Fix overflow hazards in interval input and output conversions.

DecodeInterval (interval input) was careless about integer-overflow
hazards, allowing bogus results to be obtained for sufficiently
large input values.  Also, since it initially converted the input
to a "struct tm", it was impossible to produce the full range of
representable interval values.

Meanwhile, EncodeInterval (interval output) and a few other
functions could suffer failures if asked to process sufficiently
large interval values, because they also relied on being able to
represent an interval in "struct tm" which is not designed to
handle that.

Fix all this stuff by introducing new struct types that are more
fit for purpose.

While this is clearly a bug fix, it's also an API break for any
code that's calling these functions directly.  So back-patching
doesn't seem wise, especially in view of the lack of field
complaints.

Joe Koshakow, editorialized a bit by me

Discussion: https://postgr.es/m/CAAvxfHff0JLYHwyBrtMx_=6wr=k2Xp+D+-X3vEhHjJYMj+mQcg@mail.gmail.com

Author: tglsfdc

src/backend/utils/adt/datetime.c

@@ -491,11 +491,28 @@ typedef struct
 
 /* ----------
  * Datetime to char conversion
+ *
+ * To support intervals as well as timestamps, we use a custom "tm" struct
+ * that is almost like struct pg_tm, but has a 64-bit tm_hour field.
+ * We omit the tm_isdst and tm_zone fields, which are not used here.
  * ----------
  */
+struct fmt_tm
+{
+	int			tm_sec;
+	int			tm_min;
+	int64		tm_hour;
+	int			tm_mday;
+	int			tm_mon;
+	int			tm_year;
+	int			tm_wday;
+	int			tm_yday;
+	long int	tm_gmtoff;
+};
+
 typedef struct TmToChar
 {
-	struct pg_tm tm;			/* classic 'tm' struct */
+	struct fmt_tm tm;			/* almost the classic 'tm' struct */
 	fsec_t		fsec;			/* fractional seconds */
 	const char *tzn;			/* timezone */
 } TmToChar;
@@ -504,12 +521,25 @@ typedef struct TmToChar
 #define tmtcTzn(_X) ((_X)->tzn)
 #define tmtcFsec(_X)	((_X)->fsec)
 
+/* Note: this is used to copy pg_tm to fmt_tm, so not quite a bitwise copy */
+#define COPY_tm(_DST, _SRC) \
+do {	\
+	(_DST)->tm_sec = (_SRC)->tm_sec; \
+	(_DST)->tm_min = (_SRC)->tm_min; \
+	(_DST)->tm_hour = (_SRC)->tm_hour; \
+	(_DST)->tm_mday = (_SRC)->tm_mday; \
+	(_DST)->tm_mon = (_SRC)->tm_mon; \
+	(_DST)->tm_year = (_SRC)->tm_year; \
+	(_DST)->tm_wday = (_SRC)->tm_wday; \
+	(_DST)->tm_yday = (_SRC)->tm_yday; \
+	(_DST)->tm_gmtoff = (_SRC)->tm_gmtoff; \
+} while(0)
+
+/* Caution: this is used to zero both pg_tm and fmt_tm structs */
 #define ZERO_tm(_X) \
 do {	\
-	(_X)->tm_sec  = (_X)->tm_year = (_X)->tm_min = (_X)->tm_wday = \
-	(_X)->tm_hour = (_X)->tm_yday = (_X)->tm_isdst = 0; \
-	(_X)->tm_mday = (_X)->tm_mon  = 1; \
-	(_X)->tm_zone = NULL; \
+	memset(_X, 0, sizeof(*(_X))); \
+	(_X)->tm_mday = (_X)->tm_mon = 1; \
 } while(0)
 
 #define ZERO_tmtc(_X) \
@@ -2649,7 +2679,7 @@ DCH_to_char(FormatNode *node, bool is_interval, TmToChar *in, char *out, Oid col
 {
 	FormatNode *n;
 	char	   *s;
-	struct pg_tm *tm = &in->tm;
+	struct fmt_tm *tm = &in->tm;
 	int			i;
 
