the number of test times it
+ * matches.  (The test times are ordered later-to-earlier, but this routine
+ * doesn't actually know that; it just scans until the first non-match.)
+ *
+ * We return -1 for a completely unusable setting; this is worse than the
+ * score of zero for a setting that works but matches not even the first
+ * test time.
+ */
+static int
+score_timezone(const char *tzname, struct tztry *tt)
+{
+	int			i;
+	pg_time_t	pgtt;
+	struct tm  *systm;
+	struct pg_tm *pgtm;
+	char		cbuf[TZ_STRLEN_MAX + 1];
+	pg_tz	   *tz;
+
+	/* Load timezone definition */
+	tz = pg_load_tz(tzname);
+	if (!tz)
+		return -1;				/* unrecognized zone name */
+
+	/* Reject if leap seconds involved */
+	if (!pg_tz_acceptable(tz))
+	{
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+		fprintf(stderr, "Reject TZ \"%s\": uses leap seconds\n", tzname);
+#endif
+		return -1;
+	}
+
+	/* Check for match at all the test times */
+	for (i = 0; i < tt->n_test_times; i++)
+	{
+		pgtt = (pg_time_t) (tt->test_times[i]);
+		pgtm = pg_localtime(&pgtt, tz);
+		if (!pgtm)
+			return -1;			/* probably shouldn't happen */
+		systm = localtime(&(tt->test_times[i]));
+		if (!systm)
+		{
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+			fprintf(stderr, "TZ \"%s\" scores %d: at %ld %04d-%02d-%02d %02d:%02d:%02d %s, system had no data\n",
+					tzname, i, (long) pgtt,
+					pgtm->tm_year + 1900, pgtm->tm_mon + 1, pgtm->tm_mday,
+					pgtm->tm_hour, pgtm->tm_min, pgtm->tm_sec,
+					pgtm->tm_isdst ? "dst" : "std");
+#endif
+			return i;
+		}
+		if (!compare_tm(systm, pgtm))
+		{
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+			fprintf(stderr, "TZ \"%s\" scores %d: at %ld %04d-%02d-%02d %02d:%02d:%02d %s versus %04d-%02d-%02d %02d:%02d:%02d %s\n",
+					tzname, i, (long) pgtt,
+					pgtm->tm_year + 1900, pgtm->tm_mon + 1, pgtm->tm_mday,
+					pgtm->tm_hour, pgtm->tm_min, pgtm->tm_sec,
+					pgtm->tm_isdst ? "dst" : "std",
+					systm->tm_year + 1900, systm->tm_mon + 1, systm->tm_mday,
+					systm->tm_hour, systm->tm_min, systm->tm_sec,
+					systm->tm_isdst ? "dst" : "std");
+#endif
+			return i;
+		}
+		if (systm->tm_isdst >= 0)
+		{
+			/* Check match of zone names, too */
+			if (pgtm->tm_zone == NULL)
+				return -1;		/* probably shouldn't happen */
+			memset(cbuf, 0, sizeof(cbuf));
+			strftime(cbuf, sizeof(cbuf) - 1, "%Z", systm);	/* zone abbr */
+			if (strcmp(cbuf, pgtm->tm_zone) != 0)
+			{
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+				fprintf(stderr, "TZ \"%s\" scores %d: at %ld \"%s\" versus \"%s\"\n",
+						tzname, i, (long) pgtt,
+						pgtm->tm_zone, cbuf);
+#endif
+				return i;
+			}
+		}
+	}
+
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+	fprintf(stderr, "TZ \"%s\" gets max score %d\n", tzname, i);
+#endif
+
+	return i;
+}
+
+/*
+ * Test whether given zone name is a perfect match to localtime() behavior
+ */
+static bool
+perfect_timezone_match(const char *tzname, struct tztry *tt)
+{
+	return (score_timezone(tzname, tt) == tt->n_test_times);
+}
+
+
+/*
+ * Try to identify a timezone name (in our terminology) that best matches the
+ * observed behavior of the system localtime() function.
+ */
+static const char *
+identify_system_timezone(void)
+{
+	static char resultbuf[TZ_STRLEN_MAX + 1];
+	time_t		tnow;
+	time_t		t;
+	struct tztry tt;
+	struct tm  *tm;
+	int			thisyear;
+	int			bestscore;
+	char		tmptzdir[MAXPGPATH];
+	int			std_ofs;
+	char		std_zone_name[TZ_STRLEN_MAX + 1],
+				dst_zone_name[TZ_STRLEN_MAX + 1];
+	char		cbuf[TZ_STRLEN_MAX + 1];
+
+	/* Initialize OS timezone library */
+	tzset();
+
+	/*
+	 * Set up the list of dates to be probed to see how well our timezone
+	 * matches the system zone.  We first probe January and July of the
+	 * current year; this serves to quickly eliminate the vast majority of the
+	 * TZ database entries.  If those dates match, we probe every week for 100
+	 * years backwards from the current July.  (Weekly resolution is good
+	 * enough to identify DST transition rules, since everybody switches on
+	 * Sundays.)  This is sufficient to cover most of the Unix time_t range,
+	 * and we don't want to look further than that since many systems won't
+	 * have sane TZ behavior further back anyway.  The further back the zone
+	 * matches, the better we score it.  This may seem like a rather random
+	 * way of doing things, but experience has shown that system-supplied
+	 * timezone definitions are likely to have DST behavior that is right for
+	 * the recent past and not so accurate further back. Scoring in this way
+	 * allows us to recognize zones that have some commonality with the IANA
+	 * database, without insisting on exact match. (Note: we probe Thursdays,
+	 * not Sundays, to avoid triggering DST-transition bugs in localtime
+	 * itself.)
+	 */
+	tnow = time(NULL);
+	tm = localtime(&tnow);
+	if (!tm)
+		return NULL;			/* give up if localtime is broken... */
+	thisyear = tm->tm_year + 1900;
+
+	t = build_time_t(thisyear, 1, 15);
+
+	/*
+	 * Round back to GMT midnight Thursday.  This depends on the knowledge
+	 * that the time_t origin is Thu Jan 01 1970.  (With a different origin
+	 * we'd be probing some other day of the week, but it wouldn't matter
+	 * anyway unless localtime() had DST-transition bugs.)
+	 */
+	t -= (t % T_WEEK);
+
+	tt.n_test_times = 0;
+	tt.test_times[tt.n_test_times++] = t;
+
+	t = build_time_t(thisyear, 7, 15);
+	t -= (t % T_WEEK);
+
+	tt.test_times[tt.n_test_times++] = t;
+
+	while (tt.n_test_times < MAX_TEST_TIMES)
+	{
+		t -= T_WEEK;
+		tt.test_times[tt.n_test_times++] = t;
+	}
+
+	/*
+	 * Try to avoid the brute-force search by seeing if we can recognize the
+	 * system's timezone setting directly.
+	 *
+	 * Currently we just check /etc/localtime; there are other conventions for
+	 * this, but that seems to be the only one used on enough platforms to be
+	 * worth troubling over.
