[Development] C++20 comparisons @ Qt (was: Re: C++20 @ Qt)

[Ivan Solovev]

Marc wrote:
> I think I speak for Ivan, too, if I say that we'd rather
> today than tomorrow see this stuff merged. The next FF is already
> approaching again.

Right! This now seems to be the only thing blocking the whole
chain, and I think Marc's proposal solves all the issues.
I really do not want to miss yet another FF.

Best regards,
Ivan

________________________________
From: Development <development-bounces at qt-project.org> on behalf of Marc Mutz via Development <development at qt-project.org>
Sent: Monday, November 13, 2023 6:15 PM
To: development at qt-project.org <development at qt-project.org>
Subject: Re: [Development] C++20 comparisons @ Qt (was: Re: C++20 @ Qt)

On 13.11.23 17:15, Thiago Macieira wrote:
> On Monday, 13 November 2023 01:34:08 PST Ivan Solovev via Development wrote:
>> Thiago wrote:
>>> The problem is that QPartialOrdering::Unordered has been in our ABI since
>>> 6.1 and we can't change that any more.
>>
>> Well, Marc already suggested a solution for this problem.
>> Let's just introduce Qt::{strong,weak,partial}_ordering and deprecate
>> QPartialOrdering in favor of the new types.
>>
>> We need to provide conversion between QPartialOrdering and
>> Qt::partial_ordering, but the new types can be fully BC with std.
>
> I don't think this minor thing is worth the hassle. It uglifies our API for
> little gain.

What, specifically, is ugly? That we have two Qt partial_ordering types?

Anyway, that's subjective. Objectively, it breaks the impasse between
full efficiency in future-looking C++20 builds and Qt BC guarantees.

Given that Qt 7.0 is many years away, I don't think it's too much to ask
to go the extra mile and remove the overhead. We seem to agree how to do
it technically, and it won't be on you to implement all this, but on
Ivan and me. I think I speak for Ivan, too, if I say that we'd rather
today than tomorrow see this stuff merged. The next FF is already
approaching again.

Thanks,
Marc

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Marc Mutz <marc.mutz at qt.io>
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