Re: boost.threads [was RE: [boost] Re: sockets /network programming Requirements]

From: Alexander Terekhov (terekhov_at_[hidden])
Date: 2001-08-03 10:50:09

> > > I've considered including a thread::exit() routine,
> > > but don't expect one in the first release.
> >
> > hmm.. why not static void thread::exit( ..<return value>.. )
> > that would simply throw some termination exception which
> > you would catch in your internal bootstrap routine?
>
> Simply because it's not safe.
>
> void foo()
> {
>   try
>   {
>      bar();
>   }
>   catch (...)
>   {
>      // Log that an error occured.
>   }
> }
>
> void bar()
> {
>    thread::exit();
> }
>
> > that exception could carry the reason (normal exit
> > or cancellation) and return value to be made available
> > for join (in the case of thread cancellation, posix join
> > returns PTHREAD_CANCELED pointer).
>
> Other libraries have tried to do this with exceptions, and the above
> code points out the hole in the concept.  At first you might think
> that you can simply avoid catch(...) in your thread code, but if your
> thread code calls library routines that include catch(...) blocks...

...how about something like:

class auto_rethrow_exception {
public:

  auto_rethrow_exception() :
                             m_rethrow( 1 )
  {

    cout << this << " ctor" << endl;

  }

 ~auto_rethrow_exception()
  {

    cout << this << " dtor" << endl;

    if ( m_rethrow ) {

      cout << "re-throw..." << endl;

      m_rethrow = 0;

      throw auto_rethrow_exception();

    }

  }

  void catched()
  {

    cout << this << " catched()" << endl;

    m_rethrow = 0;

  }

private:

  int m_rethrow;

};

int main()
{

  try {

    try {

      throw auto_rethrow_exception();

    }
    catch(...) {

      cout << "catch(...)" << endl;

    }

  }
  catch( auto_rethrow_exception& ex ) {

    cout << "catched!" << endl;

    ex.catched();

  }

  cout << "done" << endl;

  return 0;

}

MS Visual C++ 6.0:

0x0012FF64 ctor
catch(...)
0x0012FF68 dtor
re-throw...
0x0012F980 ctor
catched!
0x0012F984 catched()
0x0012F984 dtor
done

IBM VisualAge C++ 3.5:

0x12ff78 ctor
catch(...)
0x12ff78 dtor
re-throw...
0x12fa08 ctor
catched!
0x12fa08 catched()
0x12fa08 dtor
0x12ff78 dtor
done

regards,
alexander.