Unmarshal complex type from QDBus

[sajmplus]

Hello,

i have problem with unmarshaling complex type from QDBusArgument. Method returns a{sa{sv}}. I declared typedef for this complex type:

typedef QMap<QString, QMap<QString, QVariant>> ConnectionSettings;
Q_DECLARE_METATYPE(ConnectionSettings)

typedef QMap<QString, QMap<QString, QVariant>> ConnectionSettings;
Q_DECLARE_METATYPE(ConnectionSettings)

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And i'm trying to call method:

ConnectionSettings NetworkConnection::getSettings()
{
    QDBusInterface iface(m_serviceName, m_objectPath, m_interfaceName,
                         SystemBusConnectionFactory::getInstance());
 
    auto msg = iface.call("GetSettings");
    qDebug() << msg;
    auto retVal = msg.arguments()
            .first()
            .value<QDBusArgument>();
 
    ConnectionSettings cs;
 
    retVal.beginMap();
    while( !retVal.atEnd() ) {
        QString key;
        QVariantMap value;
        retVal.beginMapEntry();
        retVal >> key >> value; //This line crashes!
        retVal.endMapEntry();
        cs.insert(key, value);
        qDebug() << key << value;
    }
    retVal.endMap();
 
    return cs;
}

ConnectionSettings NetworkConnection::getSettings()
{
    QDBusInterface iface(m_serviceName, m_objectPath, m_interfaceName,
                         SystemBusConnectionFactory::getInstance());

    auto msg = iface.call("GetSettings");
    qDebug() << msg;
    auto retVal = msg.arguments()
            .first()
            .value<QDBusArgument>();

    ConnectionSettings cs;

    retVal.beginMap();
    while( !retVal.atEnd() ) {
        QString key;
        QVariantMap value;
        retVal.beginMapEntry();
        retVal >> key >> value; //This line crashes!
        retVal.endMapEntry();
        cs.insert(key, value);
        qDebug() << key << value;
    }
    retVal.endMap();

    return cs;
}

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Unfortunately there is a segfault - debugger show line 331 in qdbusargument.h:

...
template<typename Key, typename T>
inline const QDBusArgument &operator>>(const QDBusArgument &arg, QMap<Key, T> &map)
{
    arg.beginMap();
    map.clear();
    while (!arg.atEnd()) {
        Key key;
        T value;
        arg.beginMapEntry(); // SIGSEGV here!
        arg >> key >> value;
        map.insertMulti(key, value);
        arg.endMapEntry();
    }
    arg.endMap();
    return arg;
}
...

...
template<typename Key, typename T>
inline const QDBusArgument &operator>>(const QDBusArgument &arg, QMap<Key, T> &map)
{
    arg.beginMap();
    map.clear();
    while (!arg.atEnd()) {
        Key key;
        T value;
        arg.beginMapEntry(); // SIGSEGV here!
        arg >> key >> value;
        map.insertMulti(key, value);
        arg.endMapEntry();
    }
    arg.endMap();
    return arg;
}
...

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Where should I search for the problem?

[anda_skoa]

Have you tried separating the two stream reads?

Does it crash on the key or the value?

Cheers,
_

[sajmplus]

Its crashing on value.

How can I separate stream?

[anda_skoa]

Maybe try other value types instead of QVariantMap, e.g. maybe it is a QDBusVariant which contains a map.

Or maybe it is possible to handle a nested map by first streaming the key and then calling beginMap() for the inner map, handling it in an inner loop.

Cheers,
_