[Bug libstdc++/114240] sys_days not being parsed with only a date in the stream
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114240 Jonathan Wakely changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution|--- |FIXED Target Milestone|--- |14.0 --- Comment #8 from Jonathan Wakely --- This should be fixed now. Thanks for the report.
[Bug libstdc++/114240] sys_days not being parsed with only a date in the stream
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114240 --- Comment #7 from GCC Commits --- The master branch has been updated by Jonathan Wakely : https://gcc.gnu.org/g:3e8ee03edd018eed43444755f601cdb9d5931654 commit r14-9406-g3e8ee03edd018eed43444755f601cdb9d5931654 Author: Jonathan Wakely Date: Fri Mar 8 16:15:57 2024 + libstdc++: Do not require a time-of-day when parsing sys_days [PR114240] When parsing a std::chrono::sys_days (or a sys_time with an even longer period) we should not require a time-of-day to be present in the input, because we can't represent that in the result type anyway. Rather than trying to decide which specializations should require a time-of-date and which should not, follow the direction of Howard Hinnant's date library, which allows extracting a sys_time of any period from input that only contains a date, defaulting the time-of-day part to 00:00:00. This seems consistent with the intent of the standard, which says it's an error "If the parse fails to decode a valid date" (i.e., it doesn't care about decoding a valid time, only a date). libstdc++-v3/ChangeLog: PR libstdc++/114240 * include/bits/chrono_io.h (_Parser::operator()): Assume hours(0) for a time_point, so that a time is not required to be present. * testsuite/std/time/parse/114240.cc: New test.
[Bug libstdc++/114240] sys_days not being parsed with only a date in the stream
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114240 --- Comment #6 from Jonathan Wakely --- Actually the standard does support Howard's intended behaviour: "If the parse fails to decode a valid date, is.setstate(ios_base::failbit) is called and tp is not modified." It says "date", not "time point" or "UTC time" or anything like that.
[Bug libstdc++/114240] sys_days not being parsed with only a date in the stream
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114240 --- Comment #5 from Jonathan Wakely --- >using __format::_ChronoParts; >auto __need = _ChronoParts::_Year | _ChronoParts::_Month > - | _ChronoParts::_Day | _ChronoParts::_TimeOfDay; > + | _ChronoParts::_Day; > + if constexpr (ratio_less_v) > + __need |= _ChronoParts::_TimeOfDay; This condition's not right. If we have a period of days, but a floating-point rep, we probably do want to parse and use a time if one is present in the input. "2024-03-07 00:05" can be represented by sys_time> and is not the same time as "2024-03-07". And if we have a period like ratio then it's greater than days, but not using the time of day in the result will lose accuracy. I'm leaning towards Howard's approach of just assuming 00:00:00 if no time is present, rather than making it depend on the period in any way.
[Bug libstdc++/114240] sys_days not being parsed with only a date in the stream
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114240 --- Comment #4 from Jonathan Wakely --- This has revealed another bug in some of the from_stream overloads, due to Clock::from_sys / Clock::from_utc sometimes returning a higher precision value than the input argument (due to using the common_type with seconds).
[Bug libstdc++/114240] sys_days not being parsed with only a date in the stream
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114240
--- Comment #3 from Jonathan Wakely ---
So this would fix it:
--- a/libstdc++-v3/include/bits/chrono_io.h
+++ b/libstdc++-v3/include/bits/chrono_io.h
@@ -2826,7 +2826,9 @@ namespace __detail
__offset = &__off;
using __format::_ChronoParts;
auto __need = _ChronoParts::_Year | _ChronoParts::_Month
- | _ChronoParts::_Day | _ChronoParts::_TimeOfDay;
+ | _ChronoParts::_Day;
+ if constexpr (ratio_less_v)
+ __need |= _ChronoParts::_TimeOfDay;
__detail::_Parser_t<_Duration> __p(__need);
if (__p(__is, __fmt, __abbrev, __offset))
{
A similar fix is needed for the from_stream overload for local_time, but
utc_time, gps_time and tai_time will be fixed by changing the sys_time
overload.
[Bug libstdc++/114240] sys_days not being parsed with only a date in the stream
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114240 --- Comment #2 from Howard Hinnant --- In my date lib I just presumed 00:00:00 time of day when parsing time_points, unless the parse produced another time of day. Though I must admit that this didn't come through in the spec. So there is a little grey area here. We're going to hit the same issue for other timepoints as well: local_time, utc_time, etc.
[Bug libstdc++/114240] sys_days not being parsed with only a date in the stream
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114240
--- Comment #1 from Jonathan Wakely ---
I think the problem is that I just have some generic logic that assumes all
sys_time specializations are a date time, and so require both a date and a
time. But obviously for sys_days we only need a date.
template>
basic_istream<_CharT, _Traits>&
from_stream(basic_istream<_CharT, _Traits>& __is, const _CharT* __fmt,
sys_time<_Duration>& __tp,
basic_string<_CharT, _Traits, _Alloc>* __abbrev = nullptr,
minutes* __offset = nullptr)
{
minutes __off{};
if (!__offset)
__offset = &__off;
using __format::_ChronoParts;
auto __need = _ChronoParts::_Year | _ChronoParts::_Month
| _ChronoParts::_Day | _ChronoParts::_TimeOfDay;
This should depend on _Duration::period.
[Bug libstdc++/114240] sys_days not being parsed with only a date in the stream
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114240 Jonathan Wakely changed: What|Removed |Added Last reconfirmed||2024-03-05 Ever confirmed|0 |1 Status|UNCONFIRMED |ASSIGNED Assignee|unassigned at gcc dot gnu.org |redi at gcc dot gnu.org
