On Thu, Jun 26, 2025 at 12:31 PM Tomasz Kamiński <tkami...@redhat.com>
wrote:

> This patch extract calls to _M_locale_fmt and construction of the struct
> tm,
> from the functions dedicated to each specifier, to main format loop in
> _M_format_to functions. This removes duplicated code repeated for
> specifiers.
>
> To allow _M_locale_fmt to only be called if localized formatting is enabled
> ('L' is present in chrono-format-spec), we provide a implementations for
> locale specific specifiers (%c, %r, %x, %X) that produces the same result
> as locale::classic():
>  * %c is implemented as separate _M_c method
>  * %r is implemented as separate _M_r method
>  * %x is implemented together with %D, as they provide same behavior,
>  * %X is implemented together with %R as _M_R_X, as both of them do not
> include
>    subseconds.
>
> The handling of subseconds was also extracted to _M_subsecs function that
> is
> used by _M_S and _M_T specifier. The _M_T is now implemented in terms of
> _M_R_X (printing time without subseconds) and _M_subs.
>
> The __mod responsible for triggering localized formatting was removed from
> method handling most of specifiers, except:
>  * _M_S (for %S) for which it determines if subseconds should be included,
>  * _M_z (for %z) for which it determines if ':' is used as separator.
>
>         PR libstdc++/110739
>
> libstdc++-v3/ChangeLog:
>
>         * include/bits/chrono_io.h (__formatter_chrono::_M_use_locale_fmt):
>         Define.
>         (__formatter_chrono::_M_locale_fmt): Moved to front of the class.
>         (__formatter_chrono::_M_format_to): Construct and initialize
>         struct tm and call _M_locale_fmt if needed.
>         (__formatter_chrono::_M_c_r_x_X): Split into separate methods.
>         (__formatter_chrono::_M_c, __formatter_chrono::_M_r): Define.
>         (__formatter_chrono::_M_D): Renamed to _M_D_x.
>         (__formatter_chrono::_M_D_x): Renamed from _M_D.
>         (__formatter_chrono::_M_R_T): Split into _M_R_X and _M_T.
>         (__formatter_chrono::_M_R_X): Extracted from _M_R_T.
>         (__formatter_chrono::_M_T): Define in terms of _M_R_X and
> _M_subsecs.
>         (__formatter_chrono::_M_subsecs): Extracted from _M_S.
>         (__formatter_chrono::_M_S): Replaced __mod with __subs argument,
>         removed _M_locale_fmt call, and delegate to _M_subsecs.
>         (__formatter_chrono::_M_C_y_Y, __formatter_chrono::_M_d_e)
>         (__formatter_chrono::_M_H_I, __formatter_chrono::_M_m)
>         (__formatter_chrono::_M_u_w, __formatter_chrono::_M_U_V_W): Remove
>         __mod argument and call to _M_locale_fmt.
> ---
>  libstdc++-v3/include/bits/chrono_io.h | 340 +++++++++++++-------------
>  1 file changed, 172 insertions(+), 168 deletions(-)
>
> diff --git a/libstdc++-v3/include/bits/chrono_io.h
> b/libstdc++-v3/include/bits/chrono_io.h
> index 35e95906e6a..d451bde722d 100644
> --- a/libstdc++-v3/include/bits/chrono_io.h
> +++ b/libstdc++-v3/include/bits/chrono_io.h
> @@ -906,6 +906,40 @@ namespace __format
>           return __format::__write(std::move(__out), __s);
>         }
>
> +      [[__gnu__::__always_inline__]]
> +      static bool
> +      _S_localized_spec(_CharT __conv, _CharT __mod)
> +      {
> +       switch (__conv)
> +         {
> +         case 'c':
> +         case 'r':
> +         case 'x':
> +         case 'X':
> +           return true;
> +         case 'z':
> +           return false;
> +         default:
> +           return (bool)__mod;
> +         };
> +      }
> +
> +      // Use the formatting locale's std::time_put facet to produce
> +      // a locale-specific representation.
