[PATCH] libstdc++: Implement std::chrono::current_zone() for Windows
Björn Schäpers
gcc@hazardy.de
Wed Jul 9 19:21:07 GMT 2025
Am 09.07.2025 um 16:16 schrieb Jonathan Wakely:
> On Wed, 9 Jul 2025 at 15:13, Jonathan Wakely <jwakely@redhat.com> wrote:
>>
>> On Tue, 8 Jul 2025 at 21:47, Björn Schäpers <gcc@hazardy.de> wrote:
>>>
>>> From: Björn Schäpers <bjoern@hazardy.de>
>>>
>>> I have based this on my previous (not yet landed) patch, but it only
>>> reuses the #ifdef to include <array>. Since std::array isn't used
>>> anywhere else I thought that was the right place to put it.
>>>
>>> I hope the formatting is okay.
>>>
>>> I've used wide strings for the Windows zone name and territory, since
>>> the Windows API returns wide strings and thus they can be compared
>>> directly. For the territory there exists a narrow string API, but
>>> internally it calls the wide string version and narrows it down. If
>>> desired I can switch to narrow strings, the conversion can be done by
>>> static_cast per character since only ASCII chars are used.
>>
>> Working with wide strings seems fine, that's the native format.
>>
>> I think the generated header should be written to src/c++20/ directory
>> though, since it doesn't need to be installed alongside the public
>> headers and doesn't need to be included by anything except tzdb.cc.
>> That would mean you can just do #include "windows_zones-map.h" in tzdb.cc
>>
Will do.
>>>
>>> -- >8 --
>>> On Windows there is no API to get the current time zone as IANA name,
>>> instead Windows has its own zones. But there exists a mapping provided
>>> by the Unicode Consortium. This patch adds a script to convert the XML
>>> file with the mapping to a lookup table and adds a Windows code path to
>>> use that mapping.
>>>
>>> libstdc++-v3/Changelog:
>>>
>>> Implement std::chrono::current_zone() for Windows
>>>
>>> * include/bits/windows_zones-map.h: New file, contains the look
>>> up table.
>>> * scripts/gen_windows_zones_map.py: New file, generates
>>> windows_zones-map.h.
>>> * src/c++20/tzdb.cc (tzdb::current_zone): Add Windows code path.
>>>
>>> Signed-off-by: Björn Schäpers <bjoern@hazardy.de>
>>> ---
>>> libstdc++-v3/include/bits/windows_zones-map.h | 407 ++++++++++++++++++
>>> libstdc++-v3/scripts/gen_windows_zones_map.py | 128 ++++++
>>> libstdc++-v3/src/c++20/tzdb.cc | 102 ++++-
>>> 3 files changed, 635 insertions(+), 2 deletions(-)
>>> create mode 100644 libstdc++-v3/include/bits/windows_zones-map.h
>>> create mode 100644 libstdc++-v3/scripts/gen_windows_zones_map.py
>>>
>>> diff --git a/libstdc++-v3/include/bits/windows_zones-map.h b/libstdc++-v3/include/bits/windows_zones-map.h
>>> new file mode 100644
>>> index 00000000000..7be736b063d
>>> --- /dev/null
>>> +++ b/libstdc++-v3/include/bits/windows_zones-map.h
>>> @@ -0,0 +1,407 @@
>>> +// Generated by scripts/gen_windows_zones_map.py, do not edit.
>>> +
>>> +// Copyright The GNU Toolchain Authors.
>>> +//
>>> +// This file is part of the GNU ISO C++ Library. This library is free
>>> +// software; you can redistribute it and/or modify it under the
>>> +// terms of the GNU General Public License as published by the
>>> +// Free Software Foundation; either version 3, or (at your option)
>>> +// any later version.
>>> +
>>> +// This library is distributed in the hope that it will be useful,
>>> +// but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>>> +// GNU General Public License for more details.
>>> +
>>> +// Under Section 7 of GPL version 3, you are granted additional
>>> +// permissions described in the GCC Runtime Library Exception, version
>>> +// 3.1, as published by the Free Software Foundation.
>>> +
>>> +// You should have received a copy of the GNU General Public License and
>>> +// a copy of the GCC Runtime Library Exception along with this program;
>>> +// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
>>> +// <http://www.gnu.org/licenses/>.
>>> +
>>> +/** @file bits/windows_zones-map.h
>>> + * This is an internal header file, included by other library headers.
>>> + * Do not attempt to use it directly. @headername{chrono}
>>> + */
>>> +
>>> +#ifndef _GLIBCXX_GET_WINDOWS_ZONES_MAP
>>> +# error "This is not a public header, do not include it directly"
>>> +#endif
>>> +
>>> +struct windows_zone_map_entry
>>> +{
>>> + wstring_view windows_name;
>>> + wstring_view territory;
>>> + string_view iana_name;
>>> +};
>>> +
>>> +static constexpr array<windows_zone_map_entry, 361> windows_zone_map{
>>> + {
>>> + {L"AUS Central Standard Time", L"001", "Australia/Darwin"},
>>> + {L"AUS Eastern Standard Time", L"001", "Australia/Sydney"},
>>> + {L"Afghanistan Standard Time", L"001", "Asia/Kabul"},
>>> + {L"Alaskan Standard Time", L"001", "America/Anchorage"},
