[gcc(refs/users/mikael/heads/pr121185_v01)] libstdc++: Format %a/%A/%b/%h/%B/%p without using locale::classic [PR110739]
Mikael Morin
mikael@gcc.gnu.org
Thu Jul 24 07:57:45 GMT 2025
https://gcc.gnu.org/g:d3f9782b9efcdd500b3b4560811aca4e1e38d3ea
commit d3f9782b9efcdd500b3b4560811aca4e1e38d3ea
Author: Tomasz Kamiński <tkaminsk@redhat.com>
Date: Fri Jun 27 15:04:19 2025 +0200
libstdc++: Format %a/%A/%b/%h/%B/%p without using locale::classic [PR110739]
With changes r16-2063-g8ad5968a8dcb47 the _M_a_A, _M_b_B and _M_p functions
are called only if the locale is equal to the locale::classic(), for which
the behavior is know. This patch changes they implementation, so instead of
reffering to __timepunct facet members, they use hardcoded list of English
weekday, months names. Only one list is needed, as in case of locale::classic()
abbreviated name corresponds to first tree letters of the full name.
For _M_p, _M_r we use a new _M_fill_ampm helper, that fills provided buffer
with "AM"/"PM" depending on the hours value.
In _M_S we no longer guard querying of numpuct facet, with check that requires
potentially equally expensive construction of locale::classic. We also mark
localized path as unlikely.
The _M_locale method is no longer used in __formatter_chrono, and thus was
moved to __formatter_duration.
PR libstdc++/110739
libstdc++-v3/ChangeLog:
* include/bits/chrono_io.h (__formatter_chrono::_S_weekdays)
(__formatter_chrono::_S_months, __formatter_chrono::_S_fill_ampm):
Define.
(__formatter_chrono::_M_format_to): Do not pass context parameter
to functions listed below.
(__formatter_chrono::_M_a_A, __formatter_chrono::_M_b_B): Implement
using harcoded list of names, and remove format context parameter.
(__formatter_chrono::_M_p, __formatter_chrono::_M_r): Implement
using _S_fill_ampm.
(__formatter_chrono::_M_c): Removed format context parameter.
(__formatter_chrono::_M_subsecs): Call __ctx.locale() directly,
instead of _M_locale and do not compare with locale::classic().
Add [[unlikely]] attributes.
(__formatter_chrono::_M_locale): Move to __formatter_duration.
(__formatter_duration::_M_locale): Moved from __formatter_chrono.
Diff:
---
libstdc++-v3/include/bits/chrono_io.h | 154 +++++++++++++++++++---------------
1 file changed, 87 insertions(+), 67 deletions(-)
diff --git a/libstdc++-v3/include/bits/chrono_io.h b/libstdc++-v3/include/bits/chrono_io.h
index 75ee7e818b2f..fe3c91267497 100644
--- a/libstdc++-v3/include/bits/chrono_io.h
+++ b/libstdc++-v3/include/bits/chrono_io.h
@@ -881,16 +881,32 @@ namespace __format
_S_empty_fs()
{ return _Runtime_format_string<_CharT>(_S_empty_spec); }
- // Return the formatting locale.
- template<typename _FormatContext>
- std::locale
- _M_locale(_FormatContext& __fc) const
- {
- if (!_M_spec._M_localized)
- return std::locale::classic();
- else
- return __fc.locale();
- }
+ static constexpr const _CharT* _S_weekdays[]
+ {
+ _GLIBCXX_WIDEN("Sunday"),
+ _GLIBCXX_WIDEN("Monday"),
+ _GLIBCXX_WIDEN("Tuesday"),
+ _GLIBCXX_WIDEN("Wednesday"),
+ _GLIBCXX_WIDEN("Thursday"),
+ _GLIBCXX_WIDEN("Friday"),
+ _GLIBCXX_WIDEN("Saturday"),
+ };
+
+ static constexpr const _CharT* _S_months[]
+ {
+ _GLIBCXX_WIDEN("January"),
+ _GLIBCXX_WIDEN("February"),
+ _GLIBCXX_WIDEN("March"),
+ _GLIBCXX_WIDEN("April"),
+ _GLIBCXX_WIDEN("May"),
+ _GLIBCXX_WIDEN("June"),
+ _GLIBCXX_WIDEN("July"),
+ _GLIBCXX_WIDEN("August"),
+ _GLIBCXX_WIDEN("September"),
+ _GLIBCXX_WIDEN("October"),
+ _GLIBCXX_WIDEN("November"),
+ _GLIBCXX_WIDEN("December"),
+ };
private:
template<typename _OutIter>
@@ -1051,15 +1067,15 @@ namespace __format
break;
case 'a':
case 'A':
- __out = _M_a_A(__t._M_weekday, std::move(__out), __fc, __c == 'A');
+ __out = _M_a_A(__t._M_weekday, std::move(__out), __c == 'A');
break;
