https://gcc.gnu.org/g:e39c7121bc643ded1304ea73248390ee8ed5eac6
commit r15-11158-ge39c7121bc643ded1304ea73248390ee8ed5eac6 Author: Jonathan Wakely <[email protected]> Date: Mon Mar 16 21:48:30 2026 +0000 libstdc++: Partial fix for interpretation of non-UTC UNTIL times in tzdata.zi [PR116110] This is a partial fix for PR 116110, so that zone changes that occur at a time specified as standard time will be parsed correctly. Previously all UNTIL times were assumed to be UTC, which is incorrect according to the spec. Only times with a 'u' suffix (or the equivalent 'g' or 'z') are UTC times. An 's' suffix means standard time (i.e. the zone's usual offset from UTC, without any DST adjustment) and a 'w' suffix (or no suffix) means wall time, so the offset and any DST adjustment. This commit fixes the handling of 's' suffixes, so that the ZoneInfo::m_until member is set correctly. It also fixes the handling of some UNTIL times using wall time, specifically those where the DST adjustment is known during parsing of the tzdata.zi file. This is not a complete fix, because as noted in PR 116110 a Zone line that refers to a named Rule and uses wall time cannot be determined while parsing tzdata.zi. We need to remember that the m_until member is not correct, and then adjust it later when we find the rule that applies at a given time point. That requires more work. Some existing tests need to be adjusted due to the fixes in this commit. The std/time/time_zone/get_info_sys.cc and std/time/zoned_time/1.cc tests are corrected to check that the changes happens at midnight local time, not midnight UTC as previously assumed. One of the FIXME comments in std/time/time_zone/116110.cc can be removed now, because the UNTIL time is correctly interpreted as midnight local time. The other FIXME needs to be changed to midnight at the local standard time, which is still wrong but we don't currently adjust it for the DST save time of one hour. It also still needs the incorrect +24h due to Bug 124513. libstdc++-v3/ChangeLog: PR libstdc++/116110 * src/c++20/tzdb.cc (operator>>(istream&, ZoneInfo&)): Adjust inf.m_until according to indicator suffix on AT time in UNTIL. * testsuite/std/time/time_zone/116110.cc (test_kiritimati): Remove FIXME now that the UNTIL time is adjusted for STDOFF. (test_apia): Adjust FIXME now that UNTIL time is adusted for STDOFF. * testsuite/std/time/time_zone/get_info_sys.cc: Adjust expected results to account for corrected logic. * testsuite/std/time/zoned_time/1.cc: Likewise. Reviewed-by: Tomasz Kamiński <[email protected]> (cherry picked from commit cddf4111c4c4383f8d686ab822a9f3fc3ed6db44) Diff: --- libstdc++-v3/src/c++20/tzdb.cc | 15 +++++++++++---- .../testsuite/std/time/time_zone/116110.cc | 6 ++++-- .../testsuite/std/time/time_zone/get_info_sys.cc | 22 +++++++++++++--------- libstdc++-v3/testsuite/std/time/zoned_time/1.cc | 20 ++++++++++++-------- 4 files changed, 40 insertions(+), 23 deletions(-) diff --git a/libstdc++-v3/src/c++20/tzdb.cc b/libstdc++-v3/src/c++20/tzdb.cc index 5c54606a9761..367f056b12e1 100644 --- a/libstdc++-v3/src/c++20/tzdb.cc +++ b/libstdc++-v3/src/c++20/tzdb.cc @@ -2157,11 +2157,18 @@ namespace std::chrono at_time t{}; // XXX DAY should support ON format, e.g. lastSun or Sun>=8 in >> m >> d >> t; - // XXX UNTIL field should be interpreted - // "using the rules in effect just before the transition" - // so might need to store as year_month_day and hh_mm_ss and only - // convert to a sys_time once we know the offset in effect. inf.m_until = sys_days(year(y)/m.m/day(d)) + seconds(t.time); + if (t.indicator != at_time::Universal) + { // UNTIL uses "the rules in effect just before the transition" + // adjust by STDOFF + inf.m_until -= seconds(inf.m_offset); + if (t.indicator != at_time::Standard) + { + if (inf.m_expanded) // Not a named Rule, SAVE is known now. + inf.m_until -= inf.m_save; + // else Named Rule, SAVE is unknown. FIXME: PR 116110 + } + } } else inf.m_until = sys_days(year::max()/December/31); diff --git a/libstdc++-v3/testsuite/std/time/time_zone/116110.cc b/libstdc++-v3/testsuite/std/time/time_zone/116110.cc index d86011cf5739..0f3e09690e0e 100644 --- a/libstdc++-v3/testsuite/std/time/time_zone/116110.cc +++ b/libstdc++-v3/testsuite/std/time/time_zone/116110.cc @@ -39,7 +39,7 @@ test_kiritimati() auto* tz = locate_zone("Pacific/Kiritimati"); local_seconds t = local_days(1994y/December/31); - sys_seconds ut(t.time_since_epoch() /* FIXME: should be + 10h */); + sys_seconds ut(t.time_since_epoch() + 10h); sys_info info; info = tz->get_info(ut - 1s); VERIFY( info.offset == -10h ); @@ -65,7 +65,9 @@ test_apia() auto* tz = locate_zone("Pacific/Apia"); local_seconds t = local_days(2011y/December/29) + 24h; - sys_seconds ut(t.time_since_epoch() /* FIXME: should be + 10h */ - 24h ); + // FIXME: this should be + 10h but we do not account for DST yet, so + 11h. + // The 24h is because we don't parse the "24" in the Zone line (PR 124513). + sys_seconds ut(t.time_since_epoch() + 11h - 24h ); sys_info info; info = tz->get_info(ut - 1s); VERIFY( info.offset == (-11h + info.save) ); diff --git a/libstdc++-v3/testsuite/std/time/time_zone/get_info_sys.cc b/libstdc++-v3/testsuite/std/time/time_zone/get_info_sys.cc index 769c7744017b..88f16b76ff48 100644 --- a/libstdc++-v3/testsuite/std/time/time_zone/get_info_sys.cc +++ b/libstdc++-v3/testsuite/std/time/time_zone/get_info_sys.cc @@ -12,33 +12,37 @@ test_zurich() const time_zone* const tz = locate_zone("Europe/Zurich"); { - sys_days d = 1853y/July/16; + sys_days d = 1853y/July/16; // On this date ... + auto offset = 34min + 8s; // ... local time is this far ahead of UTC, + auto t = d - offset; // so LMT to BMT transition is at this time. - auto info = tz->get_info(d - 1s); - VERIFY( info.offset == (34min + 8s) ); + auto info = tz->get_info(t - 1s); + VERIFY( info.offset == offset ); VERIFY( info.abbrev == "LMT" ); - info = tz->get_info(d); + info = tz->get_info(t); VERIFY( info.offset == (29min + 46s) ); VERIFY( info.abbrev == "BMT" ); - info = tz->get_info(d + 1s); + info = tz->get_info(t + 1s); VERIFY( info.offset == (29min + 46s) ); VERIFY( info.abbrev == "BMT" ); - info = tz->get_info(d + 0.001s); + info = tz->get_info(t + 0.001s); VERIFY( info.offset == (29min + 46s) ); VERIFY( info.abbrev == "BMT" ); } { sys_days d = 1894y/June/1; + auto offset = 29min + 46s; + auto t = d - offset; - auto info = tz->get_info(d - 1s); - VERIFY( info.offset == (29min + 46s) ); + auto info = tz->get_info(t - 1s); + VERIFY( info.offset == offset ); VERIFY( info.abbrev == "BMT" ); - info = tz->get_info(d); + info = tz->get_info(t); VERIFY( info.offset == 1h ); VERIFY( info.abbrev == "CET" ); } diff --git a/libstdc++-v3/testsuite/std/time/zoned_time/1.cc b/libstdc++-v3/testsuite/std/time/zoned_time/1.cc index 1623aca1c7a8..a77cd99dd550 100644 --- a/libstdc++-v3/testsuite/std/time/zoned_time/1.cc +++ b/libstdc++-v3/testsuite/std/time/zoned_time/1.cc @@ -48,24 +48,26 @@ test_zurich() const time_zone* const zurich = locate_zone("Europe/Zurich"); { - sys_days d = 1853y/July/16; + sys_days d = 1853y/July/16; // On this date ... + auto offset = 34min + 8s; // ... local time is this far ahead of UTC, + auto t = d - offset; // so LMT to BMT transition is at this time. - auto z = zoned_seconds(zurich, sys_seconds(d) - 1s); + auto z = zoned_seconds(zurich, t - 1s); auto info = z.get_info(); - VERIFY( info.offset == (34min + 8s) ); + VERIFY( info.offset == offset ); VERIFY( info.abbrev == "LMT" ); - z = zoned_seconds(zurich, d); + z = zoned_seconds(zurich, t); info = z.get_info(); VERIFY( info.offset == (29min + 46s) ); VERIFY( info.abbrev == "BMT" ); - z = zoned_seconds(zurich, d + 1s); + z = zoned_seconds(zurich, t + 1s); info = z.get_info(); VERIFY( info.offset == (29min + 46s) ); VERIFY( info.abbrev == "BMT" ); - auto z2 = zoned_time(zurich, d + 0.001s); + auto z2 = zoned_time(zurich, t + 0.001s); info = z2.get_info(); VERIFY( info.offset == (29min + 46s) ); VERIFY( info.abbrev == "BMT" ); @@ -73,13 +75,15 @@ test_zurich() { sys_days d = 1894y/June/1; + auto offset = 29min + 46s; + auto t = d - offset; - auto z = zoned_seconds(zurich, sys_seconds(d) - 1s); + auto z = zoned_seconds(zurich, t - 1s); auto info = z.get_info(); VERIFY( info.offset == (29min + 46s) ); VERIFY( info.abbrev == "BMT" ); - z = zoned_seconds(zurich, d); + z = zoned_seconds(zurich, t); info = z.get_info(); VERIFY( info.offset == 1h ); VERIFY( info.abbrev == "CET" );
