Consolidate several near-identical uses of mktime() into a single

routine DetermineLocalTimeZone().  In that routine, be more wary of
broken mktime() implementations than the original code was: don't allow
mktime to change the already-set y/m/d/h/m/s information, and don't
use tm_gmtoff if mktime failed.  Possibly this will resolve some of
the complaints we've been hearing from users of Middle Eastern timezones
on RedHat.

diff --git a/src/backend/utils/adt/datetime.c b/src/backend/utils/adt/datetime.c
index cee97b84812e3a69027ab5e6e681175ca83c6226..65e6af5de2bc81810b732d8f4a847e984fdf6ad3 100644 (file)
--- a/src/backend/utils/adt/datetime.c
+++ b/src/backend/utils/adt/datetime.c
@@ -869,37 +869,75 @@ DecodeDateTime(char **field, int *ftype, int nf,
                        if (fmask & DTK_M(DTZMOD))
                                return -1;
 
-                       if (IS_VALID_UTIME(tm->tm_year, tm->tm_mon, tm->tm_mday))
-                       {
+                       *tzp = DetermineLocalTimeZone(tm);
+               }
+       }
+
+       return 0;
+}      /* DecodeDateTime() */
+
+
+/* DetermineLocalTimeZone()
+ * Given a struct tm in which tm_year, tm_mon, tm_mday, tm_hour, tm_min, and
+ * tm_sec fields are set, attempt to determine the applicable local zone
+ * (ie, regular or daylight-savings time) at that time.  Set the struct tm's
+ * tm_isdst field accordingly, and return the actual timezone offset.
+ *
+ * This subroutine exists mainly to centralize uses of mktime() and defend
+ * against mktime() bugs on various platforms...
+ */
+int
+DetermineLocalTimeZone(struct tm * tm)
+{
+       int                     tz;
+
+       if (IS_VALID_UTIME(tm->tm_year, tm->tm_mon, tm->tm_mday))
+       {
 #if defined(HAVE_TM_ZONE) || defined(HAVE_INT_TIMEZONE)
-                               tm->tm_year -= 1900;
-                               tm->tm_mon -= 1;
-                               tm->tm_isdst = -1;
-                               mktime(tm);
-                               tm->tm_year += 1900;
-                               tm->tm_mon += 1;
+               /*
+                * Some buggy mktime() implementations may change the year/month/day
+                * when given a time right at a DST boundary.  To prevent corruption
+                * of the caller's data, give mktime() a copy...
+                */
+               struct tm       tt,
+                                  *tmp = &tt;
+
+               *tmp = *tm;
+               /* change to Unix conventions for year/month */
+               tmp->tm_year -= 1900;
+               tmp->tm_mon -= 1;
+
+               /* indicate timezone unknown */
+               tmp->tm_isdst = -1;
+
+               mktime(tmp);
+
+               tm->tm_isdst = tmp->tm_isdst;
 
 #if defined(HAVE_TM_ZONE)
-                               *tzp = -(tm->tm_gmtoff);                /* tm_gmtoff is
-                                                                                                * Sun/DEC-ism */
+               /* tm_gmtoff is Sun/DEC-ism */
+               if (tmp->tm_isdst >= 0)
+                       tz = -(tmp->tm_gmtoff);
+               else
+                       tz = 0;                         /* assume GMT if mktime failed */
 #elif defined(HAVE_INT_TIMEZONE)
-                               *tzp = ((tm->tm_isdst > 0) ? (TIMEZONE_GLOBAL - 3600) : TIMEZONE_GLOBAL);
+               tz = ((tmp->tm_isdst > 0) ? (TIMEZONE_GLOBAL - 3600) : TIMEZONE_GLOBAL);
 #endif  /* HAVE_INT_TIMEZONE */
 
