Hi,

 

I have a small example program that crashes from time to time.

I would appreciate some help to understand why.

 

In function run() executed on the main thread I create a packaged_task (pt), put it in a queue (_q) and wait for it to get executed (fu.get()).

In another thread the tasks are executed when the queue _q is populated.

The task I'm running always throws/rethrows intentionally.

 

It results (from time to time) in an access violation when the unique_future, fu, is deleted.

See the stack trace at the bottom.

 

Anybody see any flaws in this design?

 

I have tried 1.47.0 and 1.48.0,  MSVC 2005.

 

Here's the code.

 

*****************************************************

 

#include <boost/exception/all.hpp>

#include <boost/thread.hpp>

#include <sstream>

#include <iostream>

 

 

struct Exception

  : public virtual std::exception

  , public virtual boost::exception

{

};

 

struct TheException  : public virtual Exception {};

 

void throwf()

{

  try

  {

    BOOST_THROW_EXCEPTION(TheException());

  }

  catch (...)

  {

    boost::current_exception_diagnostic_information();

    throw;

  }

}

 

struct Test

{

  Test()

  {

    _t.reset(new boost::thread(boost::bind(&Test::executor, this)));

  }

 

  ~Test()

  {

    _t->join();

  }

 

  void executor()

  {

    for (;;)

    {

      boost::unique_lock<boost::mutex> lk(_mx);

 

      while(_q.empty())

      {

        _cv.wait(lk);

      }

 

      boost::shared_ptr< boost::packaged_task<void> > pt = _q.front();

      _q.pop_front();

      lk.unlock();

 

      (*pt)();

    }

  }

 

  void run()

  {

    for (;;)

    {

      const int N = 20000;   

      for (int j = 0; j < N; ++j)

      {

        boost::shared_ptr< boost::packaged_task<void> > pt(new boost::packaged_task<void>(throwf));

        boost::unique_future<void> fu = pt->get_future();

       

        {

          boost::unique_lock<boost::mutex> lk(_mx);

          _q.push_back(pt);

          pt.reset();

        }

      

        _cv.notify_one();

 

        try

        {

          fu.get();

          assert(false);

        }

        catch (const TheException& )

        {

        }

        catch (const boost::exception& )

        {

          assert(false);

        }

        catch (...) {

          assert(false);

        }

      }

      std::cout << ".";

    }

  }

 

private:

  boost::mutex _mx;

  std::list< boost::shared_ptr< boost::packaged_task<void> > > _q;

  boost::shared_ptr<boost::thread> _t;

  boost::condition_variable_any _cv;

};

 

 

int main(int, char*)

{

  Test test;

  test.run();

}

 

*****************************************************

 

Here is the callstack, program terminated with access violation.

 

Unhandled exception at 0x0043196b in crasher.exe: 0xC0000005: Access violation reading location 0xdddddded.

 

>                 crasher.exe!boost::exception_detail::refcount_ptr<boost::exception_detail::error_info_container>::release()  Line 78 + 0x18 bytes       C++

                  crasher.exe!boost::exception_detail::refcount_ptr<boost::exception_detail::error_info_container>::~refcount_ptr<boost::exception_detail::error_info_container>()  Line 35        C++

                 crasher.exe!boost::exception::~exception()  Line 278 + 0xb bytes                C++

                 crasher.exe!boost::exception_detail::clone_impl<TheException>::`vbase destructor'()  + 0x41 bytes          C++

                 crasher.exe!boost::exception_detail::clone_impl<TheException>::`scalar deleting destructor'()  + 0x2b bytes   C++

                 crasher.exe!boost::checked_delete<boost::exception_detail::clone_base const >(const boost::exception_detail::clone_base * x=0x006f7d10)  Line 34 + 0x35 bytes  C++

                 crasher.exe!boost::detail::sp_counted_impl_p<boost::exception_detail::clone_base const >::dispose()  Line 78 + 0xc bytes       C++

                 crasher.exe!boost::detail::sp_counted_base::release()  Line 102 + 0xf bytes  C++

                 crasher.exe!boost::detail::shared_count::~shared_count()  Line 309             C++

                 crasher.exe!boost::shared_ptr<boost::exception_detail::clone_base const >::~shared_ptr<boost::exception_detail::clone_base const >()  + 0x2e bytes                 C++

                 crasher.exe!boost::exception_ptr::~exception_ptr()  + 0x2b bytes               C++

                 crasher.exe!boost::detail::future_object_base::~future_object_base()  Line 106 + 0x9c bytes                 C++

                 crasher.exe!boost::detail::future_object<void>::~future_object<void>()  + 0x2b bytes    C++

                 crasher.exe!boost::detail::task_base<void>::~task_base<void>()  + 0x2b bytes             C++

                 crasher.exe!boost::detail::task_object<void,void (__cdecl*)(void)>::~task_object<void,void (__cdecl*)(void)>()  + 0x2b bytes      C++

                 crasher.exe!boost::detail::task_object<void,void (__cdecl*)(void)>::`scalar deleting destructor'()  + 0x2b bytes                 C++

                 crasher.exe!boost::checked_delete<boost::detail::task_object<void,void (__cdecl*)(void)> >(boost::detail::task_object<void,void (__cdecl*)(void)> * x=0x006f7b10)  Line 34 + 0x34 bytes        C++

                 crasher.exe!boost::detail::sp_counted_impl_p<boost::detail::task_object<void,void (__cdecl*)(void)> >::dispose()  Line 78 + 0xc bytes                 C++

                 crasher.exe!boost::detail::sp_counted_base::release()  Line 102 + 0xf bytes  C++

                 crasher.exe!boost::detail::shared_count::~shared_count()  Line 309             C++

                 crasher.exe!boost::shared_ptr<boost::detail::future_object<void> >::~shared_ptr<boost::detail::future_object<void> >()  + 0x2e bytes         C++

                 crasher.exe!boost::unique_future<void>::~unique_future<void>()  Line 644 + 0x2b bytes                 C++

                 crasher.exe!Test::run()  Line 95 + 0xc bytes          C++

                 crasher.exe!main(int __formal=1, int __formal=1)  Line 112      C++

                 crasher.exe!__tmainCRTStartup()  Line 597 + 0x19 bytes          C

                 crasher.exe!mainCRTStartup()  Line 414                C

                 kernel32.dll!7c817067()   

                 [Frames below may be incorrect and/or missing, no symbols loaded for kernel32.dll]