[Development] HEADS UP: QT_NO_SINGLE_ARG_QHASH_OVERLOAD issues

[Volker Hilsheimer]

> On 22 Apr 2026, at 09:52, Marc Mutz via Development <development at qt-project.org> wrote:
> 
> Hi,
> 
> TL;DR:
> - QT_NO_SINGLE_ARG_QHASH_OVERLOAD changes semantics in 6.11.1 and dev
> - delayed from strict mode 6.11 to 6.12 to give everyone more time
> - check impact by buiding with macro enabled and qtbase past abb639bea4df011b19607df4509187ebe91bbb59 (https://codereview.qt-project.org/c/qt/qtbase/+/729320)
> - do not push a fix for public types without approval of the likes of Thiago, Peppe, Ahmad, Ivan, Mårten, or me: BC is involved
> - see Action Points at end of email


Thanks for a thorough analysis and write-up, Marc!


> Sorry for the bad news, but this just goes to show that BC in a huge library like Qt will only ever be a probabilistics game, at least until AI takes over.

:D

Volker