On 7/25/23 9:17 PM, Hubert Tong via SG16 wrote:
> On Sat, Jul 22, 2023 at 9:15 PM Tom Honermann via SG16
> <sg16_at_[hidden]> wrote:
>
> SG16 will hold a telecon on Wednesday, July 26th, at 19:30 UTC
> (timezone conversion
> <https://www.timeanddate.com/worldclock/converter.html?iso=20230726T193000&p1=1440&p2=tz_pt&p3=tz_mt&p4=tz_ct&p5=tz_et&p6=tz_cest>).
>
> The agenda follows.
>
> * WG14 N3145: $ in Identifiers v2
> <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3145.pdf>:
> o Determine whether a corresponding proposal for WG21 is
> desired.
> * P2811R7: Contract-Violation Handlers <https://wg21.link/p2811r7>:
> o Discuss character encoding considerations for the
> std::contracts::contract_violation::comment() member function.
> * LWG 3944: Formatters converting sequences of char to sequences
> of wchar_t <https://wg21.link/lwg3944>:
> o Continue review pending a proposed resolution or related
> paper.
>
> Hubert suggested in a post to the SG16 mailing list
> <https://lists.isocpp.org/sg16/2023/07/3891.php> that SG16
> consider whether similar changes to those adopted for C2x via WG14
> N3145 <https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3145.pdf>
> to allow $ in identifiers as a sanctioned implementation-defined
> allowance are desirable. All major C++ implementations currently
> allow $ in identifiers by default with no warning, even with
> -Wall; https://godbolt.org/z/M154z7bGf. Some implementations issue
> a warning in their pedantic modes. All implementations provide an
> option to prohibit $ in identifiers. We'll discuss the impact (or
> lack thereof) to implementations regarding an
> implementation-defined allowance vs a conforming extension.
>
> There can be no conforming extension without a change to the standard.
> As it stands, parsing for an identifier must end when a dollar sign is
> encountered because it is considered a separate pp-token. Furthermore,
> as a member of the basic character set, attempts to use a UCN for it
> outside of character/string literals is ill-formed.

Ah, yes, thank you for that correction, Hubert!

The extension has been non-conforming since before P25582 (Add @, $, and
` to the basic character set) <https://wg21.link/p2558> due to the
pp-token issue, correct? So this isn't actually a new concern; just one
that is slightly changed due to the new prohibition against use of a UCN
to name the $ character outside of literals.

Tom.

> SG21 has been making good progress on a contracts feature for
> C++26 and recently approved P2811R7 <https://wg21.link/p2811r7>.
> When a contract violation occurs, a violation handler is invoked
> and passed a std::contracts::contract_violation object whose
> comment() member function is expected to reflect portions of the
> source code. Per proposal 1.3 ("The comment property") in section
> 4.1 ("An Extensible contract_violation Type"), the intent is that
> the function return text encoded in the literal encoding. The
> proposed wording simply states that the function returns
> implementation-defined text. We'll discuss whether to recommend
> any changes.
>
> LWG 3944 <https://wg21.link/lwg3944> was discussed during the
> 2023-07-12 SG16 meeting
> <https://github.com/sg16-unicode/sg16-meetings/#june-7th-2023>
> (that link will work soon) and is pending a proposed resolution or
> paper. If an update is provided and time permits, we'll continue
> discussion.
>
> Tom.
>
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