case 'b':
case 'h':
case 'B':
- __out = _M_b_B(__t._M_month, std::move(__out), __fc, __c == 'B');
+ __out = _M_b_B(__t._M_month, std::move(__out), __c == 'B');
break;
case 'c':
- __out = _M_c(__t, std::move(__out), __fc);
+ __out = _M_c(__t, std::move(__out));
break;
case 'C':
case 'y':
@@ -1095,7 +1111,7 @@ namespace __format
__out = _M_M(__t._M_minutes, __print_sign());
break;
case 'p':
- __out = _M_p(__t._M_hours, std::move(__out), __fc);
+ __out = _M_p(__t._M_hours, std::move(__out));
break;
case 'q':
__out = _M_q(__t._M_unit_suffix, std::move(__out));
@@ -1104,7 +1120,7 @@ namespace __format
__out = _M_Q(__t, __print_sign(), __fc);
break;
case 'r':
- __out = _M_r(__t, __print_sign(), __fc);
+ __out = _M_r(__t, __print_sign());
break;
case 'R':
case 'X':
@@ -1183,10 +1199,9 @@ namespace __format
return std::move(__out);
}
- template<typename _OutIter, typename _FormatContext>
+ template<typename _OutIter>
_OutIter
- _M_a_A(chrono::weekday __wd, _OutIter __out,
- _FormatContext& __ctx, bool __full) const
+ _M_a_A(chrono::weekday __wd, _OutIter __out, bool __full) const
{
// %a Locale's abbreviated weekday name.
// %A Locale's full weekday name.
@@ -1199,21 +1214,15 @@ namespace __format
__string_view(_GLIBCXX_WIDEN(" is not a valid weekday")));
}
- locale __loc = _M_locale(__ctx);
- const auto& __tp = use_facet<__timepunct<_CharT>>(__loc);
- const _CharT* __days[7];
- if (__full)
- __tp._M_days(__days);
- else
- __tp._M_days_abbreviated(__days);
- __string_view __str(__days[__wd.c_encoding()]);
- return _M_write(std::move(__out), __loc, __str);
+ __string_view __str = _S_weekdays[__wd.c_encoding()];
+ if (!__full)
+ __str = __str.substr(0, 3);
+ return __format::__write(std::move(__out), __str);
}
- template<typename _OutIter, typename _FormatContext>
+ template<typename _OutIter>
_OutIter
- _M_b_B(chrono::month __m, _OutIter __out,
- _FormatContext& __ctx, bool __full) const
+ _M_b_B(chrono::month __m, _OutIter __out, bool __full) const
{
// %b Locale's abbreviated month name.
// %B Locale's full month name.
@@ -1226,28 +1235,22 @@ namespace __format
__string_view(_GLIBCXX_WIDEN(" is not a valid month")));
}
- locale __loc = _M_locale(__ctx);
- const auto& __tp = use_facet<__timepunct<_CharT>>(__loc);
- const _CharT* __months[12];
- if (__full)
- __tp._M_months(__months);
- else
- __tp._M_months_abbreviated(__months);
- __string_view __str(__months[(unsigned)__m - 1]);
- return _M_write(std::move(__out), __loc, __str);
+ __string_view __str = _S_months[(unsigned)__m - 1];
+ if (!__full)
+ __str = __str.substr(0, 3);
+ return __format::__write(std::move(__out), __str);
}
- template<typename _OutIter, typename _FormatContext>
+ template<typename _OutIter>
_OutIter
- _M_c(const _ChronoData<_CharT>& __t, _OutIter __out,
- _FormatContext& __ctx) const
+ _M_c(const _ChronoData<_CharT>& __t, _OutIter __out) const
{
// %c Locale's date and time representation, for C-locale: %a %b %e %T %Y
// %Ec Locale's alternate date and time representation, for C-locale same as above
- __out = _M_a_A(__t._M_weekday, std::move(__out), __ctx, false);
+ __out = _M_a_A(__t._M_weekday, std::move(__out), false);
*__out = _S_space;
- __out = _M_b_B(__t._M_month, std::move(++__out), __ctx, false);
+ __out = _M_b_B(__t._M_month, std::move(++__out), false);
*__out = _S_space;
__out = _M_d_e(__t._M_day, std::move(++__out), 'e');
*__out = _S_space;
@@ -1489,20 +1492,15 @@ namespace __format
return __format::__write(std::move(__out), _S_two_digits(__i));
}
- template<typename _OutIter, typename _FormatContext>
+ template<typename _OutIter>
_OutIter
- _M_p(chrono::hours __h, _OutIter __out, _FormatContext& __ctx) const
+ _M_p(chrono::hours __h, _OutIter __out) const
{
// %p The locale's equivalent of the AM/PM designations.
