static void do_complete(void* owner, operation* base,
      const boost::system::error_code& /*ec*/,
      std::size_t /*bytes_transferred*/)
  {
    // Take ownership of the handler object.
    signal_handler* h(static_cast<signal_handler*>(base));
    ptr p = { boost::asio::detail::addressof(h->handler_), h, h };
    handler_work<Handler, IoExecutor> w(h->handler_, h->io_executor_);

    BOOST_ASIO_HANDLER_COMPLETION((*h));

    // Make a copy of the handler so that the memory can be deallocated before
    // the upcall is made. Even if we're not about to make an upcall, a
    // sub-object of the handler may be the true owner of the memory associated
    // with the handler. Consequently, a local copy of the handler is required
    // to ensure that any owning sub-object remains valid until after we have
    // deallocated the memory here.
    detail::binder2<Handler, boost::system::error_code, int>
      handler(h->handler_, h->ec_, h->signal_number_);
    p.h = boost::asio::detail::addressof(handler.handler_);
    p.reset();

    // Make the upcall if required.
    if (owner)
    {
      fenced_block b(fenced_block::half);
      BOOST_ASIO_HANDLER_INVOCATION_BEGIN((handler.arg1_, handler.arg2_));
      w.complete(handler, handler.handler_);
      BOOST_ASIO_HANDLER_INVOCATION_END;
    }
  }

  static void do_complete(io_service_impl* owner, operation* base,
      const lslboost::system::error_code& /*ec*/,
      std::size_t /*bytes_transferred*/)
  {
    // Take ownership of the handler object.
    descriptor_read_op* o(static_cast<descriptor_read_op*>(base));
    ptr p = { lslboost::addressof(o->handler_), o, o };

    BOOST_ASIO_HANDLER_COMPLETION((o));

    // Make a copy of the handler so that the memory can be deallocated before
    // the upcall is made. Even if we're not about to make an upcall, a
    // sub-object of the handler may be the true owner of the memory associated
    // with the handler. Consequently, a local copy of the handler is required
    // to ensure that any owning sub-object remains valid until after we have
    // deallocated the memory here.
    detail::binder2<Handler, lslboost::system::error_code, std::size_t>
      handler(o->handler_, o->ec_, o->bytes_transferred_);
    p.h = lslboost::addressof(handler.handler_);
    p.reset();

    // Make the upcall if required.
    if (owner)
    {
      fenced_block b(fenced_block::half);
      BOOST_ASIO_HANDLER_INVOCATION_BEGIN((handler.arg1_, handler.arg2_));
      lslboost_asio_handler_invoke_helpers::invoke(handler, handler.handler_);
      BOOST_ASIO_HANDLER_INVOCATION_END;
    }
  }

  static void do_complete(io_service_impl* owner, operation* base,
      riakboost::system::error_code /*ec*/, std::size_t /*bytes_transferred*/)
  {
    // Take ownership of the handler object.
    wait_handler* h(static_cast<wait_handler*>(base));
    ptr p = { riakboost::addressof(h->handler_), h, h };

    BOOST_ASIO_HANDLER_COMPLETION((h));

    // Make a copy of the handler so that the memory can be deallocated before
    // the upcall is made. Even if we're not about to make an upcall, a
    // sub-object of the handler may be the true owner of the memory associated
    // with the handler. Consequently, a local copy of the handler is required
    // to ensure that any owning sub-object remains valid until after we have
    // deallocated the memory here.
    detail::binder1<Handler, riakboost::system::error_code>
      handler(h->handler_, h->ec_);
    p.h = riakboost::addressof(handler.handler_);
    p.reset();

    // Make the upcall if required.
    if (owner)
    {
      riakboost::asio::detail::fenced_block b;
      BOOST_ASIO_HANDLER_INVOCATION_BEGIN((handler.arg1_));
      riakboost_asio_handler_invoke_helpers::invoke(handler, handler.handler_);
      BOOST_ASIO_HANDLER_INVOCATION_END;
    }
  }

  static void do_complete(void* owner, operation* base,
      const boost::system::error_code& /*ec*/,
      std::size_t /*bytes_transferred*/)
  {
    // Take ownership of the operation object.
    resolve_query_op* o(static_cast<resolve_query_op*>(base));
    ptr p = { boost::asio::detail::addressof(o->handler_), o, o };

    if (owner && owner != &o->io_context_impl_)
    {
      // The operation is being run on the worker io_context. Time to perform
      // the resolver operation.
    
