The following code causes a fatal error, QMap doesn't have this problem.

    QCborMap mapBeforeCopy;
    map[1] = "Value1";
    map[2] = "Value2";

    QCborMap copyMap(mapBeforeCopy);

    QCborMap::iterator it = copyMap.find(3);
    if(it != copyMap.end()){        //always true!
        it.value() = "Value4";      //fatal error
    }

Function QCborMap::find() doesn't call detach() if key is not in the map, so the iterator "it" points to the end of "mapBeforeCopy". But QCborMap::end() always calls detach() and iterator returned by it points to the end of "copyMap", so these iterators are always not equal.