>>> + {L"Aleutian Standard Time", L"001", "America/Adak"},
>>> + {L"Altai Standard Time", L"001", "Asia/Barnaul"},
>>> + {L"Arab Standard Time", L"001", "Asia/Riyadh"},
>>> + {L"Arab Standard Time", L"BH", "Asia/Bahrain"},
>>> + {L"Arab Standard Time", L"KW", "Asia/Kuwait"},
>>> + {L"Arab Standard Time", L"QA", "Asia/Qatar"},
>>> + {L"Arab Standard Time", L"YE", "Asia/Aden"},
>>> + {L"Arabian Standard Time", L"001", "Asia/Dubai"},
>>> + {L"Arabian Standard Time", L"OM", "Asia/Muscat"},
>>> + {L"Arabian Standard Time", L"ZZ", "Etc/GMT-4"},
>>> + {L"Arabic Standard Time", L"001", "Asia/Baghdad"},
>>> + {L"Argentina Standard Time", L"001", "America/Buenos_Aires"},
>>> + {L"Astrakhan Standard Time", L"001", "Europe/Astrakhan"},
>>> + {L"Atlantic Standard Time", L"001", "America/Halifax"},
>>> + {L"Atlantic Standard Time", L"BM", "Atlantic/Bermuda"},
>>> + {L"Atlantic Standard Time", L"GL", "America/Thule"},
>>> + {L"Aus Central W. Standard Time", L"001", "Australia/Eucla"},
>>> + {L"Azerbaijan Standard Time", L"001", "Asia/Baku"},
>>> + {L"Azores Standard Time", L"001", "Atlantic/Azores"},
>>> + {L"Azores Standard Time", L"GL", "America/Scoresbysund"},
>>> + {L"Bahia Standard Time", L"001", "America/Bahia"},
>>> + {L"Bangladesh Standard Time", L"001", "Asia/Dhaka"},
>>> + {L"Bangladesh Standard Time", L"BT", "Asia/Thimphu"},
>>> + {L"Belarus Standard Time", L"001", "Europe/Minsk"},
>>> + {L"Bougainville Standard Time", L"001", "Pacific/Bougainville"},
>>> + {L"Canada Central Standard Time", L"001", "America/Regina"},
>>> + {L"Cape Verde Standard Time", L"001", "Atlantic/Cape_Verde"},
>>> + {L"Cape Verde Standard Time", L"ZZ", "Etc/GMT+1"},
>>> + {L"Caucasus Standard Time", L"001", "Asia/Yerevan"},
>>> + {L"Cen. Australia Standard Time", L"001", "Australia/Adelaide"},
>>> + {L"Central America Standard Time", L"001", "America/Guatemala"},
>>> + {L"Central America Standard Time", L"BZ", "America/Belize"},
>>> + {L"Central America Standard Time", L"CR", "America/Costa_Rica"},
>>> + {L"Central America Standard Time", L"EC", "Pacific/Galapagos"},
>>> + {L"Central America Standard Time", L"HN", "America/Tegucigalpa"},
>>> + {L"Central America Standard Time", L"NI", "America/Managua"},
>>> + {L"Central America Standard Time", L"SV", "America/El_Salvador"},
>>> + {L"Central America Standard Time", L"ZZ", "Etc/GMT+6"},
>>> + {L"Central Asia Standard Time", L"001", "Asia/Bishkek"},
>>> + {L"Central Asia Standard Time", L"AQ", "Antarctica/Vostok"},
>>> + {L"Central Asia Standard Time", L"CN", "Asia/Urumqi"},
>>> + {L"Central Asia Standard Time", L"IO", "Indian/Chagos"},
>>> + {L"Central Asia Standard Time", L"ZZ", "Etc/GMT-6"},
>>> + {L"Central Brazilian Standard Time", L"001", "America/Cuiaba"},
>>> + {L"Central Europe Standard Time", L"001", "Europe/Budapest"},
>>> + {L"Central Europe Standard Time", L"AL", "Europe/Tirane"},
>>> + {L"Central Europe Standard Time", L"CZ", "Europe/Prague"},
>>> + {L"Central Europe Standard Time", L"ME", "Europe/Podgorica"},
>>> + {L"Central Europe Standard Time", L"RS", "Europe/Belgrade"},
>>> + {L"Central Europe Standard Time", L"SI", "Europe/Ljubljana"},
>>> + {L"Central Europe Standard Time", L"SK", "Europe/Bratislava"},
>>> + {L"Central European Standard Time", L"001", "Europe/Warsaw"},
>>> + {L"Central European Standard Time", L"BA", "Europe/Sarajevo"},
>>> + {L"Central European Standard Time", L"HR", "Europe/Zagreb"},
>>> + {L"Central European Standard Time", L"MK", "Europe/Skopje"},
>>> + {L"Central Pacific Standard Time", L"001", "Pacific/Guadalcanal"},
>>> + {L"Central Pacific Standard Time", L"AQ", "Antarctica/Casey"},
>>> + {L"Central Pacific Standard Time", L"FM", "Pacific/Ponape"},
>>> + {L"Central Pacific Standard Time", L"NC", "Pacific/Noumea"},
>>> + {L"Central Pacific Standard Time", L"VU", "Pacific/Efate"},
>>> + {L"Central Pacific Standard Time", L"ZZ", "Etc/GMT-11"},
>>> + {L"Central Standard Time", L"001", "America/Chicago"},
>>> + {L"Central Standard Time", L"CA", "America/Winnipeg"},
>>> + {L"Central Standard Time", L"MX", "America/Matamoros"},
>>> + {L"Central Standard Time (Mexico)", L"001", "America/Mexico_City"},
>>> + {L"Chatham Islands Standard Time", L"001", "Pacific/Chatham"},
>>> + {L"China Standard Time", L"001", "Asia/Shanghai"},
>>> + {L"China Standard Time", L"HK", "Asia/Hong_Kong"},
>>> + {L"China Standard Time", L"MO", "Asia/Macau"},
>>> + {L"Cuba Standard Time", L"001", "America/Havana"},
>>> + {L"Dateline Standard Time", L"001", "Etc/GMT+12"},
>>> + {L"E. Africa Standard Time", L"001", "Africa/Nairobi"},
>>> + {L"E. Africa Standard Time", L"AQ", "Antarctica/Syowa"},
>>> + {L"E. Africa Standard Time", L"DJ", "Africa/Djibouti"},
>>> + {L"E. Africa Standard Time", L"ER", "Africa/Asmera"},
