For what it's worth: Clang treats CR LF[opt] and LF CR[opt] as line
termination sequences. So long as that remains a conforming option, and
both LF and CRLF are guaranteed to work, that seems fine to me. Guaranteed
support for portable use of CR and LFCR seem nice to have but less
important.

On Tue, 8 Nov 2022 at 07:32, William M. (Mike) Miller via Core <
core_at_[hidden]> wrote:

> On Tue, Nov 8, 2022 at 12:41 AM Tom Honermann via Core <
> core_at_[hidden]> wrote:
>
>> Thanks, Corentin.
>>
>> I agree that, if ~all existing implementations already treat a lone CR as
>> a new-line, then we might as well standardize it. However, if some don't,
>> then we'll be adding a (probably small) implementation burden for something
>> that I suspect is rare. LF and CR+LF are common occurrences. Do you have
>> data that shows that lone CR is 1) recognized by ~all existing
>> implementations, and 2) is used sufficiently often that it is worth
>> standardizing? Do we want to encourage use of lone CR as a portable
>> new-line? As mentioned, implementations can still support it regardless.
>> Unicode also recognizes U+0085 (NEXT LINE), U+2028 (LINE SEPARATOR), and
>> U+2029 (PARAGRAPH SEPARATOR) as line-break characters.
>>
>> I think it would be worth adding such analysis to a future revision of
>> P2348.
>>
>> In the interest of time, is anyone opposed to the CWG direction of
>> requiring both LF and CR+LF in portable UTF-8 source files for C++23 with
>> support for other new-line sequences left to a future standard?
>>
>
> Actually, CWG changed direction in the late afternoon session and decided
> to accept CR as a line-termination character. I'm about to upload drafting
> implementing that direction for discussion today.
>
> I don't know about the ubiquity of that support, but the EDG front end has
> it as a build-time configuration option that customers can enable or not,
> as they choose. Here's the description of the flag (note that it cites
> gcc's processing as its basis):
>
> /*
>> Flag that is TRUE to indicate that carriage return or carriage return
>> followed by newline can be used as a line terminator in GNU-compatible
>> modes. This feature is provided to allow files with old MacOS line
>> terminators to be accepted. The implementation is compatible with the way
>> in which the GNU compiler handles such line terminators. It is disabled
>> by
>> default because it is not required by most users.
>> */
>>
>
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