[asio-users] host_resolver and demuxer::work

[Arvid N. <c9...@cs...>]

Hi.

I was a bit surprised that waiting for an async_get_host_by_name() on  
a host_resolver wouldn't be considered as "work" by the demuxer::run 
() function. i.e. it returned when the only operation I had pending  
was a name lookup.

I find this to be a bit unexpected.

Anyway, my attempt to work around this was to us a demuxer::work  
instance to pass along with my handler (by value) for the  
async_get_host_by_name() operation. That's when I encountered the  
second problem.

 From what I can understand (didn't investigate too thoroughly), it  
looks like asio deadlocks when the handler object is being copied,  
and the work instance is destructed. The destructor will lock the  
demuxer/reactor before it decrements the work counter, but the lock  
is already held by that thread, and it is not a recursive mutex. I  
found this a bit strange too, considering the text from the manual:

"The work class is copy-constructible so that it may be used as a  
data member in a handler class. It is not assignable."

So, am I doing something wrong?

My use case is simply to:
1. look up name
2. connect
3. send data
4. receive data

where each step is an async operation.

I'm using MacOS X with the boost review version of asio.

thanks.
--
Arvid Norberg