FR-007-012 22.14.2.2 [format.string.std] codepoints with width 2

[wg21bot]

The range of codepoints to be considered of width 2 is not compatible with recent and future Unicode versions.

Please adopt LWG3780 for C++23, backported to C++20.

[cor3ntin]

Paper cplusplus/papers#1341

[brycelelbach]

@tahonermann you get first crack at this. Send it back to us when it's ready.

[tahonermann]

SG16 discussed this issue during its 2022-12-14 telecon. The following polls were taken:

• Poll 0.1: Forward D2675R1
  "format's width estimation is too approximate and not forward compatible",
  with improved presentation, to LEWG as the recommended resolution of LWG3780
  and NB comment FR-007-012.
  • Attendees: 6

    SF	F	N	A	SA
    3	3	0	0	0

  • Unanimous consent.
• Poll 0.2: Recommend that D2675R1 be applied to the C++23 working paper.
  • Attendees: 6

    SF	F	N	A	SA
    2	4	0	0	0

  • Unanimous consent.

P2675R1 reflects the presentation improvements requested in the first poll.

@brycelelbach, this is now ready for LEWG. I'm removing the SG16 label.

[brycelelbach]

This has an issue (LWG3780, cplusplus/papers#1313) and a paper (P2675, cplusplus/papers#1341).

[JeffGarland]

Reviewed and approved at Issaquah -- see paper issue for details.

[jensmaurer]

Accepted.