- auto __hi = __h.count();
- if (__hi >= 24) [[unlikely]]
- __hi %= 24;
-
- locale __loc = _M_locale(__ctx);
- const auto& __tp = use_facet<__timepunct<_CharT>>(__loc);
- const _CharT* __ampm[2];
- __tp._M_am_pm(__ampm);
- return _M_write(std::move(__out), __loc, __ampm[__hi >= 12]);
+
+ _CharT __buf[2];
+ _S_fill_ampm(__buf, __h);
+ return __format::__write(std::move(__out), __string_view(__buf, 2));
}
template<typename _OutIter>
@@ -1522,27 +1520,25 @@ namespace __format
return std::vformat_to(std::move(__out), _S_empty_spec, __t._M_ereps);
}
- template<typename _OutIter, typename _FormatContext>
+ template<typename _OutIter>
_OutIter
- _M_r(const _ChronoData<_CharT>& __t, _OutIter __out,
- _FormatContext& __ctx) const
+ _M_r(const _ChronoData<_CharT>& __t, _OutIter __out) const
{
// %r Locale's 12-hour clock time, for C-locale: %I:%M:%S %p
auto __hi = __t._M_hours.count() % 12;
if (__hi == 0)
__hi = 12;
- _CharT __buf[9];
+ _CharT __buf[11];
__buf[2] = _S_colon;
__buf[5] = _S_colon;
__buf[8] = _S_space;
_S_fill_two_digits(__buf, __hi);
_S_fill_two_digits(__buf + 3, __t._M_minutes.count());
_S_fill_two_digits(__buf + 6, __t._M_seconds.count());
+ _S_fill_ampm(__buf + 9, __t._M_hours);
- __string_view __sv(__buf, 9);
- __out = __format::__write(std::move(__out), __sv);
- return _M_p(__t._M_hours, std::move(__out), __ctx);
+ return __format::__write(std::move(__out), __string_view(__buf, 11));
}
template<typename _OutIter>
@@ -1606,9 +1602,9 @@ namespace __format
return __out;
_CharT __dot = _S_dot;
- if (_M_spec._M_localized)
- if (auto __loc = __ctx.locale(); __loc != locale::classic())
+ if (_M_spec._M_localized) [[unlikely]]
{
+ auto __loc = __ctx.locale();
const auto& __np = use_facet<numpunct<_CharT>>(__loc);
__dot = __np.decimal_point();
}
@@ -1618,8 +1614,8 @@ namespace __format
if (_M_spec._M_floating_point_rep)
{
_Str_sink<_CharT> __sink;
- if (_M_spec._M_localized && _M_spec._M_custom_rep)
- std::vformat_to(__sink.out(), _M_locale(__ctx),
+ if (_M_spec._M_localized && _M_spec._M_custom_rep) [[unlikely]]
+ std::vformat_to(__sink.out(), __ctx.locale(),
_GLIBCXX_WIDEN("{1:0.{2}Lf}"), __t._M_ereps);
else
std::vformat_to(__sink.out(),
@@ -1778,6 +1774,20 @@ namespace __format
__buf[1] = __sv[1];
}
+ // Fills __buf[0] and __buf[1] with "AM", "PM" depending on __h.
+ [[__gnu__::__always_inline__]]
+ static void
+ _S_fill_ampm(_CharT* __buf, chrono::hours __h)
+ {
+ auto __hi = __h.count();
+ if (__hi >= 24) [[unlikely]]
+ __hi %= 24;
+
+ constexpr const _CharT* __apm = _GLIBCXX_WIDEN("APM");
+ __buf[0] = __apm[__hi >= 12];
+ __buf[1] = __apm[2];
+ }
+
// Returns decimal representation of __n.
// Returned string_view may point to __buf.
[[__gnu__::__always_inline__]]
@@ -1879,7 +1889,6 @@ namespace __format
};
using __formatter_chrono<_CharT>::__formatter_chrono;
- using __formatter_chrono<_CharT>::_M_locale;
using __formatter_chrono<_CharT>::_M_spec;
template<typename _Duration, typename _ParseContext>
@@ -1909,6 +1918,17 @@ namespace __format
return __res;
}
+ // Return the formatting locale.
+ template<typename _FormatContext>
+ std::locale
+ _M_locale(_FormatContext& __fc) const
+ {
+ if (!_M_spec._M_localized)
+ return std::locale::classic();
+ else
+ return __fc.locale();
+ }
+
// Format duration for empty chrono-specs, e.g. "{}" (C++20 [time.format] p6).
template<typename _Rep, typename _Period, typename _FormatContext>
typename _FormatContext::iterator
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