[Development] QArrayDataObs/Pointer UB post-mortem

[Ville Voutilainen]

On Tue, 26 May 2026 at 18:06, Marc Mutz via Development
<development at qt-project.org> wrote:
> - only features shouldn't be picked back, in particular
>   - test changes should always be picked back, with a XFAIL, if necessary
>
> (I don't know what this is trying to say. What sort of test changes?
> Are there examples of this?
> If there's no functionality being backported, why would test changes
> be backported?)
>
> Anything under tests/: cleanups, test extensions prior to src/ refactorings, bugfixes, etc, xfail bug reproducers, ...

In other words, a very clear not-always case, here, too.

> You would be surprised how many cherry-picks conflict in tests/ and not src/
>
>   - refactorings should always be picked back (or not done at all)
>
> ..this is completely false, and at best depends on the refactoring.
> And that's at best, and there's absolutely
> certainly no "always" in any of it, and even less so if the
> refactorings are large.
>
>
> Refactoring, even huge ones, are completely safe and never change behaviour. If they do, they're not refactorings, but something else.

Spare me the theoretical ideals.

>
>   - bugfixes should always be picked back
>
> ..and this depends on the nature and severity of the bug.
>
> Does it, now?

Yes, it does.

> Which customer wants to sit on a version of Qt with a known, unfixed bug?

Every customer who is not affected by such a bug and wants to avoid
large changes that might cause regression bugs
that would actually impact them.

> I think if we could guarantee "no regressions", customers would very much prefer to have _all_ bugfixes. So that's just conflating two orthogonal issues, IMHO.

Maybe. But considering that we can't guarantee that, prudence dictates
avoiding nonsense like suggestions that we should "always" cherry-pick
refactorings.