[PATCH v2 2/2] libstdc++: Lift chrono localized formatting to main chrono format loop [PR110739]
Tomasz Kamiński
tkaminsk@redhat.com
Thu Jun 26 09:39:58 GMT 2025
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');
}
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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