`double free or corruption (out)` error on a stack QDialog with the `WA

Given the following fragments of code :

class MyDialog : public QDialog
{
    ...
};

MyDialog::~MyDialog()
{
    qInfo() << "~MyDialog()";
}

and

// scope begins
MyDialog d;
d.setAttribute( WA_DeleteOnClose, true );
int result = d.exec();
qInfo() << "After exec";
// scope ends

I get the following output

~MyDialog()

double free or corruption (out)

Aborted (core dumped)

Without d.setAttribute( WA_DeleteOnClose, true ); everything is fine and expected.

NOTE : I know that there is no need to use the delete on close in this case as the dialog deletes when leaving the scope. I also don't need for a "better solution" etc (I've read a lot of posts on SO and Qt Centre Forum with these irrelevant answers). The question is Why the error occurs at the first time the ~QDialog() is called ? And maybe Am I right that the error occurs at the first time the ~QDialog() is called?

CodePudding user response：

Try this instead:

MyDialog* d = new MyDialog;
d->setAttribute( WA_DeleteOnClose, true );
int result = d->exec();

Either new QobjectDerived or new QobjectDerived(this) for dynamic allocation and then the dynamic deallocation could finalize the object destruction just once. That attribute WA_DeleteOnClose set is obviously provoking internal delete when the dialog getting closed but no second destructor call as in case with that object allocated on stack.

CodePudding user response：

You're creating an object on the stack and then try to delete it with delete (indirectly via the WA_DeleteOnClose - flag). I don't see why you would not get a double delete then.