>>> + {L"E. Africa Standard Time", L"ET", "Africa/Addis_Ababa"},
>>> + {L"E. Africa Standard Time", L"KM", "Indian/Comoro"},
>>> + {L"E. Africa Standard Time", L"MG", "Indian/Antananarivo"},
>>> + {L"E. Africa Standard Time", L"SO", "Africa/Mogadishu"},
>>> + {L"E. Africa Standard Time", L"TZ", "Africa/Dar_es_Salaam"},
>>> + {L"E. Africa Standard Time", L"UG", "Africa/Kampala"},
>>> + {L"E. Africa Standard Time", L"YT", "Indian/Mayotte"},
>>> + {L"E. Africa Standard Time", L"ZZ", "Etc/GMT-3"},
>>> + {L"E. Australia Standard Time", L"001", "Australia/Brisbane"},
>>> + {L"E. Europe Standard Time", L"001", "Europe/Chisinau"},
>>> + {L"E. South America Standard Time", L"001", "America/Sao_Paulo"},
>>> + {L"Easter Island Standard Time", L"001", "Pacific/Easter"},
>>> + {L"Eastern Standard Time", L"001", "America/New_York"},
>>> + {L"Eastern Standard Time", L"BS", "America/Nassau"},
>>> + {L"Eastern Standard Time", L"CA", "America/Toronto"},
>>> + {L"Eastern Standard Time (Mexico)", L"001", "America/Cancun"},
>>> + {L"Egypt Standard Time", L"001", "Africa/Cairo"},
>>> + {L"Ekaterinburg Standard Time", L"001", "Asia/Yekaterinburg"},
>>> + {L"FLE Standard Time", L"001", "Europe/Kiev"},
>>> + {L"FLE Standard Time", L"AX", "Europe/Mariehamn"},
>>> + {L"FLE Standard Time", L"BG", "Europe/Sofia"},
>>> + {L"FLE Standard Time", L"EE", "Europe/Tallinn"},
>>> + {L"FLE Standard Time", L"FI", "Europe/Helsinki"},
>>> + {L"FLE Standard Time", L"LT", "Europe/Vilnius"},
>>> + {L"FLE Standard Time", L"LV", "Europe/Riga"},
>>> + {L"Fiji Standard Time", L"001", "Pacific/Fiji"},
>>> + {L"GMT Standard Time", L"001", "Europe/London"},
>>> + {L"GMT Standard Time", L"ES", "Atlantic/Canary"},
>>> + {L"GMT Standard Time", L"FO", "Atlantic/Faeroe"},
>>> + {L"GMT Standard Time", L"GG", "Europe/Guernsey"},
>>> + {L"GMT Standard Time", L"IE", "Europe/Dublin"},
>>> + {L"GMT Standard Time", L"IM", "Europe/Isle_of_Man"},
>>> + {L"GMT Standard Time", L"JE", "Europe/Jersey"},
>>> + {L"GMT Standard Time", L"PT", "Europe/Lisbon"},
>>> + {L"GTB Standard Time", L"001", "Europe/Bucharest"},
>>> + {L"GTB Standard Time", L"CY", "Asia/Nicosia"},
>>> + {L"GTB Standard Time", L"GR", "Europe/Athens"},
>>> + {L"Georgian Standard Time", L"001", "Asia/Tbilisi"},
>>> + {L"Greenland Standard Time", L"001", "America/Godthab"},
>>> + {L"Greenwich Standard Time", L"001", "Atlantic/Reykjavik"},
>>> + {L"Greenwich Standard Time", L"BF", "Africa/Ouagadougou"},
>>> + {L"Greenwich Standard Time", L"CI", "Africa/Abidjan"},
>>> + {L"Greenwich Standard Time", L"GH", "Africa/Accra"},
>>> + {L"Greenwich Standard Time", L"GL", "America/Danmarkshavn"},
>>> + {L"Greenwich Standard Time", L"GM", "Africa/Banjul"},
>>> + {L"Greenwich Standard Time", L"GN", "Africa/Conakry"},
>>> + {L"Greenwich Standard Time", L"GW", "Africa/Bissau"},
>>> + {L"Greenwich Standard Time", L"LR", "Africa/Monrovia"},
>>> + {L"Greenwich Standard Time", L"ML", "Africa/Bamako"},
>>> + {L"Greenwich Standard Time", L"MR", "Africa/Nouakchott"},
>>> + {L"Greenwich Standard Time", L"SH", "Atlantic/St_Helena"},
>>> + {L"Greenwich Standard Time", L"SL", "Africa/Freetown"},
>>> + {L"Greenwich Standard Time", L"SN", "Africa/Dakar"},
>>> + {L"Greenwich Standard Time", L"TG", "Africa/Lome"},
>>> + {L"Haiti Standard Time", L"001", "America/Port-au-Prince"},
>>> + {L"Hawaiian Standard Time", L"001", "Pacific/Honolulu"},
>>> + {L"Hawaiian Standard Time", L"CK", "Pacific/Rarotonga"},
>>> + {L"Hawaiian Standard Time", L"PF", "Pacific/Tahiti"},
>>> + {L"Hawaiian Standard Time", L"ZZ", "Etc/GMT+10"},
>>> + {L"India Standard Time", L"001", "Asia/Calcutta"},
>>> + {L"Iran Standard Time", L"001", "Asia/Tehran"},
>>> + {L"Israel Standard Time", L"001", "Asia/Jerusalem"},
>>> + {L"Jordan Standard Time", L"001", "Asia/Amman"},
>>> + {L"Kaliningrad Standard Time", L"001", "Europe/Kaliningrad"},
>>> + {L"Korea Standard Time", L"001", "Asia/Seoul"},
>>> + {L"Libya Standard Time", L"001", "Africa/Tripoli"},
>>> + {L"Line Islands Standard Time", L"001", "Pacific/Kiritimati"},
>>> + {L"Line Islands Standard Time", L"ZZ", "Etc/GMT-14"},
>>> + {L"Lord Howe Standard Time", L"001", "Australia/Lord_Howe"},
>>> + {L"Magadan Standard Time", L"001", "Asia/Magadan"},
>>> + {L"Magallanes Standard Time", L"001", "America/Punta_Arenas"},
>>> + {L"Marquesas Standard Time", L"001", "Pacific/Marquesas"},
>>> + {L"Mauritius Standard Time", L"001", "Indian/Mauritius"},
>>> + {L"Mauritius Standard Time", L"RE", "Indian/Reunion"},
>>> + {L"Mauritius Standard Time", L"SC", "Indian/Mahe"},
>>> + {L"Middle East Standard Time", L"001", "Asia/Beirut"},
>>> + {L"Montevideo Standard Time", L"001", "America/Montevideo"},
>>> + {L"Morocco Standard Time", L"001", "Africa/Casablanca"},
