[slime-devel] Slime, SBCL and add-fd-handler

Helmut Eller heller at common-lisp.net
Fri Jan 6 09:10:27 UTC 2006

* Dmitri Hrapof [2006-01-05 17:03+0100] writes:

> Hello!
> I'm using add-fd-handler in my server, 
> and everything works in raw terminal.
> However, when I start server from Slime, 
> I have to call (SB-IMPL::SERVE-EVENT) manually to
> get my callbacks called and client's request
> answered.
> Is this expected behaviour?


> What is idiomatic solution? 

I think the most idiomatic solution would be use threads instead of

> It seems to me
> I've done everything as Araneida does:
> (defun make-repl-friendly (s)
>  (when *repl-friendly*
>   (%SYSDEP
>    "adds callbacks for socket"
>    #+sbcl
>    (sb-sys:add-fd-handler
>     (sb-bsd-sockets:socket-file-descriptor s)
>      :input
>      #'(lambda (fd)
>         (declare (ignore fd))
>         (loop while (op:work_pending *the-orb*)
>            do (op:perform_work *the-orb*)))))))
> Where should I dig?

How do you wait for incoming requests?  Fd-handlers are usually called
when an I/O operation would block (and, of course, explicit calls to
serve-event).  In the usual SLIME/SBCL setup, the main thread blocks
in a call to READ and should call fd-handlers.  Note that the main
thread writes its output to the *inferior-lisp* buffer and not the
*slime-repl* buffer (SLIME creates its own "repl thread" for the its

Maybe you can find out something by looking at the backtraces for each
thread: list the thread with `M-x slime-list-threads' and press `d' to
invoke the debugger on the selected thread.


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