Qt QML context object garbage collected

main.cpp

#include <QQmlEngine>
#include <QObject>
#include <QGuiApplication>
#include <QQmlComponent>
#include <QQmlContext>
#include <QQuickWindow>
#include <QDebug>

class App : public QObject
{
    Q_OBJECT
public:
    virtual ~App() = default;
    Q_INVOKABLE bool f() const {
        return false;
    }
};

int main(int argc, char *argv[]) {
    QGuiApplication app(argc, argv);

    QQmlEngine engine;
    QQmlComponent component(&engine);

    QObject* ctx = new App();
    QQmlEngine::setObjectOwnership(ctx, QQmlEngine::JavaScriptOwnership);
    engine.rootContext()->setContextObject(ctx);

    QObject::connect(&component, &QQmlComponent::statusChanged, [&component, &engine](QQmlComponent::Status status) {
        switch(status) {
            case QQmlComponent::Ready: {
                QObject* obj = component.create();
                QQuickWindow* win = qobject_cast<QQuickWindow*>(obj);
                engine.setIncubationController(win->incubationController());
                break;
            }
            case QQmlComponent::Error: {
                QList<QQmlError> errs = component.errors();
                for(QQmlError err : errs) qCritical() << "Error: " << err.toString() << "\n";
            }
        }
    });
    component.loadUrl(QUrl::fromLocalFile("main.qml"));

    return app.exec();
}

main.qml

import QtQuick 2.0
import QtQuick.Window 2.2

Window {

    Timer {
        interval: 1; running: true; repeat: true
        onTriggered: {
            console.log("call f");
            f(); gc();
            console.log("done");
        }
    }

}

output

$ ./main
qml: call f
qml: done
qml: call f
file:///data/libs/hsqml/member-undefined/main.qml:10: ReferenceError: f is not defined
qml: call f
fish: './main' terminated by signal SIGSEGV (Adressbereichsfehler)