New subject: Unable to catch exception using boost::asio

15 Jul 2009

      (Response is below)
...
On Tue, Jul 14, 2009 at 7:49 PM, Alex Black wrote:
...
...
...
I'm using boost::asio for sockets, writing a response out to a
client.
If the client stops part way through getting the 
response, then my 
server process dies:
terminate called after throwing an instance of
'boost::exception_detail::clone_impl
...
...
...
fo_injectorboost::system::system_error
...
'
? what():? Broken pipe
The code though is surrounded by try catch like this:
try
{
??? ...
}
catch ( std::exception& e )
{
??? cout << e.what() << endl;
}
catch ( ... )
{
???? cout << "unexpected exception" << endl; }
How do I prevent my process from aborting/terminating like this?
v
...
Have you verified that the code inside the try block executes on the
same thread that the exception is occuring in?
Not explicitly, how would I do that?
thx
First put a breakpoint inside the try block.  When it gets 
hit use whatever mechanism your debugger provides to see what 
thread you're in.  In windows using MSVC, for example, you'd 
just add a watch for a variable called $TID which a special 
pseudo-variable that shows you the thread id.  For other 
debuggers you'd have to consult the manual.
 Next register an unhandled exception handler.
#include <exception>
void unhandled_exception_handler()
{
   std::cout << "Got an unhandled exception!" << std::endl; }
int main(int argc, char** argv)
{
   std::set_terminate(unhandled_exception_handler);
//rest of your program.
}
Then put a breakpoint inside unhandled_exception_handler and 
when it gets hit walk up the callstack in the debugger to see 
where the exception is occuring.  In addition you can 
determine the thread id again using the same method you used 
in the first step.  My guess is that they're not in the same 
thread.  I'm not sure if it applies to your scenario, but 
remember that the operation's completion handler is invoked 
on is not necessarily the same thread that the request is 
issued on depending on how you're using the io_service 
object.  So while you have a try {} catch(...) {} in the 
completion handler, if the exception is on the other thread 
that does you no good.
Thanks for the tip, I didn't know about set_terminate, I made that
change.

I put a breakpoint in my terminate handler, and the callstack looks
like:

32 unhandled_exception_handler() /home/noirs/workspace/myfile.cpp:35
0x0000000000438764	
31 <symbol is not available> 0x00007f9ceb0d04b6	
30 <symbol is not available> 0x00007f9ceb0cf6ab	
29 __gxx_personality_v0()  0x00007f9ceb0d0278	
28 <symbol is not available> 0x00007f9ceab7cff3	
27 _Unwind_Resume()  0x00007f9ceab7d0b8	
26 ~ProtoBufStreamAdaptor() /home/noirs/workspace/myfile2.cpp:10
0x000000000042c6e5	
25 CWebServer::HandleGetNeighbors()
/home/noirs/workspace/myfile3.cpp:215 0x000000000041d2d8	
24 CWebServer::OnHttpRequest() /home/noirs/workspace/myfile3.cpp:89
0x000000000041e790	
23 CBaseWebServer::HandleHTTPRequest()
/home/noirs/workspace/myfile4.cpp:92 0x00000000004092ef	
22 CBaseWebServer::HandleAccept() /home/noirs/workspace/myfile4.cpp:61
0x0000000000409a9e	

HandleAccept looks like:

void CBaseWebServer::HandleAccept(shared_ptrtcp::socket pSocket, const
boost::system::error_code& error)
{	if ( !error )
	{
		try
		{
			HandleHTTPRequest(pSocket);

			StartAccept();
		}
		catch ( ... )
		{
			cout << "Unhandled exception in HandleAccept";
		}
	}
	else
	{
		cout << "HandleAccept received error: " <<
error.message().c_str() << endl;
	}
}

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

Alex Black

Etienne Philip Pretorius

tags

participants (2)