On 06/06/25 12:41 +0200, Tomasz Kamiński wrote:
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 empty chrono-spec (with padding), they
now
use a separate __formatter_chrono_info formatter.
The __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.
libstdc++-v3/ChangeLog:
* include/bits/chrono_io.h (__format::__formatter_chrono_info):
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.
---
libstdc++-v3/include/bits/chrono_io.h | 132 +++++++++++++++++++++++---
1 file changed, 117 insertions(+), 15 deletions(-)
diff --git a/libstdc++-v3/include/bits/chrono_io.h
b/libstdc++-v3/include/bits/chrono_io.h
index 24c7dfb91c9..bbbae3d3064 100644
--- a/libstdc++-v3/include/bits/chrono_io.h
+++ b/libstdc++-v3/include/bits/chrono_io.h
@@ -1948,6 +1948,104 @@ namespace __format
}
};
+ template<typename _CharT>
+ struct __formatter_chrono_info
+ {
+ constexpr typename basic_format_parse_context<_CharT>::iterator
+ _M_parse(basic_format_parse_context<_CharT>& __pc)
+ {
+ auto __first = __pc.begin();
+ auto __last = __pc.end();
+
+ _Spec<_CharT> __spec{};
+
+ auto __finished = [&] {
+ if (__first == __last || *__first == '}')
+ {
+ _M_spec = __spec;
+ return true;
+ }
+ return false;
+ };
+
+ if (__finished())
+ return __first;
+
+ __first = __spec._M_parse_fill_and_align(__first, __last);
+ if (__finished())
+ return __first;
+
+ __first = __spec._M_parse_width(__first, __last, __pc);
+ if (__finished())
+ return __first;
+
+ return __spec._M_parse_locale(__first, __last);
It looks like if we reach this point, i.e. the L option is present,
then we don't do _M_spec = __spec?
And do we want to cause parsing to fail if __finished() == false after
parsing the locale option? Otherwise doesn't it mean we will ignore
any garbage after the L in the format string?
Ah no, I see you handle that in formatter::parse after calling
_M_f._M_parse.
But I don't think it's true that the chrono-specs must be empty for
local_info and sys_info, consider:
std::format("{:%n %t %%}", std::chrono::sys_info{})
Does __formatter_chrono_info need to parse and store the chrono-specs,
and then handle that in its _M_format? Only whitespace characters are
valid, and if there's a non-empty chrono-specs then we don't use the
format arg at all, just loop over the chrono-specs and output the
relevant whitespace chars. And that loop can be [[unlikely]] because
I doubt anybody will ever do this!
+ }
+
+ template<typename _Info, typename _Out>
+ typename basic_format_context<_Out, _CharT>::iterator
+ format(const _Info& __i,
+ basic_format_context<_Out, _CharT>& __fc) const
+ {
+ const size_t __padwidth = _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_spec._M_align, _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);
+ }
+
+ _Spec<_CharT> _M_spec;
+ };
+
} // namespace __format
/// @endcond
@@ -2438,16 +2536,22 @@ 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{}); }
+ {
+ auto __res = _M_f._M_parse(__pc);
+ if (__res == __pc.end() || *__res == '}')
+ return __res;
+ std::__throw_format_error("format error: invalid format-spec for "
+ "std::chrono::sys_info");
+ }
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>
@@ -2455,16 +2559,22 @@ 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{}); }
+ {
+ auto __res = _M_f._M_parse(__pc);
+ if (__res == __pc.end() || *__res == '}')
+ return __res;
+ std::__throw_format_error("format error: invalid format-spec for "
+ "std::chrono::local_info");
+ }
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
@@ -3326,15 +3436,7 @@ 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.
--
2.49.0