+	 */
+	if (check_system_link_file("/etc/localtime", &tt, resultbuf))
+		return resultbuf;
+
+	/* No luck, so search for the best-matching timezone file */
+	strlcpy(tmptzdir, pg_TZDIR(), sizeof(tmptzdir));
+	bestscore = -1;
+	resultbuf[0] = '\0';
+	scan_available_timezones(tmptzdir, tmptzdir + strlen(tmptzdir) + 1,
+							 &tt,
+							 &bestscore, resultbuf);
+	if (bestscore > 0)
+	{
+		/* Ignore IANA's rather silly "Factory" zone; use GMT instead */
+		if (strcmp(resultbuf, "Factory") == 0)
+			return NULL;
+		return resultbuf;
+	}
+
+	/*
+	 * Couldn't find a match in the database, so next we try constructed zone
+	 * names (like "PST8PDT").
+	 *
+	 * First we need to determine the names of the local standard and daylight
+	 * zones.  The idea here is to scan forward from today until we have seen
+	 * both zones, if both are in use.
+	 */
+	memset(std_zone_name, 0, sizeof(std_zone_name));
+	memset(dst_zone_name, 0, sizeof(dst_zone_name));
+	std_ofs = 0;
+
+	tnow = time(NULL);
+
+	/*
+	 * Round back to a GMT midnight so results don't depend on local time of
+	 * day
+	 */
+	tnow -= (tnow % T_DAY);
+
+	/*
+	 * We have to look a little further ahead than one year, in case today is
+	 * just past a DST boundary that falls earlier in the year than the next
+	 * similar boundary.  Arbitrarily scan up to 14 months.
+	 */
+	for (t = tnow; t <= tnow + T_MONTH * 14; t += T_MONTH)
+	{
+		tm = localtime(&t);
+		if (!tm)
+			continue;
+		if (tm->tm_isdst < 0)
+			continue;
+		if (tm->tm_isdst == 0 && std_zone_name[0] == '\0')
+		{
+			/* found STD zone */
+			memset(cbuf, 0, sizeof(cbuf));
+			strftime(cbuf, sizeof(cbuf) - 1, "%Z", tm); /* zone abbr */
+			strcpy(std_zone_name, cbuf);
+			std_ofs = get_timezone_offset(tm);
+		}
+		if (tm->tm_isdst > 0 && dst_zone_name[0] == '\0')
+		{
+			/* found DST zone */
+			memset(cbuf, 0, sizeof(cbuf));
+			strftime(cbuf, sizeof(cbuf) - 1, "%Z", tm); /* zone abbr */
+			strcpy(dst_zone_name, cbuf);
+		}
+		/* Done if found both */
+		if (std_zone_name[0] && dst_zone_name[0])
+			break;
+	}
+
+	/* We should have found a STD zone name by now... */
+	if (std_zone_name[0] == '\0')
+	{
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+		fprintf(stderr, "could not determine system time zone\n");
+#endif
+		return NULL;			/* go to GMT */
+	}
+
+	/* If we found DST then try STD<ofs>DST */
+	if (dst_zone_name[0] != '\0')
+	{
+		snprintf(resultbuf, sizeof(resultbuf), "%s%d%s",
+				 std_zone_name, -std_ofs / 3600, dst_zone_name);
+		if (score_timezone(resultbuf, &tt) > 0)
+			return resultbuf;
+	}
+
+	/* Try just the STD timezone (works for GMT at least) */
+	strcpy(resultbuf, std_zone_name);
+	if (score_timezone(resultbuf, &tt) > 0)
+		return resultbuf;
+
+	/* Try STD<ofs> */
+	snprintf(resultbuf, sizeof(resultbuf), "%s%d",
+			 std_zone_name, -std_ofs / 3600);
+	if (score_timezone(resultbuf, &tt) > 0)
+		return resultbuf;
+
+	/*
+	 * Did not find the timezone.  Fallback to use a GMT zone.  Note that the
+	 * IANA timezone database names the GMT-offset zones in POSIX style: plus
+	 * is west of Greenwich.  It's unfortunate that this is opposite of SQL
+	 * conventions.  Should we therefore change the names? Probably not...
+	 */
+	snprintf(resultbuf, sizeof(resultbuf), "Etc/GMT%s%d",
+			 (-std_ofs > 0) ? "+" : "", -std_ofs / 3600);
+
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+	fprintf(stderr, "could not recognize system time zone, using \"%s\"\n",
+			resultbuf);
+#endif
+	return resultbuf;
+}
+
+/*
+ * Examine a system-provided symlink file to see if it tells us the timezone.
+ *
+ * Unfortunately, there is little standardization of how the system default
+ * timezone is determined in the absence of a TZ environment setting.
+ * But a common strategy is to create a symlink at a well-known place.
+ * If "linkname" identifies a readable symlink, and the tail of its contents
+ * matches a zone name we know, and the actual behavior of localtime() agrees
+ * with what we think that zone means, then we may use that zone name.
+ *
+ * We insist on a perfect behavioral match, which might not happen if the
+ * system has a different IANA database version than we do; but in that case
+ * it seems best to fall back to the brute-force search.
+ *
+ * linkname is the symlink file location to probe.
+ *
+ * tt tells about the system timezone behavior we need to match.
+ *
+ * If we successfully identify a zone name, store it in *bestzonename and
+ * return true; else return false.  bestzonename must be a buffer of length
+ * TZ_STRLEN_MAX + 1.
+ */
+static bool
+check_system_link_file(const char *linkname, struct tztry *tt,
+					   char *bestzonename)
+{
+#ifdef HAVE_READLINK
+	char		link_target[MAXPGPATH];
+	int			len;
+	const char *cur_name;
+
+	/*
+	 * Try to read the symlink.  If not there, not a symlink, etc etc, just
+	 * quietly fail; the precise reason needn't concern us.
+	 */
+	len = readlink(linkname, link_target, sizeof(link_target));
+	if (len < 0 || len >= sizeof(link_target))
+		return false;
+	link_target[len] = '\0';
+
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+	fprintf(stderr, "symbolic link \"%s\" contains \"%s\"\n",
+			linkname, link_target);
+#endif
+
+	/*
+	 * The symlink is probably of the form "/path/to/zones/zone/name", or
+	 * possibly it is a relative path.  Nobody puts their zone DB directly in
+	 * the root directory, so we can definitely skip the first component; but
+	 * after that it's trial-and-error to identify which path component begins
+	 * the zone name.
+	 */
+	cur_name = link_target;
+	while (*cur_name)
+	{
+		/* Advance to next segment of path */
+		cur_name = strchr(cur_name + 1, '/');
+		if (cur_name == NULL)
+			break;
+		/* If there are consecutive slashes, skip all, as the kernel would */
+		do
+		{
+			cur_name++;
+		} while (*cur_name == '/');
+
+		/*
+		 * Test remainder of path to see if it is a matching zone name.
+		 * Relative paths might contain ".."; we needn't bother testing if the
+		 * first component is that.  Also defend against overlength names.
