[PATCH] D144334: [Clang] Add C++2b attribute [[assume(expression)]]

Tue Feb 21 11:48:27 PST 2023

erichkeane added a comment.

In D144334#4142462 <https://reviews.llvm.org/D144334#4142462>, @Izaron wrote:

> In D144334#4141646 <https://reviews.llvm.org/D144334#4141646>, @erichkeane wrote:
>
>> I'm on the fence as to whether we want to implement this feature at all.  As was discussed extensively during the EWG meetings on this: multiple implementers are against this attribute for a variety of reasons, and at least 1 other implementer has stated they might 'implementer veto' this.
>
> I don't quite understand how it works. The feature has been approved for C++2b, but it should have not been approved if there were concerns from implementers.

You're preaching to the choir on that one.  Two of the implementers (including our code owner, and MSVC reps) stated a distinct dislike for this, and that they were considering implementer veto on it.

> A friend of mine got his proposal rejected because MSVC said they are unable to support the new feature.

"Unable to support" and "dont want to support" are different, but EWG is nothing if not consistently inconsistent.

> But it seems like not the case with the `assume` attribute. Could you please elaborate: if you decide to not implement this feature, you will kind of revoke the proposal or just deliberately do not support a part of C++2b in Clang?

Just deliberately not support a part of C++2b.  Implementers have veto'ed features in the past exactly that way.

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  https://reviews.llvm.org/D144334/new/

https://reviews.llvm.org/D144334