[gcc r16-1496] libstdc++: Format empty chrono-spec for the sys_info and local_info directly.
Tomasz Kaminski
tkaminsk@gcc.gnu.org
Fri Jun 13 06:36:37 GMT 2025
https://gcc.gnu.org/g:c550b5aff5227ff1298d43b060bbf3823559f383
commit r16-1496-gc550b5aff5227ff1298d43b060bbf3823559f383
Author: Tomasz Kamiński <tkaminsk@redhat.com>
Date: Fri Jun 6 11:56:08 2025 +0200
libstdc++: Format empty chrono-spec for the sys_info and local_info directly.
This patch change implementation of the formatters for sys_info and local_info,
so they no longer delegate to operator<< for ostream in case of empty spec.
As this types may be only formatted with chrono-spec containing only %%, %t, %n
specifiers and fill characters, we use a separate __formatter_chrono_info formatter.
For empty chron-spec __formatter_chrono_info formats sys_info using format_to call
with format specifier extracted from corresponding operator<<, that now delegates
to format with empty spec. For local_info we replicate functionality of the operator<<.
The alignment and padding is handled using an _Padding_sink.
For non-empty spec, we delegate to __formatter_chrono::_M_format. As non-of the
format specifiers depends on the formatted object, we pass chrono::day to avoid
triggering additional specializations.
libstdc++-v3/ChangeLog:
* include/bits/chrono_io.h (__format::__formatter_chrono_info)
[_GLIBCXX_USE_CXX11_ABI || ! _GLIBCXX_USE_DUAL_ABI]: Define.
(std::formatter<chrono::sys_info, _CharT>)
(std::formatter<chrono::local_inf, _CharT>): Delegate to
__format::__formatter_chrono_info.
(std::operator<<(basic_ostream<_CharT, _Traits>& const sys_info&)):
Use format on sys_info with empty format spec.
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
Diff:
---
libstdc++-v3/include/bits/chrono_io.h | 100 +++++++++++++++++++++++++++++-----
1 file changed, 85 insertions(+), 15 deletions(-)
diff --git a/libstdc++-v3/include/bits/chrono_io.h b/libstdc++-v3/include/bits/chrono_io.h
index 247d40c82d76..8b3b777559e3 100644
--- a/libstdc++-v3/include/bits/chrono_io.h
+++ b/libstdc++-v3/include/bits/chrono_io.h
@@ -1940,6 +1940,84 @@ namespace __format
}
};
+#if _GLIBCXX_USE_CXX11_ABI || ! _GLIBCXX_USE_DUAL_ABI
+ template<typename _CharT>
+ struct __formatter_chrono_info
+ {
+ constexpr typename basic_format_parse_context<_CharT>::iterator
+ parse(basic_format_parse_context<_CharT>& __pc)
+ { return _M_f._M_parse(__pc, _ChronoParts(), {}); }
+
+ template<typename _Info, typename _Out>
+ typename basic_format_context<_Out, _CharT>::iterator
+ format(const _Info& __i,
+ basic_format_context<_Out, _CharT>& __fc) const
+ {
+ // n.b. only acceptable chrono-spec for info is one containing
+ // only whitespaces and %%, that do not depend on formatted object.
+ if (!_M_f._M_spec._M_chrono_specs.empty()) [[unlikely]]
+ return _M_f._M_format(chrono::day(1), __fc);
+
+ const size_t __padwidth = _M_f._M_spec._M_get_width(__fc);
+ if (__padwidth == 0)
+ return _M_format_to(__fc.out(), __i);
+
+ _Padding_sink<_Out, _CharT> __sink(__fc.out(), __padwidth);
+ _M_format_to(__sink.out(), __i);
+ return __sink._M_finish(_M_f._M_spec._M_align, _M_f._M_spec._M_fill);
+ }
+
+ private:
+ template<typename _Out>
+ _Out
+ _M_format_to(_Out __out, const chrono::sys_info& __si) const
+ {
+ using _FmtStr = _Runtime_format_string<_CharT>;
+ // n.b. only decimal separator is locale dependent for specifiers
+ // used below, as sys_info uses seconds and minutes duration, the
+ // output is locale-independent.