+		 */
+		if (*cur_name && *cur_name != '.' &&
+			strlen(cur_name) <= TZ_STRLEN_MAX &&
+			perfect_timezone_match(cur_name, tt))
+		{
+			/* Success! */
+			strcpy(bestzonename, cur_name);
+			return true;
+		}
+	}
+
+	/* Couldn't extract a matching zone name */
+	return false;
+#else
+	/* No symlinks?  Forget it */
+	return false;
+#endif
+}
+
+/*
+ * Given a timezone name, determine whether it should be preferred over other
+ * names which are equally good matches. The output is arbitrary but we will
+ * use 0 for "neutral" default preference; larger values are more preferred.
+ */
+static int
+zone_name_pref(const char *zonename)
+{
+	/*
+	 * Prefer UTC over alternatives such as UCT.  Also prefer Etc/UTC over
+	 * Etc/UCT; but UTC is preferred to Etc/UTC.
+	 */
+	if (strcmp(zonename, "UTC") == 0)
+		return 50;
+	if (strcmp(zonename, "Etc/UTC") == 0)
+		return 40;
+
+	/*
+	 * We don't want to pick "localtime" or "posixrules", unless we can find
+	 * no other name for the prevailing zone.  Those aren't real zone names.
+	 */
+	if (strcmp(zonename, "localtime") == 0 ||
+		strcmp(zonename, "posixrules") == 0)
+		return -50;
+
+	return 0;
+}
+
+/*
+ * Recursively scan the timezone database looking for the best match to
+ * the system timezone behavior.
+ *
+ * tzdir points to a buffer of size MAXPGPATH.  On entry, it holds the
+ * pathname of a directory containing TZ files.  We internally modify it
+ * to hold pathnames of sub-directories and files, but must restore it
+ * to its original contents before exit.
+ *
+ * tzdirsub points to the part of tzdir that represents the subfile name
+ * (ie, tzdir + the original directory name length, plus one for the
+ * first added '/').
+ *
+ * tt tells about the system timezone behavior we need to match.
+ *
+ * *bestscore and *bestzonename on entry hold the best score found so far
+ * and the name of the best zone.  We overwrite them if we find a better
+ * score.  bestzonename must be a buffer of length TZ_STRLEN_MAX + 1.
+ */
+static void
+scan_available_timezones(char *tzdir, char *tzdirsub, struct tztry *tt,
+						 int *bestscore, char *bestzonename)
+{
+	int			tzdir_orig_len = strlen(tzdir);
+	char	  **names;
+	char	  **namep;
+
+	names = pgfnames(tzdir);
+	if (!names)
+		return;
+
+	for (namep = names; *namep; namep++)
+	{
+		char	   *name = *namep;
+		struct stat statbuf;
+
+		/* Ignore . and .., plus any other "hidden" files */
+		if (name[0] == '.')
+			continue;
+
+		snprintf(tzdir + tzdir_orig_len, MAXPGPATH - tzdir_orig_len,
+				 "/%s", name);
+
+		if (stat(tzdir, &statbuf) != 0)
+		{
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+			fprintf(stderr, "could not stat \"%s\": %s\n",
+					tzdir, strerror(errno));
+#endif
+			tzdir[tzdir_orig_len] = '\0';
+			continue;
+		}
+
+		if (S_ISDIR(statbuf.st_mode))
+		{
+			/* Recurse into subdirectory */
+			scan_available_timezones(tzdir, tzdirsub, tt,
+									 bestscore, bestzonename);
+		}
+		else
+		{
+			/* Load and test this file */
+			int			score = score_timezone(tzdirsub, tt);
+
+			if (score > *bestscore)
+			{
+				*bestscore = score;
+				strlcpy(bestzonename, tzdirsub, TZ_STRLEN_MAX + 1);
+			}
+			else if (score == *bestscore)
+			{
+				/* Consider how to break a tie */
+				int			namepref = (zone_name_pref(tzdirsub) -
+										zone_name_pref(bestzonename));
+
+				if (namepref > 0 ||
+					(namepref == 0 &&
+					 (strlen(tzdirsub) < strlen(bestzonename) ||
+					  (strlen(tzdirsub) == strlen(bestzonename) &&
+					   strcmp(tzdirsub, bestzonename) < 0))))
+					strlcpy(bestzonename, tzdirsub, TZ_STRLEN_MAX + 1);
+			}
+		}
+
+		/* Restore tzdir */
+		tzdir[tzdir_orig_len] = '\0';
+	}
+
+	pgfnames_cleanup(names);
+}
+#else							/* WIN32 */
+
+static const struct
+{
+	const char *stdname;		/* Windows name of standard timezone */
+	const char *dstname;		/* Windows name of daylight timezone */
+	const char *pgtzname;		/* Name of pgsql timezone to map to */
+}			win32_tzmap[] =
+
+{
+	/*
+	 * This list was built from the contents of the registry at
+	 * HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time
+	 * Zones on Windows 7, Windows 10, and Windows Server 2019.  Some recent
+	 * additions have been made by comparing to the CLDR project's
+	 * windowsZones.xml file.
+	 *
+	 * The zones have been matched to IANA timezones based on CLDR's mapping
+	 * for "territory 001".