>>> + {L"Morocco Standard Time", L"EH", "Africa/El_Aaiun"},
>>> + {L"Mountain Standard Time", L"001", "America/Denver"},
>>> + {L"Mountain Standard Time", L"CA", "America/Edmonton"},
>>> + {L"Mountain Standard Time", L"MX", "America/Ciudad_Juarez"},
>>> + {L"Mountain Standard Time (Mexico)", L"001", "America/Mazatlan"},
>>> + {L"Myanmar Standard Time", L"001", "Asia/Rangoon"},
>>> + {L"Myanmar Standard Time", L"CC", "Indian/Cocos"},
>>> + {L"N. Central Asia Standard Time", L"001", "Asia/Novosibirsk"},
>>> + {L"Namibia Standard Time", L"001", "Africa/Windhoek"},
>>> + {L"Nepal Standard Time", L"001", "Asia/Katmandu"},
>>> + {L"New Zealand Standard Time", L"001", "Pacific/Auckland"},
>>> + {L"New Zealand Standard Time", L"AQ", "Antarctica/McMurdo"},
>>> + {L"Newfoundland Standard Time", L"001", "America/St_Johns"},
>>> + {L"Norfolk Standard Time", L"001", "Pacific/Norfolk"},
>>> + {L"North Asia East Standard Time", L"001", "Asia/Irkutsk"},
>>> + {L"North Asia Standard Time", L"001", "Asia/Krasnoyarsk"},
>>> + {L"North Korea Standard Time", L"001", "Asia/Pyongyang"},
>>> + {L"Omsk Standard Time", L"001", "Asia/Omsk"},
>>> + {L"Pacific SA Standard Time", L"001", "America/Santiago"},
>>> + {L"Pacific Standard Time", L"001", "America/Los_Angeles"},
>>> + {L"Pacific Standard Time", L"CA", "America/Vancouver"},
>>> + {L"Pacific Standard Time (Mexico)", L"001", "America/Tijuana"},
>>> + {L"Pakistan Standard Time", L"001", "Asia/Karachi"},
>>> + {L"Paraguay Standard Time", L"001", "America/Asuncion"},
>>> + {L"Qyzylorda Standard Time", L"001", "Asia/Qyzylorda"},
>>> + {L"Romance Standard Time", L"001", "Europe/Paris"},
>>> + {L"Romance Standard Time", L"BE", "Europe/Brussels"},
>>> + {L"Romance Standard Time", L"DK", "Europe/Copenhagen"},
>>> + {L"Romance Standard Time", L"ES", "Europe/Madrid"},
>>> + {L"Russia Time Zone 10", L"001", "Asia/Srednekolymsk"},
>>> + {L"Russia Time Zone 11", L"001", "Asia/Kamchatka"},
>>> + {L"Russia Time Zone 3", L"001", "Europe/Samara"},
>>> + {L"Russian Standard Time", L"001", "Europe/Moscow"},
>>> + {L"Russian Standard Time", L"UA", "Europe/Simferopol"},
>>> + {L"SA Eastern Standard Time", L"001", "America/Cayenne"},
>>> + {L"SA Eastern Standard Time", L"AQ", "Antarctica/Rothera"},
>>> + {L"SA Eastern Standard Time", L"BR", "America/Fortaleza"},
>>> + {L"SA Eastern Standard Time", L"FK", "Atlantic/Stanley"},
>>> + {L"SA Eastern Standard Time", L"SR", "America/Paramaribo"},
>>> + {L"SA Eastern Standard Time", L"ZZ", "Etc/GMT+3"},
>>> + {L"SA Pacific Standard Time", L"001", "America/Bogota"},
>>> + {L"SA Pacific Standard Time", L"BR", "America/Rio_Branco"},
>>> + {L"SA Pacific Standard Time", L"CA", "America/Coral_Harbour"},
>>> + {L"SA Pacific Standard Time", L"EC", "America/Guayaquil"},
>>> + {L"SA Pacific Standard Time", L"JM", "America/Jamaica"},
>>> + {L"SA Pacific Standard Time", L"KY", "America/Cayman"},
>>> + {L"SA Pacific Standard Time", L"PA", "America/Panama"},
>>> + {L"SA Pacific Standard Time", L"PE", "America/Lima"},
>>> + {L"SA Pacific Standard Time", L"ZZ", "Etc/GMT+5"},
>>> + {L"SA Western Standard Time", L"001", "America/La_Paz"},
>>> + {L"SA Western Standard Time", L"AG", "America/Antigua"},
>>> + {L"SA Western Standard Time", L"AI", "America/Anguilla"},
>>> + {L"SA Western Standard Time", L"AW", "America/Aruba"},
>>> + {L"SA Western Standard Time", L"BB", "America/Barbados"},
>>> + {L"SA Western Standard Time", L"BL", "America/St_Barthelemy"},
>>> + {L"SA Western Standard Time", L"BQ", "America/Kralendijk"},
>>> + {L"SA Western Standard Time", L"BR", "America/Manaus"},
>>> + {L"SA Western Standard Time", L"CA", "America/Blanc-Sablon"},
>>> + {L"SA Western Standard Time", L"CW", "America/Curacao"},
>>> + {L"SA Western Standard Time", L"DM", "America/Dominica"},
>>> + {L"SA Western Standard Time", L"DO", "America/Santo_Domingo"},
>>> + {L"SA Western Standard Time", L"GD", "America/Grenada"},
>>> + {L"SA Western Standard Time", L"GP", "America/Guadeloupe"},
>>> + {L"SA Western Standard Time", L"GY", "America/Guyana"},
>>> + {L"SA Western Standard Time", L"KN", "America/St_Kitts"},
>>> + {L"SA Western Standard Time", L"LC", "America/St_Lucia"},
>>> + {L"SA Western Standard Time", L"MF", "America/Marigot"},
>>> + {L"SA Western Standard Time", L"MQ", "America/Martinique"},
>>> + {L"SA Western Standard Time", L"MS", "America/Montserrat"},
>>> + {L"SA Western Standard Time", L"PR", "America/Puerto_Rico"},
>>> + {L"SA Western Standard Time", L"SX", "America/Lower_Princes"},
>>> + {L"SA Western Standard Time", L"TT", "America/Port_of_Spain"},
>>> + {L"SA Western Standard Time", L"VC", "America/St_Vincent"},
>>> + {L"SA Western Standard Time", L"VG", "America/Tortola"},
>>> + {L"SA Western Standard Time", L"VI", "America/St_Thomas"},
