Strange Bug: Signal <-> Slot connection not working in Qt 4.4 - works in Qt 4.5

[Milian Wolff]

Hello fellow developers!

I'm working on KDevelop and I stumbled upon a strange bug which I cannot 
solve. Basically we do a connect() which returns true but at the point we have 
the emit of the signal receivers() returns 0 (and the slot never gets called 
of course).

This problem only seems to occur in Qt 4.4 / Kde 4.2 and not in Qt 4.5... I 
already showed this problem to zwabel, adymo, apol, apaku and other KDevelop 
people but they are clueless as well. Apaku could reproduce the problem on his 
Qt 4.4 machine at work.

So, does anyone of you can help me? Or do you guys at least can give me a hint 
on where to look? I don't actually want to start to debug QObject (not even 
sure I'd be up to it). Here's a description on how to (possibly) reproduce the 
problem:

compile a recent version of KDevplatform and KDevelop, start KDevelop
attach to that instance with gdb and set the following breakpoint:

break 'KDevelop::DUChain::documentLoadedPrepare(KDevelop::IDocument*)'

Open up any .cpp / .h file and see if it hits the breakpoint. For me (and apaku 
on his Qt 4.4 machine) this slot is never getting called... In Qt 4.5 it 
magically works.

I checked the code and could not find a cause why the signal<->slot connection 
should would be released... Neither the duchain nor the document get 
removed...

A bit more in-depth information:
KDevelop::DUChain::DUChain
-> connects it's documentLoadedPrepare slot to the
   documentLoadedPrepare signal from KDevelop::IDocument

KDevelop::IDocument::notifyLoaded
-> emits the documentLoadedPrepare signal

NOTE: notifyLoaded is getting called! it's just that the emit in there has no 
receivers...

KDevelop::TextDocument::slotDocumentLoaded
-> calls notifyLoaded on the IDocument

KDevelop::TextDocument::slotDocumentLoaded is connected in the TextDocument 
ctor to the textchanged and documentloaded signals of KTextEditor::Document.

It would be great if somebody could give us a hint!

--
Milian Wolff
http://milianw.de

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