diff options
Diffstat (limited to 'backport-mktime-improve-heuristic-for-ca-1986-Indiana-DST.patch')
| -rw-r--r-- | backport-mktime-improve-heuristic-for-ca-1986-Indiana-DST.patch | 78 |
1 files changed, 78 insertions, 0 deletions
diff --git a/backport-mktime-improve-heuristic-for-ca-1986-Indiana-DST.patch b/backport-mktime-improve-heuristic-for-ca-1986-Indiana-DST.patch new file mode 100644 index 0000000..0142918 --- /dev/null +++ b/backport-mktime-improve-heuristic-for-ca-1986-Indiana-DST.patch @@ -0,0 +1,78 @@ +From 675ba1f361ea424626b48a40cfd24d113dfc1b65 Mon Sep 17 00:00:00 2001 +From: Paul Eggert <eggert@cs.ucla.edu> +Date: Thu, 8 Sep 2022 20:08:32 -0500 +Subject: [PATCH] mktime: improve heuristic for ca-1986 Indiana DST + +This patch syncs mktime.c from Gnulib, fixing a +problem reported by Mark Krenz <https://bugs.gnu.org/48085>, +and it should fix BZ#29035 too. +* time/mktime.c (__mktime_internal): Be more generous about +accepting arguments with the wrong value of tm_isdst, by falling +back to a one-hour DST difference if we find no nearby DST that is +unusual. This fixes a problem where "1986-04-28 00:00 EDT" was +rejected when TZ="America/Indianapolis" because the nearest DST +timestamp occurred in 1970, a temporal distance too great for the +old heuristic. This also also narrows the search a bit, which +is a minor performance win. + +(cherry picked from commit 83859e1115269cf56d21669361d4ddbe2687831c) +--- + time/mktime.c | 28 ++++++++++++++++++++-------- + 1 file changed, 20 insertions(+), 8 deletions(-) + +diff --git a/time/mktime.c b/time/mktime.c +index 8e78006eea..74d9bbaa5b 100644 +--- a/time/mktime.c ++++ b/time/mktime.c +@@ -429,8 +429,13 @@ __mktime_internal (struct tm *tp, + time with the right value, and use its UTC offset. + + Heuristic: probe the adjacent timestamps in both directions, +- looking for the desired isdst. This should work for all real +- time zone histories in the tz database. */ ++ looking for the desired isdst. If none is found within a ++ reasonable duration bound, assume a one-hour DST difference. ++ This should work for all real time zone histories in the tz ++ database. */ ++ ++ /* +1 if we wanted standard time but got DST, -1 if the reverse. */ ++ int dst_difference = (isdst == 0) - (tm.tm_isdst == 0); + + /* Distance between probes when looking for a DST boundary. In + tzdata2003a, the shortest period of DST is 601200 seconds +@@ -441,12 +446,14 @@ __mktime_internal (struct tm *tp, + periods when probing. */ + int stride = 601200; + +- /* The longest period of DST in tzdata2003a is 536454000 seconds +- (e.g., America/Jujuy starting 1946-10-01 01:00). The longest +- period of non-DST is much longer, but it makes no real sense +- to search for more than a year of non-DST, so use the DST +- max. */ +- int duration_max = 536454000; ++ /* In TZDB 2021e, the longest period of DST (or of non-DST), in ++ which the DST (or adjacent DST) difference is not one hour, ++ is 457243209 seconds: e.g., America/Cambridge_Bay with leap ++ seconds, starting 1965-10-31 00:00 in a switch from ++ double-daylight time (-05) to standard time (-07), and ++ continuing to 1980-04-27 02:00 in a switch from standard time ++ (-07) to daylight time (-06). */ ++ int duration_max = 457243209; + + /* Search in both directions, so the maximum distance is half + the duration; add the stride to avoid off-by-1 problems. */ +@@ -483,6 +490,11 @@ __mktime_internal (struct tm *tp, + } + } + ++ /* No unusual DST offset was found nearby. Assume one-hour DST. */ ++ t += 60 * 60 * dst_difference; ++ if (mktime_min <= t && t <= mktime_max && convert_time (convert, t, &tm)) ++ goto offset_found; ++ + __set_errno (EOVERFLOW); + return -1; + } +-- +2.43.5 + |