> +      template<typename _Iter>
> +       _Iter
> +       _M_locale_fmt(_Iter __out, const locale& __loc, const struct tm&
> __tm,
> +                     char __fmt, char __mod) const
> +       {
> +         basic_ostringstream<_CharT> __os;
> +         __os.imbue(__loc);
> +         const auto& __tp = use_facet<time_put<_CharT>>(__loc);
> +         __tp.put(__os, __os, _S_space, &__tm, __fmt, __mod);
> +         if (__os)
> +           __out = _M_write(std::move(__out), __loc, __os.view());
> +         return __out;
> +       }
> +
>        template<typename _Out, typename _FormatContext>
>         _Out
>         _M_format_to(const _ChronoData<_CharT>& __t, _Out __out,
> @@ -923,6 +957,36 @@ namespace __format
>             return std::move(__out);
>           };
>
> +         struct tm __tm{};
> +         bool __use_locale_fmt = false;
> +         if (_M_spec._M_localized && _M_spec._M_locale_specific)
> +           if (__fc.locale() != locale::classic())
> +             {
> +               __use_locale_fmt = true;
> +
> +               __tm.tm_year = (int)__t._M_year - 1900;
> +               __tm.tm_yday = __t._M_day_of_year.count();
> +               __tm.tm_mon = (unsigned)__t._M_month - 1;
> +               __tm.tm_mday = (unsigned)__t._M_day;
> +               __tm.tm_wday = __t._M_weekday.c_encoding();
> +               __tm.tm_hour = __t._M_hours.count();
> +               __tm.tm_min = __t._M_minutes.count();
> +               __tm.tm_sec = __t._M_seconds.count();
> +
> +               // Some locales use %Z in their %c format but we don't
> want strftime
> +               // to use the system's local time zone (from
> /etc/localtime or $TZ)
> +               // as the output for %Z. Setting tm_isdst to -1 says there
> is no
> +               // time zone info available for the time in __tm.
> +               __tm.tm_isdst = -1;
> +
> +#ifdef _GLIBCXX_USE_STRUCT_TM_TM_ZONE
> +               // POSIX.1-2024 adds tm.tm_zone which will be used for %Z.
> +               // BSD has had tm_zone since 1987 but as char* so cast
> away const.
> +               if (__t._M_zone_cstr)
> +                 __tm.tm_zone = const_cast<char*>(__t._M_zone_cstr);
> +#endif
> +             }
> +
>           // Characters to output for "%n", "%t" and "%%" specifiers.
>           constexpr const _CharT* __literals = _GLIBCXX_WIDEN("\n\t%");
>
> @@ -932,7 +996,10 @@ namespace __format
>           do
>             {
>               _CharT __c = *__first++;
> -             switch (__c)
> +             if (__use_locale_fmt && _S_localized_spec(__c, __mod))
> [[unlikely]]
> +               __out = _M_locale_fmt(std::move(__out), __fc.locale(),
> +                                     __tm, __c, __mod);
> +             else switch (__c)
>                 {
>                 // %\0 is extension for handling weekday index
>                 case '\0':
> @@ -948,22 +1015,20 @@ namespace __format
>                   __out = _M_b_B(__t._M_month, std::move(__out), __fc, __c
> == 'B');
>                   break;
>                 case 'c':
> -               case 'r':
> -               case 'x':
> -               case 'X':
> -                 __out = _M_c_r_x_X(__t, std::move(__out), __fc, __c,
> __mod);
> +                 __out = _M_c(__t, std::move(__out), __fc);
>                   break;
>                 case 'C':
>                 case 'y':
>                 case 'Y':
> -                 __out = _M_C_y_Y(__t._M_year, std::move(__out), __fc,
> __c, __mod);
> +                 __out = _M_C_y_Y(__t._M_year, std::move(__out), __fc,
> __c);
>                   break;
>                 case 'd':
>                 case 'e':
> -                 __out = _M_d_e(__t._M_day, std::move(__out), __fc, __c,
> __mod == 'O');
> +                 __out = _M_d_e(__t._M_day, std::move(__out), __fc, __c);
>                   break;
>                 case 'D':
> -                 __out = _M_D(__t, std::move(__out), __fc);
