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Subject: Re: [wg14/wg21 liaison] Draft WG14 N2653: char8_t: A type for UTF-8 characters and strings (Revision 1)
From: Richard Smith (richardsmith_at_[hidden])
Date: 2021-06-02 12:47:27


On Sun, May 30, 2021 at 6:33 PM Tom Honermann via Liaison <
liaison_at_[hidden]> wrote:

> I am seeking review feedback on a draft of N2653: char8_t: A type for
> UTF-8 characters and strings (Revision 1)
> <https://rawgit.com/sg16-unicode/sg16/master/papers/n2653.html>. This
> paper revises an earlier paper, N2231
> <http://www.open-std.org/jtc1/sc22/wg14/www/docs/n2231.htm>, from 2018.
>
> The revision is a rewrite of much of the original paper and follows the
> C++20 adoption of P0482R6 <https://wg21.link/p0482r6>. The primary
> motivation is to maintain source code compatibility between C and C++.
>
> Notable differences between what was adopted in C++20 and what is proposed
> for C2X in N2653
> <https://rawgit.com/sg16-unicode/sg16/master/papers/n2653.html> are:
>
> 1. In C++20, char8_t is a fundamental type. The C2X proposal is for a
> char8_t typedef name of unsigned char. This is consistent with
> existing differences between the languages for wchar_t, char16_t, and
> char32_t.
>
> One of the important properties of char8_t in C++20 is that it's not an
"aliases everything" type. Having that diverge between C and C++ seems
likely to be problematic.

>
> 1. In C++20, a UTF-8 string literal may no longer be used to
> initialize an array of char, signed char, or unsigned char. The C2X
> proposal retains these initializations. This is also consistent with
> existing differences for array initialization by a string literal with a
> mismatched encoding prefix.
>
> The Design Options section discusses these design decisions in more detail.
>
> I intend to submit this revision to WG14 later this week. Any feedback is
> appreciated.
>
> Tom.
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> Link to this post: http://lists.isocpp.org/liaison/2021/05/0597.php
>



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