Since the adoption of P2736 C++23 and the current C++ working draft just refer to "the Unicode Standard", with a URL referring to the latest version. We removed the bibliography entry for TR29 revision 35. P2736 gives the justification for this that the revision of #29 included in Unicode 15 (revision 41) is just a bug fix, so there's no problem referring to that instead.

That might have been true last year, but the current Unicode Standard (15.1.0) includes revision 43 of UAX #29, which makes significant changes to the extended grapheme cluster breaking rules. A new state machine is needed (and new lookup tables of properties) to implement rule GB9c. That's not just a bug fix, is it?

Are C++ implementations expected to implement rule GB9c, despite it not being part of the standard when C++23 was published? If not, where in the C++23 standard does it say that implementations should conform to version 15.0.0 of the Unicode Standard, rather than version 15.1.0, or whatever version they publish next? How can we conform to a moving target?

Am I missing some reference that names Unicode 15.0.0?

Thank you for raising this issue, Jonathan.

For reference, relevant SG16 discussions are recorded as follows:

• 2022-11-02 SG16 meeting:
• Includes discussion of FR-010-133 and FR-021-013. The following polls were taken:
• Poll 3: [FR-010-133][FR-021-013]: SG16 requests that the project editor discuss with the ISO the option of eschewing references to ISO/IEC 10646 in favor of the Unicode Standard both for technical consistency and release frequency.
  Attendees: 9 (1 abstention)
  Objection to unanimous consent.
  

  SF	F	N	A	SA
  3	3	0	1	1

  Weak consensus
  SA: Use of the ISO/IEC 10646 document benefits from ISO governance.
  SA: Would prefer to explore expansion of ISO/IEC 10646 to include more components of Unicode.
  
• Poll 4: [FR-010-133][FR-021-013]: SG16 recommends resolving these comments by restricting all references to the Unicode Standard to the version that corresponds to the referenced version of ISO/IEC 10646.
  Attendees: 9 (1 abstention)
  

  SF	F	N	A	SA
  2	3	0	3	0

  No consensus.
  A: It doesn't benefit the community to reference a Unicode version that is outdated by the time the standard is published.
  
• 2022-11-30 SG16 meeting:
• Includes discussion of FR-010-133 and FR-021-013. No polls were taken.
• 2022-12-14 SG16 meeting:
• Includes discussion of a draft of P2736R0. No polls were taken.
• 2023-01-11 SG16 meeting:
• Includes discussion of P2736R0. No polls were taken.
  
• 2023-01-25 SG16 meeting:
• Includes discussion of P2736R0. The following polls were taken:
  
• Poll 1.1: Whether __STDC_ISO_10646__ is predefined and if so, what its value is, are implementation-defined, retaining the mandated yyyymmL form.
  Attendees: 11 (3 abstentions)
  

  SF	F	N	A	SA
  6	2	0	0	0

  Unanimous consent.
• Poll 1.2: Forward P2736R1, amended as discussed, to CWG and LWG as the recommended resolution of NB comments FR-010-133 and FR-021-013.
  Attendees: 10 (1 abstention)
  

  SF	F	N	A	SA
  7	2	0	0	0

  Unanimous consent.