> +               case 'x':
> +                 __out = _M_D_x(__t, std::move(__out), __fc);
>                   break;
>                 case 'F':
>                   __out = _M_F(__t, std::move(__out), __fc);
> @@ -974,16 +1039,16 @@ namespace __format
>                   break;
>                 case 'H':
>                 case 'I':
> -                 __out = _M_H_I(__t._M_hours, __print_sign(), __fc, __c,
> __mod == 'O');
> +                 __out = _M_H_I(__t._M_hours, __print_sign(), __fc, __c);
>                   break;
>                 case 'j':
>                   __out = _M_j(__t, __print_sign(), __fc);
>                   break;
>                 case 'm':
> -                 __out = _M_m(__t._M_month, std::move(__out), __fc, __mod
> == 'O');
> +                 __out = _M_m(__t._M_month, std::move(__out), __fc);
>                   break;
>                 case 'M':
> -                 __out = _M_M(__t._M_minutes, __print_sign(), __fc, __mod
> == 'O');
> +                 __out = _M_M(__t._M_minutes, __print_sign(), __fc);
>                   break;
>                 case 'p':
>                   __out = _M_p(__t._M_hours, std::move(__out), __fc);
> @@ -994,22 +1059,28 @@ namespace __format
>                 case 'Q':
>                   __out = _M_Q(__t, __print_sign(), __fc);
>                   break;
> +               case 'r':
> +                 __out = _M_r(__t, __print_sign(), __fc);
> +                 break;
>                 case 'R':
> +               case 'X':
> +                 __out = _M_R_X(__t, __print_sign(), __fc, __c != 'R');
> +                 break;
>                 case 'T':
> -                 __out = _M_R_T(__t, __print_sign(), __fc, __c == 'T');
> +                 __out = _M_T(__t, __print_sign(), __fc);
>                   break;
> +
>                 case 'S':
> -                 __out = _M_S(__t, __print_sign(), __fc, __mod == 'O');
> +                 __out = _M_S(__t, __print_sign(), __fc, __mod != 'O');
>                   break;
>                 case 'u':
>                 case 'w':
> -                 __out = _M_u_w(__t._M_weekday, std::move(__out), __fc,
> __c, __mod == 'O');
> +                 __out = _M_u_w(__t._M_weekday, std::move(__out), __fc,
> __c);
>                   break;
>                 case 'U':
>                 case 'V':
>                 case 'W':
> -                 __out = _M_U_V_W(__t, std::move(__out), __fc, __c,
> -                                  __mod == 'O');
> +                 __out = _M_U_V_W(__t, std::move(__out), __fc, __c);
>                   break;
>                 case 'z':
>                   __out = _M_z(__t._M_zone_offset, std::move(__out), __fc,
> (bool)__mod);
> @@ -1132,50 +1203,27 @@ namespace __format
>
>        template<typename _FormatContext>
>         typename _FormatContext::iterator
> -       _M_c_r_x_X(const _ChronoData<_CharT>& __t, typename
> _FormatContext::iterator __out,
> -                  _FormatContext& __ctx, _CharT __conv, _CharT __mod)
> const
> +       _M_c(const _ChronoData<_CharT>& __t, typename
> _FormatContext::iterator __out,
> +            _FormatContext& __ctx) const
>         {
> -         // %c  Locale's date and time representation.
> -         // %Ec Locale's alternate date and time representation.
> -         // %r  Locale's 12-hour clock time.
> -         // %x  Locale's date rep
> -         // %Ex Locale's alternative date representation.
> -         // %X  Locale's time rep
> -         // %EX Locale's alternative time representation.
> -
> -         using namespace chrono;
> -         struct tm __tm{};
> -
> -         // Some locales use %Z in their %c format but we don't want
> strftime
> -         // to use the system's local time zone (from /etc/localtime or
> $TZ)
> -         // as the output for %Z. Setting tm_isdst to -1 says there is no
> -         // time zone info available for the time in __tm.
