memory leak in listview usage (QQuickItemView)

I ran the provided test code from the key customer and confirmed that a memory leak occurs when executing the test. The test was performed on version v6.2.2, and the same issue occurs in not only v5.5.18 but also v6.8.2.
(os: ubuntu24.04, qt version: v6.2.2, v6.8.2, v5.5.18)

I have attached the heaptrack results from both v6.2.2 and v6.8.2.

From the heaptrack analysis, I observed that in the "consumed page" section, the memory usage continuously increases at a steady rate due to the connectImpl function.(yellow in below image)

Even though the same test code was executed, the "Largest Memory Leaks" section on the "summary page" sometimes shows results and sometimes doesn't. This might be a separate issue, so it can be considered for reference only.

Now, getting back to the main issue, while analyzing the memory leak, I noticed that the setModel function in the "QQuickItemView" class was present in the call stack. Upon checking, I found that the disconnect and connect functions do not match as pairs.

If we consider disconnect and Private::disconnect as disconnect, and connect and Private::connect as connect, the delegateChanged item only has connect but no disconnect.

After fixing this issue and running the heaptrack test again, the graph in the "consumed page" now resembles a near-horizontal line, which seems to be the expected result.

I would like to confirm whether this is the intended implementation or a bug.

If it is the intended behavior, please share information on which part needs to be modified to fix the memory leak.

• test code Qml file
  (png file is not attached, it could be anything in my opnion)

  import QtQuick
  Window {
      width: 640
      height: 480
      visible: true
      title: qsTr("Hello World")    Item {
        id: defaultLayers      property int indexValue : 0
        property int indexCount : 0      Item {
            id: indicatorTest
            x: 20
            y: 20
            width: 90
            height: 244          Component {
                 id: indicatorComponent
                 Image {
                     id: componentImage
                     width: 12
                     height: 12
                     source: "file:/Users/jaejin/Downloads/penguin.png"
                 }
            }          ListView {
                 id: indicatorListview
                 width: 12
                 height: (defaultLayers.indexValue * 12) + ((defaultLayers.indexValue - 1) * 6)
                 anchors.centerIn: parent
                 model: defaultLayers.indexValue
                 delegate: indicatorComponent
                 spacing: 6
                 focus: true
            }          Timer {
                 id: testTimer
                 interval: 100
                 running: true
                 repeat: true
                 onTriggered: {
                     defaultLayers.indexValue = (defaultLayers.indexValue + 1) % 10
                     defaultLayers.indexCount = defaultLayers.indexCount + 1
                     if (defaultLayers.indexCount >= 20000) {
                          Qt.quit();
                     }
                 }
            }
        }      Component.onCompleted: {
            testTimer.start()
        }
      }}
   

  what I changed code

in qtdeclarative repo,  src/quick/items/qquickitemview.cpp

// code placeholder

void QQuickItemView::setModel(const QVariant &m)
{
    ....
    if (d->model) {
        disconnect(... modelUpdated ...);
        disconnect(... initItem ...);
        disconnect(... createdItem ...);
        disconnect(... destroyItem ...);
        if ( ... delegateModel = ... (d->model)) {
            disconnect(delegateModel, ... itemPooled ...);
            disconnect(delegateModel, ... itemReused ...);
            // could not find delegateChanged disconnect 
            // QObjectPrivate::disconnect(delegateModel, &QQmlDelegateModel::delegateChanged, d, &QQuickItemViewPrivate::applyDelegateChanged);
        }
    }
    ....
    ....

    if (d->model) {
        d->bufferMode ... 
        connect(d->model, ... createdItem ...);
        connect(d->model, ... initItem ...);
        connect(d->model, ... destroyingItem ...);
        if (... delegateModel = ... (d->model)) {
            connect(delegateModel, ... itemPooled ...);
            connect(delegateModel, ... itemReused ... );        
        }
        if (isComponentComplete()) {
            ...
        }
        connect(... modelUpdated ... )
        if ( ... dataModel = ...(d->model))
            QObjectPrivate::connect(dataModel, &QQmlDelegateModel::delegatedChanged, d, &QQuickItemViewPrivate::applyDelegateChange);
        emit ...

    }
    ...
}

• test with below command
  • QT_WAYLAND_DISABLE_WINDOWDECORATION=1 WAYLAND_DISPLAY=wayland-1 XDG_RUNTIME_DIR=/run/user/1000 QT_QPA_PLATFORM=wayland