QAuthenticator methods setUser and setPassword need better documentation

Whenever an authentication fails once and QNetworkAccessManager::authenticationRequired is re-called it is not clear that for the authentication process to be interrupted the methods setUser/setPassword must not be called.
For example, the following code results in endless stream of signal authenticationRequired.

void AccessNetwork::authenticationRequired(QNetworkReply *reply, QAuthenticator *auth) {
    auth->setUser(QString(username.c_str()));
    auth->setPassword(QString(password.c_str()));
}

Also the following code will result in a loop.

void AccessNetwork::authenticationRequired(QNetworkReply *reply, QAuthenticator *auth) {
    if (auth->user() == QString(username.c_str()) && auth->password() == QString(password.c_str())) {
	auth->setUser(QString());
	auth->setPassword(QString());
    } else {
	auth->setUser(QString(username.c_str()));
	auth->setPassword(QString(password.c_str()));
    }
}

That seems to happen in the code of void QAuthenticator::detach() that creates a new QAuthenticatorPrivate everytime setUser/setPassword methods are called.
I suggest that the documentation of setUser/setPassword have a warning about this behaviour.