On 26/01/2023 18.54, Fraser Gordon wrote:
> Thanks Tom & Jens, submitted with your proposed change: https://github.com/cplusplus/CWG/issues/230 <https://github.com/cplusplus/CWG/issues/230>

This is now CWG2691:

https://cplusplus.github.io/CWG/issues/2691.html

Thanks,
Jens


> Fraser
>
> On Thu, 26 Jan 2023 at 12:45, Tom Honermann via Std-Proposals <std-proposals_at_[hidden] <mailto:std-proposals_at_[hidden]>> wrote:
>
> Ha! Despite it looking very much like I just copied and resent essentially the same thing Jens did two minutes earlier, I swear I didn't! :)
>
> Tom.
>
> On 1/26/23 12:44 PM, Tom Honermann via Std-Proposals wrote:
>> On 1/26/23 12:23 PM, Fraser Gordon via Std-Proposals wrote:
>>> Hi folks,
>>>
>>> I was reading the [lex.ccon] section of the current draft and noticed an oddity in the hexadecimal-escape-sequence <https://eel.is/c++draft/lex.ccon#nt:hexadecimal-escape-sequence> production:
>>>
>>> /hexadecimal-escape-sequence:/
>>>
>>> \x /hexadecimal-digit-sequence/
>>> /hexadecimal-escape-sequence hexadecimal-digit/
>>> \x{ /simple-hexadecimal-digit-sequence/ }
>>>
>>> The combination of the 2nd and 3rd rules seems to say that \x{20}20 should be parsed as a hex escape sequence (presumably representing u+2020). Octal doesn't have this issue as /octal-escape-sequence/ doesn't have a recursive definition.
>>>
>>> I tried this on Godbolt. GCC and Clang interpret '\x{20}20' as a multicharacter literal and "\x{20}{20}" as the string " 20". MSVC and icc appear not to support \x{}.
>>>
>>> I'd guess this isn't intentional as it would defeat the purpose of having \x{} sequences? At least two implementations seem to agree.
>>
>> Good catch!
>>
>> I think we want:/
>> /
>>
>> /hexadecimal-escape-sequence:/
>> / /\x /hexadecimal-digit-sequence_simple-hexadecimal-digit-sequence_ //
>> hexadecimal-escape-sequence hexadecimal-digit/
>> / /\x{ /simple-hexadecimal-digit-sequence/ }
>>
>> Would you be so kind as to file a CWG issue at https://github.com/cplusplus/CWG <https://github.com/cplusplus/CWG>?
>>
>> Tom.
>>
>>>
>>> Fraser
>>>
>>
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