 #else                                                  /* not (HAVE_TM_ZONE || HAVE_INT_TIMEZONE) */
-                               *tzp = CTimeZone;
+               tm->tm_isdst = 0;
+               tz = CTimeZone;
 #endif
-                       }
-                       else
-                       {
-                               tm->tm_isdst = 0;
-                               *tzp = 0;
-                       }
-               }
+       }
+       else
+       {
+               /* Given date is out of range, so assume GMT */
+               tm->tm_isdst = 0;
+               tz = 0;
        }
 
-       return 0;
-}      /* DecodeDateTime() */
+       return tz;
+}
 
 
 /* DecodeTimeOnly()
@@ -1119,22 +1157,8 @@ DecodeTimeOnly(char **field, int *ftype, int nf,
                tmp->tm_min = tm->tm_min;
                tmp->tm_sec = tm->tm_sec;
 
-#if defined(HAVE_TM_ZONE) || defined(HAVE_INT_TIMEZONE)
-               tmp->tm_year -= 1900;
-               tmp->tm_mon -= 1;
-               tmp->tm_isdst = -1;
-               mktime(tmp);
+               *tzp = DetermineLocalTimeZone(tmp);
                tm->tm_isdst = tmp->tm_isdst;
-
-#if defined(HAVE_TM_ZONE)
-               *tzp = -(tmp->tm_gmtoff);               /* tm_gmtoff is Sun/DEC-ism */
-#elif defined(HAVE_INT_TIMEZONE)
-               *tzp = ((tmp->tm_isdst > 0) ? (TIMEZONE_GLOBAL - 3600) : TIMEZONE_GLOBAL);
-#endif
-
-#else                                                  /* not (HAVE_TM_ZONE || HAVE_INT_TIMEZONE) */
-               *tzp = CTimeZone;
-#endif
        }
 
        return 0;

diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c
index d2c3ca19389b692dc2354923db108731d87fc41d..8225b5bd3006aaa43fbd9c1768eb2e2302ceb6d5 100644 (file)
--- a/src/backend/utils/adt/formatting.c
+++ b/src/backend/utils/adt/formatting.c
@@ -2936,37 +2936,7 @@ to_timestamp(PG_FUNCTION_ARGS)
 #ifdef DEBUG_TO_FROM_CHAR
        NOTICE_TM;
 #endif
-       if (IS_VALID_UTIME(tm->tm_year, tm->tm_mon, tm->tm_mday))
-       {
-
-#if defined(HAVE_TM_ZONE) || defined(HAVE_INT_TIMEZONE)
-               tm->tm_isdst = -1;
-               tm->tm_year -= 1900;
-               tm->tm_mon -= 1;
-
-#ifdef DEBUG_TO_FROM_CHAR
-               elog(DEBUG_elog_output, "TO-FROM_CHAR: Call mktime()");
-               NOTICE_TM;
-#endif
-               mktime(tm);
-               tm->tm_year += 1900;
-               tm->tm_mon += 1;
-
-#if defined(HAVE_TM_ZONE)
-               tz = -(tm->tm_gmtoff);  /* tm_gmtoff is Sun/DEC-ism */
-#elif defined(HAVE_INT_TIMEZONE)
-               tz = ((tm->tm_isdst > 0) ? (TIMEZONE_GLOBAL - 3600) : TIMEZONE_GLOBAL);
-#endif
-
-#else                                                  /* not (HAVE_TM_ZONE || HAVE_INT_TIMEZONE) */
-               tz = CTimeZone;
-#endif
-       }
-       else
-       {
-               tm->tm_isdst = 0;
-               tz = 0;
-       }
+       tz = DetermineLocalTimeZone(tm);
 #ifdef DEBUG_TO_FROM_CHAR
        NOTICE_TM;
 #endif

diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index d8e0d4e68850b41e575bc44f959464d030fc0fa6..eeeaa6ba0ab4ac79593be17a071f4299f404b27a 100644 (file)
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -990,32 +990,7 @@ timestamp_pl_span(PG_FUNCTION_ARGS)
                                if (tm->tm_mday > day_tab[isleap(tm->tm_year)][tm->tm_mon - 1])
                                        tm->tm_mday = (day_tab[isleap(tm->tm_year)][tm->tm_mon - 1]);
 
