qmlRegisterType and qmlRegisterUncreatableType leads to kind of leak

Hi,

Tracking down why I got sometime a OOM killer in my app, I found that multiple calls to the same qmlRegisterType or qmlRegisterUncreatableType leads to the memory growing again and again. I had a loop every 10ms, that created an object by copy which has in it's constructor, a call to the qmlRegisterUncreatableType function. Commenting this line let the issue disappear.

Workaround is to create a static boolean variable to init the qml type only once.

The issue is NOT present with qRegisterMetaType. I didn't tried all function available.

Issue is not visible with valgrind, so it's not some kind of dynamic allocation not freed.

Minimal example code to reproduce in Qt6.0.0 :
I created a minimal QtQuick Application - Empty and changed the main function.
The example use quint8 as class to register but it fail with any other class.

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QTimer>

int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);

    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;
    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                     &app, [url](QObject *obj, const QUrl &objUrl) {
        if (!obj && url == objUrl)
            QCoreApplication::exit(-1);
    }, Qt::QueuedConnection);
    engine.load(url);

    QTimer timerTestLeak;
    QObject::connect(&timerTestLeak,&QTimer::timeout, [] () {
        qmlRegisterUncreatableType<quint8>("quint8", 1, 0, "quint8", "Error: only enums and function call from qml");
    });
    timerTestLeak.start(2);


    return app.exec();
}

Start the app, launch htop and look the RES column,
then comment the qmlRegisterUncreatableType, and compare the RES column.

We should not get a growing memory usage for a call to the exact same registered object.