[Development] QArrayDataObs/Pointer UB post-mortem

[Ville Voutilainen]

On Tue, 26 May 2026 at 10:55, Marc Mutz via Development
<development at qt-project.org> wrote:
> To me, this issue reinforces what I have known to be true for years, to wit:
> - the compiler is more clever than you, you MUST NOT fall into UB, regardless of whether _you_ think it's benign (even if you think you can prove it)

This part is correct, and non-controversial.

At the same time, what I have known to be true for years, with
evidence, is that (after the parenthetical)..

> - 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?)

>   - 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.

>   - bugfixes should always be picked back

..and this depends on the nature and severity of the bug.

None of the story illustrated in the original convinces me an inch to
the suggested direction of aggressive picking.