Shared pointer and threading

shared_pointer_threads.cpp

#include <cstdlib>
#include <map>
#include <string>
#include <memory>
#include <thread>
#include <iostream>
#include <functional>
#include <unistd.h>

using std::shared_ptr;
using std::cout;
using std::endl;
using std::thread;


class Example {
public:
    Example() {
        cout << "New Example constructed" << endl;
    }

    ~Example() {
        cout << "Example has been deleted." << endl;
    }
};

void callback(shared_ptr<Example> str) {
    cout << "Starting thread." << endl;
    sleep(1);
    cout << "Ending thread." << endl;
}


int main(int argc, char** argv) {

    thread* t1;
    thread* t2;
    thread* t3;

    Example* example = new Example();

    {
        shared_ptr<Example> shared(example);

        t1 = new thread(callback, shared);
        t2 = new thread(callback, shared);
        t3 = new thread(callback, shared);

        cout << "Shared runs out of scope." << endl;
    }

    t3->join();
    t2->join();
    t1->join();

    delete t3;
    delete t2;
    delete t1;

    // It would appear that by this point, the "example" pointer is deleted, too!

    return 0;
}