> -         __tm.tm_isdst = -1;
> -
> -#ifdef _GLIBCXX_USE_STRUCT_TM_TM_ZONE
> -         // POSIX.1-2024 adds tm.tm_zone which will be used for %Z.
> -         // BSD has had tm_zone since 1987 but as char* so cast away
> const.
> -         if (__t._M_zone_cstr)
> -           __tm.tm_zone = const_cast<char*>(__t._M_zone_cstr);
> -#endif
> -
> -         __tm.tm_year = (int)__t._M_year - 1900;
> -         __tm.tm_yday = __t._M_day_of_year.count();
> -         __tm.tm_mon = (unsigned)__t._M_month - 1;
> -         __tm.tm_mday = (unsigned)__t._M_day;
> -         __tm.tm_wday = __t._M_weekday.c_encoding();
> -         __tm.tm_hour = __t._M_hours.count();
> -         __tm.tm_min = __t._M_minutes.count();
> -         __tm.tm_sec = __t._M_seconds.count();
> -
> -         return _M_locale_fmt(std::move(__out), _M_locale(__ctx), __tm,
> -                              __conv, __mod);
> +         // %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 = _S_space;
> +         __out = _M_b_B(__t._M_month, std::move(++__out), __ctx, false);
> +         *__out = _S_space;
> +         __out = _M_d_e(__t._M_day, std::move(++__out), __ctx, 'e');
> +         *__out = _S_space;
> +         __out = _M_R_X(__t, std::move(++__out), __ctx, true);
> +         *__out = _S_space;
> +         return _M_C_y_Y(__t._M_year, std::move(__out), __ctx, 'Y');
>
This should be ++__out. This does not make different for _Sink_iter, that
it de-facto only iterator that we use here,
but I will fix it.

>         }
>
>        template<typename _FormatContext>
>         typename _FormatContext::iterator
>         _M_C_y_Y(chrono::year __y, typename _FormatContext::iterator __out,
> -                _FormatContext& __ctx, _CharT __conv, _CharT __mod = 0)
> const
> +                _FormatContext& __ctx, _CharT __conv) const
>         {
>           // %C  Year divided by 100 using floored division.
>           // %EC Locale's alternative preresentation of the century (era
> name).
> @@ -1185,15 +1233,6 @@ namespace __format
>           // %Y  Year as a decimal number.
>           // %EY Locale's alternative full year representation.
>
> -         if (__mod && _M_spec._M_localized) [[unlikely]]
> -           if (auto __loc = __ctx.locale(); __loc != locale::classic())
> -             {
> -               struct tm __tm{};
> -               __tm.tm_year = (int)__y - 1900;
> -               return _M_locale_fmt(std::move(__out), __loc, __tm,
> -                                    __conv, __mod);
> -             }
> -
>           int __yi = (int)__y;
>           const bool __is_neg = __yi < 0;
>           __yi = __builtin_abs(__yi);
> @@ -1235,9 +1274,13 @@ namespace __format
>
>        template<typename _FormatContext>
>         typename _FormatContext::iterator
> -       _M_D(const _ChronoData<_CharT>& __t, typename
> _FormatContext::iterator __out,
> -            _FormatContext&) const
> +       _M_D_x(const _ChronoData<_CharT>& __t, typename
> _FormatContext::iterator __out,
> +              _FormatContext&) const
>         {
> +         // %D  Equivalent to %m/%d/%y
> +         // %x  Locale's date rep, for C-locale: %m/%d/%y
> +         // %Ex Locale's alternative date representation, for C-locale
> same as above
> +
>           auto __di = (unsigned)__t._M_day;
>           auto __mi = (unsigned)__t._M_month;
>           auto __yi = __builtin_abs((int)__t._M_year) % 100;
> @@ -1267,7 +1310,7 @@ namespace __format
>        template<typename _FormatContext>
>         typename _FormatContext::iterator
>         _M_d_e(chrono::day __d, typename _FormatContext::iterator __out,
> -              _FormatContext& __ctx, _CharT __conv, bool __mod = false)
> const
> +              _FormatContext& __ctx, _CharT __conv) const
>         {
>           // %d  The day of month as a decimal number.
