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Commit86f2732

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Work around mktime() brain damage in recent versions of glibc by using
a series of localtime() calls to determine the local timezone offsetwhen mktime() fails. This eliminates regression failures on RHL 7.3,and should continue to work until it occurs to the glibc boys to breaklocaltime() as well. By then I hope we'll have our own timezone code...
1 parent4885dab commit86f2732

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1 file changed

+87
-12
lines changed

1 file changed

+87
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lines changed

‎src/backend/utils/adt/datetime.c‎

Lines changed: 87 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $Header: /cvsroot/pgsql/src/backend/utils/adt/datetime.c,v 1.94 2002/09/02 02:47:04 momjian Exp $
11+
* $Header: /cvsroot/pgsql/src/backend/utils/adt/datetime.c,v 1.95 2002/09/03 19:46:32 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -1446,21 +1446,26 @@ DecodeDateTime(char **field, int *ftype, int nf,
14461446

14471447

14481448
/* DetermineLocalTimeZone()
1449+
*
14491450
* Given a struct tm in which tm_year, tm_mon, tm_mday, tm_hour, tm_min, and
14501451
* tm_sec fields are set, attempt to determine the applicable local zone
14511452
* (ie, regular or daylight-savings time) at that time. Set the struct tm's
14521453
* tm_isdst field accordingly, and return the actual timezone offset.
14531454
*
1454-
* This subroutine exists mainly to centralize uses of mktime() and defend
1455-
* against mktime() bugs on various platforms...
1455+
* This subroutine exists to centralize uses of mktime() and defend against
1456+
* mktime() bugs/restrictions on various platforms. This should be
1457+
* the *only* call of mktime() in the backend.
14561458
*/
14571459
int
14581460
DetermineLocalTimeZone(structtm*tm)
14591461
{
14601462
inttz;
14611463

14621464
if (HasCTZSet)
1465+
{
1466+
tm->tm_isdst=0;/* for lack of a better idea */
14631467
tz=CTimeZone;
1468+
}
14641469
elseif (IS_VALID_UTIME(tm->tm_year,tm->tm_mon,tm->tm_mday))
14651470
{
14661471
#if defined(HAVE_TM_ZONE)|| defined(HAVE_INT_TIMEZONE)
@@ -1482,20 +1487,90 @@ DetermineLocalTimeZone(struct tm * tm)
14821487
/* indicate timezone unknown */
14831488
tmp->tm_isdst=-1;
14841489

1485-
mktime(tmp);
1486-
1487-
tm->tm_isdst=tmp->tm_isdst;
1490+
if (mktime(tmp)!= ((time_t)-1)&&
1491+
tmp->tm_isdst >=0)
1492+
{
1493+
/* mktime() succeeded, trust its result */
1494+
tm->tm_isdst=tmp->tm_isdst;
14881495

14891496
#if defined(HAVE_TM_ZONE)
1490-
/* tm_gmtoff is Sun/DEC-ism */
1491-
if (tmp->tm_isdst >=0)
1497+
/* tm_gmtoff is Sun/DEC-ism */
14921498
tz=-(tmp->tm_gmtoff);
1493-
else
1494-
tz=0;/* assume UTC if mktime failed */
14951499
#elif defined(HAVE_INT_TIMEZONE)
1496-
tz= ((tmp->tm_isdst>0) ? (TIMEZONE_GLOBAL-3600) :TIMEZONE_GLOBAL);
1500+
tz= ((tmp->tm_isdst>0) ? (TIMEZONE_GLOBAL-3600) :TIMEZONE_GLOBAL);
14971501
#endif/* HAVE_INT_TIMEZONE */
1498-
1502+
}
1503+
else
1504+
{
1505+
/*
1506+
* We have a buggy (not to say deliberately brain damaged)
1507+
* mktime(). Work around it by using localtime() instead.
1508+
*
1509+
* First, generate the time_t value corresponding to the given
1510+
* y/m/d/h/m/s taken as GMT time. This will not overflow (at
1511+
* least not for time_t taken as signed) because of the range
1512+
* check we did above.
1513+
*/
1514+
longday,
1515+
mysec,
1516+
locsec,
1517+
delta1,
1518+
delta2;
1519+
time_tmytime;
1520+
1521+
day= (date2j(tm->tm_year,tm->tm_mon,tm->tm_mday)-
1522+
date2j(1970,1,1));
1523+
mysec=tm->tm_sec+ (tm->tm_min+ (day*24+tm->tm_hour)*60)*60;
1524+
mytime= (time_t)mysec;
1525+
/*
1526+
* Use localtime to convert that time_t to broken-down time, and
1527+
* reassemble to get a representation of local time.
1528+
*/
1529+
tmp=localtime(&mytime);
1530+
day= (date2j(tmp->tm_year+1900,tmp->tm_mon+1,tmp->tm_mday)-
1531+
date2j(1970,1,1));
1532+
locsec=tmp->tm_sec+ (tmp->tm_min+ (day*24+tmp->tm_hour)*60)*60;
1533+
/*
1534+
* The local time offset corresponding to that GMT time is
1535+
* now computable as mysec - locsec.
1536+
*/
1537+
delta1=mysec-locsec;
1538+
/*
1539+
* However, if that GMT time and the local time we are actually
1540+
* interested in are on opposite sides of a daylight-savings-time
1541+
* transition, then this is not the time offset we want. So,
1542+
* adjust the time_t to be what we think the GMT time corresponding
1543+
* to our target local time is, and repeat the localtime() call
1544+
* and delta calculation. We may have to do it twice before we
1545+
* have a trustworthy delta.
1546+
*
1547+
* Note: think not to put a loop here, since if we've been given
1548+
* an "impossible" local time (in the gap during a spring-forward
1549+
* transition) we'd never get out of the loop. Twice is enough
1550+
* to give the behavior we want, which is that "impossible" times
1551+
* are taken as standard time, while at a fall-back boundary
1552+
* ambiguous times are also taken as standard.
1553+
*/
1554+
mysec+=delta1;
1555+
mytime= (time_t)mysec;
1556+
tmp=localtime(&mytime);
1557+
day= (date2j(tmp->tm_year+1900,tmp->tm_mon+1,tmp->tm_mday)-
1558+
date2j(1970,1,1));
1559+
locsec=tmp->tm_sec+ (tmp->tm_min+ (day*24+tmp->tm_hour)*60)*60;
1560+
delta2=mysec-locsec;
1561+
if (delta2!=delta1)
1562+
{
1563+
mysec+= (delta2-delta1);
1564+
mytime= (time_t)mysec;
1565+
tmp=localtime(&mytime);
1566+
day= (date2j(tmp->tm_year+1900,tmp->tm_mon+1,tmp->tm_mday)-
1567+
date2j(1970,1,1));
1568+
locsec=tmp->tm_sec+ (tmp->tm_min+ (day*24+tmp->tm_hour)*60)*60;
1569+
delta2=mysec-locsec;
1570+
}
1571+
tm->tm_isdst=tmp->tm_isdst;
1572+
tz= (int)delta2;
1573+
}
14991574
#else/* not (HAVE_TM_ZONE || HAVE_INT_TIMEZONE) */
15001575
tm->tm_isdst=0;
15011576
tz=CTimeZone;

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