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<chrono: Rewrite %r spec for C locale #1865

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Merged
eldakesh-ms merged 1 commit into from
Apr 20, 2021
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<chrono: Rewrite %r spec for C locale #1865

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14 changes: 14 additions & 0 deletions stl/inc/chrono
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Original file line number Diff line number Diff line change
Expand Up @@ -5999,6 +5999,20 @@ namespace chrono {
}
_Os << _Time.tm_mday;
return true;
case 'r':
if constexpr (_Is_specialization_v<_Ty, hh_mm_ss>) {
// put_time uses _Strftime in order to bypass reference-counting that locale uses. This function
// takes the locale information by pointer, but the pointer (from _Gettnames) returns a copy.
// _Strftime delegates to other functions but eventually (for the C locale) has the %r specifier
// rewritten. It checks for the locale by comparing pointers, which do not compare equal as we have
// a copy of the pointer instead of the original. Therefore, we replace %r for the C locale
// ourselves.
Comment on lines +6004 to +6009
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@mnatsuhara mnatsuhara Apr 20, 2021

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If we're reporting this as a UCRT bug (which I think was our conclusion in the internal chat), should this be marked as // TRANSITION, ... with a bug number? Theoretically, we won't have to special-case this forever!

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@eldakesh-ms eldakesh-ms Apr 20, 2021

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It's not exactly a UCRT bug. They can't really tell we mean the C locale when we pass it in through _Strftime because they are fundamentally different pointers. And we are the ones trying to circumvent the ref counting of locale. Maybe we can fix time_put? People might rely on the %r behavior though...

if (_Os.getloc() == locale::classic()) {
_Os << _STD put_time(&_Time, _STATICALLY_WIDEN(_CharT, "%I:%M:%S %p"));
return true;
}
}
return false;
case 'j':
if constexpr (_Is_specialization_v<_Ty, duration>) {
_Os << _STD abs(_CHRONO duration_cast<days>(_Val).count());
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4 changes: 2 additions & 2 deletions tests/std/tests/P0355R7_calendars_and_time_zones_formatting/test.cpp
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Expand Up @@ -560,10 +560,10 @@ void test_hh_mm_ss_formatter() {
empty_braces_helper(hh_mm_ss{65745s}, STR("18:15:45"));

assert(format(STR("{:%H %I %M %S %r %R %T %p}"), hh_mm_ss{13h + 14min + 15351ms})
== STR("13 01 14 15.351 13:14:15 13:14 13:14:15.351 PM"));
== STR("13 01 14 15.351 01:14:15 PM 13:14 13:14:15.351 PM"));

assert(format(STR("{:%H %I %M %S %r %R %T %p}"), hh_mm_ss{-13h - 14min - 15351ms})
== STR("-13 01 14 15.351 13:14:15 13:14 13:14:15.351 PM"));
== STR("-13 01 14 15.351 01:14:15 PM 13:14 13:14:15.351 PM"));

throw_helper(STR("{}"), hh_mm_ss{24h});
throw_helper(STR("{}"), hh_mm_ss{-24h});
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