[cffi-devel] Thread callback problem

[Luís Oliveira]

On Wed, Jun 17, 2009 at 2:21 AM, Luke J Crook<luke at balooga.com> wrote:
> Corman Common Lisp FFI allows a thread to be blessed. I don't know if any
> other Lisp supports this though.

Clozure CL seems to this automagically. Gary Byers described the issue
in detail in this message
<http://www.clozure.com/pipermail/openmcl-devel/2003-May/004781.html>.
Although he says "that code isn't written yet", apparently it has been
written since then.

Here's a quick test to check whether your Lisp supports callbacks from
random threads.

(in-package :cffi)

(load-foreign-library "libpthread.so.0")

(defcallback foo :pointer ((arg :pointer))
  (declare (ignore arg))
  (print 'called-into-lisp-from-foreign-thread)
  (null-pointer))

(defctype pthread-t :unsigned-long)

(with-foreign-object (th 'pthread-t)
  (foreign-funcall "pthread_create" :pointer th :pointer (null-pointer)
                   :pointer (callback foo) :pointer (null-pointer))
  (foreign-funcall "pthread_join" pthread-t (mem-ref th 'pthread-t)
                   :pointer (null-pointer)))

We should at some point run it on the supported Lisps and note down
which ones support this. Then add that information to the manual and
possibly push something informative to *FEATURES* on Lisps that don't
support this.

-- 
Luís Oliveira
http://student.dei.uc.pt/~lmoliv/