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

    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, asio::error_code>
      handler(h->handler_, h->ec_);
    p.h = boost::addressof(handler.handler_);
    p.reset();

    // Make the upcall if required.
    if (owner)
    {
      asio::detail::fenced_block b;
      ASIO_HANDLER_INVOCATION_BEGIN((handler.arg1_));
      asio_handler_invoke_helpers::invoke(handler, handler.handler_);
      ASIO_HANDLER_INVOCATION_END;
    }
  }

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

    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, asio::error_code, std::size_t>
      handler(o->handler_, ec, bytes_transferred);
    p.h = asio::detail::addressof(handler.handler_);
    p.reset();

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

  static void do_complete(void* owner, Operation* base,
      const asio::error_code& /*ec*/,
      std::size_t /*bytes_transferred*/)
  {
    // Take ownership of the handler object.
    executor_op* o(static_cast<executor_op*>(base));
    ptr p = { o->allocator_, o, o };

    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.
    Handler handler(ASIO_MOVE_CAST(Handler)(o->handler_));
    p.reset();

    // Make the upcall if required.
    if (owner)
    {
      fenced_block b(fenced_block::half);
      ASIO_HANDLER_INVOCATION_BEGIN(());
      asio_handler_invoke_helpers::invoke(handler, handler);
      ASIO_HANDLER_INVOCATION_END;
    }
  }

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

    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.
    Handler handler(ASIO_MOVE_CAST(Handler)(h->handler_));
    p.h = asio::detail::addressof(handler);
    p.reset();

    // Make the upcall if required.
    if (owner)
    {
      fenced_block b(fenced_block::half);
      ASIO_HANDLER_INVOCATION_BEGIN(());
      w.complete(handler, handler);
      ASIO_HANDLER_INVOCATION_END;
    }
  }

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

    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.

      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, asio::error_code, results_type>
        handler(o->handler_, o->ec_, results_type());
      p.h = 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);
        ASIO_HANDLER_INVOCATION_BEGIN((handler.arg1_, "..."));
        w.complete(handler, handler.handler_);
        ASIO_HANDLER_INVOCATION_END;
      }
    }
  }

            static void do_complete( io_service_impl* owner,
                                     operation* base,
                                     const asio::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 = {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.

                    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, asio::error_code, iterator_type> handler( o->handler_, o->ec_, o->iter_ );
                    p.h = asio::detail::addressof( handler.handler_ );
                    p.reset( );

                    if ( owner )
                    {
                        fenced_block b( fenced_block::half );
                        ASIO_HANDLER_INVOCATION_BEGIN( ( handler.arg1_, "..." ) );
                        asio_handler_invoke_helpers::invoke( handler, handler.handler_ );
                        ASIO_HANDLER_INVOCATION_END;
                    }
                }
            }

  static void do_complete(void* owner, operation* base,
      const asio::error_code& result_ec,
      std::size_t bytes_transferred)
  {
    asio::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 = { asio::detail::addressof(o->handler_), o, o };
    handler_work<Handler> w(o->handler_);

    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 = asio::error::operation_aborted;
      else
        ec = asio::error::connection_reset;
    }
    else if (ec.value() == ERROR_PORT_UNREACHABLE)
    {
      ec = 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, asio::error_code, std::size_t>
      handler(o->handler_, ec, bytes_transferred);
    p.h = asio::detail::addressof(handler.handler_);
    p.reset();

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

  static void do_complete(void* owner, operation* base,
      const asio::error_code& result_ec,
      std::size_t bytes_transferred)
  {
    asio::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 = { asio::detail::addressof(o->handler_), o, o };
    handler_work<Handler> w(o->handler_);

    ASIO_HANDLER_COMPLETION((o));

#if defined(ASIO_ENABLE_BUFFER_DEBUGGING)
    // Check whether buffers are still valid.
    if (owner)
    {
      buffer_sequence_adapter<asio::mutable_buffer,
          MutableBufferSequence>::validate(o->buffers_);
    }
#endif // defined(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, asio::error_code, std::size_t>
      handler(o->handler_, ec, bytes_transferred);
    p.h = asio::detail::addressof(handler.handler_);
    p.reset();

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

  static void do_complete(void* owner, operation* base,
      const asio::error_code& result_ec,
      std::size_t bytes_transferred)
  {
    asio::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 = { asio::detail::addressof(o->handler_), o, o };
    handler_work<Handler, IoExecutor> w(o->handler_, o->io_executor_);

    ASIO_HANDLER_COMPLETION((*o));

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

    // Map non-portable errors to their portable counterparts.
    if (ec.value() == ERROR_HANDLE_EOF)
      ec = 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, asio::error_code, std::size_t>
      handler(o->handler_, ec, bytes_transferred);
    p.h = asio::detail::addressof(handler.handler_);
    p.reset();

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

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

    ASIO_HANDLER_COMPLETION((o));

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

    socket_ops::complete_iocp_recv(o->state_, o->cancel_token_,
        buffer_sequence_adapter<asio::mutable_buffer,
          MutableBufferSequence>::all_empty(o->buffers_),
        ec, bytes_transferred);

    // 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, asio::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)
    {
      asio::detail::fenced_block b;
      ASIO_HANDLER_INVOCATION_BEGIN((handler.arg1_, handler.arg2_));
      asio_handler_invoke_helpers::invoke(handler, handler.handler_);
      ASIO_HANDLER_INVOCATION_END;
    }
  }

  static void do_complete(void* owner, operation* base,
      const asio::error_code& result_ec,
      std::size_t /*bytes_transferred*/)
  {
    asio::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 = { asio::detail::addressof(o->handler_), o, o };
    handler_work<Handler> w(o->handler_);

    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 == 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;
    }

    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, asio::error_code>
      handler(o->handler_, ec);
    p.h = asio::detail::addressof(handler.handler_);
    p.reset();

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