https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114279
--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: 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.