>>> + {L"SA Western Standard Time", L"ZZ", "Etc/GMT+4"},
>>> + {L"SE Asia Standard Time", L"001", "Asia/Bangkok"},
>>> + {L"SE Asia Standard Time", L"AQ", "Antarctica/Davis"},
>>> + {L"SE Asia Standard Time", L"CX", "Indian/Christmas"},
>>> + {L"SE Asia Standard Time", L"ID", "Asia/Jakarta"},
>>> + {L"SE Asia Standard Time", L"KH", "Asia/Phnom_Penh"},
>>> + {L"SE Asia Standard Time", L"LA", "Asia/Vientiane"},
>>> + {L"SE Asia Standard Time", L"VN", "Asia/Saigon"},
>>> + {L"SE Asia Standard Time", L"ZZ", "Etc/GMT-7"},
>>> + {L"Saint Pierre Standard Time", L"001", "America/Miquelon"},
>>> + {L"Sakhalin Standard Time", L"001", "Asia/Sakhalin"},
>>> + {L"Samoa Standard Time", L"001", "Pacific/Apia"},
>>> + {L"Sao Tome Standard Time", L"001", "Africa/Sao_Tome"},
>>> + {L"Saratov Standard Time", L"001", "Europe/Saratov"},
>>> + {L"Singapore Standard Time", L"001", "Asia/Singapore"},
>>> + {L"Singapore Standard Time", L"BN", "Asia/Brunei"},
>>> + {L"Singapore Standard Time", L"ID", "Asia/Makassar"},
>>> + {L"Singapore Standard Time", L"MY", "Asia/Kuala_Lumpur"},
>>> + {L"Singapore Standard Time", L"PH", "Asia/Manila"},
>>> + {L"Singapore Standard Time", L"ZZ", "Etc/GMT-8"},
>>> + {L"South Africa Standard Time", L"001", "Africa/Johannesburg"},
>>> + {L"South Africa Standard Time", L"BI", "Africa/Bujumbura"},
>>> + {L"South Africa Standard Time", L"BW", "Africa/Gaborone"},
>>> + {L"South Africa Standard Time", L"CD", "Africa/Lubumbashi"},
>>> + {L"South Africa Standard Time", L"LS", "Africa/Maseru"},
>>> + {L"South Africa Standard Time", L"MW", "Africa/Blantyre"},
>>> + {L"South Africa Standard Time", L"MZ", "Africa/Maputo"},
>>> + {L"South Africa Standard Time", L"RW", "Africa/Kigali"},
>>> + {L"South Africa Standard Time", L"SZ", "Africa/Mbabane"},
>>> + {L"South Africa Standard Time", L"ZM", "Africa/Lusaka"},
>>> + {L"South Africa Standard Time", L"ZW", "Africa/Harare"},
>>> + {L"South Africa Standard Time", L"ZZ", "Etc/GMT-2"},
>>> + {L"South Sudan Standard Time", L"001", "Africa/Juba"},
>>> + {L"Sri Lanka Standard Time", L"001", "Asia/Colombo"},
>>> + {L"Sudan Standard Time", L"001", "Africa/Khartoum"},
>>> + {L"Syria Standard Time", L"001", "Asia/Damascus"},
>>> + {L"Taipei Standard Time", L"001", "Asia/Taipei"},
>>> + {L"Tasmania Standard Time", L"001", "Australia/Hobart"},
>>> + {L"Tocantins Standard Time", L"001", "America/Araguaina"},
>>> + {L"Tokyo Standard Time", L"001", "Asia/Tokyo"},
>>> + {L"Tokyo Standard Time", L"ID", "Asia/Jayapura"},
>>> + {L"Tokyo Standard Time", L"PW", "Pacific/Palau"},
>>> + {L"Tokyo Standard Time", L"TL", "Asia/Dili"},
>>> + {L"Tokyo Standard Time", L"ZZ", "Etc/GMT-9"},
>>> + {L"Tomsk Standard Time", L"001", "Asia/Tomsk"},
>>> + {L"Tonga Standard Time", L"001", "Pacific/Tongatapu"},
>>> + {L"Transbaikal Standard Time", L"001", "Asia/Chita"},
>>> + {L"Turkey Standard Time", L"001", "Europe/Istanbul"},
>>> + {L"Turks And Caicos Standard Time", L"001", "America/Grand_Turk"},
>>> + {L"US Eastern Standard Time", L"001", "America/Indianapolis"},
>>> + {L"US Mountain Standard Time", L"001", "America/Phoenix"},
>>> + {L"US Mountain Standard Time", L"CA", "America/Creston"},
>>> + {L"US Mountain Standard Time", L"MX", "America/Hermosillo"},
>>> + {L"US Mountain Standard Time", L"ZZ", "Etc/GMT+7"},
>>> + {L"UTC", L"001", "Etc/UTC"},
>>> + {L"UTC+12", L"001", "Etc/GMT-12"},
>>> + {L"UTC+12", L"KI", "Pacific/Tarawa"},
>>> + {L"UTC+12", L"MH", "Pacific/Majuro"},
>>> + {L"UTC+12", L"NR", "Pacific/Nauru"},
>>> + {L"UTC+12", L"TV", "Pacific/Funafuti"},
>>> + {L"UTC+12", L"UM", "Pacific/Wake"},
>>> + {L"UTC+12", L"WF", "Pacific/Wallis"},
>>> + {L"UTC+13", L"001", "Etc/GMT-13"},
>>> + {L"UTC+13", L"KI", "Pacific/Enderbury"},
>>> + {L"UTC+13", L"TK", "Pacific/Fakaofo"},
>>> + {L"UTC-02", L"001", "Etc/GMT+2"},
>>> + {L"UTC-02", L"BR", "America/Noronha"},
>>> + {L"UTC-02", L"GS", "Atlantic/South_Georgia"},
>>> + {L"UTC-08", L"001", "Etc/GMT+8"},
>>> + {L"UTC-08", L"PN", "Pacific/Pitcairn"},
>>> + {L"UTC-09", L"001", "Etc/GMT+9"},
>>> + {L"UTC-09", L"PF", "Pacific/Gambier"},
>>> + {L"UTC-11", L"001", "Etc/GMT+11"},
>>> + {L"UTC-11", L"AS", "Pacific/Pago_Pago"},
>>> + {L"UTC-11", L"NU", "Pacific/Niue"},
>>> + {L"UTC-11", L"UM", "Pacific/Midway"},
>>> + {L"Ulaanbaatar Standard Time", L"001", "Asia/Ulaanbaatar"},
>>> + {L"Venezuela Standard Time", L"001", "America/Caracas"},
>>> + {L"Vladivostok Standard Time", L"001", "Asia/Vladivostok"},
>>> + {L"Volgograd Standard Time", L"001", "Europe/Volgograd"},
>>> + {L"W. Australia Standard Time", L"001", "Australia/Perth"},
>>> + {L"W. Central Africa Standard Time", L"001", "Africa/Lagos"},
>>> + {L"W. Central Africa Standard Time", L"AO", "Africa/Luanda"},
>>> + {L"W. Central Africa Standard Time", L"BJ", "Africa/Porto-Novo"},
