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Subject: Re: [SG10] nodiscard updates after Cologne?
From: Aaron Ballman (aaron_at_[hidden])
Date: 2019-08-29 18:55:49


On Thu, Aug 29, 2019 at 7:49 PM Barry Revzin <barry.revzin_at_[hidden]> wrote:
>
> We had two changes to [[nodiscard]] in Cologne:
>
> - P1301R4: [[nodiscard("should have a reason")]], for C++20
> - P1771R1: [[nodiscard]] for constructors, as a DR
>
> Currently, I put both under the 201907 block (https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations#nodiscard). But that means we have a [retroactive] C++17 feature whose macro has a value two years later. Is that fine? Alternatively, we could invent an earlier value for P1771R1 that's in the C++17 timeline.
>
> Thoughts?

I raised this issue in Core and my understanding of the room was that
this is not a serious problem for implementations. Implementations are
expected to use the new value once they've implemented both features.

~Aaron

>
> Barry
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