[QGIS-Developer] qgis4 segfaults with qt6 6.11.0, ok with 6.10.2

[Greg Troxel]

Yesterday I wrote that starting up qgis 4.0.2(+18 commits) (from
pkgsrc-wip/qgis) resulted in a crash.  It turns out the thing that
matters for crash vs works is not qgis version, but qt6 version.

(This is all about qgis 4, because qgis 3.44 uses qt5 (and both qgis 3.44
and qt5 are apparently stable).)

This is all on NetBSD 10 amd64.

QGIS	QT	RESULT	
4.0.0	6.10.2	works
4.0.2   6.10.2	works
4.0.0	6.11.0	crashes on opening project file
4.0.2	6.11.0	crashes on opening project file

Have other people tried to run qgis, or other complicated qt programs
built against qt6 6.11.0?   It looks to me like 6.11.0 redid a bunch of
things and I'm guessing they broke things.  But there could be a latent
bug in qgis.