Ticket #3848: exc1.cc

#include <boost/exception.hpp>
#include <boost/thread.hpp>
#include <string>

typedef boost::error_info<struct tag_throw_string, std::string> err_info;

class err
  : public boost::exception
  , public std::exception
{
};

// transferres exception_ptr from producer to consumer thread
class future
{
  public:
  future () : ready_ (false) {}

  // called in producer thread, gets exception_ptr
  void set_exception (boost::exception_ptr const& e)
  {
    boost::unique_lock<boost::mutex> lck (mux_);
    exc_ = e;
    ready_ = true;
    cond_.notify_all();
  }

  // called in consumer thread, returns exception_ptr
  boost::exception_ptr get_exception () const
  {
    boost::unique_lock<boost::mutex> lck (mux_);
    while (! ready_)
    cond_.wait (lck);
    return exc_; // was: rethrow_exception (exc_);
  }

  private:
    bool ready_;
    boost::exception_ptr exc_;
    mutable boost::mutex mux_;
    mutable boost::condition_variable cond_;
};

void producer (future& f, boost::barrier& b)
{
  b.wait ();

  // 1. create temp boost::exception object
  // 2. take exception_ptr to it
  f.set_exception (boost::copy_exception (err () << err_info ("stub")));
  // 3. destroying temp boost::exception object
}

void consumer ()
{
  // barrier used to increase probablity to get a fault
  boost::barrier b (2);

  future f;
  boost::thread thr (boost::bind (&producer, boost::ref (f), boost::ref (b)));

  b.wait ();

  if (boost::exception_ptr e=f.get_exception() )
  {
    try { rethrow_exception (e); }
    catch (err const& e) {}
  }

  thr.join ();
}


void consume ()
{
  for (int i=0;i<100;++i)
  consumer ();
}

int main ()
{
  boost::thread_group grp;
  for (int i=0; i<50; ++i)
  grp.create_thread (&consume);

  grp.join_all ();
}