[PATCH] D105759: Implement P2361 Unevaluated string literals

Fri Jul 28 23:40:44 PDT 2023

cor3ntin added a comment.

In D105759#4543685 <https://reviews.llvm.org/D105759#4543685>, @hubert.reinterpretcast wrote:

> In D105759#4543246 <https://reviews.llvm.org/D105759#4543246>, @aaron.ballman wrote:
>
>> I'd recommend we change the diagnostic to be a warning that defaults to an error so that users who are caught by the changes can still disable the diagnostic rather than be stuck; for Clang 18, we can explore other solutions to the issue. Would this work for you @hubert.reinterpretcast?
>
> I think there are questions about whether an error (or even warning) by default is appropriate. This seems to be a change for C++2c that does not have "DR" treatment from the committee. Considering this a warning controlled by `c++2c-compat` is a potential direction. Indeed, if we are going to accept the code, we might as well allow it as an extension in C++2c modes. With this line of logic, I don't see why we would want user-side churn of making a migration effort.

I will endeavor to have a patch by the beginning of the week.

I think the implementation effort is going to be the same whether it is an error by default or not so we can discuss that. I don't have a strong opinion.
Ideally, that would depend on how many users are affected.

However, I don't think nothing at all is a reasonable expectation here, `L` in `static_assert` message does either not work or is ignored. In no case does it do what the user wants https://godbolt.org/z/fYnMqT38P
Text encodings are sufficiently confusing that we should not add to the confusion by not telling users their encodings prefix have no effects.

And, given that prior to c++20 the standard simply ignores encoding prefixes, we could also discuss whether it was ever intended for prefixes to be supported or whether it was an oversight to begin with.

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https://reviews.llvm.org/D105759