      // Perform the blocking host resolution operation.
      socket_ops::background_getaddrinfo(o->cancel_token_,
          o->query_.host_name().c_str(), o->query_.service_name().c_str(),
          o->query_.hints(), &o->addrinfo_, o->ec_);

      // Pass operation back to main io_context for completion.
      o->io_context_impl_.post_deferred_completion(o);
      p.v = p.p = 0;
    }
    else
    {
      // The operation has been returned to the main io_context. The completion
      // handler is ready to be delivered.

      // Take ownership of the operation's outstanding work.
      handler_work<Handler> w(o->handler_);

      BOOST_ASIO_HANDLER_COMPLETION((*o));

      // Make a copy of the handler so that the memory can be deallocated
      // before the upcall is made. Even if we're not about to make an upcall,
      // a sub-object of the handler may be the true owner of the memory
      // associated with the handler. Consequently, a local copy of the handler
      // is required to ensure that any owning sub-object remains valid until
      // after we have deallocated the memory here.
      detail::binder2<Handler, boost::system::error_code, results_type>
        handler(o->handler_, o->ec_, results_type());
      p.h = boost::asio::detail::addressof(handler.handler_);
      if (o->addrinfo_)
      {
        handler.arg2_ = results_type::create(o->addrinfo_,
            o->query_.host_name(), o->query_.service_name());
      }
      p.reset();

      if (owner)
      {
        fenced_block b(fenced_block::half);
        BOOST_ASIO_HANDLER_INVOCATION_BEGIN((handler.arg1_, "..."));
        w.complete(handler, handler.handler_);
        BOOST_ASIO_HANDLER_INVOCATION_END;
      }
    }
  }

  static void do_complete(io_service_impl* owner, operation* base,
      const pdalboost::system::error_code& /*ec*/,
      std::size_t /*bytes_transferred*/)
  {
    // Take ownership of the operation object.
    resolve_endpoint_op* o(static_cast<resolve_endpoint_op*>(base));
    ptr p = { pdalboost::asio::detail::addressof(o->handler_), o, o };

    if (owner && owner != &o->io_service_impl_)
    {
      // The operation is being run on the worker io_service. Time to perform
      // the resolver operation.
    
      // Perform the blocking endpoint resolution operation.
      char host_name[NI_MAXHOST];
      char service_name[NI_MAXSERV];
      socket_ops::background_getnameinfo(o->cancel_token_, o->endpoint_.data(),
          o->endpoint_.size(), host_name, NI_MAXHOST, service_name, NI_MAXSERV,
          o->endpoint_.protocol().type(), o->ec_);
      o->iter_ = iterator_type::create(o->endpoint_, host_name, service_name);

      // Pass operation back to main io_service for completion.
      o->io_service_impl_.post_deferred_completion(o);
      p.v = p.p = 0;
    }
    else
    {
      // The operation has been returned to the main io_service. The completion
      // handler is ready to be delivered.

      BOOST_ASIO_HANDLER_COMPLETION((o));

      // Make a copy of the handler so that the memory can be deallocated
      // before the upcall is made. Even if we're not about to make an upcall,
      // a sub-object of the handler may be the true owner of the memory
      // associated with the handler. Consequently, a local copy of the handler
      // is required to ensure that any owning sub-object remains valid until
      // after we have deallocated the memory here.
      detail::binder2<Handler, pdalboost::system::error_code, iterator_type>
        handler(o->handler_, o->ec_, o->iter_);
      p.h = pdalboost::asio::detail::addressof(handler.handler_);
      p.reset();

      if (owner)
      {
        fenced_block b(fenced_block::half);
        BOOST_ASIO_HANDLER_INVOCATION_BEGIN((handler.arg1_, "..."));
        pdalboost_asio_handler_invoke_helpers::invoke(handler, handler.handler_);
        BOOST_ASIO_HANDLER_INVOCATION_END;
      }
    }
  }

  static void do_complete(io_service_impl* owner, operation* base,
      const pdalboost::system::error_code& result_ec,
      std::size_t bytes_transferred)
  {
    pdalboost::system::error_code ec(result_ec);