>>> + {L"W. Central Africa Standard Time", L"CD", "Africa/Kinshasa"},
>>> + {L"W. Central Africa Standard Time", L"CF", "Africa/Bangui"},
>>> + {L"W. Central Africa Standard Time", L"CG", "Africa/Brazzaville"},
>>> + {L"W. Central Africa Standard Time", L"CM", "Africa/Douala"},
>>> + {L"W. Central Africa Standard Time", L"DZ", "Africa/Algiers"},
>>> + {L"W. Central Africa Standard Time", L"GA", "Africa/Libreville"},
>>> + {L"W. Central Africa Standard Time", L"GQ", "Africa/Malabo"},
>>> + {L"W. Central Africa Standard Time", L"NE", "Africa/Niamey"},
>>> + {L"W. Central Africa Standard Time", L"TD", "Africa/Ndjamena"},
>>> + {L"W. Central Africa Standard Time", L"TN", "Africa/Tunis"},
>>> + {L"W. Central Africa Standard Time", L"ZZ", "Etc/GMT-1"},
>>> + {L"W. Europe Standard Time", L"001", "Europe/Berlin"},
>>> + {L"W. Europe Standard Time", L"AD", "Europe/Andorra"},
>>> + {L"W. Europe Standard Time", L"AT", "Europe/Vienna"},
>>> + {L"W. Europe Standard Time", L"CH", "Europe/Zurich"},
>>> + {L"W. Europe Standard Time", L"GI", "Europe/Gibraltar"},
>>> + {L"W. Europe Standard Time", L"IT", "Europe/Rome"},
>>> + {L"W. Europe Standard Time", L"LI", "Europe/Vaduz"},
>>> + {L"W. Europe Standard Time", L"LU", "Europe/Luxembourg"},
>>> + {L"W. Europe Standard Time", L"MC", "Europe/Monaco"},
>>> + {L"W. Europe Standard Time", L"MT", "Europe/Malta"},
>>> + {L"W. Europe Standard Time", L"NL", "Europe/Amsterdam"},
>>> + {L"W. Europe Standard Time", L"NO", "Europe/Oslo"},
>>> + {L"W. Europe Standard Time", L"SE", "Europe/Stockholm"},
>>> + {L"W. Europe Standard Time", L"SJ", "Arctic/Longyearbyen"},
>>> + {L"W. Europe Standard Time", L"SM", "Europe/San_Marino"},
>>> + {L"W. Europe Standard Time", L"VA", "Europe/Vatican"},
>>> + {L"W. Mongolia Standard Time", L"001", "Asia/Hovd"},
>>> + {L"West Asia Standard Time", L"001", "Asia/Tashkent"},
>>> + {L"West Asia Standard Time", L"AQ", "Antarctica/Mawson"},
>>> + {L"West Asia Standard Time", L"KZ", "Asia/Oral"},
>>> + {L"West Asia Standard Time", L"MV", "Indian/Maldives"},
>>> + {L"West Asia Standard Time", L"TF", "Indian/Kerguelen"},
>>> + {L"West Asia Standard Time", L"TJ", "Asia/Dushanbe"},
>>> + {L"West Asia Standard Time", L"TM", "Asia/Ashgabat"},
>>> + {L"West Asia Standard Time", L"ZZ", "Etc/GMT-5"},
>>> + {L"West Bank Standard Time", L"001", "Asia/Hebron"},
>>> + {L"West Pacific Standard Time", L"001", "Pacific/Port_Moresby"},
>>> + {L"West Pacific Standard Time", L"AQ", "Antarctica/DumontDUrville"},
>>> + {L"West Pacific Standard Time", L"FM", "Pacific/Truk"},
>>> + {L"West Pacific Standard Time", L"GU", "Pacific/Guam"},
>>> + {L"West Pacific Standard Time", L"MP", "Pacific/Saipan"},
>>> + {L"West Pacific Standard Time", L"ZZ", "Etc/GMT-10"},
>>> + {L"Yakutsk Standard Time", L"001", "Asia/Yakutsk"},
>>> + {L"Yukon Standard Time", L"001", "America/Whitehorse"},
>>> + }
>>> +};
>>> +
>>> +#undef _GLIBCXX_GET_WINDOWS_ZONES_MAP
>>> diff --git a/libstdc++-v3/scripts/gen_windows_zones_map.py b/libstdc++-v3/scripts/gen_windows_zones_map.py
>>> new file mode 100644
>>> index 00000000000..9edfe457a5f
>>> --- /dev/null
>>> +++ b/libstdc++-v3/scripts/gen_windows_zones_map.py
>>> @@ -0,0 +1,128 @@
>>> +#!/usr/bin/env python3
>>> +#
>>> +# Script to generate the map for libstdc++ std::chrono::current_zone under Windows.
>>> +#
>>> +# This file is part of GCC.
>>> +#
>>> +# GCC is free software; you can redistribute it and/or modify it under
>>> +# the terms of the GNU General Public License as published by the Free
>>> +# Software Foundation; either version 3, or (at your option) any later
>>> +# version.
>>> +#
>>> +# GCC is distributed in the hope that it will be useful, but WITHOUT ANY
>>> +# WARRANTY; without even the implied warranty of MERCHANTABILITY or
>>> +# FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
>>> +# for more details.
>>> +#
>>> +# You should have received a copy of the GNU General Public License
>>> +# along with GCC; see the file COPYING3. If not see
>>> +# <http://www.gnu.org/licenses/>.
>>> +
>>> +# To update the Libstdc++ static data in <bits/windows_zones-map.h> download
>>> +# the latest:
>>> +# https://raw.githubusercontent.com/unicode-org/cldr/master/common/supplemental/windowsZones.xml
>>> +# Then run this script and save the output to
>>> +# include/bits/windows_zones-map.h
>>> +
>>> +import os
>>> +import sys
>>> +import xml.etree.ElementTree as et
>>> +
>>> +if len(sys.argv) != 2:
>>> + print("Usage: %s <windows zones xml>" % sys.argv[0], file=sys.stderr)
>>> + sys.exit(1)
>>> +
>>> +self = os.path.basename(__file__)
>>> +print("// Generated by scripts/{}, do not edit.".format(self))
>>> +print("""
>>> +// Copyright The GNU Toolchain Authors.
