On Wed, Jun 24, 2026 at 3:17 AM Steve Downey via SG16 <sg16@lists.isocpp.org> wrote:
SG16 Will meet tomorrow at 3:30 PM Zoom link https://iso.zoom.us/j/98307328424

Full link on the WG21 Calendar and on Mattermost

Agenda will be cleaning up some queued items:

finishing polling on UTF transcoding

Assuming you mean p2728r12

- not having an unchecked mode (which of course should never be the default) leaves some performance on the table, for simd/ branchless decoding - especially given how.. comprehensive error checking is in this proposal.
We should discuss that

- as_utfN allows narrowing conversion. I think we should put a lot more requirements on that,
namely. Preventing as_utfN over charX_t seems like the minimum, but I'm also concerned about conversion where the underlying type has a different sizeof.

- I do not understand the motivation for UTF Tags. It seems to try to make a deduction guide for to_utf_view work - even if we probably don't need one (use the adaptor objects), 
  and I question the ergonomics of trying to use these tags in practice.

- I am not sure I like the contortions around string literals, but I guess this can be relaxed later.

- reserve_hint() could be specified to return an implementation-defined value greater or equal to that of the underlying range
 
"$ in identifier", and

I don't think there is more we could say here, from an SG16 perspective. rubber-stamp/ship it
 


  wg21:       TODO [[https://github.com/cplusplus/papers/issues/2690][LWG4541]] Unclear behavior for parsing locale-dependent format                                                                                      :sg16:

Having an example would help.
 
  wg21:       TODO [[https://github.com/cplusplus/papers/issues/1895][LWG4087]] Standard exception messages have unspecified encoding                                                                                     :sg16:

If we are going to do that, can we also strike the nonsensical first sentence of the next remark
"The message may be a null-terminated multibyte string (16.3.3.3.4.3 [multibyte.strings]), suitable for conversion and display as a wstring (27.4 [string.classes], 28.3.4.2.5 [locale.codecvt])"
 
  wg21:       TODO [[https://github.com/cplusplus/papers/issues/1572][LWG2959]] char_traits<char16_t>::eof is a valid UTF-16 code unit                                                                                    :sg16:

We should ask Louis/STL if they are happy to change int_type, or, alternatively explain LEWG the only solution is to change int_type, and see if they care.
 

which are tagged SG16 input wanted.


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