+	 */
+	{
+		/* (UTC+04:30) Kabul */
+		"Afghanistan Standard Time", "Afghanistan Daylight Time",
+		"Asia/Kabul"
+	},
+	{
+		/* (UTC-09:00) Alaska */
+		"Alaskan Standard Time", "Alaskan Daylight Time",
+		"America/Anchorage"
+	},
+	{
+		/* (UTC-10:00) Aleutian Islands */
+		"Aleutian Standard Time", "Aleutian Daylight Time",
+		"America/Adak"
+	},
+	{
+		/* (UTC+07:00) Barnaul, Gorno-Altaysk */
+		"Altai Standard Time", "Altai Daylight Time",
+		"Asia/Barnaul"
+	},
+	{
+		/* (UTC+03:00) Kuwait, Riyadh */
+		"Arab Standard Time", "Arab Daylight Time",
+		"Asia/Riyadh"
+	},
+	{
+		/* (UTC+04:00) Abu Dhabi, Muscat */
+		"Arabian Standard Time", "Arabian Daylight Time",
+		"Asia/Dubai"
+	},
+	{
+		/* (UTC+03:00) Baghdad */
+		"Arabic Standard Time", "Arabic Daylight Time",
+		"Asia/Baghdad"
+	},
+	{
+		/* (UTC-03:00) City of Buenos Aires */
+		"Argentina Standard Time", "Argentina Daylight Time",
+		"America/Buenos_Aires"
+	},
+	{
+		/* (UTC+04:00) Baku, Tbilisi, Yerevan */
+		"Armenian Standard Time", "Armenian Daylight Time",
+		"Asia/Yerevan"
+	},
+	{
+		/* (UTC+04:00) Astrakhan, Ulyanovsk */
+		"Astrakhan Standard Time", "Astrakhan Daylight Time",
+		"Europe/Astrakhan"
+	},
+	{
+		/* (UTC-04:00) Atlantic Time (Canada) */
+		"Atlantic Standard Time", "Atlantic Daylight Time",
+		"America/Halifax"
+	},
+	{
+		/* (UTC+09:30) Darwin */
+		"AUS Central Standard Time", "AUS Central Daylight Time",
+		"Australia/Darwin"
+	},
+	{
+		/* (UTC+08:45) Eucla */
+		"Aus Central W. Standard Time", "Aus Central W. Daylight Time",
+		"Australia/Eucla"
+	},
+	{
+		/* (UTC+10:00) Canberra, Melbourne, Sydney */
+		"AUS Eastern Standard Time", "AUS Eastern Daylight Time",
+		"Australia/Sydney"
+	},
+	{
+		/* (UTC+04:00) Baku */
+		"Azerbaijan Standard Time", "Azerbaijan Daylight Time",
+		"Asia/Baku"
+	},
+	{
+		/* (UTC-01:00) Azores */
+		"Azores Standard Time", "Azores Daylight Time",
+		"Atlantic/Azores"
+	},
+	{
+		/* (UTC-03:00) Salvador */
+		"Bahia Standard Time", "Bahia Daylight Time",
+		"America/Bahia"
+	},
+	{
+		/* (UTC+06:00) Dhaka */
+		"Bangladesh Standard Time", "Bangladesh Daylight Time",
+		"Asia/Dhaka"
+	},
+	{
+		/* (UTC+03:00) Minsk */
+		"Belarus Standard Time", "Belarus Daylight Time",
+		"Europe/Minsk"
+	},
+	{
+		/* (UTC+11:00) Bougainville Island */
+		"Bougainville Standard Time", "Bougainville Daylight Time",
+		"Pacific/Bougainville"
+	},
+	{
+		/* (UTC-01:00) Cabo Verde Is. */
+		"Cabo Verde Standard Time", "Cabo Verde Daylight Time",
+		"Atlantic/Cape_Verde"
+	},
+	{
+		/* (UTC-06:00) Saskatchewan */
+		"Canada Central Standard Time", "Canada Central Daylight Time",
+		"America/Regina"
+	},
+	{
+		/* (UTC-01:00) Cape Verde Is. */
+		"Cape Verde Standard Time", "Cape Verde Daylight Time",
+		"Atlantic/Cape_Verde"
+	},
+	{
+		/* (UTC+04:00) Yerevan */
+		"Caucasus Standard Time", "Caucasus Daylight Time",
+		"Asia/Yerevan"
+	},
+	{
+		/* (UTC+09:30) Adelaide */
+		"Cen. Australia Standard Time", "Cen. Australia Daylight Time",
+		"Australia/Adelaide"
+	},
+	{
+		/* (UTC-06:00) Central America */
+		"Central America Standard Time", "Central America Daylight Time",
+		"America/Guatemala"
+	},
+	{
+		/* (UTC+06:00) Astana */
+		"Central Asia Standard Time", "Central Asia Daylight Time",
+		"Asia/Almaty"
+	},
+	{
+		/* (UTC-04:00) Cuiaba */
+		"Central Brazilian Standard Time", "Central Brazilian Daylight Time",
+		"America/Cuiaba"
+	},
+	{
+		/* (UTC+01:00) Belgrade, Bratislava, Budapest, Ljubljana, Prague */
+		"Central Europe Standard Time", "Central Europe Daylight Time",
+		"Europe/Budapest"
+	},
+	{
+		/* (UTC+01:00) Sarajevo, Skopje, Warsaw, Zagreb */
+		"Central European Standard Time", "Central European Daylight Time",
+		"Europe/Warsaw"
+	},
+	{
+		/* (UTC+11:00) Solomon Is., New Caledonia */
+		"Central Pacific Standard Time", "Central Pacific Daylight Time",
+		"Pacific/Guadalcanal"
+	},
+	{
+		/* (UTC-06:00) Central Time (US & Canada) */
+		"Central Standard Time", "Central Daylight Time",
+		"America/Chicago"
+	},
+	{
+		/* (UTC-06:00) Guadalajara, Mexico City, Monterrey */
+		"Central Standard Time (Mexico)", "Central Daylight Time (Mexico)",
+		"America/Mexico_City"
+	},
+	{
+		/* (UTC+12:45) Chatham Islands */
+		"Chatham Islands Standard Time", "Chatham Islands Daylight Time",
+		"Pacific/Chatham"
+	},
+	{
+		/* (UTC+08:00) Beijing, Chongqing, Hong Kong, Urumqi */
+		"China Standard Time", "China Daylight Time",
+		"Asia/Shanghai"
+	},
+	{
+		/* (UTC) Coordinated Universal Time */
+		"Coordinated Universal Time", "Coordinated Universal Time",
+		"UTC"
+	},
+	{
+		/* (UTC-05:00) Havana */
+		"Cuba Standard Time", "Cuba Daylight Time",
+		"America/Havana"
+	},
+	{
+		/* (UTC-12:00) International Date Line West */
+		"Dateline Standard Time", "Dateline Daylight Time",
+		"Etc/GMT+12"
+	},
+	{
+		/* (UTC+03:00) Nairobi */
+		"E. Africa Standard Time", "E. Africa Daylight Time",
+		"Africa/Nairobi"
+	},
+	{
+		/* (UTC+10:00) Brisbane */
+		"E. Australia Standard Time", "E. Australia Daylight Time",
+		"Australia/Brisbane"
+	},
+	{
+		/* (UTC+02:00) Chisinau */
+		"E. Europe Standard Time", "E. Europe Daylight Time",
+		"Europe/Chisinau"
+	},
+	{
+		/* (UTC-03:00) Brasilia */
+		"E. South America Standard Time", "E. South America Daylight Time",
+		"America/Sao_Paulo"
+	},
+	{
+		/* (UTC-06:00) Easter Island */
+		"Easter Island Standard Time", "Easter Island Daylight Time",
+		"Pacific/Easter"
+	},
+	{
+		/* (UTC-05:00) Eastern Time (US & Canada) */
+		"Eastern Standard Time", "Eastern Daylight Time",
+		"America/New_York"
+	},
+	{
+		/* (UTC-05:00) Chetumal */
+		"Eastern Standard Time (Mexico)", "Eastern Daylight Time (Mexico)",
+		"America/Cancun"
+	},
+	{
+		/* (UTC+02:00) Cairo */
+		"Egypt Standard Time", "Egypt Daylight Time",
+		"Africa/Cairo"
+	},
+	{
+		/* (UTC+05:00) Ekaterinburg */
+		"Ekaterinburg Standard Time", "Ekaterinburg Daylight Time",
+		"Asia/Yekaterinburg"
+	},
+	{
+		/* (UTC+12:00) Fiji */
+		"Fiji Standard Time", "Fiji Daylight Time",
+		"Pacific/Fiji"
+	},
+	{
+		/* (UTC+02:00) Helsinki, Kyiv, Riga, Sofia, Tallinn, Vilnius */
+		"FLE Standard Time", "FLE Daylight Time",
+		"Europe/Kiev"
+	},
+	{
+		/* (UTC+04:00) Tbilisi */
+		"Georgian Standard Time", "Georgian Daylight Time",
+		"Asia/Tbilisi"
+	},
+	{
+		/* (UTC+00:00) Dublin, Edinburgh, Lisbon, London */
+		"GMT Standard Time", "GMT Daylight Time",
+		"Europe/London"
+	},
+	{
+		/* (UTC-03:00) Greenland */
+		"Greenland Standard Time", "Greenland Daylight Time",
+		"America/Godthab"
+	},
+	{
+		/*
+		 * Windows uses this zone name in various places that lie near the
+		 * prime meridian, but are not in the UK.  However, most people
+		 * probably think that "Greenwich" means UK civil time, or maybe even
+		 * straight-up UTC.  Atlantic/Reykjavik is a decent match for that
+		 * interpretation because Iceland hasn't observed DST since 1968.
