I don't see this as being a bugfix for C++20 features - the only timeline/features discussed are C++14-era. Much as I'd love to see this happen, I don't think it meets the criteria for C++20-focus.

That said, it's also an LWG matter as far as I'm concerned. I'm dropping the LEWG tag, and recommend dropping the C++20 tag, but defer to Marshall.

The paper that was mailed, pre-Cologne, is http://wg21.link/p1715r0
The reflectors reported a problem with that version, regarding function template argument deduction. This is corrected in http://wiki.edg.com/pub/Wg21cologne2019/LibraryWorkingGroup/D1715r1.html

This was not adopted for C++20. Removing the "C++20" label.

2022-11-07 10:00 to 11:30 UTC-10 Kona Library Evolution Meeting

P1715R0: Loosen restrictions on "_t" typedefs and "_v" values

2022-11-07 10:00 to 11:30 UTC-10 Kona Library Evolution Minutes

Champion: Corentin Jabot

Chair: Fabio Fracassi & Billy Baker

Minute Taker: Steve Downey

Key Insights:

• Add missing type traits.
• Look at existing traits and make sure they do not introduce deduced context. e.g. common_type
• Existing implementations might not want to make use of the new liberties for ABI reasons
• deployment/experience

Summary

We feel this paper has some merits, but there was also some skepticism. Potential ABI and API inconsistencies have to be carefully surveyed.

Since this paper does not prescribe the changes but only gives implementors more freedom for better QoI.

Next Steps

Champion will provide an updated revision, which we will review.

Why is this listed for C++23? The world wonders.

Ah, this was listed for C++23 because we have an NB comment for it, FR-017-016 cplusplus/nbballot#419

New version addresses comments more specifically, corrects naming to be "P" rather than "D". => https://isocpp.org/files/papers/P1715R1.html

2023-02-06 13:00 to 15:15 Issaquah Library Evolution Meeting

P1715R1: Loosen restrictions on _t typedefs

2023-02-06 13:00 to 15:15 UTC-8 Issaquah Library Evolution Minutes

Champion: Jorg Brown (IP)

Chair: Bryce Adelstein Lelbach (IP) & Billy Baker (IP)

Minute Taker: Robert Leahy (IP)

Start: 2023-02-06 14:46 UTC-8

Does this paper have:

• Examples?
  • Yes.
• Field experience?
  • Some, but not of the entire proposal in a production Standard Library.
• Performance considerations?
  • Not in the paper - such performance data should be included.
• Discussion of prior art?
  • Yes.
• Changes Library Evolution previously requested?
  • Yes.
• Wording?
  • Yes.
• Breaking changes?
  • Yes. The impact hasn't been sufficiently evaluated.
• Feature test macro?
  • Not needed.
• Freestanding?
  • N/A.

POLL: Send P1715R1 (Loosen restrictions on _t typedefs) to Library for C++23 as the resolution to C++23 National Body comment FR-017-016, classified as B2 - improvement.

Attendance: 23 (in person) + 14 (remote)

# of Authors: 1

Author Position: SF

Outcome: No consensus.

Break: 15:16

Resume: 15:31

POLL: Send P1715R1 (Loosen restrictions on _t typedefs) to Library for C++23 as the resolution to C++23 National Body comment FR-017-016, classified as B2 - improvement.

Attendance: 25 (in person) + 14 (remote)

# of Authors: 1

Author Position: SF

Outcome: No consensus.

End: 15:58

Summary

We discussed this proposal to give implementations freedom to improve the compile time performance of the _t typedefs.

Some implementers said they'd be unable to use this freedom as it would break ABIs. Others said they hoped to use it in their unstable ABI modes. It is believed that some implementations may be able to make the change without breaking ABI. Also, new implementations could take advantage of the freedom.

There was a desire to learn more about the performance implications of this change. An addition to the paper with benchmark results would be helpful.

The proposed change could be source breaking in some cases. There was a general belief that the impact on real-world code would be small. More discussion and analysis of this in the paper may help.

Since there was an NB comment requesting this for C++23, we discussed whether we should try to squeeze it in. Some felt that there was no great urgency, and that adding it at this late stage might be risky. Ultimately, we did not have consensus to pursue it for C++23.

Next Steps

Revise P1715R1 (Loosen restrictions on _t typedefs) and return to Library Evolution for further design review for C++26.

Reject C++23 National Body comment FR-017-016 as we have no consensus for change.

@brycelelbach @billy-baker

I think there's something off in the notes here -- looks like copy-pasta w.r.t the 23/26 votes -- same poll two different outcomes?

No, the polls are right. We took it once then learned new information afterwards.