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fix: improper use of ucal_inDaylightTime #6097

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fix: improper use of ucal_inDaylightTime #6097

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f8d207b
fix: improper use of ucal_inDaylightTime
daksh-goyal Feb 21, 2026
851bdb6
fix: dropped lingering bad references and removed dead code
daksh-goyal Feb 22, 2026
4e26d2b
test: implement tests for historical DST abolition offsets
daksh-goyal Feb 22, 2026
97426cc
fix: code formatting
daksh-goyal Feb 22, 2026
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16 changes: 2 additions & 14 deletions stl/src/tzdb.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,6 @@ namespace {
_STD atomic<decltype(&::ucal_getTimeZoneDisplayName)> _Pfn_ucal_getTimeZoneDisplayName{nullptr};
_STD atomic<decltype(&::ucal_getTimeZoneTransitionDate)> _Pfn_ucal_getTimeZoneTransitionDate{nullptr};
_STD atomic<decltype(&::ucal_getTZDataVersion)> _Pfn_ucal_getTZDataVersion{nullptr};
_STD atomic<decltype(&::ucal_inDaylightTime)> _Pfn_ucal_inDaylightTime{nullptr};
_STD atomic<decltype(&::ucal_open)> _Pfn_ucal_open{nullptr};
_STD atomic<decltype(&::ucal_openTimeZoneIDEnumeration)> _Pfn_ucal_openTimeZoneIDEnumeration{nullptr};
_STD atomic<decltype(&::ucal_setMillis)> _Pfn_ucal_setMillis{nullptr};
Expand Down Expand Up @@ -78,7 +77,6 @@ namespace {
_Load_address(_Icu_module, _Icu_functions._Pfn_ucal_getTimeZoneTransitionDate,
"ucal_getTimeZoneTransitionDate", _Last_error);
_Load_address(_Icu_module, _Icu_functions._Pfn_ucal_getTZDataVersion, "ucal_getTZDataVersion", _Last_error);
_Load_address(_Icu_module, _Icu_functions._Pfn_ucal_inDaylightTime, "ucal_inDaylightTime", _Last_error);
_Load_address(_Icu_module, _Icu_functions._Pfn_ucal_open, "ucal_open", _Last_error);
_Load_address(_Icu_module, _Icu_functions._Pfn_ucal_openTimeZoneIDEnumeration,
"ucal_openTimeZoneIDEnumeration", _Last_error);
Expand Down Expand Up @@ -146,11 +144,6 @@ namespace {
return _Fun(status);
}

[[nodiscard]] UBool __icu_ucal_inDaylightTime(const UCalendar* cal, UErrorCode* status) noexcept {
const auto _Fun = _Icu_functions._Pfn_ucal_inDaylightTime.load(_STD memory_order_relaxed);
return _Fun(cal, status);
}

[[nodiscard]] UCalendar* __icu_ucal_open(
const UChar* zoneID, int32_t len, const char* locale, UCalendarType type, UErrorCode* status) noexcept {
const auto _Fun = _Icu_functions._Pfn_ucal_open.load(_STD memory_order_relaxed);
Expand Down Expand Up @@ -519,12 +512,7 @@ void __stdcall __std_tzdb_delete_current_zone(__std_tzdb_current_zone_info* cons
return _Report_error(_Info, __std_tzdb_error::_Icu_error);
}

const auto _Is_daylight = __icu_ucal_inDaylightTime(_Cal.get(), &_UErr);
if (U_FAILURE(_UErr)) {
return _Report_error(_Info, __std_tzdb_error::_Icu_error);
}

_Info->_Save = _Is_daylight ? __icu_ucal_get(_Cal.get(), UCalendarDateFields::UCAL_DST_OFFSET, &_UErr) : 0;
_Info->_Save = __icu_ucal_get(_Cal.get(), UCalendarDateFields::UCAL_DST_OFFSET, &_UErr);
if (U_FAILURE(_UErr)) {
return _Report_error(_Info, __std_tzdb_error::_Icu_error);
}
Expand Down Expand Up @@ -560,7 +548,7 @@ void __stdcall __std_tzdb_delete_current_zone(__std_tzdb_current_zone_info* cons
}

int32_t _Abbrev_len{};
const auto _Abbrev = _Get_timezone_short_id(_Cal.get(), _Is_daylight, _Abbrev_len, _Info->_Err);
const auto _Abbrev = _Get_timezone_short_id(_Cal.get(), _Info->_Save != 0, _Abbrev_len, _Info->_Err);
if (_Abbrev == nullptr) {
return _Propagate_error(_Info);
}
Expand Down
26 changes: 26 additions & 0 deletions tests/std/tests/P0355R7_calendars_and_time_zones_time_zones/test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -402,6 +402,31 @@ void timezone_sorted_vectors_test() {
assert(ranges::is_sorted(my_tzdb.leap_seconds));
}

void timezone_historical_dst_abolished_test() {
// Regression test: timezones that abolished DST must still report
// correct historical offsets for dates when DST was active.
const auto& my_tzdb = get_tzdb();

{ // America/Sao_Paulo - abolished DST Feb 2019
auto tz = my_tzdb.locate_zone("America/Sao_Paulo");
auto info = tz->get_info(sys_days{year{2019} / January / day{1}});
assert(info.offset == seconds{-7200});
assert(info.save == minutes{60});
}
{ // Europe/Istanbul - abolished DST Sep 2016
auto tz = my_tzdb.locate_zone("Europe/Istanbul");
auto info = tz->get_info(sys_days{year{2016} / July / day{1}});
assert(info.offset == seconds{10800});
assert(info.save == minutes{60});
}
{ // Europe/Moscow - abolished DST Oct 2014
auto tz = my_tzdb.locate_zone("Europe/Moscow");
auto info = tz->get_info(sys_days{year{2010} / July / day{1}});
assert(info.offset == seconds{14400});
assert(info.save == minutes{60});
}
}

void test() {
timezone_tzdb_list_test();
timezone_version_test();
Expand All @@ -411,6 +436,7 @@ void test() {
timezone_local_info_test();
timezone_precision_test();
timezone_sorted_vectors_test();
timezone_historical_dst_abolished_test();
}

int main() {
Expand Down