+		 */
+		/* (UTC+00:00) Monrovia, Reykjavik */
+		"Greenwich Standard Time", "Greenwich Daylight Time",
+		"Atlantic/Reykjavik"
+	},
+	{
+		/* (UTC+02:00) Athens, Bucharest */
+		"GTB Standard Time", "GTB Daylight Time",
+		"Europe/Bucharest"
+	},
+	{
+		/* (UTC-05:00) Haiti */
+		"Haiti Standard Time", "Haiti Daylight Time",
+		"America/Port-au-Prince"
+	},
+	{
+		/* (UTC-10:00) Hawaii */
+		"Hawaiian Standard Time", "Hawaiian Daylight Time",
+		"Pacific/Honolulu"
+	},
+	{
+		/* (UTC+05:30) Chennai, Kolkata, Mumbai, New Delhi */
+		"India Standard Time", "India Daylight Time",
+		"Asia/Calcutta"
+	},
+	{
+		/* (UTC+03:30) Tehran */
+		"Iran Standard Time", "Iran Daylight Time",
+		"Asia/Tehran"
+	},
+	{
+		/* (UTC+02:00) Jerusalem */
+		"Israel Standard Time", "Israel Daylight Time",
+		"Asia/Jerusalem"
+	},
+	{
+		/* (UTC+02:00) Jerusalem (old spelling of zone name) */
+		"Jerusalem Standard Time", "Jerusalem Daylight Time",
+		"Asia/Jerusalem"
+	},
+	{
+		/* (UTC+02:00) Amman */
+		"Jordan Standard Time", "Jordan Daylight Time",
+		"Asia/Amman"
+	},
+	{
+		/* (UTC+02:00) Kaliningrad */
+		"Kaliningrad Standard Time", "Kaliningrad Daylight Time",
+		"Europe/Kaliningrad"
+	},
+	{
+		/* (UTC+12:00) Petropavlovsk-Kamchatsky - Old */
+		"Kamchatka Standard Time", "Kamchatka Daylight Time",
+		"Asia/Kamchatka"
+	},
+	{
+		/* (UTC+09:00) Seoul */
+		"Korea Standard Time", "Korea Daylight Time",
+		"Asia/Seoul"
+	},
+	{
+		/* (UTC+02:00) Tripoli */
+		"Libya Standard Time", "Libya Daylight Time",
+		"Africa/Tripoli"
+	},
+	{
+		/* (UTC+14:00) Kiritimati Island */
+		"Line Islands Standard Time", "Line Islands Daylight Time",
+		"Pacific/Kiritimati"
+	},
+	{
+		/* (UTC+10:30) Lord Howe Island */
+		"Lord Howe Standard Time", "Lord Howe Daylight Time",
+		"Australia/Lord_Howe"
+	},
+	{
+		/* (UTC+11:00) Magadan */
+		"Magadan Standard Time", "Magadan Daylight Time",
+		"Asia/Magadan"
+	},
+	{
+		/* (UTC-03:00) Punta Arenas */
+		"Magallanes Standard Time", "Magallanes Daylight Time",
+		"America/Punta_Arenas"
+	},
+	{
+		/* (UTC+08:00) Kuala Lumpur, Singapore */
+		"Malay Peninsula Standard Time", "Malay Peninsula Daylight Time",
+		"Asia/Kuala_Lumpur"
+	},
+	{
+		/* (UTC-09:30) Marquesas Islands */
+		"Marquesas Standard Time", "Marquesas Daylight Time",
+		"Pacific/Marquesas"
+	},
+	{
+		/* (UTC+04:00) Port Louis */
+		"Mauritius Standard Time", "Mauritius Daylight Time",
+		"Indian/Mauritius"
+	},
+	{
+		/* (UTC-06:00) Guadalajara, Mexico City, Monterrey */
+		"Mexico Standard Time", "Mexico Daylight Time",
+		"America/Mexico_City"
+	},
+	{
+		/* (UTC-07:00) Chihuahua, La Paz, Mazatlan */
+		"Mexico Standard Time 2", "Mexico Daylight Time 2",
+		"America/Chihuahua"
+	},
+	{
+		/* (UTC-02:00) Mid-Atlantic - Old */
+		"Mid-Atlantic Standard Time", "Mid-Atlantic Daylight Time",
+		"Atlantic/South_Georgia"
+	},
+	{
+		/* (UTC+02:00) Beirut */
+		"Middle East Standard Time", "Middle East Daylight Time",
+		"Asia/Beirut"
+	},
+	{
+		/* (UTC-03:00) Montevideo */
+		"Montevideo Standard Time", "Montevideo Daylight Time",
+		"America/Montevideo"
+	},
+	{
+		/* (UTC+01:00) Casablanca */
+		"Morocco Standard Time", "Morocco Daylight Time",
+		"Africa/Casablanca"
+	},
+	{
+		/* (UTC-07:00) Mountain Time (US & Canada) */
+		"Mountain Standard Time", "Mountain Daylight Time",
+		"America/Denver"
+	},
+	{
+		/* (UTC-07:00) Chihuahua, La Paz, Mazatlan */
+		"Mountain Standard Time (Mexico)", "Mountain Daylight Time (Mexico)",
+		"America/Chihuahua"
+	},
+	{
+		/* (UTC+06:30) Yangon (Rangoon) */
+		"Myanmar Standard Time", "Myanmar Daylight Time",
+		"Asia/Rangoon"
+	},
+	{
+		/* (UTC+07:00) Novosibirsk */
+		"N. Central Asia Standard Time", "N. Central Asia Daylight Time",
+		"Asia/Novosibirsk"
+	},
+	{
+		/* (UTC+02:00) Windhoek */
+		"Namibia Standard Time", "Namibia Daylight Time",
+		"Africa/Windhoek"
+	},
+	{
+		/* (UTC+05:45) Kathmandu */
+		"Nepal Standard Time", "Nepal Daylight Time",
+		"Asia/Katmandu"
+	},
+	{
+		/* (UTC+12:00) Auckland, Wellington */
+		"New Zealand Standard Time", "New Zealand Daylight Time",
+		"Pacific/Auckland"
+	},
+	{
+		/* (UTC-03:30) Newfoundland */
+		"Newfoundland Standard Time", "Newfoundland Daylight Time",
+		"America/St_Johns"
+	},
+	{
+		/* (UTC+11:00) Norfolk Island */
+		"Norfolk Standard Time", "Norfolk Daylight Time",
+		"Pacific/Norfolk"
+	},
+	{
+		/* (UTC+08:00) Irkutsk */
+		"North Asia East Standard Time", "North Asia East Daylight Time",
+		"Asia/Irkutsk"
+	},
+	{
+		/* (UTC+07:00) Krasnoyarsk */
+		"North Asia Standard Time", "North Asia Daylight Time",
+		"Asia/Krasnoyarsk"
+	},
+	{
+		/* (UTC+09:00) Pyongyang */
+		"North Korea Standard Time", "North Korea Daylight Time",
+		"Asia/Pyongyang"
+	},
+	{
