Thanks, that works.  

Now, how do you pass a string by address?  Of course, the 
documentation is very misleading.  I tried the same thing on a 
string but that did not work. 

(ff:def-foreign-call test_string ((mesg (* :unsigned-byte) (simple-array simple-string (*))))
   :returning :void)


Johannes Beck <informatik.uni-wuerzburg.de at beck> writes:

> Hi,
> 
> > I am trying to call a c function with an argument passed by address.
> > Reading the documentation in
> > file:/usr/local/acl5/doc/cl/foreign_functions.htm#5.1,
> > Modifying arguments called by address: use arrays
> > I found the example:
> > 
> > (ff:def-foreign-call `itimes2 ((simple-array fixnum (1)))
> >             :convention :fortran :returning :void)
> > 
> > However, changing the obvious mistakes to:
> > 
> > (ff:def-foreign-call itimes2 ((dice (simple-array fixnum (1))))
> >             :convention :c  :returning :void)
> > 
> > I get the error:
> > 
> > Error: don't know how to convert type: (SIMPLE-ARRAY FIXNUM (1))
> >   [condition type: SIMPLE-ERROR]
> IMO the given example has more mistakes than the ones you already
> detected. I think it should look like this (although I didnt test it):
> 
> (ff:def-foreign-call itimes2 
>                      ((dice                      ;;; Name of the
> Argument
>                       (* :unsigned-byte)         ;;; The foreign
> argument is a 
>                                                  ;;; pointer to some
> numbers
>                       (simple-array fixnum (1))) ;;; which should be
> converted to the
>                                                  ;;; LISP type
> simple-array of fixnum
>                      )
>                      :convention :c :returning :void)
> 
> Hope that helps
> 	Joe
> 
> -- 
> Johannes Beck   beck at informatik.uni-wuerzburg.de
>                 
> PGP Public Key available by
> <www-info6.informatik.uni-wuerzburg.de at finger://beck>
> 

-- 
                                         
                                          myriam

Go Proverb:

In the corner, five stones in a row on the third line are alive.