[Development] Releasing memory after clear() in Qt containers (Qt 5.X)

Kevin Kofler kevin.kofler at chello.at
Sat Apr 24 01:41:37 CEST 2021

Giuseppe D'Angelo via Development wrote:
> 3) Unrelated to your problem, your code works in Qt 5, but in Qt 6 if
> the QHash gets modified in any way that'll invalidate your entire
> QVector you're keeping as a cache. If you want to future proof your code
> you'll need to redesign that.

This particular issue has come up so frequently in the last few weeks that 
this behavior change in Qt 6 sounds like a major design flaw of the Qt 6 
QHash to me. Also because it subtly breaks source compatibility in a way the 
compiler cannot possibly detect, with the worst possible outcome (undefined 
behavior). Only a sophisticated static analysis tool has any chance of 
catching this, if a dedicated check is written.

        Kevin Kofler

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