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Subject: Re: [SG10] [isocpp-core] No __cpp_concepts in the C++20 draft
From: Jason Merrill (jason_at_[hidden])
Date: 2019-11-07 08:33:15


On Mon, Sep 16, 2019 at 5:34 PM Casey Carter via Core <core_at_[hidden]>
wrote:

> We haven't had a __cpp_concepts since the TS specified its value as 201507
> - which GCC defines. I've been making up values since then for various
> compilers which cmcstl2 supports to various degrees:
> * clang-concepts defines __cpp_concepts to 201707L - the date of the
> Toronto merge - to indicate support for concepts as merged.
> * MSVC uses 201811L - the date of the P1084 merge - to indicate that it
> supports the above plus P1084's changes to return-type-requirements.
> (Unfortunately MSVC does not yet support the changes in P1141 which were
> merged at the same meeting.)
>
> I'd appreciate a bump for the changes in Cologne. P1452 seems significant
> enough to me, but regardless it would be nice to have a way to discriminate
> between what MSVC will support in 16.3 and C++20 concepts' final form.
>

FYI http://wiki.edg.com/pub/Wg21belfast/CoreWorkingGroup/d1902r1.html does
not propose to bump the value beyond 201811L.

> On Mon, Sep 16, 2019 at 8:26 AM John Spicer <jhs_at_[hidden]> wrote:
>
>> Yes, I think we should have one.
>>
>> John.
>>
>> On Sep 14, 2019, at 4:07 PM, Barry Revzin <barry.revzin_at_[hidden]> wrote:
>>
>> On Sat, Sep 14, 2019, 2:38 PM Jason Merrill via Core <
>> core_at_[hidden]> wrote:
>>
>>> This doesn't seem to have been addressed at Cologne. I don't think
>>> any of the changes at Cologne (conditionally trivial, unconstrained
>>> TTP, dropping return-type requirements) require a version bump, does
>>> anyone else?
>>>
>>> So I'd stick with the 201811 value.
>>>
>>> Jason
>>>
>>
>> Wait, do we even have a __cpp_concepts? We have a __cpp_lib_concepts (...
>> that def needs to be bumped to 201907), but not one for the language. We
>> should add one...
>>
>> Barry
>>
>>> _______________________________________________
>> Features mailing list
>> Features_at_[hidden]
>> http://www.open-std.org/mailman/listinfo/features
>>
>>
>> _______________________________________________
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>> Features_at_[hidden]
>> http://www.open-std.org/mailman/listinfo/features
>>
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