What happens after closing and before destruction?

[mchara]

try

connect(ui.tlbclose,SIGNAL(clicked(bool)),mdi,SLOT (close(void)));

connect returns bool that is true if connection was successfull.

And improper connects generates also messages (output window of visual studio)

[Raccoon29]

We're just guessing here. If we can't reproduce a bug, how can we solve it? You are the one having access to the buggy code [...]

wysota, you are right.

Ok, guessing is over.
Today I "lost" my morning, but now I have the essential code to reproduce the bug, I attach it here.

Environment
Qt: v 4.3.4
OS: Windows Xp Professional
Compiler: MinGW make 3.80 (mingw32-make)
Qmake: v 2.01a

How to reproduce the bug
From the program start:
1) Menu: Anagraph->Article managing
2) Click on "New" button
3) Position the cursor on a short field below and press F4
4) Close the appeared window by "Close" button (not the X)
5) Close the "Article data" window by "Close" button (not the X)
now the program should exit unexpectedly.

If between points 4 and 5 you give focus to an underneat window (or to another program), the program will not exit and will close the "Article data" window normally (the infamous focus trick).

So, what to say... have a nice debugging

I want to thank you all very much for being still giving help to me, even in a so desperate situation... I'm touched , no other forum gives so much!

[wysota]

Hmm... It seems I am unable to reproduce the bug with Qt 4.4. Which version of Qt are you using? Qt 4.3.4 indeed segfaults. The reason is probably that you destroy a window that contains a button that is currently the source of an emitted signal. Calling deleteLater() instead of deleting the object immediately might be enough to overcome the problem. I'm not sure what your "viewport" does, though, so the problem might be completely elsewhere. Based on what the debugger says, the crash happens while the click on the button is being handled. Taking a look at QMdiSubWindow::closeEvent() and QMdiArea::viewportEvent() might reveal the exact cause.

[Raccoon29]

It seems I am unable to reproduce the bug with Qt 4.4. Which version of Qt are you using? Qt 4.3.4 indeed segfaults.

Uhm, I see.
So, does it mean that upgrading to Qt4.4 fixes the problem? (As I wrote, mine is Qt 4.3.4)

Calling deleteLater() instead of deleting the object immediately might be enough to overcome the problem.

But I don't delete it, I leave this task to the WA_DeleteOnClose...

I'm not sure what your "viewport" does, though, so the problem might be completely elsewhere.

"viewport" is nothing special, it just wraps the opening/closing of the mdisubwindows, and several other not dangerous functions (hidden in the debug version I sent you).

[Raccoon29]

I can't believe it! Finally we solved it!
touched...

What I did to solve it:

1_ I forced off the automated desctruction disabling WA_DeleteOnClose

void CViewports::open(EViewport win, QWidget* parent)
{
   [...]
   wArticle->setAttribute(Qt::WA_DeleteOnClose,false); //forced off for every widget
   [...]
}

void CViewports::open(EViewport win, QWidget* parent)
{
   [...]
   wArticle->setAttribute(Qt::WA_DeleteOnClose,false); //forced off for every widget
   [...]
}

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2_ CViewports desctructor uses deleteLater() instead of delete for every widget,ensures that every widget is destroyed in the right way:

if(pArticle)
{
    //delete pArticle;
    pArticle->deleteLater();
    pArticle=NULL;
    wArticle=NULL;
}

if(pArticle)
{
    //delete pArticle;
    pArticle->deleteLater();
    pArticle=NULL;
    wArticle=NULL;
}

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3_ Every closeEvent (of every widget) calls its destruction with deleteLater(), instead to delegate it to WA_DeleteOnClose:

void frmcustomerorder::closeEvent(QCloseEvent *event)
{
	if(!maybeSave())
	{
		event->ignore();
		return;
	}
 
	viewport->close(CustomerOrder);
	//event->accept();   -> no more relies on WA_DeleteOnClose
	deleteLater();     // calls its destruction
}

void frmcustomerorder::closeEvent(QCloseEvent *event)
{
	if(!maybeSave())
	{
		event->ignore();
		return;
	}

	viewport->close(CustomerOrder);
	//event->accept();   -> no more relies on WA_DeleteOnClose
	deleteLater();     // calls its destruction
}

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And in this way it is working (at least until now).

After N posts we finally found the solution, this forum is simply great.
Thank you from deep my heart to everyone!

By the way: wysota, you gave me the main tip to solve it (with deleteLater), and since you answered kindly to my (I admit) boring request, from now on, I'll call you SaintWysota (or shorted S.wysota)

[wysota]

Oh, I am not saint

As for your problem - it must have been related to the signal emission I mentioned.