Segmentation fault within some specific conditions

[Erwan Mathieu]

Hello,

I'm running into a segmentation fault when using PyQt 6.6.0/6.6.1. I could
reproduce it with a very basic project, here is how to make it happen:

// File test.py
from PyQt6.QtCore import QObject
from PyQt6.QtGui import QGuiApplication
from PyQt6.QtQml import QQmlApplicationEngine, qmlRegisterType

class MyModel(QObject):
    def __init__(self, parent = None):
        super().__init__(parent = parent)
        print("I am alive")
    def __del__(self):
        print("I am dead ")

app = QGuiApplication([])
qmlRegisterType(MyModel, "Test", 1, 0, "MyModel")
engine = QQmlApplicationEngine()
engine.load("./Main.qml")
app.exec()

// File Main.qml
import QtQuick
import QtQuick.Controls

import Test 1.0

Window
{
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")

    Loader { id: loader; sourceComponent: superComponent; }

    Button
    {
        anchors.centerIn: parent
        text: "Unload"
        onClicked: loader.sourceComponent = null
    }

    Component
    {
        id: superComponent

        Item
        {
            MyModel
            {
                property var superProperty: "hello"
            }
        }
    }
}

Now start the test.py file, and click on the "Unload" button. The Component
instance is destroyed, which also destroys the MyModel instance. We can see
the print instructions that says so. Just after that, I get a segmentation
fault.

For some reason, this happens only when declaring a property on the MyModel
instance. If you comment the superProperty declaration, everything is fine.

We were previously working with version 6.4.2, and this caused no issue. I
have it starting from 6.6.0 (but didn't try intermediate versions).

I also tried to make this example directly in C++, and I don't get the
error, so I think this is related to PyQt.

If it is of any help, gdb gives me the following crash point:
0x00007ffff636abb0 in QMetaObject::methodOffset() const () from
/..../lib/python3.10/site-packages/PyQt6/Qt6/lib/libQt6Core.so.6

Any idea of why this is happening, and if there is a workaround/fix ?

Kind regards,

Erwan MATHIEU

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