https://gcc.gnu.org/g:f4a52c184d608325c14338b57f464f7d0bbc7526
commit r14-9405-gf4a52c184d608325c14338b57f464f7d0bbc7526 Author: Jonathan Wakely <jwak...@redhat.com> Date: Fri Mar 8 14:41:47 2024 +0000 libstdc++: Fix parsing of leap seconds as chrono::utc_time [PR114279] Implementing all chrono::from_stream overloads in terms of chrono::sys_time meant that a leap second time like 23:59:60.001 cannot be parsed, because that cannot be represented in a sys_time. The fix to support parsing leap seconds as utc_time is to convert the parsed date to utc_time<days> and then add the parsed time to that, which allows the result to land in a leap second, rather than doing all the arithmetic with sys_time which doesn't have leap seconds. For local_time we also allow %S to parse a 60s value, because doing otherwise might disallow some valid uses. We can't know all use cases users have for treating times as local_time. For all other clocks, we can reject times that have 60 or 60.nnn as the seconds part, because that cannot occur in a valid UNIX, GPS, or TAI time. Since our chrono::file_clock uses sys_time, it can't occur for that clock either. In order to support this a new _M_is_leap_second member is needed in the _Parser type. This can be added at the end, where most targets currently have padding bytes. Similar to what I did recently for formatter _Spec structs, we can also reserve additional padding bits for future expansion. This also fixes bugs in the from_stream overloads for utc_time, tai_time, gps_time, and file_time, which were not using time_point_cast to explicitly convert to the result type. That's needed because the result type might have lower precision than the value returned from from_sys or from_utc, which has a precision no lower than seconds. libstdc++-v3/ChangeLog: PR libstdc++/114279 * include/bits/chrono_io.h (_Parser::_M_is_leap_second): New data member. (_Parser::_M_reserved): Reserve padding bits for future use. (_Parser::operator()): Set _M_is_leap_second if %S reads 60s. (from_stream): Only allow _M_is_leap_second for utc_time and local_time. Adjust arithmetic for utc_time so that leap seconds are preserved. Use time_point_cast to convert to a possibly lower-precision result type. * testsuite/std/time/parse.cc: Move to ... * testsuite/std/time/parse/parse.cc: ... here. * testsuite/std/time/parse/114279.cc: New test. Diff: --- libstdc++-v3/include/bits/chrono_io.h | 74 ++++++++++++++++++---- libstdc++-v3/testsuite/std/time/parse/114279.cc | 53 ++++++++++++++++ .../testsuite/std/time/{ => parse}/parse.cc | 0 3 files changed, 115 insertions(+), 12 deletions(-) diff --git a/libstdc++-v3/include/bits/chrono_io.h b/libstdc++-v3/include/bits/chrono_io.h index 412e8b83fb7..eaa36b8a074 100644 --- a/libstdc++-v3/include/bits/chrono_io.h +++ b/libstdc++-v3/include/bits/chrono_io.h @@ -2164,6 +2164,8 @@ namespace __detail year_month_day _M_ymd{}; weekday _M_wd{}; __format::_ChronoParts _M_need; + unsigned _M_is_leap_second : 1 {}; + unsigned _M_reserved : 15 {}; template<typename _CharT, typename _Traits, typename _Alloc> basic_istream<_CharT, _Traits>& @@ -2742,8 +2744,13 @@ namespace __detail __detail::_Parser_t<_Duration> __p(__need); if (__p(__is, __fmt, __abbrev, __offset)) { - auto __st = __p._M_sys_days + __p._M_time - *__offset; - __tp = chrono::time_point_cast<_Duration>(__st); + if (__p._M_is_leap_second) + __is.setstate(ios_base::failbit); + else + { + auto __st = __p._M_sys_days + __p._M_time - *__offset; + __tp = chrono::time_point_cast<_Duration>(__st); + } } return __is; } @@ -2765,9 +2772,21 @@ namespace __detail basic_string<_CharT, _Traits, _Alloc>* __abbrev = nullptr, minutes* __offset = nullptr) { - sys_time<_Duration> __st; - if (chrono::from_stream(__is, __fmt, __st, __abbrev, __offset)) - __tp = utc_clock::from_sys(__st); + minutes __off{}; + if (!