no luck with Qt 5.9.2

[Thiago Macieira]

On Tuesday, 24 October 2017 08:30:14 PDT Tomaz Canabrava wrote:
> > I found one commit that is in Qt 5.9.2 (and not in 5.9.1) called "Fix qml
> > cache invalidation when changing dependent C++ registered QML singletons"
> > (commit 98358715930739ca8de172d88c5ce6941c275ff3 in qtdeclarative).
> > Related
> > to QTBUG-62243.
> > 
> > The rationale of that commit is fully sane to me, but ... I reverted this
> > one, and my problem of unable to start Subsurface-mobile build with 5.9.2
> > (on desktop, for now) due to a silent failure of engine.load("main.qml")
> > is
> > gone, and the mobile-on-desktop app runs correctly as before.
> > 
> > So, now the big question is ... how to proceed? I still cannot rule out
> > that
> > the whole issue is a result of some (still unknown) bug in Subsurface
> > itself, or Kirigami or ... But, building a tiny bug demonstrator for Qt
> > might be over my skill set :-)
> > 
> > For anyone that might wonder how I found this suspicious commit ... I
> > found
> > earlier that the Kirigami file Units.qml was involved, and that is a
> > singleton type object. That made me search for singleton related code
> > changes in Qt.
> 
> This is something that we can poke thiago, and thiago can poke more people.
> And it's a serious issue as this can break a lot of usecases of qt.

And he did.

The first thing we should do is file a bug with the findings so far and the 
symptoms, even if we can't provide a reduced testcase.

Further from that, I can't directly help, since I have no idea about the QML 
internals. I do know that the QML caching feature is something I have problems 
with, but that's usually because I build from sources and not from releases. 
Intermediary builds can leave corrupt caches.

I can help poke people, though. Can you report the current findings so I'll 
poke people?	

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
   Software Architect - Intel Open Source Technology Center