diff options
| -rw-r--r-- | time/mktime.c | 28 |
1 files changed, 20 insertions, 8 deletions
diff --git a/time/mktime.c b/time/mktime.c index aa12e28..7dc9d67 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; } |