Re: [Boost-users] Unable to catch exception using boost::asio

Subject: Re: [Boost-users] Unable to catch exception using boost::asio
From: Alex Black (alex_at_[hidden])
Date: 2009-07-15 13:10:33

> 
> Message: 3
> Date: Wed, 15 Jul 2009 10:56:22 -0500
> From: Zachary Turner <divisortheory_at_[hidden]>
> Subject: Re: [Boost-users] Unable to catch exception using boost::asio
> To: boost-users_at_[hidden]
> Message-ID:
> 	<478231340907150856x12c9fd92w3b06630d349eef36_at_[hidden]>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> > I wrapped my call to run() in a try-catch, no luck, no exception 
> > appears to be being thrown by io_service.run().
> >
> > void CBaseWebServer::RunIoService()
> > {
> > ? ? ? ?try
> > ? ? ? ?{
> > ? ? ? ? ? ? ? ?m_IoService.run();
> > ? ? ? ?}
> > ? ? ? ?catch ( ... )
> > ? ? ? ?{
> > ? ? ? ? ? ? ? ?cout << "Unhandled exception in 
> RunIoService"; ? ? ? ?} 
> > } _______________________________________________
> > Boost-users mailing list
> > Boost-users_at_[hidden]
> > http://lists.boost.org/mailman/listinfo.cgi/boost-users
> >
> 
> 
> That probably won't help.  Notice that 
> CBaseWebServer::RunIoService() is not in the call stack at 
> the point you're seeing the exception.
> After looking at your callstack again, I believe you're 
> throwing from a destructor.  In particular, notice in your 
> callstack that you have
> this:
> 
> 26 ~ProtoBufStreamAdaptor() /home/noirs/workspace/myfile2.cpp:10
> 0x000000000042c6e5
> 25 CWebServer::HandleGetNeighbors()
> /home/noirs/workspace/myfile3.cpp:215 0x000000000041d2d8
> 
> 
> These appear to both be in your own code.  My suspicion is 
> that an exception occurs in CWebServer::HandleGetNeighbors(), 
> which causes it to unwind the stack and execute destructors.  
> In particular a destructor for an object of type 
> ProtoBufStreamAdaptor() is called, and this destructor then 
> throws another exception.  At this point your program will 
> definitely terminate immediately.
> 
> First check the destructor of ProtoBufStreamAdaptor() to see 
> why it's throwing (destructors should _never_ throw under any 
> circumstances), and then check the code of 
> CWebServer::HandleGetNeighbors() to find the original error.

Thanks for continuing to help with this.

I had the same thoughts as you, and I've looked into that with no luck.
For example, here is the code for ~ProtoBufStreamAdaptor():

ProtoBufStreamAdaptor::~ProtoBufStreamAdaptor(void)
{}

The original error is related to the client (on the other end of the
socket) being interrupted.  Presumably some socket operation is throwing
an exception, e.g. I'm writing to the socket after the client has
disconnected.

You mentioned never throwing exceptions in destructors - sounds like
good advice, thx. Two points though:
1. If an exception is thrown in a destructor can it not be caught with a
try catch( ... )?
2. I'll look over the code more closely and see if there are any
destructors throwing.