callback function for advertise is not called

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I have a publisher node and I would like to get a callback when a subscriber connects. I followed the example in the documentation, but I get a compilation warning and no callback. For example, I start a rostopic echo before I launch my node, and I do receive the message, but the publisher is never notified that a subscriber connected.

Here is the warning:

In function ‘int main(int, char**)’: .../AppTestCallbackSubscription.cpp:20:88: warning: the address of ‘void connectCallback(const ros::SingleSubscriberPublisher&)’ will always evaluate as ‘true’ [-Waddress]

Here is the code:

#include <ros/ros.h>
#include <std_msgs/String.h>

//typedef boost::function<void(const SingleSubscriberPublisher&)> SubscriberStatusCallback;
void connectCallback(const ros::SingleSubscriberPublisher& pub)
{
    ROS_INFO("Subscriber connected");
}

int main(int argc, char** argv)
{
    const std::string TOPIC_NAME = "/foo";

    ros::init(argc, argv, "MyPublisher");

    ros::NodeHandle nh("~");

    // None of these two lines triggers the callback
    //ros::Publisher pub = nh.advertise<std_msgs::String>(TOPIC_NAME, 10, connectCallback, ros::SubscriberStatusCallback(), ros::VoidConstPtr(), false);
    ros::Publisher pub = nh.advertise<std_msgs::String>(TOPIC_NAME, 10, connectCallback);

    // Gives time to the subscribers to connect
    ros::Time maxTime(ros::Time::now()+ros::Duration(1)); // Will wait at most 1000 ms
    while(ros::Time::now()<maxTime)
    {
        ros::spinOnce();
    }

    std_msgs::String msg;
    msg.data = "Hello World!";
    pub.publish(msg);

    ROS_INFO("Message published");

    return 0;
}