>           // %Od Locale's alternative representation.
> @@ -1276,15 +1319,6 @@ namespace __format
>
>           unsigned __i = (unsigned)__d;
>
> -         if (__mod && _M_spec._M_localized) [[unlikely]]
> -           if (auto __loc = __ctx.locale(); __loc != locale::classic())
> -             {
> -               struct tm __tm{};
> -               __tm.tm_mday = __i;
> -               return _M_locale_fmt(std::move(__out), __loc, __tm,
> -                                    (char)__conv, 'O');
> -             }
> -
>           _CharT __buf[3];
>           auto __sv = _S_str_d2(__buf, __i);
>           if (__conv == _CharT('e') && __i < 10)
> @@ -1360,7 +1394,7 @@ namespace __format
>        template<typename _FormatContext>
>         typename _FormatContext::iterator
>         _M_H_I(chrono::hours __h, typename _FormatContext::iterator __out,
> -              _FormatContext& __ctx, _CharT __conv, bool __mod = false)
> const
> +              _FormatContext& __ctx, _CharT __conv) const
>         {
>           // %H  The hour (24-hour clock) as a decimal number.
>           // %OH Locale's alternative representation.
> @@ -1369,15 +1403,6 @@ namespace __format
>
>           int __i = __h.count();
>
> -         if (__mod && _M_spec._M_localized) [[unlikely]]
> -           if (auto __loc = __ctx.locale(); __loc != locale::classic())
> -             {
> -               struct tm __tm{};
> -               __tm.tm_hour = __i;
> -               return _M_locale_fmt(std::move(__out), __loc, __tm,
> -                                    (char)__conv, 'O');
> -             }
> -
>           if (__conv == _CharT('I'))
>             {
>               __i %= 12;
> @@ -1409,22 +1434,13 @@ namespace __format
>        template<typename _FormatContext>
>         typename _FormatContext::iterator
>         _M_m(chrono::month __m, typename _FormatContext::iterator __out,
> -            _FormatContext& __ctx, bool __mod) const
> +            _FormatContext& __ctx) const
>         {
>           // %m  month as a decimal number.
>           // %Om Locale's alternative representation.
>
>           auto __i = (unsigned)__m;
>
> -         if (__mod && _M_spec._M_localized) [[unlikely]] // %Om
> -           if (auto __loc = __ctx.locale(); __loc != locale::classic())
> -             {
> -               struct tm __tm{};
> -               __tm.tm_mon = __i - 1;
> -               return _M_locale_fmt(std::move(__out), __loc, __tm,
> -                                    'm', 'O');
> -             }
> -
>           _CharT __buf[3];
>           return __format::__write(std::move(__out), _S_str_d2(__buf,
> __i));
>         }
> @@ -1432,22 +1448,12 @@ namespace __format
>        template<typename _FormatContext>
>         typename _FormatContext::iterator
>         _M_M(chrono::minutes __m, typename _FormatContext::iterator __out,
> -            _FormatContext& __ctx, bool __mod) const
> +            _FormatContext& __ctx) const
>         {
>           // %M  The minute as a decimal number.
>           // %OM Locale's alternative representation.
