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?
>
> Tom.
>
>>
>> Fraser
>>
>