Hi Tom,

I didn't realize that the meeting would be moved and so will only be
present for the first half an hour due to a conflict. Is it possible to
review P3395R0 first?

Cheers,
Victor

On Wed, Mar 12, 2025 at 9:49 AM Tom Honermann via SG16 <
sg16_at_[hidden]> wrote:

> 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.
>
> --
> SG16 mailing list
> SG16_at_[hidden]
> https://lists.isocpp.org/mailman/listinfo.cgi/sg16
>