    // Take ownership of the operation object.
    win_iocp_null_buffers_op* o(static_cast<win_iocp_null_buffers_op*>(base));
    ptr p = { pdalboost::asio::detail::addressof(o->handler_), o, o };

    BOOST_ASIO_HANDLER_COMPLETION((o));

    // The reactor may have stored a result in the operation object.
    if (o->ec_)
      ec = o->ec_;

    // Map non-portable errors to their portable counterparts.
    if (ec.value() == ERROR_NETNAME_DELETED)
    {
      if (o->cancel_token_.expired())
        ec = pdalboost::asio::error::operation_aborted;
      else
        ec = pdalboost::asio::error::connection_reset;
    }
    else if (ec.value() == ERROR_PORT_UNREACHABLE)
    {
      ec = pdalboost::asio::error::connection_refused;
    }

    // Make a copy of the handler so that the memory can be deallocated before
    // the upcall is made. Even if we're not about to make an upcall, a
    // sub-object of the handler may be the true owner of the memory associated
    // with the handler. Consequently, a local copy of the handler is required
    // to ensure that any owning sub-object remains valid until after we have
    // deallocated the memory here.
    detail::binder2<Handler, pdalboost::system::error_code, std::size_t>
      handler(o->handler_, ec, bytes_transferred);
    p.h = pdalboost::asio::detail::addressof(handler.handler_);
    p.reset();

    // Make the upcall if required.
    if (owner)
    {
      fenced_block b(fenced_block::half);
      BOOST_ASIO_HANDLER_INVOCATION_BEGIN((handler.arg1_, handler.arg2_));
      pdalboost_asio_handler_invoke_helpers::invoke(handler, handler.handler_);
      BOOST_ASIO_HANDLER_INVOCATION_END;
    }
  }

  static void do_complete(io_service_impl* owner, operation* base,
      const boost::system::error_code& result_ec,
      std::size_t bytes_transferred)
  {
    boost::system::error_code ec(result_ec);

    // Take ownership of the operation object.
    win_iocp_socket_recvfrom_op* o(
        static_cast<win_iocp_socket_recvfrom_op*>(base));
    ptr p = { boost::addressof(o->handler_), o, o };

    BOOST_ASIO_HANDLER_COMPLETION((o));

#if defined(BOOST_ASIO_ENABLE_BUFFER_DEBUGGING)
    // Check whether buffers are still valid.
    if (owner)
    {
      buffer_sequence_adapter<boost::asio::mutable_buffer,
          MutableBufferSequence>::validate(o->buffers_);
    }
#endif // defined(BOOST_ASIO_ENABLE_BUFFER_DEBUGGING)

    socket_ops::complete_iocp_recvfrom(o->cancel_token_, ec);

    // Record the size of the endpoint returned by the operation.
    o->endpoint_.resize(o->endpoint_size_);

    // Make a copy of the handler so that the memory can be deallocated before
    // the upcall is made. Even if we're not about to make an upcall, a
    // sub-object of the handler may be the true owner of the memory associated
    // with the handler. Consequently, a local copy of the handler is required
    // to ensure that any owning sub-object remains valid until after we have
    // deallocated the memory here.
    detail::binder2<Handler, boost::system::error_code, std::size_t>
      handler(o->handler_, ec, bytes_transferred);
    p.h = boost::addressof(handler.handler_);
    p.reset();

