My layman’s reading is that implementation defined behavior can include rejecting the program with a diagnostic; in this case we have an implementation defined value, which implies that there is a value to define, and I infer that code must we well-defined.

I yield to Jens for a more accurate description though ;)

AlisdairM

Sent from my iPhone

On Jul 8, 2020, at 18:54, Tom Honermann <tom@honermann.net> wrote:


On 7/8/20 6:43 AM, Alisdair Meredith wrote:
Minor nit: I dislike normatively stating that a null character is
appended after string concatenation in two places.  I do like
the addition of this directly to the phase 6 wording, so suggest
that the original in [lex.string]p12 with its extra flowery language
be demoted to a note.
That seems reasonable to me, I'll do so.
In the normative text, AFAICT, in C++20 wide multi character
literals must be supported, with an implementation-defined value,
but after this paper they will be conditionally supported.  I don’t
see that design change addressed in the front matter.  Same
applies to non-encodable wide characters .

That is addressed in the "Proposed resolution overview" section.  I can add a statement about this to the introduction if you like.

I've been under the impression that the lack of conditionally-supported for these is an oversight.  My understanding (and someone please correct me if I'm mistaken; I don't recall where I was informed of this) is that, in the C standard, implementation-defined includes an allowance for rejecting the code as ill-formed, but in the C++ standard, implementation-defined implies well-formed; hence the addition of conditionally-supported.  If that understanding is correct, then the updated wording corrects alignment with the intent of the C standard.

(I thought this also applied to ordinary multi character literals,
but it turns out they are already conditionally supported.)

Yup, in [lex.ccon]p1.

Tom.

AlisdairM


On Jul 7, 2020, at 16:33, Tom Honermann via Core <core@lists.isocpp.org> wrote:

An update of D2029R2 (Proposed resolution for core issues 411, 1656, and 2333; numeric and universal character escapes in character and string literals) is now available at https://rawgit.com/sg16-unicode/sg16/master/papers/d2029r2.html. This addresses the feedback provided on the core mailing list in the thread starting at https://lists.isocpp.org/core/2020/06/9455.php.

Wording review feedback prior to the next Core issues processing teleconference would be much appreciated!

Tom.

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