> Am 26.05.2026 um 17:04 schrieb Marc Mutz via Development 
> <[email protected]>:
> 
> 
> Refactoring, even huge ones, are completely safe and never change behaviour. 
> If they do, they're not refactorings, but something else.

With that definition for "Refactoring", refactorings do not exist, because you 
cannot guarantee this  (at least not for more than trivial changes). For me 
that is fine then - there are no refactorings, so nothing to cherry-pick to 
stable branches...
If it was possible to guarantee, bug fixes would always only change the 
behavior that they want to change, and unintended regressions would not exist.

Reality shows different.

> As for bug-fixes: they ought to be clearly communicated to users via 
> [ChangeLog], so users know what will come with the next update instead of 
> showing up as regressions in their projects.

That leaves the unintended behavior changes of a bug fix which still show up as 
regressions.

>>> - bugfixes should always be picked back
>> ..and this depends on the nature and severity of the bug.
> 
> Does it, now? Which customer wants to sit on a version of Qt with a known, 
> unfixed bug? Just because it hasn't hit them, yet, doesn't mean it won't hit 
> them in the future, or, worse, hit a customer of theirs.

Yes it does depend. A bug that has been known for 5 years with a JIRA entry and 
existing workarounds is a known risk. A bugfix for that issue in a "stable" 
branch is an unknown risk. An unintended regression could be much worse, 
affects code that worked and was tested before, might not have workarounds etc.

> what is more important? Regression-free stable branches, or TTM for security 
> fixes?

Faster TTM for security fixes doesn't matter if app developers cannot upgrade 
Qt (or if the upgrade takes longer) because the upgrade breaks their 
applications. If stability is sacrificed for faster TTM for security fixes in 
the Qt code base that doesn't necessarily result in faster TTM of the security 
fixes in the actual applications if the update of Qt is made harder because of 
breakages / behavior changes, intended or not. Aside from the question how much 
faster security fixes actually could be done in general (how much effort is 
backporting security fixes on average now? You own statement "your typical 
security fix (which tend to be one-liners more often than not)" seems to 
indicate that for most the effort is not high.) and the question of the risk of 
introducing new security issues in "stable" branches because of a "backport 
everything except features" policy.

++ Eike

— 
Eike Ziller
Principal Software Engineer

The Qt Company GmbH
Erich-Thilo-Str. 10
12489 Berlin, Germany
[email protected]
https://www.qt.io

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