    // Make the upcall if required.
    if (owner)
    {
      fenced_block b(fenced_block::half);
      BOOST_ASIO_HANDLER_INVOCATION_BEGIN((handler.arg1_, handler.arg2_));
      boost_asio_handler_invoke_helpers::invoke(handler, handler.handler_);
      BOOST_ASIO_HANDLER_INVOCATION_END;
    }
  }

  static void do_complete(void* owner, operation* base,
      const boost::system::error_code& result_ec,
      std::size_t bytes_transferred)
  {
    boost::system::error_code ec(result_ec);

    // Take ownership of the operation object.
    win_iocp_handle_read_op* o(static_cast<win_iocp_handle_read_op*>(base));
    ptr p = { boost::asio::detail::addressof(o->handler_), o, o };
    handler_work<Handler, IoExecutor> w(o->handler_, o->io_executor_);

    BOOST_ASIO_HANDLER_COMPLETION((*o));

#if defined(BOOST_ASIO_ENABLE_BUFFER_DEBUGGING)
    if (owner)
    {
      // Check whether buffers are still valid.
      buffer_sequence_adapter<boost::asio::mutable_buffer,
          MutableBufferSequence>::validate(o->buffers_);
    }
#endif // defined(BOOST_ASIO_ENABLE_BUFFER_DEBUGGING)

    // Map non-portable errors to their portable counterparts.
    if (ec.value() == ERROR_HANDLE_EOF)
      ec = boost::asio::error::eof;

    // Make a copy of the handler so that the memory can be deallocated before
    // the upcall is made. Even if we're not about to make an upcall, a
    // sub-object of the handler may be the true owner of the memory associated
    // with the handler. Consequently, a local copy of the handler is required
    // to ensure that any owning sub-object remains valid until after we have
    // deallocated the memory here.
    detail::binder2<Handler, boost::system::error_code, std::size_t>
      handler(o->handler_, ec, bytes_transferred);
    p.h = boost::asio::detail::addressof(handler.handler_);
    p.reset();

    // Make the upcall if required.
    if (owner)
    {
      fenced_block b(fenced_block::half);
      BOOST_ASIO_HANDLER_INVOCATION_BEGIN((handler.arg1_, handler.arg2_));
      w.complete(handler, handler.handler_);
      BOOST_ASIO_HANDLER_INVOCATION_END;
    }
  }

  static void do_complete(void* owner, operation* base,
      const boost::system::error_code& result_ec,
      std::size_t /*bytes_transferred*/)
  {
    boost::system::error_code ec(result_ec);

    // Take ownership of the operation object.
    win_iocp_socket_connect_op* o(
        static_cast<win_iocp_socket_connect_op*>(base));
    ptr p = { boost::asio::detail::addressof(o->handler_), o, o };
    handler_work<Handler> w(o->handler_);

    if (owner)
    {
      if (o->connect_ex_)
        socket_ops::complete_iocp_connect(o->socket_, ec);
      else
        ec = o->ec_;
    }

    BOOST_ASIO_HANDLER_COMPLETION((*o));

    // Make a copy of the handler so that the memory can be deallocated before
    // the upcall is made. Even if we're not about to make an upcall, a
    // sub-object of the handler may be the true owner of the memory associated
    // with the handler. Consequently, a local copy of the handler is required
    // to ensure that any owning sub-object remains valid until after we have
    // deallocated the memory here.
    detail::binder1<Handler, boost::system::error_code>
      handler(o->handler_, ec);
    p.h = boost::asio::detail::addressof(handler.handler_);
    p.reset();

    // Make the upcall if required.
    if (owner)
    {
      fenced_block b(fenced_block::half);
      BOOST_ASIO_HANDLER_INVOCATION_BEGIN((handler.arg1_));
      w.complete(handler, handler.handler_);
      BOOST_ASIO_HANDLER_INVOCATION_END;
    }
  }

  static void do_complete(void* owner, operation* base,
      const boost::system::error_code& /*ec*/,
      std::size_t /*bytes_transferred*/)
  {
    // Take ownership of the handler object.
    reactive_socket_move_accept_op* o(
        static_cast<reactive_socket_move_accept_op*>(base));
    ptr p = { boost::asio::detail::addressof(o->handler_), o, o };
    handler_work<Handler> w(o->handler_);

