Hi,
I just pushed the v2/2 patch, thanks again for contribution. As we are
closing to 16.2
release I will not be able to look at your ostream patches soon (there are
some things
I want to double-check them).
As a side note, in the v4 version that I merged, I removed passing of locale
for sys_info, as the output is not really locally depended. I have realized
that the same
apply to any time_point that uses seconds (or greater precision). I wonder
if there would
be measurable benefit in defining operator<< for sys_time (utc_time,
etc...) as:
if constexpr (Duration::period::den == 1)
chrono_write<64>(os, __t);
else
chrono_write<64>(os, __t, os.getloc());
(Maybe we could have time_point_write with above, or time_point overload of
chrono_write).
I think this also works for zoned_time, as the offset are defined in
seconds, so converting
will add subseconds. And hh_mm_ss.
Is this something you would be interested in taking a look and measuring?
Regards,
Tomasz
On Tue, Jul 14, 2026 at 5:35 AM Anlai Lu <[email protected]> wrote:
> PING
>
> > On Jun 30, 2026, at 20:49, Anlai Lu <[email protected]> wrote:
> >
> > This is v3 of the patch series. Performance data: see v2 cover letter.
> > Results are unchanged -- same stack-buffer + __ostream_insert approach.
> >
> > Patch 1 is unchanged from v2.
> >
> > Changes in Patch 2 from v2:
> >
> > - Dropped the format string parameter from __chrono_write.
> > _S_empty_fs() is used directly, per Tomasz Kaminski's suggestion.
> > All chrono types now share the same two call forms:
> > __detail::__chrono_write(__os, __arg);
> > __detail::__chrono_write(__os, __arg, __os.getloc());
> >
> > - Removed __detail::__empty_fmt: no longer needed.
> >
> > - All remaining operator<< that used basic_stringstream now use
> > __chrono_write (month_day, month_day_last, month_weekday,
> > month_weekday_last, year_month, year_month_day_last,
> > year_month_weekday, year_month_weekday_last, sys_days, local_time).
> >
> > - The only types not converted: duration (must forward stream flags
> > and precision) and local_info (uses __formatter_chrono_info).
> >
> > - Uses std::format_to_n (public API) instead of __do_vformat_to_n.
> >
> > Tested on x86_64-linux-gnu. libstdc++ testsuite (std/time/*) clean.
> > All converted types verified byte-identical across C, en_US, de_DE,
> > fr_FR, and zh_CN locales.
> >
> > Anlai Lu (2):
> > libstdc++: Add stream state tests for chrono operator<<
> > libstdc++: Use __chrono_write via _S_empty_fs for chrono ostream
> > insertion
> >
> > libstdc++-v3/include/bits/chrono_io.h | 227 ++++--------------
> > .../testsuite/std/time/ostream_insert.cc | 163 +++++++++++++
> > 2 files changed, 212 insertions(+), 178 deletions(-)
> > create mode 100644 libstdc++-v3/testsuite/std/time/ostream_insert.cc
> >
> > --
> > 2.34.1
>
>
