CODEWITHSUNDEEP
c++qtmemory-leaksqt4
Stefano
Stefano

Reputation: 3259

Memory leak returning QIcon

I started using Qt but I'm facing a big problem: I implemented my custom model that inhrerits from the QAbstractListModel class. What I want to do is to display a list with icon. All works and the image is shown with my code but it creates a memory leak. If I don't return the icon no memory leak is detected.

class MyModel : public QAbstractListModel
{
public:
    ...

private:
    QIcon myicon;
}

QVariant MyModel::data(const QModelIndex &index, int role) const
{
    ...

    if (role == Qt::DecorationRole)
    {
        return this->myicon;
    }

    ...
}

EDIT 1

#define _CRTDBG_MAP_ALLOC
#include <stdlib.h>
#include <crtdbg.h>

_CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);

MyModel::MyModel(...)
{
    ...

    ui.listWidget->addItem(new QListWidgetItem(QIcon("myicon"), "my text"));
}

Upvotes: 0

Views: 948

Answers (2)

Lol4t0
Lol4t0

Reputation: 12547

I don't think memory leak is in the code, you showed.

QIcon has conversion to QVarint (defined with operator QVariant), it widely used by standard item model/item widgets.

You also do not manage any pointers and do not use some explicit conversions.

So, this code seems OK, but it can be a memory in code, that uses icon.

Upvotes: 0

UmNyobe
UmNyobe

Reputation: 22890

I don't see a constructor of QVariant with QIcon as parameter, and I am surprised it compiles. As you are returning a QIcon when a QVariant is expected, there must be some crazy implicit conversions going. You have to know that in some cases when you create a QVariantthere is a deep copy of the initial object. Keep track of the qvariants you create and use QVariant::clear() when you don't need them anymore.

EDIT:
By the way you are implicitly using the operator 

QIcon::operator QVariant () const

which returns a QVariant. this variant doesn't contain the initial QIcon, but a deep copy. So follow my earlier advice to get rid of the leak.

Upvotes: 1

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