#include <cstdlib>
#include <iostream>
#include <memory>

#include <pthread.h>

class Thread
{
private:
    pthread_t thread;

    Thread(const Thread& copy);         // copy constructor denied
    static void *thread_func(void *d)   { ((Thread *)d)->run(); return NULL; }

public:
    Thread()             {}
    virtual ~Thread()    {}

    virtual void run() = 0;

    int start()          { return pthread_create(&thread, NULL,
                           Thread::thread_func, (void*)this); }
    int wait ()          { return pthread_join  (thread, NULL); }
};

typedef std::auto_ptr<Thread> ThreadPtr;

int main(void)
{
    class Thread_a:public Thread
    {
    public:
        void run()
        {
            for (int i=0; i<20; i++, sleep(1))
                std::cout << "a  " << std::endl;
        }
    };

    class Thread_b:public Thread
    {
    public:
	void run()
        {
            for(int i=0; i<20; i++, sleep(1))
                std::cout << "  b" << std::endl;
        }
    };

    ThreadPtr a( new Thread_a() );
    ThreadPtr b( new Thread_b() );

    if (a->start() != 0 || b->start() != 0)
        return EXIT_FAILURE;

    if (a->wait() != 0 || b->wait() != 0)
        return EXIT_FAILURE;

    return EXIT_SUCCESS;
}