Sync our copy of the timezone library with IANA release tzcode2020a.

This absorbs a leap-second-related bug fix in localtime.c, and
teaches zic to handle an expiration marker in the leapseconds file.
Neither are of any interest to us (for the foreseeable future
anyway), but we need to stay more or less in sync with upstream.

Also adjust some over-eager changes in the README from commit 957338418.
I have no intention of making changes that require C99 in this code,
until such time as all the live back branches require C99.  Otherwise
back-patching will get too exciting.

For the same reason, absorb assorted whitespace and other cosmetic
changes from HEAD into the back branches; mostly this reflects use of
improved versions of pgindent.

All in all then, quite a boring update.  But I figured I'd get it
done while I was looking at this code.

1 files changed, 28 insertions, 9 deletions

diff --git a/src/timezone/localtime.c b/src/timezone/localtime.c
index 0fc0a824ae4..f9b39195fad 100644
--- a/src/timezone/localtime.c
+++ b/src/timezone/localtime.c
@@ -36,7 +36,7 @@
  *		in which Daylight Saving Time is never observed.
  *	4.	They might reference tzname[0] after setting to a time zone
  *		in which Standard Time is never observed.
- *	5.	They might reference tm.TM_ZONE after calling offtime.
+ *	5.	They might reference tm.tm_zone after calling offtime.
  * What's best to do in the above cases is open to debate;
  * for now, we just set things up so that in any of the five cases
  * WILDABBR is used. Another possibility: initialize tzname[0] to the
@@ -92,8 +92,9 @@ struct rule
 static struct pg_tm *gmtsub(pg_time_t const *, int32, struct pg_tm *);
 static bool increment_overflow(int *, int);
 static bool increment_overflow_time(pg_time_t *, int32);
+static int64 leapcorr(struct state const *, pg_time_t);
 static struct pg_tm *timesub(pg_time_t const *, int32, struct state const *,
-		struct pg_tm *);
+							 struct pg_tm *);
 static bool typesequiv(struct state const *, int, int);
 
 
@@ -138,7 +139,7 @@ detzcode(const char *const codep)
 		 * Do two's-complement negation even on non-two's-complement machines.
 		 * If the result would be minval - 1, return minval.
 		 */
-		result -= !TWOS_COMPLEMENT(int32) &&result != 0;
+		result -= !TWOS_COMPLEMENT(int32) && result != 0;
 		result += minval;
 	}
 	return result;
@@ -152,7 +153,7 @@ detzcode64(const char *const codep)
 	int64		one = 1;
 	int64		halfmaxval = one << (64 - 2);
 	int64		maxval = halfmaxval - 1 + halfmaxval;
-	int64		minval = -TWOS_COMPLEMENT(int64) -maxval;
+	int64		minval = -TWOS_COMPLEMENT(int64) - maxval;
 
 	result = codep[0] & 0x7f;
 	for (i = 1; i < 8; ++i)
@@ -164,7 +165,7 @@ detzcode64(const char *const codep)
 		 * Do two's-complement negation even on non-two's-complement machines.
 		 * If the result would be minval - 1, return minval.
 		 */
-		result -= !TWOS_COMPLEMENT(int64) &&result != 0;
+		result -= !TWOS_COMPLEMENT(int64) && result != 0;
 		result += minval;
 	}
 	return result;
@@ -173,7 +174,7 @@ detzcode64(const char *const codep)
 static bool
 differ_by_repeat(const pg_time_t t1, const pg_time_t t0)
 {
-	if (TYPE_BIT(pg_time_t) -TYPE_SIGNED(pg_time_t) <SECSPERREPEAT_BITS)
+	if (TYPE_BIT(pg_time_t) - TYPE_SIGNED(pg_time_t) < SECSPERREPEAT_BITS)
 		return 0;
 	return t1 - t0 == SECSPERREPEAT;
 }
@@ -477,12 +478,14 @@ tzloadbody(char const *name, char *canonname, struct state *sp, bool doextend,
 
 				for (i = 0; i < ts->timecnt; i++)
 					if (sp->timecnt == 0
-						|| sp->ats[sp->timecnt - 1] < ts->ats[i])
+						|| (sp->ats[sp->timecnt - 1]
+							< ts->ats[i] + leapcorr(sp, ts->ats[i])))
 						break;
 				while (i < ts->timecnt
 					   && sp->timecnt < TZ_MAX_TIMES)
 				{
-					sp->ats[sp->timecnt] = ts->ats[i];
+					sp->ats[sp->timecnt]
+						= ts->ats[i] + leapcorr(sp, ts->ats[i]);
 					sp->types[sp->timecnt] = (sp->typecnt
 											  + ts->types[i]);
 					sp->timecnt++;
@@ -1480,7 +1483,7 @@ timesub(const pg_time_t *timep, int32 offset,
 		int			leapdays;
 
 		tdelta = tdays / DAYSPERLYEAR;
-		if (!((!TYPE_SIGNED(pg_time_t) ||INT_MIN <= tdelta)
+		if (!((!TYPE_SIGNED(pg_time_t) || INT_MIN <= tdelta)
 			  && tdelta <= INT_MAX))
 			goto out_of_range;
 		idelta = tdelta;
@@ -1601,6 +1604,22 @@ increment_overflow_time(pg_time_t *tp, int32 j)
 	return false;
 }
 
+static int64
+leapcorr(struct state const *sp, pg_time_t t)
+{
+	struct lsinfo const *lp;
+	int			i;
+
+	i = sp->leapcnt;
+	while (--i >= 0)
+	{
+		lp = &sp->lsis[i];
+		if (t >= lp->ls_trans)
+			return lp->ls_corr;
+	}
+	return 0;
+}
+
 /*
  * Find the next DST transition time in the given zone after the given time
  *