[Boost-users] [Boost-Threads] Assertion during a second call to thread::join

From: Aubrey, Jason (jason.aubrey_at_[hidden])
Date: 2006-08-23 03:25:03

Hi,

My Environment:
  * MSVC 8.0
  * boost v1.33.1

Using the example program below, I'm getting an assertion within boost's
thread class during a call to join.    join() is being called twice: 1)
in main() 2) in ~Thread().  If I remove one of the calls to join() the
assertion goes away.  Though this example's usage seems redundant such
behavior should be similar to the scenario of multiple threads waiting
on the same thread via join().

Help would be appreciated.

Regards,
Jason

// --------------------------------- BEGIN EXAMPLE PROGRAM
---------------------------
// Assertion failed: m_joinable, file
C:\...\boost\boost_1_33_1\libs\thread\build\..\src\thread.cpp, line 223
// Call Stack begins in the following code at the end of main() within
~Thread() in the call to join().

#include <boost/bind.hpp>
#include <boost/noncopyable.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/thread/thread.hpp>
#include <boost/thread/xtime.hpp>

// This class misuses inheritance, but is provided for those
// familiar with Java syntax that don't care
class Thread : public boost::noncopyable
{
private:
    boost::shared_ptr<boost::thread> _thread;

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

    void join()
    {
        if ( _thread )
           _thread->join();
    }

    virtual void run() = 0;
    
    void start()
    {
        if ( !_thread )
            _thread.reset( // Reference to the thread
                new boost::thread( // New thread of execution
                    boost::bind(&Thread::run, this) // Functor calls
run()
                    ));
    }
};

struct MyThread : public Thread 
{
    void run() {}
};

void main()
{
    MyThread t;
    t.start();
    t.join(); // No assertion if this line is commented
    return;
}

// --------------------------------- END EXAMPLE PROGRAM
---------------------------