 	/* cache localized days and months */
@@ -2698,16 +2728,17 @@ DCH_to_char(FormatNode *node, bool is_interval, TmToChar *in, char *out, Oid col
 				 * display time as shown on a 12-hour clock, even for
 				 * intervals
 				 */
-				sprintf(s, "%0*d", S_FM(n->suffix) ? 0 : (tm->tm_hour >= 0) ? 2 : 3,
-						tm->tm_hour % (HOURS_PER_DAY / 2) == 0 ? HOURS_PER_DAY / 2 :
-						tm->tm_hour % (HOURS_PER_DAY / 2));
+				sprintf(s, "%0*lld", S_FM(n->suffix) ? 0 : (tm->tm_hour >= 0) ? 2 : 3,
+						tm->tm_hour % (HOURS_PER_DAY / 2) == 0 ?
+						(long long) (HOURS_PER_DAY / 2) :
+						(long long) (tm->tm_hour % (HOURS_PER_DAY / 2)));
 				if (S_THth(n->suffix))
 					str_numth(s, s, S_TH_TYPE(n->suffix));
 				s += strlen(s);
 				break;
 			case DCH_HH24:
-				sprintf(s, "%0*d", S_FM(n->suffix) ? 0 : (tm->tm_hour >= 0) ? 2 : 3,
-						tm->tm_hour);
+				sprintf(s, "%0*lld", S_FM(n->suffix) ? 0 : (tm->tm_hour >= 0) ? 2 : 3,
+						(long long) tm->tm_hour);
 				if (S_THth(n->suffix))
 					str_numth(s, s, S_TH_TYPE(n->suffix));
 				s += strlen(s);
@@ -2755,9 +2786,10 @@ DCH_to_char(FormatNode *node, bool is_interval, TmToChar *in, char *out, Oid col
 				break;
 #undef DCH_to_char_fsec
 			case DCH_SSSS:
-				sprintf(s, "%d", tm->tm_hour * SECS_PER_HOUR +
-						tm->tm_min * SECS_PER_MINUTE +
-						tm->tm_sec);
+				sprintf(s, "%lld",
+						(long long) (tm->tm_hour * SECS_PER_HOUR +
+									 tm->tm_min * SECS_PER_MINUTE +
+									 tm->tm_sec));
 				if (S_THth(n->suffix))
 					str_numth(s, s, S_TH_TYPE(n->suffix));
 				s += strlen(s);
@@ -4088,7 +4120,8 @@ timestamp_to_char(PG_FUNCTION_ARGS)
 	text	   *fmt = PG_GETARG_TEXT_PP(1),
 			   *res;
 	TmToChar	tmtc;
-	struct pg_tm *tm;
+	struct pg_tm tt;
+	struct fmt_tm *tm;
 	int			thisdate;
 
 	if (VARSIZE_ANY_EXHDR(fmt) <= 0 || TIMESTAMP_NOT_FINITE(dt))
@@ -4097,10 +4130,11 @@ timestamp_to_char(PG_FUNCTION_ARGS)
 	ZERO_tmtc(&tmtc);
 	tm = tmtcTm(&tmtc);
 
-	if (timestamp2tm(dt, NULL, tm, &tmtcFsec(&tmtc), NULL, NULL) != 0)
+	if (timestamp2tm(dt, NULL, &tt, &tmtcFsec(&tmtc), NULL, NULL) != 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
 				 errmsg("timestamp out of range")));
+	COPY_tm(tm, &tt);
 
 	thisdate = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday);
 	tm->tm_wday = (thisdate + 1) % 7;
@@ -4120,7 +4154,8 @@ timestamptz_to_char(PG_FUNCTION_ARGS)
 			   *res;
 	TmToChar	tmtc;
 	int			tz;
-	struct pg_tm *tm;
+	struct pg_tm tt;
+	struct fmt_tm *tm;
 	int			thisdate;
 
 	if (VARSIZE_ANY_EXHDR(fmt) <= 0 || TIMESTAMP_NOT_FINITE(dt))
@@ -4129,10 +4164,11 @@ timestamptz_to_char(PG_FUNCTION_ARGS)
 	ZERO_tmtc(&tmtc);
 	tm = tmtcTm(&tmtc);
 
-	if (timestamp2tm(dt, &tz, tm, &tmtcFsec(&tmtc), &tmtcTzn(&tmtc), NULL) != 0)
+	if (timestamp2tm(dt, &tz, &tt, &tmtcFsec(&tmtc), &tmtcTzn(&tmtc), NULL) != 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
 				 errmsg("timestamp out of range")));
+	COPY_tm(tm, &tt);
 
 	thisdate = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday);
 	tm->tm_wday = (thisdate + 1) % 7;
@@ -4156,16 +4192,24 @@ interval_to_char(PG_FUNCTION_ARGS)
 	text	   *fmt = PG_GETARG_TEXT_PP(1),
 			   *res;
 	TmToChar	tmtc;
-	struct pg_tm *tm;
+	struct fmt_tm *tm;
+	struct pg_itm tt,
+			   *itm = &tt;
 
 	if (VARSIZE_ANY_EXHDR(fmt) <= 0)
 		PG_RETURN_NULL();
 
 	ZERO_tmtc(&tmtc);
 	tm = tmtcTm(&tmtc);
 
-	if (interval2tm(*it, tm, &tmtcFsec(&tmtc)) != 0)
-		PG_RETURN_NULL();
+	interval2itm(*it, itm);
+	tmtc.fsec = itm->tm_usec;
+	tm->tm_sec = itm->tm_sec;
+	tm->tm_min = itm->tm_min;
+	tm->tm_hour = itm->tm_hour;
+	tm->tm_mday = itm->tm_mday;
+	tm->tm_mon = itm->tm_mon;
+	tm->tm_year = itm->tm_year;
 
 	/* wday is meaningless, yday approximates the total span in days */
 	tm->tm_yday = (tm->tm_year * MONTHS_PER_YEAR + tm->tm_mon) * DAYS_PER_MONTH + tm->tm_mday;