On Thu, 26 Jun 2025 at 13:30, Tomasz Kaminski <tkami...@redhat.com> wrote:
>
>
>
> On Thu, Jun 26, 2025 at 2:13 PM Tomasz Kaminski <tkami...@redhat.com> wrote:
>>
>>
>>
>> On Thu, Jun 26, 2025 at 2:09 PM Jonathan Wakely <jwak...@redhat.com> wrote:
>>>
>>> On 26/06/25 11:39 +0200, Tomasz Kamiński 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.
>>>
>>> Great, this is exactly what I wanted to do. Removing all the branches
>>> to call _M_locale_fmt from each of the _M_xxx member functions makes
>>> them smaller and potentially faster.
>>>
>>> >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.
>>>
>>> Nice.
>>>
>>> >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');
>>> > }
>>> >
>>> > 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.
>>>
>>> Doesn't this function still handle %S formats? Should this comment be kept?
>>
>> Yes, it gets called to handle '%S' in the big switch. It is no longer called
>> by _M_T, which calls _M_subsecs
>> directly.
>
> Ah, you are referring to 'OS'. Yes, it is still-handled here, if the format
> is not localized, or the locale is the same
> as classic. The effect is that we do not print subseconds.
What I mean is that the _M_S function handles both %S and %OS, but you
remove the comment about %S which suggests to me that it only handles
%OS now (but that's not correct).
Should the first comment line be restored?