__offset) + __offset = &__off; + using __format::_ChronoParts; + auto __need = _ChronoParts::_Year | _ChronoParts::_Month + | _ChronoParts::_Day | _ChronoParts::_TimeOfDay; + __detail::_Parser_t<_Duration> __p(__need); + if (__p(__is, __fmt, __abbrev, __offset)) + { + // Converting to utc_time before adding _M_time is necessary for + // "23:59:60" to correctly produce a time within a leap second. + auto __ut = utc_clock::from_sys(__p._M_sys_days) + __p._M_time + - *__offset; + __tp = chrono::time_point_cast<_Duration>(__ut); + } return __is; } @@ -2788,9 +2807,24 @@ namespace __detail basic_string<_CharT, _Traits, _Alloc>* __abbrev = nullptr, minutes* __offset = nullptr) { - utc_time<_Duration> __ut; - if (chrono::from_stream(__is, __fmt, __ut, __abbrev, __offset)) - __tp = tai_clock::from_utc(__ut); + minutes __off{}; + if (!__offset) + __offset = &__off; + using __format::_ChronoParts; + auto __need = _ChronoParts::_Year | _ChronoParts::_Month + | _ChronoParts::_Day | _ChronoParts::_TimeOfDay; + __detail::_Parser_t<_Duration> __p(__need); + if (__p(__is, __fmt, __abbrev, __offset)) + { + if (__p._M_is_leap_second) + __is.setstate(ios_base::failbit); + else + { + auto __st = __p._M_sys_days + __p._M_time - *__offset; + auto __tt = tai_clock::from_utc(utc_clock::from_sys(__st)); + __tp = chrono::time_point_cast<_Duration>(__tt); + } + } return __is; } @@ -2811,9 +2845,24 @@ namespace __detail basic_string<_CharT, _Traits, _Alloc>* __abbrev = nullptr, minutes* __offset = nullptr) { - utc_time<_Duration> __ut; - if (chrono::from_stream(__is, __fmt, __ut, __abbrev, __offset)) - __tp = gps_clock::from_utc(__ut); + minutes __off{}; + if (!__offset) + __offset = &__off; + using __format::_ChronoParts; + auto __need = _ChronoParts::_Year | _ChronoParts::_Month + | _ChronoParts::_Day | _ChronoParts::_TimeOfDay; + __detail::_Parser_t<_Duration> __p(__need); + if (__p(__is, __fmt, __abbrev, __offset)) + { + if (__p._M_is_leap_second) + __is.setstate(ios_base::failbit); + else + { + auto __st = __p._M_sys_days + __p._M_time - *__offset; + auto __tt = gps_clock::from_utc(utc_clock::from_sys(__st)); + __tp = chrono::time_point_cast<_Duration>(__tt); + } + } return __is; } @@ -2836,7 +2885,7 @@ namespace __detail { sys_time<_Duration> __st; if (chrono::from_stream(__is, __fmt, __st, __abbrev, __offset)) - __tp = file_clock::from_sys(__st); + __tp = chrono::time_point_cast<_Duration>(file_clock::from_sys(__st)); return __is; } @@ -4209,6 +4258,7 @@ namespace __detail { __ok = true; __t += __s; + _M_is_leap_second = __s >= seconds(60); } if (__ok) diff --git a/libstdc++-v3/testsuite/std/time/parse/114279.cc b/libstdc++-v3/testsuite/std/time/parse/114279.cc new file mode 100644 index 00000000000..67e5cba23bd --- /dev/null +++ b/libstdc++-v3/testsuite/std/time/parse/114279.cc @@ -0,0 +1,53 @@ +// { dg-do run { target c++20 } } + +#include <chrono> +#include <sstream> +#include <testsuite_hooks.h> + +template<class Clock> +void +test_leap_second_parsing() +{ + std::chrono::time_point<Clock, std::chrono::milliseconds> tp, tp2; + + std::istringstream ss("20161231-23:59:60.05"); + ss >> std::chrono::parse("%Y%m%d-%T", tp); + + if constexpr (std::is_same_v<Clock, std::chrono::local_t>) + VERIFY( ss ); // We allow parsing "23:59:60" as local_time. + else + { + if constexpr (std::is_same_v<Clock, std::chrono::utc_clock>) + { + // Entire input was consumed. + VERIFY( ss ); + VERIFY( ss.eof() ); + // The parsed value is the leap second inserted on Jan 1 2017. + VERIFY( std::chrono::get_leap_second_info(tp).is_leap_second ); + } + else + VERIFY( !ss ); // Other clocks do not allow "HH:MM:60" + + ss.clear(); + ss.str("20161231-22:59:60.05 -0100"); // Same time at -1h offset. + ss >> std::chrono::parse("%Y%m%d-%T %z", tp2); + + if constexpr (std::is_same_v<Clock, std::chrono::utc_clock>) + { + VERIFY( ss ); + VERIFY( tp2 == tp ); + } + else + VERIFY( !ss ); + } +} + +int main() +{ + test_leap_second_parsing<std::chrono::system_clock>(); + test_leap_second_parsing<std::chrono::utc_clock>(); + test_leap_second_parsing<std::chrono::tai_clock>(); + test_leap_second_parsing<std::chrono::gps_clock>(); + test_leap_second_parsing<std::chrono::file_clock>(); + test_leap_second_parsing<std::chrono::local_t>(); +} diff --git a/libstdc++-v3/testsuite/std/time/parse.cc b/libstdc++-v3/testsuite/std/time/parse/parse.cc similarity index 100% rename from libstdc++-v3/testsuite/std/time/parse.cc rename to libstdc++-v3/testsuite/std/time/parse/parse.cc