Exception when passing pointer to QMenu

Please_Help_me_D

Hi,

I have a base class for QTreeView (H5TreeView) where I add context menu when pressing on header. This base class has one QAction. I want that all subclasses from H5TreeView had opportunity to add their QActions.
Here is the code for H5TreeView:
h5treeview.h:

#ifndef H5TREEVIEW_H
#define H5TREEVIEW_H

#include <QTreeView>

class H5TreeView : public QTreeView
{
    Q_OBJECT

public:
    H5TreeView(QWidget *parent = nullptr);

protected:
    ///
    /// \brief for subclasses to add actions
    /// \param menu add actions here
    ///
    virtual void fillHdrMenu(QMenu* menu);

private:
    void hdrMenuRequested(QPoint pos);
};

#endif // H5TREEVIEW_H

h5treeview.cpp:

#include "h5treeview.h"

#include "h5proxymodel.h"

#include <QHeaderView>
#include <QMenu>
#include <QAction>

H5TreeView::H5TreeView(QWidget *parent):
    QTreeView(parent)
{
    setSortingEnabled(true);
    setContextMenuPolicy(Qt::CustomContextMenu);
    header()->setContextMenuPolicy(Qt::CustomContextMenu);

    connect(header(), &QTreeView::customContextMenuRequested,
            this, &H5TreeView::hdrMenuRequested);
}

void H5TreeView::fillHdrMenu(QMenu* menu){

}

void H5TreeView::hdrMenuRequested(QPoint pos){
    QMenu *menu = new QMenu(this);

    QAction *checkedOnlyAct = menu->addAction("Display checked only");
    checkedOnlyAct->setCheckable(true);

    H5ProxyModel *proxyModel = qobject_cast<H5ProxyModel*>(model());
    if (proxyModel)
        checkedOnlyAct->setChecked(proxyModel->isShowCheckedOnly());
    else
        checkedOnlyAct->setDisabled(true);

    connect(checkedOnlyAct, &QAction::toggled, proxyModel, &H5ProxyModel::setShowCheckedItemsOnly);
    menu->addSeparator();

    /* HERE I INVOKE THAT METHOD FOR SUBCLASSES TO ADD ACTIONS TO QMENU */
    /* without it the app works fine */
    fillHdrMenu(menu);

    menu->popup(header()->mapToGlobal(pos));
}

As you can see it has void H5TreeView::fillHdrMenu(QMenu* menu) that all inheritors have. Even my inheritor leave void H5SeisTreeView::fillHdrMenu(QMenu* menu) empty I get the exception:

Please explain what is going wrong...

mrjj

@Please_Help_me_D
Hi
Yes if QMenu has no parent it never is deleted and hence a leak.
So if you call hdrMenuRequested many times, you will leak a QMenu which might not be good.

You could use
https://doc.qt.io/qt-5/qmenu.html#exec
which is blocking and then delete after.

menu->exec(header()->mapToGlobal(pos));
menu->deletelater();

Christian Ehrlicher

@Please_Help_me_D said in Exception when passing pointer to QMenu:

Please explain what is going wrong...

take a look at the backtrace to see where in your code you call it.

Please_Help_me_D

@Christian-Ehrlicher said in Exception when passing pointer to QMenu:

take a look at the backtrace to see where in your code you call it.

I'm sorry, I didn't understand what does it mean. What is a "backtrace"?
I call fillHdrMenu(QMenu* menu) only inside hdrMenuRequested(QPoint pos) of base H5TreeView class

Christian Ehrlicher

@Please_Help_me_D said in Exception when passing pointer to QMenu:

What is a "backtrace"?

https://doc.qt.io/qtcreator/creator-debug-mode.html#viewing-call-stack-trace

Please_Help_me_D

@Christian-Ehrlicher thank you for information

qwindowsd is it? This file is not from my project. Actually all the files from that dim grey list are not from my project :)

Christian Ehrlicher

I'm pretty sure it has nothing to do with the code you show us above. Please make sure that your build dir is clean and do a full rebuild. If it still happens please provide a minimal, compilable example so we can take a look.

Please_Help_me_D

@Christian-Ehrlicher there is no such exception in test project.
I understand that you can't help me now but one last thing: I get this exception only when I close the application. Do you have some ideas where to look?

If possible can you translate what assembler code means at the line 117024 from picture above? Can I get information about what pointer gives me such exception?

Please_Help_me_D

@Christian-Ehrlicher I 've found the problem!

All beacause of that I used to set parent for QMenu:

QMenu *menu = new QMenu(this);

As I have few TreeViews each in custom dockWidget that lead to CDockWidgets are destroyed in some order and thus when I close the app it somehow used to lead to an exception (parent this is destroyed thus menu is also destroyed but TreeView tries to send it... I think something like that).

Now I create QMenu without parent but will this lead to memory leak?

mrjj

@Please_Help_me_D
Hi
Yes if QMenu has no parent it never is deleted and hence a leak.
So if you call hdrMenuRequested many times, you will leak a QMenu which might not be good.

You could use
https://doc.qt.io/qt-5/qmenu.html#exec
which is blocking and then delete after.

menu->exec(header()->mapToGlobal(pos));
menu->deletelater();

Please_Help_me_D

@mrjj thank you! now it works without exceptions and QMenu has parent