>>> +//
>>> +// This file is part of the GNU ISO C++ Library. This library is free
>>> +// software; you can redistribute it and/or modify it under the
>>> +// terms of the GNU General Public License as published by the
>>> +// Free Software Foundation; either version 3, or (at your option)
>>> +// any later version.
>>> +
>>> +// This library is distributed in the hope that it will be useful,
>>> +// but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>>> +// GNU General Public License for more details.
>>> +
>>> +// Under Section 7 of GPL version 3, you are granted additional
>>> +// permissions described in the GCC Runtime Library Exception, version
>>> +// 3.1, as published by the Free Software Foundation.
>>> +
>>> +// You should have received a copy of the GNU General Public License and
>>> +// a copy of the GCC Runtime Library Exception along with this program;
>>> +// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
>>> +// <http://www.gnu.org/licenses/>.
>>> +
>>> +/** @file bits/windows_zones-map.h
>>> + * This is an internal header file, included by other library headers.
>>> + * Do not attempt to use it directly. @headername{chrono}
>>> + */
>>> +""")
>>> +
>>> +print("#ifndef _GLIBCXX_GET_WINDOWS_ZONES_MAP")
>>> +print('# error "This is not a public header, do not include it directly"')
>>> +print("#endif\n")
>>> +
>>> +class WindowsZoneMapEntry:
>>> + def __init__(self, windows, territory, iana):
>>> + self.windows = windows
>>> + self.territory = territory
>>> + self.iana = iana
>>> +
>>> + def __lt__(self, other):
>>> + if self.windows < other.windows:
>>> + return True
>>> + if self.windows > other.windows:
>>> + return False
>>> + return self.territory < other.territory
>>> +
>>> +windows_zone_map = []
>>> +
>>> +tree = et.parse(sys.argv[1])
>>> +xml_zone_map = tree.getroot().find("windowsZones").find("mapTimezones")
>>> +
>>> +for entry in xml_zone_map.iter("mapZone"):
>>> + iana = entry.attrib["type"]
>>> + space = iana.find(" ")
>>> + if space != -1:
>>> + iana = iana[0:space]
>>> + windows_zone_map.append(WindowsZoneMapEntry(entry.attrib["other"], entry.attrib["territory"], iana))
>>> +
>>> +# Sort so we can use binary search on the array.
>>> +windows_zone_map.sort();
>>> +
>>> +# Skip territories which have the same IANA zone as 001, so we can reduce the data.
>>> +last_windows_zone = ""
>>> +for entry in windows_zone_map[:]:
>>> + if entry.windows != last_windows_zone:
>>> + if entry.territory != "001":
>>> + raise ValueError("Territory \"001\" not the first one, this breaks assumptions in tzdb.cc!")
>>> + last_windows_zone = entry.windows
>>> + fallback_iana = entry.iana
>>> + else:
>>> + if entry.iana == fallback_iana:
>>> + windows_zone_map.remove(entry)
>>> +
>>> +print("""struct windows_zone_map_entry
>>> +{{
>>> + wstring_view windows_name;
>>> + wstring_view territory;
>>> + string_view iana_name;
>>> +}};
>>> +
>>> +static constexpr array<windows_zone_map_entry, {}> windows_zone_map{{
>>> + {{""".format(len(windows_zone_map)))
>>> +
>>> +for entry in windows_zone_map:
>>> + print(' {{L"{}", L"{}", "{}"}},'.format(entry.windows, entry.territory, entry.iana))
>>> +
>>> +print(""" }
>>> +};""")
>>> +
>>> +# <chrono> gives an error if this macro is left defined.
>>> +# Do this last, so that the generated output is not usable unless we reach here.
>>> +print("\n#undef _GLIBCXX_GET_WINDOWS_ZONES_MAP")
>>> diff --git a/libstdc++-v3/src/c++20/tzdb.cc b/libstdc++-v3/src/c++20/tzdb.cc
>>> index 9923d14b7a7..bfbba077b92 100644
>>> --- a/libstdc++-v3/src/c++20/tzdb.cc
>>> +++ b/libstdc++-v3/src/c++20/tzdb.cc
>>> @@ -48,6 +48,8 @@
>>> # define WIN32_LEAN_AND_MEAN
>>> # include <windows.h>
>>> # include <psapi.h>
>>> +
>>> +# include <array>
>>> #endif
>>>
>>> #if defined __GTHREADS && ATOMIC_POINTER_LOCK_FREE == 2
>>> @@ -1768,6 +1770,98 @@ namespace std::chrono
>>>
>>> return nullptr; // not found
>>> }
>>> +
>>> +#ifdef _GLIBCXX_HAVE_WINDOWS_H
>>> + string_view
>>> + detect_windows_zone() noexcept
>>> + {
>>> + DYNAMIC_TIME_ZONE_INFORMATION information{};
>>> + if (GetDynamicTimeZoneInformation(&information) == TIME_ZONE_ID_INVALID)
>>> + return {};
>>> +
>>> + constexpr SYSTEMTIME all_zero_time{};
>>> + const wstring_view zone_name{ information.TimeZoneKeyName };
>>> + auto equal = [](const SYSTEMTIME &lhs, const SYSTEMTIME &rhs) noexcept
>>> + { return memcmp(&lhs, &rhs, sizeof(SYSTEMTIME)) == 0; };
>>> + // The logic is copied from icu, couldn't find the source.
>>> + // Detect if DST is disabled.
>>> + if (information.DynamicDaylightTimeDisabled
>>> + && equal(information.StandardDate, information.DaylightDate)
>>> + && ((!zone_name.empty()
>>> + && equal(information.StandardDate, all_zero_time))
>>> + || (zone_name.empty()
>>> + && !equal(information.StandardDate, all_zero_time))))
>>> + {
>>> + if (information.Bias == 0)
>>> + return "Etc/UTC";
>>> +
>>> + if (information.Bias % 60 != 0)
>>> + // If the offset is not in full hours, we can't do anything really.
>>> + return {};
>>> +
>>> + const auto raw_index = information.Bias / 60;
>>> +
>>> + // The bias added to the local time equals UTC. And GMT+X corrosponds
>>> + // to UTC-X, the sign is negated. Thus we can use the hourly bias as
>>> + // an index into an array.
