[PATCH RESEND 1/1] p1689r5: initial support

[Jason Merrill]

On 10/20/22 13:31, Ben Boeckel wrote:
> On Thu, Oct 20, 2022 at 11:39:25 -0400, Jason Merrill wrote:
>> Oops, I was thinking this was in gcc as well.  In libcpp there's
>> _cpp_valid_utf8 (which calls one_utf8_to_cppchar).
> 
> This routine has a lot more logic (including UCN decoding) and the
> `one_utf8_to_cppchar` also supports out-of-bounds codepoints above
> `0x10FFFF`.

The latter seems like a bug to be fixed; presumably it hasn't been 
updated since the range of codepoints was restricted.  This sort of 
thing is why I'd like to minimize the number of separate implementations 
of UTF-8 parsing.

Jason