+		/* (UTC+07:00) Novosibirsk */
+		"Novosibirsk Standard Time", "Novosibirsk Daylight Time",
+		"Asia/Novosibirsk"
+	},
+	{
+		/* (UTC+06:00) Omsk */
+		"Omsk Standard Time", "Omsk Daylight Time",
+		"Asia/Omsk"
+	},
+	{
+		/* (UTC-04:00) Santiago */
+		"Pacific SA Standard Time", "Pacific SA Daylight Time",
+		"America/Santiago"
+	},
+	{
+		/* (UTC-08:00) Pacific Time (US & Canada) */
+		"Pacific Standard Time", "Pacific Daylight Time",
+		"America/Los_Angeles"
+	},
+	{
+		/* (UTC-08:00) Baja California */
+		"Pacific Standard Time (Mexico)", "Pacific Daylight Time (Mexico)",
+		"America/Tijuana"
+	},
+	{
+		/* (UTC+05:00) Islamabad, Karachi */
+		"Pakistan Standard Time", "Pakistan Daylight Time",
+		"Asia/Karachi"
+	},
+	{
+		/* (UTC-04:00) Asuncion */
+		"Paraguay Standard Time", "Paraguay Daylight Time",
+		"America/Asuncion"
+	},
+	{
+		/* (UTC+05:00) Qyzylorda */
+		"Qyzylorda Standard Time", "Qyzylorda Daylight Time",
+		"Asia/Qyzylorda"
+	},
+	{
+		/* (UTC+01:00) Brussels, Copenhagen, Madrid, Paris */
+		"Romance Standard Time", "Romance Daylight Time",
+		"Europe/Paris"
+	},
+	{
+		/* (UTC+04:00) Izhevsk, Samara */
+		"Russia Time Zone 3", "Russia Time Zone 3",
+		"Europe/Samara"
+	},
+	{
+		/* (UTC+11:00) Chokurdakh */
+		"Russia Time Zone 10", "Russia Time Zone 10",
+		"Asia/Srednekolymsk"
+	},
+	{
+		/* (UTC+12:00) Anadyr, Petropavlovsk-Kamchatsky */
+		"Russia Time Zone 11", "Russia Time Zone 11",
+		"Asia/Kamchatka"
+	},
+	{
+		/* (UTC+02:00) Kaliningrad */
+		"Russia TZ 1 Standard Time", "Russia TZ 1 Daylight Time",
+		"Europe/Kaliningrad"
+	},
+	{
+		/* (UTC+03:00) Moscow, St. Petersburg */
+		"Russia TZ 2 Standard Time", "Russia TZ 2 Daylight Time",
+		"Europe/Moscow"
+	},
+	{
+		/* (UTC+04:00) Izhevsk, Samara */
+		"Russia TZ 3 Standard Time", "Russia TZ 3 Daylight Time",
+		"Europe/Samara"
+	},
+	{
+		/* (UTC+05:00) Ekaterinburg */
+		"Russia TZ 4 Standard Time", "Russia TZ 4 Daylight Time",
+		"Asia/Yekaterinburg"
+	},
+	{
+		/* (UTC+06:00) Novosibirsk (RTZ 5) */
+		"Russia TZ 5 Standard Time", "Russia TZ 5 Daylight Time",
+		"Asia/Novosibirsk"
+	},
+	{
+		/* (UTC+07:00) Krasnoyarsk */
+		"Russia TZ 6 Standard Time", "Russia TZ 6 Daylight Time",
+		"Asia/Krasnoyarsk"
+	},
+	{
+		/* (UTC+08:00) Irkutsk */
+		"Russia TZ 7 Standard Time", "Russia TZ 7 Daylight Time",
+		"Asia/Irkutsk"
+	},
+	{
+		/* (UTC+09:00) Yakutsk */
+		"Russia TZ 8 Standard Time", "Russia TZ 8 Daylight Time",
+		"Asia/Yakutsk"
+	},
+	{
+		/* (UTC+10:00) Vladivostok */
+		"Russia TZ 9 Standard Time", "Russia TZ 9 Daylight Time",
+		"Asia/Vladivostok"
+	},
+	{
+		/* (UTC+11:00) Chokurdakh */
+		"Russia TZ 10 Standard Time", "Russia TZ 10 Daylight Time",
+		"Asia/Magadan"
+	},
+	{
+		/* (UTC+12:00) Anadyr, Petropavlovsk-Kamchatsky */
+		"Russia TZ 11 Standard Time", "Russia TZ 11 Daylight Time",
+		"Asia/Anadyr"
+	},
+	{
+		/* (UTC+03:00) Moscow, St. Petersburg */
+		"Russian Standard Time", "Russian Daylight Time",
+		"Europe/Moscow"
+	},
+	{
+		/* (UTC-03:00) Cayenne, Fortaleza */
+		"SA Eastern Standard Time", "SA Eastern Daylight Time",
+		"America/Cayenne"
+	},
+	{
+		/* (UTC-05:00) Bogota, Lima, Quito, Rio Branco */
+		"SA Pacific Standard Time", "SA Pacific Daylight Time",
+		"America/Bogota"
+	},
+	{
+		/* (UTC-04:00) Georgetown, La Paz, Manaus, San Juan */
+		"SA Western Standard Time", "SA Western Daylight Time",
+		"America/La_Paz"
+	},
+	{
+		/* (UTC-03:00) Saint Pierre and Miquelon */
+		"Saint Pierre Standard Time", "Saint Pierre Daylight Time",
+		"America/Miquelon"
+	},
+	{
+		/* (UTC+11:00) Sakhalin */
+		"Sakhalin Standard Time", "Sakhalin Daylight Time",
+		"Asia/Sakhalin"
+	},
+	{
+		/* (UTC+13:00) Samoa */
+		"Samoa Standard Time", "Samoa Daylight Time",
+		"Pacific/Apia"
+	},
+	{
+		/* (UTC+00:00) Sao Tome */
+		"Sao Tome Standard Time", "Sao Tome Daylight Time",
+		"Africa/Sao_Tome"
+	},
+	{
+		/* (UTC+04:00) Saratov */
+		"Saratov Standard Time", "Saratov Daylight Time",
+		"Europe/Saratov"
+	},
+	{
+		/* (UTC+07:00) Bangkok, Hanoi, Jakarta */
+		"SE Asia Standard Time", "SE Asia Daylight Time",
+		"Asia/Bangkok"
+	},
+	{
+		/* (UTC+08:00) Kuala Lumpur, Singapore */
+		"Singapore Standard Time", "Singapore Daylight Time",
+		"Asia/Singapore"
+	},
+	{
+		/* (UTC+02:00) Harare, Pretoria */
+		"South Africa Standard Time", "South Africa Daylight Time",
+		"Africa/Johannesburg"
+	},
+	{
+		/* (UTC+02:00) Juba */
+		"South Sudan Standard Time", "South Sudan Daylight Time",
+		"Africa/Juba"
+	},
+	{
+		/* (UTC+05:30) Sri Jayawardenepura */
+		"Sri Lanka Standard Time", "Sri Lanka Daylight Time",
+		"Asia/Colombo"
+	},
+	{
+		/* (UTC+02:00) Khartoum */
+		"Sudan Standard Time", "Sudan Daylight Time",
+		"Africa/Khartoum"
+	},
+	{
+		/* (UTC+02:00) Damascus */