>>> + if (raw_index < 0 && raw_index >= -14)
>>> + {
>>> + static array<string_view, 14> table{
>>> + "Etc/GMT-1", "Etc/GMT-2", "Etc/GMT-3", "Etc/GMT-4",
>>> + "Etc/GMT-5", "Etc/GMT-6", "Etc/GMT-7", "Etc/GMT-8",
>>> + "Etc/GMT-9", "Etc/GMT-10", "Etc/GMT-11", "Etc/GMT-12",
>>> + "Etc/GMT-13", "Etc/GMT-14"
>>> + };
>>> + return table[-raw_index - 1];
>>> + }
>>> + else if (raw_index > 0 && raw_index <= 12)
>>> + {
>>> + static array<string_view, 14> table{
>>> + "Etc/GMT+1", "Etc/GMT+2", "Etc/GMT+3", "Etc/GMT+4",
>>> + "Etc/GMT+5", "Etc/GMT+6", "Etc/GMT+7", "Etc/GMT+8",
>>> + "Etc/GMT+9", "Etc/GMT+10", "Etc/GMT+11", "Etc/GMT+12"
>>> + };
>>> + return table[raw_index - 1];
>>> + }
>>> + return {};
>>> + }
>>> +
>>> +#define _GLIBCXX_GET_WINDOWS_ZONES_MAP
>>> +#include <bits/windows_zones-map.h>
>>> +#ifdef _GLIBCXX_GET_WINDOWS_ZONES_MAP
>>> +# error "Invalid windows_zones map"
>>> +#endif
>>> +
>>> + const auto zone_range
>>> + = ranges::equal_range(windows_zone_map, zone_name, {},
>>> + &windows_zone_map_entry::windows_name);
>>> +
>>> + const auto size = ranges::size(zone_range);
>>> + if (size == 0)
>>> + // Unknown zone, we can't detect anything.
>>> + return {};
>>> +
>>> + if (size == 1)
>>> + // Some zones have only one territory, use the quick path.
>>> + return zone_range.front().iana_name;
>>> +
>>> + const auto geo_id = GetUserGeoID(GEOCLASS_NATION);
>>> + wstring territory;
>>> + territory.resize(2); // The terminating zero is always added on top.
>>> + if (GetGeoInfoW(geo_id, GEO_ISO2, territory.data(), 3, 0) == 0)
>>
>> I'm confused here. The buffer is 2 wchar_t values, but the cchData
>> argument is 3. The docs at
>> https://learn.microsoft.com/en-us/windows/win32/api/winnls/nf-winnls-getgeoinfoa
>> say that value should be "Size of the buffer indicated by lpGeoData.
>> The size is the number of bytes for the ANSI version of the function,
>> or the number of words for the Unicode version." I utterly despise
>> this idiotic convention in MS docs of saying "ANSI" to mean ... who
>> knows ... not something actually defined by any ANSI standard ... is
>> GetGeoInfoA the "ANSI" version and GetGeoInfoAW the "Unicode" version?
>> Why not call them that? Or narrow and wide? This has nothing to do
>> with ANSI.
>>
>> Either way, the buffer is two wchar_t so four bytes, but we tell
>> GetGeoInfoW there are three ... bytes? or "words"? Where "word" means
>> 16-bit value?!
>>
>> is the resize call supposed to be resize(3) ?
>> Ah, I think what the comment is saying is that resize(2) creates a
>> string with space for two wchar_t plus a null-terminator ... it wasn't
>> clear to me what "on top" meant.
>>
>> So we have a wstring buffer which can store three wchar_t including a
>> null, so the argument to GetGeoInfoW is 3. OK.
>>
>> But the map in the generated header includes wide strings with three
>> characters, e.g. L"001", can those entries never reach this code? Do
>> they always have zone_range.size() == 1? Or is there some other reason
>> they won't get here?
>
> Ah, GEO_ISO2 means you want a 2-letter country code, so it will never
> write L"001" to the buffer, and so GetGeoInfoW will fail, returning 0,
> and so we return the entry with territory L"001". So we don't need to
> match that string, it's our fallback.
All the territory codes in the mapping are the 2-letter country code, just "001"
for a general zone, this is as far as I understand never returned by GetGeoInfoW.
From the xml mapping to the generated header I remove those entries which have
the same IANA zone as "001" (e.g. DE for germany -> Europe/Berlin), to reduce
the size of the array. With the current version the number of entries goes from
500 to 361, which reduces the binary size and should speed up the equal_range a
bit. Also it enables for more Windows time zones the optimization of only one
territory and skipping the whole GetGeoInfoW step.
>>
>> And why use a wstring here at all, can't it just be an array?
>> wchar_t territory[3];
>>
>> The comparison iter->territory == territory will still work with
>> wchar_t[3] as the right operand, as long as it's null terminated.
Initially I assigned L"001" to the string to reach the fallback, that's why it
is a string. But yes, now I can just change that, will do.
>>
>>> + // Couldn't detect the territory, fallback to "001", which is the first
>>> + // entry.
>>> + return zone_range.front().iana_name;
>>> +
>>> + const auto iter = ranges::lower_bound(
>>> + zone_range, territory, {}, &windows_zone_map_entry::territory);
>>> + if (iter == zone_range.end() || iter->territory != territory)
>>> + // Territory not within the the map, use "001".
>>> + return zone_range.front().iana_name;
>>> +
>>> + return iter->iana_name;
>>> + }
>>> +#endif
>>> } // namespace
>>>
>>> // Implementation of std::chrono::tzdb::locate_zone(string_view).
>>> @@ -1790,7 +1884,7 @@ namespace std::chrono
>>> {
>>> // TODO cache this function's result?
>>>
>>> -#ifndef _AIX
>>> +#if !defined(_AIX) && !defined(_GLIBCXX_HAVE_WINDOWS_H)
>>> // Repeat the preprocessor condition used by filesystem::read_symlink,
>>> // to avoid a dependency on src/c++17/fs_ops.o if it won't work anyway.
>>> #if defined(_GLIBCXX_HAVE_READLINK) && defined(_GLIBCXX_HAVE_SYS_STAT_H)
>>> @@ -1847,7 +1941,11 @@ namespace std::chrono
>>> return tz;
>>> }
>>> }
>>> -#else
>>> +#elif defined(_GLIBCXX_HAVE_WINDOWS_H)
>>> + if (auto tz
>>> + = do_locate_zone(this->zones, this->links, detect_windows_zone()))
>>> + return tz;
>>> +#else // defined(_AIX)
>>> // AIX stores current zone in $TZ in /etc/environment but the value
>>> // is typically a POSIX time zone name, not IANA zone.
>>> // https://developer.ibm.com/articles/au-aix-posix/
>>> --
>>> 2.50.0
>>>
>
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