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.

Reviewed-by: Jonathan Wakely <jwak...@redhat.com>
Signed-off-by: Tomasz Kamiński <tkami...@redhat.com>
---
Changes in v3:
 - restored missing comment in _M_S
 - increment __out before calling _M_C_y_Y in _M_c

 libstdc++-v3/include/bits/chrono_io.h | 338 +++++++++++++-------------
 1 file changed, 171 insertions(+), 167 deletions(-)

diff --git a/libstdc++-v3/include/bits/chrono_io.h 
b/libstdc++-v3/include/bits/chrono_io.h
index 8811eaa5b3b..9e21152e398 100644
--- a/libstdc++-v3/include/bits/chrono_io.h
+++ b/libstdc++-v3/include/bits/chrono_io.h
@@ -908,6 +908,40 @@ 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,
@@ -925,6 +959,36 @@ 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%");
 
@@ -934,7 +998,10 @@ 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':
@@ -950,22 +1017,20 @@ 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);
@@ -976,16 +1041,16 @@ 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);
@@ -996,22 +1061,27 @@ 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);
@@ -1134,50 +1204,27 @@ 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');
        }
 
       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).
@@ -1187,15 +1234,6 @@ 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);
@@ -1237,9 +1275,13 @@ 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;
@@ -1269,7 +1311,7 @@ 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.
@@ -1278,15 +1320,6 @@ 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)
@@ -1362,7 +1395,7 @@ 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.
@@ -1371,15 +1404,6 @@ 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;
@@ -1411,22 +1435,13 @@ 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));
        }
@@ -1434,22 +1449,12 @@ 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));
        }
 
@@ -1490,17 +1495,42 @@ 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]]
            {
@@ -1511,39 +1541,40 @@ 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;
@@ -1597,25 +1628,25 @@ 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];
@@ -1625,7 +1656,7 @@ 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.
@@ -1635,17 +1666,6 @@ 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.
@@ -1757,22 +1777,6 @@ 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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