...

The code though is surrounded by try catch like this:

try { ??? ... }

What code resides in the protected block? Do you run io_service in multiple threads? What exception-related compiler options do you use?

I do call io_service.run, on a thread on startup. I call async_accept, and accept connections one at a time. So basically I a my accept_handler gets called, I enter the try, then its just business logic and writing results out onto a socket. Exception-related compiler options? Not sure. This is happening in debug (and release). In release I have march=native and O-O3 set.