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<chrono>: fix year_month_day_last::day() #1663

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Merged
StephanTLavavej merged 4 commits into from
Feb 26, 2021
Merged

<chrono>: fix year_month_day_last::day() #1663

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b6418b8
fix year_month_day_last::day()
SuperWig Feb 19, 2021
4129294
fix test
SuperWig Feb 19, 2021
792f6dc
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SuperWig Feb 20, 2021
6311ac3
STL's feedback
SuperWig Feb 21, 2021
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7 changes: 4 additions & 3 deletions stl/inc/chrono
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Original file line number Diff line number Diff line change
Expand Up @@ -1331,15 +1331,16 @@ namespace chrono {
return *this;
}

inline constexpr day _Last_day_table[] = {
day{31}, day{28}, day{31}, day{30}, day{31}, day{30}, day{31}, day{31}, day{30}, day{31}, day{30}, day{31}};
// To prevent UB by going out of bounds, four extra days with an invalid day are added.
inline constexpr day _Last_day_table[] = {day{31}, day{28}, day{31}, day{30}, day{31}, day{30}, day{31}, day{31},
day{30}, day{31}, day{30}, day{31}, day{255}, day{255}, day{255}, day{255}};

_NODISCARD constexpr day _Last_day(const year& _Year, const month& _Month) {
if (_Month == month{2} && _Year.is_leap()) {
return day{29};
}

return _Last_day_table[static_cast<unsigned int>(_Month) - 1];
return _Last_day_table[(static_cast<unsigned int>(_Month) - 1) & 0xF];
}

class year_month_day_last;
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2 changes: 2 additions & 0 deletions tests/std/tests/P0355R7_calendars_and_time_zones_dates/test.cpp
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Expand Up @@ -967,6 +967,7 @@ constexpr void year_month_day_last_test() {
if (is_constant_evaluated()) {
static_assert((2020y / 1 / last).ok());
static_assert(!(2020y / 13 / last).ok());
static_assert(!(2020y / 0 / last).day().ok()); // implementation-specific assumption, see GH-1647
} else {
for (int iy = y_min; iy <= y_max; ++iy) {
for (auto m = 0u; m <= 255u; ++m) {
Expand All @@ -976,6 +977,7 @@ constexpr void year_month_day_last_test() {
assert((y / mdl).ok());
} else {
assert(!(y / mdl).ok());
assert((y / mdl).day().ok() || (y / mdl).day() == day{255}); // implementation-specific assumption
}
}
}
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