    // On success, assign new connection to peer socket object.
    if (owner)
      o->do_assign();

    BOOST_ASIO_HANDLER_COMPLETION((*o));

    // Make a copy of the handler so that the memory can be deallocated before
    // the upcall is made. Even if we're not about to make an upcall, a
    // sub-object of the handler may be the true owner of the memory associated
    // with the handler. Consequently, a local copy of the handler is required
    // to ensure that any owning sub-object remains valid until after we have
    // deallocated the memory here.
    detail::move_binder2<Handler,
      boost::system::error_code, typename Protocol::socket>
        handler(0, BOOST_ASIO_MOVE_CAST(Handler)(o->handler_), o->ec_,
          BOOST_ASIO_MOVE_CAST(typename Protocol::socket)(*o));
    p.h = boost::asio::detail::addressof(handler.handler_);
    p.reset();

    // Make the upcall if required.
    if (owner)
    {
      fenced_block b(fenced_block::half);
      BOOST_ASIO_HANDLER_INVOCATION_BEGIN((handler.arg1_, "..."));
      w.complete(handler, handler.handler_);
      BOOST_ASIO_HANDLER_INVOCATION_END;
    }
  }

  static void do_complete(io_service_impl* owner, operation* base,
      const boost::system::error_code& result_ec,
      std::size_t /*bytes_transferred*/)
  {
    boost::system::error_code ec(result_ec);

    // Take ownership of the operation object.
    win_iocp_socket_accept_op* o(static_cast<win_iocp_socket_accept_op*>(base));
    ptr p = { boost::asio::detail::addressof(o->handler_), o, o };

    if (owner)
    {
      typename Protocol::endpoint peer_endpoint;
      std::size_t addr_len = peer_endpoint.capacity();
      socket_ops::complete_iocp_accept(o->socket_,
          o->output_buffer(), o->address_length(),
          peer_endpoint.data(), &addr_len,
          o->new_socket_.get(), ec);

      // Restart the accept operation if we got the connection_aborted error
      // and the enable_connection_aborted socket option is not set.
      if (ec == boost::asio::error::connection_aborted
          && !o->enable_connection_aborted_)
      {
        o->reset();
        o->socket_service_.restart_accept_op(o->socket_,
            o->new_socket_, o->protocol_.family(),
            o->protocol_.type(), o->protocol_.protocol(),
            o->output_buffer(), o->address_length(), o);
        p.v = p.p = 0;
        return;
      }

      // If the socket was successfully accepted, transfer ownership of the
      // socket to the peer object.
      if (!ec)
      {
        o->peer_.assign(o->protocol_,
            typename Socket::native_handle_type(
              o->new_socket_.get(), peer_endpoint), ec);
        if (!ec)
          o->new_socket_.release();
      }

      // Pass endpoint back to caller.
      if (o->peer_endpoint_)
        *o->peer_endpoint_ = peer_endpoint;
    }

    BOOST_ASIO_HANDLER_COMPLETION((o));

    // Make a copy of the handler so that the memory can be deallocated before
    // the upcall is made. Even if we're not about to make an upcall, a
    // sub-object of the handler may be the true owner of the memory associated
    // with the handler. Consequently, a local copy of the handler is required
    // to ensure that any owning sub-object remains valid until after we have
    // deallocated the memory here.
    detail::binder1<Handler, boost::system::error_code>
      handler(o->handler_, ec);
    p.h = boost::asio::detail::addressof(handler.handler_);
    p.reset();

    // Make the upcall if required.
    if (owner)
    {
      fenced_block b(fenced_block::half);
      BOOST_ASIO_HANDLER_INVOCATION_BEGIN((handler.arg1_));
      boost_asio_handler_invoke_helpers::invoke(handler, handler.handler_);
      BOOST_ASIO_HANDLER_INVOCATION_END;
    }
  }