+ constexpr auto* __fs
+ = _GLIBCXX_WIDEN("[{0:%F %T},{1:%F %T},{2:%T},{3:%Q%q},{0:%Z}]");
+ const chrono::local_seconds __lb(__si.begin.time_since_epoch());
+ return std::format_to(std::move(__out), _FmtStr(__fs),
+ chrono::local_time_format(__lb, &__si.abbrev),
+ __si.end, __si.offset, __si.save);
+ }
+
+ template<typename _Out>
+ _Out
+ _M_format_to(_Out __out, const chrono::local_info& __li) const
+ {
+ *__out = _Separators<_CharT>::_S_squares()[0];
+ ++__out;
+ if (__li.result == chrono::local_info::unique)
+ __out = _M_format_to(std::move(__out), __li.first);
+ else
+ {
+ basic_string_view<_CharT> __sv;
+ if (__li.result == chrono::local_info::nonexistent)
+ __sv =_GLIBCXX_WIDEN("nonexistent");
+ else
+ __sv = _GLIBCXX_WIDEN("ambiguous");
+ __out = __format::__write(std::move(__out), __sv);
+
+ __sv = _GLIBCXX_WIDEN(" local time between ");
+ __out = __format::__write(std::move(__out), __sv);
+ __out = _M_format_to(std::move(__out), __li.first);
+
+ __sv = _GLIBCXX_WIDEN(" and ");
+ __out = __format::__write(std::move(__out), __sv);
+ __out = _M_format_to(std::move(__out), __li.second);
+ }
+ *__out = _Separators<_CharT>::_S_squares()[1];
+ ++__out;
+ return std::move(__out);
+ }
+
+ __formatter_chrono<_CharT> _M_f;
+ };
+#endif
+
} // namespace __format
/// @endcond
@@ -2430,16 +2508,16 @@ namespace __format
{
constexpr typename basic_format_parse_context<_CharT>::iterator
parse(basic_format_parse_context<_CharT>& __pc)
- { return _M_f._M_parse(__pc, __format::_ChronoParts{}); }
+ { return _M_f.parse(__pc); }
template<typename _Out>
typename basic_format_context<_Out, _CharT>::iterator
format(const chrono::sys_info& __i,
basic_format_context<_Out, _CharT>& __fc) const
- { return _M_f._M_format(__i, __fc); }
+ { return _M_f.format(__i, __fc); }
private:
- __format::__formatter_chrono<_CharT> _M_f;
+ __format::__formatter_chrono_info<_CharT> _M_f;
};
template<__format::__char _CharT>
@@ -2447,16 +2525,16 @@ namespace __format
{
constexpr typename basic_format_parse_context<_CharT>::iterator
parse(basic_format_parse_context<_CharT>& __pc)
- { return _M_f._M_parse(__pc, __format::_ChronoParts{}); }
+ { return _M_f.parse(__pc); }
template<typename _Out>
typename basic_format_context<_Out, _CharT>::iterator
format(const chrono::local_info& __i,
basic_format_context<_Out, _CharT>& __fc) const
- { return _M_f._M_format(__i, __fc); }
+ { return _M_f.format(__i, __fc); }
private:
- __format::__formatter_chrono<_CharT> _M_f;
+ __format::__formatter_chrono_info<_CharT> _M_f;
};
#endif
@@ -3318,15 +3396,7 @@ namespace __detail
basic_ostream<_CharT, _Traits>&
operator<<(basic_ostream<_CharT, _Traits>& __os, const sys_info& __i)
{
- // n.b. only decimal separator is locale dependent for specifiers
- // used below, as sys_info uses seconds and minutes duration, the
- // output is locale-independent.
- constexpr auto* __fs
- = _GLIBCXX_WIDEN("[{0:%F %T},{1:%F %T},{2:%T},{3:%Q%q},{0:%Z}]");
- local_seconds __lb(__i.begin.time_since_epoch());
- __os << std::format(__fs, local_time_format(__lb, &__i.abbrev),
- __i.end, __i.offset, __i.save);
- return __os;
+ return __os << std::format(__os.getloc(), _GLIBCXX_WIDEN("{}"), __i);
}
/// Writes a local_info object to an ostream in an unspecified format.
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