+		"Syria Standard Time", "Syria Daylight Time",
+		"Asia/Damascus"
+	},
+	{
+		/* (UTC+08:00) Taipei */
+		"Taipei Standard Time", "Taipei Daylight Time",
+		"Asia/Taipei"
+	},
+	{
+		/* (UTC+10:00) Hobart */
+		"Tasmania Standard Time", "Tasmania Daylight Time",
+		"Australia/Hobart"
+	},
+	{
+		/* (UTC-03:00) Araguaina */
+		"Tocantins Standard Time", "Tocantins Daylight Time",
+		"America/Araguaina"
+	},
+	{
+		/* (UTC+09:00) Osaka, Sapporo, Tokyo */
+		"Tokyo Standard Time", "Tokyo Daylight Time",
+		"Asia/Tokyo"
+	},
+	{
+		/* (UTC+07:00) Tomsk */
+		"Tomsk Standard Time", "Tomsk Daylight Time",
+		"Asia/Tomsk"
+	},
+	{
+		/* (UTC+13:00) Nuku'alofa */
+		"Tonga Standard Time", "Tonga Daylight Time",
+		"Pacific/Tongatapu"
+	},
+	{
+		/* (UTC+09:00) Chita */
+		"Transbaikal Standard Time", "Transbaikal Daylight Time",
+		"Asia/Chita"
+	},
+	{
+		/* (UTC+03:00) Istanbul */
+		"Turkey Standard Time", "Turkey Daylight Time",
+		"Europe/Istanbul"
+	},
+	{
+		/* (UTC-05:00) Turks and Caicos */
+		"Turks And Caicos Standard Time", "Turks And Caicos Daylight Time",
+		"America/Grand_Turk"
+	},
+	{
+		/* (UTC+08:00) Ulaanbaatar */
+		"Ulaanbaatar Standard Time", "Ulaanbaatar Daylight Time",
+		"Asia/Ulaanbaatar"
+	},
+	{
+		/* (UTC-05:00) Indiana (East) */
+		"US Eastern Standard Time", "US Eastern Daylight Time",
+		"America/Indianapolis"
+	},
+	{
+		/* (UTC-07:00) Arizona */
+		"US Mountain Standard Time", "US Mountain Daylight Time",
+		"America/Phoenix"
+	},
+	{
+		/* (UTC) Coordinated Universal Time */
+		"UTC", "UTC",
+		"UTC"
+	},
+	{
+		/* (UTC+12:00) Coordinated Universal Time+12 */
+		"UTC+12", "UTC+12",
+		"Etc/GMT-12"
+	},
+	{
+		/* (UTC+13:00) Coordinated Universal Time+13 */
+		"UTC+13", "UTC+13",
+		"Etc/GMT-13"
+	},
+	{
+		/* (UTC-02:00) Coordinated Universal Time-02 */
+		"UTC-02", "UTC-02",
+		"Etc/GMT+2"
+	},
+	{
+		/* (UTC-08:00) Coordinated Universal Time-08 */
+		"UTC-08", "UTC-08",
+		"Etc/GMT+8"
+	},
+	{
+		/* (UTC-09:00) Coordinated Universal Time-09 */
+		"UTC-09", "UTC-09",
+		"Etc/GMT+9"
+	},
+	{
+		/* (UTC-11:00) Coordinated Universal Time-11 */
+		"UTC-11", "UTC-11",
+		"Etc/GMT+11"
+	},
+	{
+		/* (UTC-04:00) Caracas */
+		"Venezuela Standard Time", "Venezuela Daylight Time",
+		"America/Caracas"
+	},
+	{
+		/* (UTC+10:00) Vladivostok */
+		"Vladivostok Standard Time", "Vladivostok Daylight Time",
+		"Asia/Vladivostok"
+	},
+	{
+		/* (UTC+04:00) Volgograd */
+		"Volgograd Standard Time", "Volgograd Daylight Time",
+		"Europe/Volgograd"
+	},
+	{
+		/* (UTC+08:00) Perth */
+		"W. Australia Standard Time", "W. Australia Daylight Time",
+		"Australia/Perth"
+	},
+	{
+		/* (UTC+01:00) West Central Africa */
+		"W. Central Africa Standard Time", "W. Central Africa Daylight Time",
+		"Africa/Lagos"
+	},
+	{
+		/* (UTC+01:00) Amsterdam, Berlin, Bern, Rome, Stockholm, Vienna */
+		"W. Europe Standard Time", "W. Europe Daylight Time",
+		"Europe/Berlin"
+	},
+	{
+		/* (UTC+07:00) Hovd */
+		"W. Mongolia Standard Time", "W. Mongolia Daylight Time",
+		"Asia/Hovd"
+	},
+	{
+		/* (UTC+05:00) Ashgabat, Tashkent */
+		"West Asia Standard Time", "West Asia Daylight Time",
+		"Asia/Tashkent"
+	},
+	{
+		/* (UTC+02:00) Gaza, Hebron */
+		"West Bank Gaza Standard Time", "West Bank Gaza Daylight Time",
+		"Asia/Gaza"
+	},
+	{
+		/* (UTC+02:00) Gaza, Hebron */
+		"West Bank Standard Time", "West Bank Daylight Time",
+		"Asia/Hebron"
+	},
+	{
+		/* (UTC+10:00) Guam, Port Moresby */
+		"West Pacific Standard Time", "West Pacific Daylight Time",
+		"Pacific/Port_Moresby"
+	},
+	{
+		/* (UTC+09:00) Yakutsk */
+		"Yakutsk Standard Time", "Yakutsk Daylight Time",
+		"Asia/Yakutsk"
+	},
+	{
+		/* (UTC-07:00) Yukon */
+		"Yukon Standard Time", "Yukon Daylight Time",
+		"America/Whitehorse"
+	},
+	{
+		NULL, NULL, NULL
+	}
+};
+
+static const char *
+identify_system_timezone(void)
+{
+	int			i;
+	char		tzname[128];
+	char		localtzname[256];
+	time_t		t = time(NULL);
+	struct tm  *tm = localtime(&t);
+	HKEY		rootKey;
+	int			idx;
+
+	if (!tm)
+	{
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+		fprintf(stderr, "could not identify system time zone: localtime() failed\n");
+#endif
+		return NULL;			/* go to GMT */
+	}
+
+	memset(tzname, 0, sizeof(tzname));
+	strftime(tzname, sizeof(tzname) - 1, "%Z", tm);
+
+	for (i = 0; win32_tzmap[i].stdname != NULL; i++)
+	{
+		if (strcmp(tzname, win32_tzmap[i].stdname) == 0 ||
+			strcmp(tzname, win32_tzmap[i].dstname) == 0)
+		{
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+			fprintf(stderr, "TZ \"%s\" matches system time zone \"%s\"\n",
+					win32_tzmap[i].pgtzname, tzname);
+#endif
+			return win32_tzmap[i].pgtzname;
+		}
+	}
+
+	/*
+	 * Localized Windows versions return localized names for the timezone.
