SG16 will hold a meeting *today*, Wednesday, March 12th, at 19:30 UTC
(timezone conversion
<https://www.timeanddate.com/worldclock/converter.html?iso=20250312T193000&p1=1440&p2=tz_pdt&p3=tz_mdt&p4=tz_cdt&p5=tz_edt&p6=tz_cet>).

I apologize for the very late agenda. I had specifically set aside an
hour to get this done at 2am on Sunday, but that hour never happened.
Speaking of which...

*For those in North America, please note that daylight savings time has
begun, so this meeting will begin one hour later relative to the last
meeting.*

If you need a .ics file to import into your calendar, you can download
it here
<https://documents.isocpp.org/remote.php/dav/calendars/tahonermann/wg21-telecons_shared_by_hfinkel/94A3D3A0-70B9-4847-935F-9453DB2BB216.ics?export>.

The agenda follows.

  * P2873R2: Remove Deprecated locale category facets for Unicode from
    C++26 <https://wg21.link/p2873r2>.
  * P3395R0: Formatting of std::error_code <https://wg21.link/p3395r0>.

*P2873R0* <https://wg21.link/p2873r0> was previously reviewed by SG16
during the 2023-05-24
<https://github.com/sg16-unicode/sg16-meetings/blob/master/README-2023.md#may-24th-2023>
and 2023-10-25
<https://github.com/sg16-unicode/sg16-meetings/blob/master/README-2023.md#october-25th-2023>
meeting (briefly and tangentially, search for "P2873"). These reviews
followed previous discussion of the same topic/proposal in the context
of P2139R2 (Reviewing Deprecated Facilities of C++20 for C++23)
<https://wg21.link/p2139r2> section D.22 (Deprecated locale category
facets [depr.locale.category]) during the 2020-07-22 SG16 meeting
<https://github.com/sg16-unicode/sg16-meetings/blob/master/README-2020.md#july-22nd-2020>.
There was no consensus for removal during the 2020-07-22 review, but
there was consensus for no objection against removal (should LEWG decide
to do so despite no SG16 recommendation to remove). No concerns were
raised in the more recent reviews, but we never polled actually
forwarding the paper. The later revisions have not altered what is
proposed (beyond adding an annex C entry), but have significantly
expanded the history, the design concerns with these facets, the
motivation for deprecation, and the current implementation status with
regard to the deprecation. LEWG reviewed P2873R2 during its 2025-03-04
meeting
<https://wiki.edg.com/bin/view/Wg21telecons2025/P2873#Library_Evolution_Telecon-2025-03-04>
and approved it for inclusion in C++26/C++29 pending SG16 agreement.
We'll discuss and poll forwarding absent new concerns that would justify
reconsideration in LEWG. LEWG's polls were unanimously in favor of the
proposal as is.

*P3395R0 <https://wg21.link/p3395r0>* comes to us courtesy of Victor and
proposals portable formatting of std::error_code category names, values,
and messages. For example, the following code might produce the
annotated output.

    std::error_code ec((int)std::errc::no_such_file_or_directory,
    std::generic_category());
    std::print("{}\n", ec); // prints "generic:2"
    std::print("{:s}\n", ec); // prints "No such file or directory"

Of course, there wouldn't be much to talk about in SG16 if there weren't
complications. The encoding of the strings returned by
std::error_category::name() ([syserr.errcat.virtuals]p1
<https://eel.is/c++draft/syserr#errcat.virtuals-1>) and
std::error_category::message() ([syserr.errcat.virtuals]p5
<https://eel.is/c++draft/syserr#errcat.virtuals-5>) are not well
specified in the standard. The proposal acknowledges this, suggests
clarifications, and proposes that the new std::error_code formatter
perform necessary transcoding. See also LWG 4156 (error_category
messages have unspecified encoding)
<https://cplusplus.github.io/LWG/issue4156>. The concerns are similar to
those we previously discussed for LWG 4087 (Standard exception messages
have unspecified encoding) <https://cplusplus.github.io/LWG/issue4087>.

Tom.