>
>           auto __i = __m.count();
> -
> -         if (__mod && _M_spec._M_localized) [[unlikely]] // %OM
> -           if (auto __loc = __ctx.locale(); __loc != locale::classic())
> -             {
> -               struct tm __tm{};
> -               __tm.tm_min = __i;
> -               return _M_locale_fmt(std::move(__out), __loc, __tm,
> -                                    'M', 'O');
> -             }
> -
>           return __format::__write(std::move(__out), _S_two_digits(__i));
>         }
>
> @@ -1488,17 +1494,42 @@ namespace __format
>
>        template<typename _FormatContext>
>         typename _FormatContext::iterator
> -       _M_R_T(const _ChronoData<_CharT>& __t, typename
> _FormatContext::iterator __out,
> +       _M_r(const _ChronoData<_CharT>& __t, typename
> _FormatContext::iterator __out,
> +            _FormatContext& __ctx) 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];
> +         __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());
> +
> +         __string_view __sv(__buf, 9);
> +         __out = __format::__write(std::move(__out), __sv);
> +         return _M_p(__t._M_hours, std::move(__out), __ctx);
> +       }
> +
> +      template<typename _FormatContext>
> +       typename _FormatContext::iterator
> +       _M_R_X(const _ChronoData<_CharT>& __t, typename
> _FormatContext::iterator __out,
>                _FormatContext& __ctx, bool __secs) const
>         {
> -         // %R Equivalent to %H:%M
> -         // %T Equivalent to %H:%M:%S
> +         // %R  Equivalent to %H:%M
> +         // %X  Locale's time rep, for C-locale: %H:%M:%S (without
> subseconds)
> +         // %EX Locale's alternative time representation, for C-locale
> same as above
> +
>           auto __hi = __t._M_hours.count();
>
> -         _CharT __buf[6];
> +         _CharT __buf[8];
>           __buf[2] = _S_colon;
>           __buf[5] = _S_colon;
> -         __string_view __sv(__buf, 5 + __secs);
> +         __string_view __sv(__buf, 8);
>
>           if (__hi >= 100) [[unlikely]]
>             {
> @@ -1509,39 +1540,39 @@ namespace __format
>             _S_fill_two_digits(__buf, __hi);
>
>           _S_fill_two_digits(__buf + 3, __t._M_minutes.count());
> -         __out = __format::__write(std::move(__out), __sv);
>           if (__secs)
> -           __out = _M_S(__t, std::move(__out), __ctx);
> -         return __out;
> +           _S_fill_two_digits(__buf + 6, __t._M_seconds.count());
> +         else
> +           __sv.remove_suffix(3);
> +
> +         return __format::__write(std::move(__out), __sv);
>         }
>
>        template<typename _FormatContext>
>         typename _FormatContext::iterator
>         _M_S(const _ChronoData<_CharT>& __t, typename
> _FormatContext::iterator __out,
> -            _FormatContext& __ctx, bool __mod = false) const
> +            _FormatContext& __ctx, bool __subs = true) const
>         {
> -         // %S  Seconds as a decimal number.
>           // %OS The locale's alternative representation.
>           auto __s = __t._M_seconds;
>
> -         if (__mod && _M_spec._M_localized) [[unlikely]] // %OS
> -           if (auto __loc = __ctx.locale(); __loc != locale::classic())
> -             {
> -               struct tm __tm{};
> -               __tm.tm_sec = (int)__s.count();
> -               return _M_locale_fmt(std::move(__out), __loc, __tm,
> -                                    'S', 'O');
> -             }
> -
>           __out = __format::__write(std::move(__out),
> -                                    _S_two_digits(__s.count()));
> +                                   _S_two_digits(__s.count()));
> +         if (__subs)
> +           __out = _M_subsecs(__t, std::move(__out), __ctx);
> +         return __out;
> +       }
>
> +      template<typename _FormatContext>
> +       typename _FormatContext::iterator
> +       _M_subsecs(const _ChronoData<_CharT>& __t,
> +                  typename _FormatContext::iterator __out,
> +                  _FormatContext& __ctx) const
> +       {
>           unsigned __prec = _M_spec._M_prec_kind != _WP_none
>                           ? _M_spec._M_get_precision(__ctx)
>                           : _M_spec._M_prec;
> -
> -         // %OS formats don't include subseconds
> -         if (__prec == 0 || __mod)
> +         if (__prec == 0)
>             return __out;
>
>           _CharT __dot = _S_dot;
> @@ -1595,25 +1626,25 @@ namespace __format
>
>        // %t handled in _M_format
>
> +      template<typename _FormatContext>
> +       typename _FormatContext::iterator
> +       _M_T(const _ChronoData<_CharT>& __t, typename
> _FormatContext::iterator __out,
> +            _FormatContext& __ctx) const
> +       {
> +         // %T Equivalent to %H:%M:%S, with subseconds
> +         __out = _M_R_X(__t, std::move(__out), __ctx, true);
> +         return _M_subsecs(__t, std::move(__out), __ctx);
> +       }
> +
>        template<typename _FormatContext>
>         typename _FormatContext::iterator
>         _M_u_w(chrono::weekday __wd, typename _FormatContext::iterator
> __out,
> -              _FormatContext& __ctx, _CharT __conv, bool __mod = false)
> const
> +              _FormatContext& __ctx, _CharT __conv) const
>         {
>           // %u  ISO weekday as a decimal number (1-7), where Monday is 1.