-                               if (IS_VALID_UTIME(tm->tm_year, tm->tm_mon, tm->tm_mday))
-                               {
-#if defined(HAVE_TM_ZONE) || defined(HAVE_INT_TIMEZONE)
-                                       tm->tm_year -= 1900;
-                                       tm->tm_mon -= 1;
-                                       tm->tm_isdst = -1;
-                                       mktime(tm);
-                                       tm->tm_year += 1900;
-                                       tm->tm_mon += 1;
-
-#if defined(HAVE_TM_ZONE)
-                                       tz = -(tm->tm_gmtoff);          /* tm_gmtoff is
-                                                                                                * Sun/DEC-ism */
-#elif defined(HAVE_INT_TIMEZONE)
-                                       tz = ((tm->tm_isdst > 0) ? (TIMEZONE_GLOBAL - 3600) : TIMEZONE_GLOBAL);
-#endif
-
-#else                                                  /* not (HAVE_TM_ZONE || HAVE_INT_TIMEZONE) */
-                                       tz = CTimeZone;
-#endif
-                               }
-                               else
-                               {
-                                       tm->tm_isdst = 0;
-                                       tz = 0;
-                               }
+                               tz = DetermineLocalTimeZone(tm);
 
                                if (tm2timestamp(tm, fsec, &tz, &dt) != 0)
                                        elog(ERROR, "Unable to add timestamp and interval");
@@ -1631,31 +1606,7 @@ timestamp_trunc(PG_FUNCTION_ARGS)
                                        result = 0;
                        }
 
-                       if (IS_VALID_UTIME(tm->tm_year, tm->tm_mon, tm->tm_mday))
-                       {
-#if defined(HAVE_TM_ZONE) || defined(HAVE_INT_TIMEZONE)
-                               tm->tm_year -= 1900;
-                               tm->tm_mon -= 1;
-                               tm->tm_isdst = -1;
-                               mktime(tm);
-                               tm->tm_year += 1900;
-                               tm->tm_mon += 1;
-
-#if defined(HAVE_TM_ZONE)
-                               tz = -(tm->tm_gmtoff);  /* tm_gmtoff is Sun/DEC-ism */
-#elif defined(HAVE_INT_TIMEZONE)
-                               tz = ((tm->tm_isdst > 0) ? (TIMEZONE_GLOBAL - 3600) : TIMEZONE_GLOBAL);
-#endif
-
-#else                                                  /* not (HAVE_TM_ZONE || HAVE_INT_TIMEZONE) */
-                               tz = CTimeZone;
-#endif
-                       }
-                       else
-                       {
-                               tm->tm_isdst = 0;
-                               tz = 0;
-                       }
+                       tz = DetermineLocalTimeZone(tm);
 
                        if (tm2timestamp(tm, fsec, &tz, &result) != 0)
                                elog(ERROR, "Unable to truncate timestamp to '%s'", lowunits);

diff --git a/src/include/utils/datetime.h b/src/include/utils/datetime.h
index c28964afc45f6bd44d314698a7c08df5d67cdf30..be2ef0c8d9c39e626a3a36a586d4c6abf27d7b93 100644 (file)
--- a/src/include/utils/datetime.h
+++ b/src/include/utils/datetime.h
@@ -255,6 +255,8 @@ extern int DecodeDateDelta(char **field, int *ftype,
                                int nf, int *dtype,
                                struct tm * tm, double *fsec);
 
+extern int     DetermineLocalTimeZone(struct tm * tm);
+
 extern int     EncodeDateOnly(struct tm * tm, int style, char *str);
 extern int     EncodeTimeOnly(struct tm * tm, double fsec, int *tzp, int style, char *str);
 extern int     EncodeDateTime(struct tm * tm, double fsec, int *tzp, char **tzn, int style, char *str);