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List:       kde-devel
Subject:    Re: Not used QPointers showing modal dialogs via exec() - No crash
From:       Kevin Krammer <krammer () kde ! org>
Date:       2013-11-11 18:42:13
Message-ID: 1412976.LvCQpxmoBr () persephone
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On Monday, 2013-11-11, 15:53:15, Daniel Nicoletti wrote:
> This check is to prevent issues, if someone in the future changes
> the code to do something after exec() then it's very likely to
> crash due to the caller or it's child stuff already being deleted.
> If you don't do anything after exec() and the function was called
> by the event loop you are probably safe.

I think you can also run into that problem if there is nothing after exec().

If anything, D-Bus, timer, whatever, causes deletion of the dialog's parent, 
in this case KMinesMainWindow, then it will delete its child QObject.

When the C++ code of the functions cleans up the stack, it will at least also 
invoke the dialog's destructor.

Cheers,
Kevin

> 
> 2013/11/11 Harsh Kumar <harsh1kumar@gmail.com>:
> > Hi,
> > 
> > I have a question:
> > 
> > Krazy2 flags this issue in KMines - Not using QPointers when showing
> > modal dialogs via exec()
> > See: http://ebn.kde.org/krazy/reports/kde-4.x/kdegames/kmines/index.html
> > 
> > Following is the function to display High Scores dialog where the
> > problem has been flagged:
> > 
> > void KMinesMainWindow::showHighscores()
> > {
> > 
> >     KScoreDialog scoreDialog(KScoreDialog::Name | KScoreDialog::Time,
> >     this);
> >     scoreDialog.initFromDifficulty(Kg::difficulty());
> >     scoreDialog.hideField(KScoreDialog::Score);
> >     scoreDialog.exec();
> > 
> > }
> > 
> > KMines should crash when High Score dialog is open & application is
> > closed using dbus.
> > 
> > So, I did the following:
> > 1.) Started KMines
> > 2.) Opened the High Scores dialog
> > 3.) Ran the command -
> > 
> >          qdbus org.kde.kmines-[pid] /MainApplication quit
> > 
> > KMines exits without any crash. It seems nothing went wrong.
> > 
> > What can be the reason for this? Why am I not able to reproduce the crash.
> > 
> > Thanks
> > Regards
> > Harsh Kumar
> > 
> >>> Visit http://mail.kde.org/mailman/listinfo/kde-devel#unsub to
> >>> unsubscribe <<>> 
> >> Visit http://mail.kde.org/mailman/listinfo/kde-devel#unsub to unsubscribe
> >> <<
-- 
Kevin Krammer, KDE developer, xdg-utils developer
KDE user support, developer mentoring

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