>           // %Ou Locale's alternative numeric rep.
>           // %w  Weekday as a decimal number (0-6), where Sunday is 0.
>           // %Ow Locale's alternative numeric rep.
> -
> -         if (__mod && _M_spec._M_localized) [[unlikely]]
> -           if (auto __loc = __ctx.locale(); __loc != locale::classic())
> -             {
> -               struct tm __tm{};
> -               __tm.tm_wday = __wd.c_encoding();
> -               return _M_locale_fmt(std::move(__out), __loc, __tm,
> -                                    (char)__conv, 'O');
> -             }
> -
>           unsigned __wdi = __conv == 'u' ? __wd.iso_encoding()
>                                          : __wd.c_encoding();
>           _CharT __buf[3];
> @@ -1623,7 +1654,7 @@ namespace __format
>        template<typename _FormatContext>
>         typename _FormatContext::iterator
>         _M_U_V_W(const _ChronoData<_CharT>& __t, typename
> _FormatContext::iterator __out,
> -                _FormatContext& __ctx, _CharT __conv, bool __mod = false)
> const
> +                _FormatContext& __ctx, _CharT __conv) const
>         {
>           // %U  Week number of the year as a decimal number, from first
> Sunday.
>           // %OU Locale's alternative numeric rep.
> @@ -1633,17 +1664,6 @@ namespace __format
>           // %OW Locale's alternative numeric rep.
>           using namespace chrono;
>
> -         if (__mod && _M_spec._M_localized) [[unlikely]]
> -           if (auto __loc = __ctx.locale(); __loc != locale::classic())
> -             {
> -               struct tm __tm{};
> -               __tm.tm_year = (int)__t._M_year - 1900;
> -               __tm.tm_yday = __t._M_day_of_year.count();
> -               __tm.tm_wday = __t._M_weekday.c_encoding();
> -               return _M_locale_fmt(std::move(__out), __loc, __tm,
> -                                    (char)__conv, 'O');
> -             }
> -
>           auto __d = __t._M_ldays;
>           local_days __first; // First day of week 1.
>           if (__conv == 'V') // W01 begins on Monday before first Thursday.
> @@ -1755,22 +1775,6 @@ namespace __format
>         __buf[2] = _S_chars[__n % 10];
>         return __string_view(__buf.data(), 3);
>        }
> -
> -      // Use the formatting locale's std::time_put facet to produce
> -      // a locale-specific representation.
> -      template<typename _Iter>
> -       _Iter
> -       _M_locale_fmt(_Iter __out, const locale& __loc, const struct tm&
> __tm,
> -                     char __fmt, char __mod) const
> -       {
> -         basic_ostringstream<_CharT> __os;
> -         __os.imbue(__loc);
> -         const auto& __tp = use_facet<time_put<_CharT>>(__loc);
> -         __tp.put(__os, __os, _S_space, &__tm, __fmt, __mod);
> -         if (__os)
> -           __out = _M_write(std::move(__out), __loc, __os.view());
> -         return __out;
> -       }
>      };
>
>    template<typename _CharT>
> --
> 2.49.0
>
>

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