QT dialog c++ Crash on Close button

Question

Hi

I have added a push button to dialog and doing below:
closeButton->OnClick().Connect(this, &myclass::OnCloseButtonClick);

Close button click:
if (p_dialog)
{
p_dialog->Close();
auto otherDialog = _other;
delete p_dialog;
p_dialog = nullptr;
otherDialog ->Show();
}

Above works fine.
If I want to perform same action (close current and open other dialog after releasing memory from current dialog) to default close button , it crashes.

Below code causes crash:
p_dialog->OnAboutToClose().Connect(this, &myclass::OnDialogClose);

//on dialog close
if (p_dialog)
{
//p_dialog->Close();
auto otherDialog = _other;
delete p_dialog;
p_dialog = nullptr;
otherDialog ->Show();
}

both slots are same apart from the fact that close is commented. Any hint on why it is crashing?

Answer 1

you can use debugger to see why and where it crash. It is probably crash internally inside a p_dialog function because is still running some code on other thread and you free the memory without closed it properly

Answer 2

in your code below, you commented out
//p->dialog->Close();
but you did not comment out
delete p_dialog;
and
p_dialog = nullptr;

Answer 3

Hi

Is it not necessary to delete the dialog? I had not commented it out as it was not calling destructor of dialog without those lines.

Answer 4

maybe you just need to close the dialog instead of deleting and setting it to nullptr? I'm not sure how you set it up but maybe there is a hidden dependency between the otherDialog and your p_dialog?
or maybe put the
otherDialog->Show();
above the
p_dialog destructors?

Answer 5

Close button closes the current dialogue for sure. no need to close the same. Apart from that, there is no dependency between two dialogs.

Answer 6

maybe others have a better suggestion. Incomplete info can only be answered with guesses at best ...

Answer 7

My dialog is of type qdockwidget . What should I do to get the control once × is clicked on dialogue

Answer 8

https://doc.qt.io/qt-6/qcloseevent.html#:~:text=Close%20events%20are%20sent%20to,to%20close%20a%20widget%20programmatically.

Answer 9

Yes, it's crashing in hide