+	 * Scan the registry to find the English name, and then try matching
+	 * against our table again.
+	 */
+	memset(localtzname, 0, sizeof(localtzname));
+	if (RegOpenKeyEx(HKEY_LOCAL_MACHINE,
+					 "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones",
+					 0,
+					 KEY_READ,
+					 &rootKey) != ERROR_SUCCESS)
+	{
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+		fprintf(stderr, "could not open registry key to identify system time zone: error code %lu\n",
+				GetLastError());
+#endif
+		return NULL;			/* go to GMT */
+	}
+
+	for (idx = 0;; idx++)
+	{
+		char		keyname[256];
+		char		zonename[256];
+		DWORD		namesize;
+		FILETIME	lastwrite;
+		HKEY		key;
+		LONG		r;
+
+		memset(keyname, 0, sizeof(keyname));
+		namesize = sizeof(keyname);
+		if ((r = RegEnumKeyEx(rootKey,
+							  idx,
+							  keyname,
+							  &namesize,
+							  NULL,
+							  NULL,
+							  NULL,
+							  &lastwrite)) != ERROR_SUCCESS)
+		{
+			if (r == ERROR_NO_MORE_ITEMS)
+				break;
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+			fprintf(stderr, "could not enumerate registry subkeys to identify system time zone: %d\n",
+					(int) r);
+#endif
+			break;
+		}
+
+		if ((r = RegOpenKeyEx(rootKey, keyname, 0, KEY_READ, &key)) != ERROR_SUCCESS)
+		{
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+			fprintf(stderr, "could not open registry subkey to identify system time zone: %d\n",
+					(int) r);
+#endif
+			break;
+		}
+
+		memset(zonename, 0, sizeof(zonename));
+		namesize = sizeof(zonename);
+		if ((r = RegQueryValueEx(key, "Std", NULL, NULL, (unsigned char *) zonename, &namesize)) != ERROR_SUCCESS)
+		{
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+			fprintf(stderr, "could not query value for key \"std\" to identify system time zone \"%s\": %d\n",
+					keyname, (int) r);
+#endif
+			RegCloseKey(key);
+			continue;			/* Proceed to look at the next timezone */
+		}
+		if (strcmp(tzname, zonename) == 0)
+		{
+			/* Matched zone */
+			strcpy(localtzname, keyname);
+			RegCloseKey(key);
+			break;
+		}
+		memset(zonename, 0, sizeof(zonename));
+		namesize = sizeof(zonename);
+		if ((r = RegQueryValueEx(key, "Dlt", NULL, NULL, (unsigned char *) zonename, &namesize)) != ERROR_SUCCESS)
+		{
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+			fprintf(stderr, "could not query value for key \"dlt\" to identify system time zone \"%s\": %d\n",
+					keyname, (int) r);
+#endif
+			RegCloseKey(key);
+			continue;			/* Proceed to look at the next timezone */
+		}
+		if (strcmp(tzname, zonename) == 0)
+		{
+			/* Matched DST zone */
+			strcpy(localtzname, keyname);
+			RegCloseKey(key);
+			break;
+		}
+
+		RegCloseKey(key);
+	}
+
+	RegCloseKey(rootKey);
+
+	if (localtzname[0])
+	{
+		/* Found a localized name, so scan for that one too */
+		for (i = 0; win32_tzmap[i].stdname != NULL; i++)
+		{
+			if (strcmp(localtzname, win32_tzmap[i].stdname) == 0 ||
+				strcmp(localtzname, win32_tzmap[i].dstname) == 0)
+			{
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+				fprintf(stderr, "TZ \"%s\" matches localized system time zone \"%s\" (\"%s\")\n",
+						win32_tzmap[i].pgtzname, tzname, localtzname);
+#endif
+				return win32_tzmap[i].pgtzname;
+			}
+		}
+	}
+
+#ifdef DEBUG_IDENTIFY_TIMEZONE
+	fprintf(stderr, "could not find a match for system time zone \"%s\"\n",
+			tzname);
+#endif
+	return NULL;				/* go to GMT */
+}
+#endif							/* WIN32 */
+
+
+/*
+ * Return true if the given zone name is valid and is an "acceptable" zone.
+ */
+static bool
+validate_zone(const char *tzname)
+{
+	pg_tz	   *tz;
+
+	if (!tzname || !tzname[0])
+		return false;
+
+	tz = pg_load_tz(tzname);
+	if (!tz)
+		return false;
+
+	if (!pg_tz_acceptable(tz))
+		return false;
+
+	return true;
+}
+
+/*
+ * Identify a suitable default timezone setting based on the environment.
+ *
+ * The installation share_path must be passed in, as that is the default
+ * location for the timezone database directory.
+ *
+ * We first look to the TZ environment variable.  If not found or not
+ * recognized by our own code, we see if we can identify the timezone
+ * from the behavior of the system timezone library.  When all else fails,
+ * return NULL, indicating that we should default to GMT.
+ */
+const char *
+select_default_timezone(const char *share_path)
+{
+	const char *tzname;
+
+	/* Initialize timezone directory path, if needed */
+#ifndef SYSTEMTZDIR
+	snprintf(tzdirpath, sizeof(tzdirpath), "%s/timezone", share_path);
+#endif
+
+	/* Check TZ environment variable */
+	tzname = getenv("TZ");
+	if (validate_zone(tzname))
+		return tzname;
+
+	/* Nope, so try to identify the system timezone */
+	tzname = identify_system_timezone();
+	if (validate_zone(tzname))
+		return tzname;
+
+	return NULL;
+}