>>>>> On Sun, 08 May 2011 14:39:41 +0200, Nitralime said:
>
> Using a finalizer seems to be a possible way to go. But I'm not sure how
> this can be done by just using the finalizer parameters "object" and
> "function"
> where "function" can't reliablely access "object" (cf. documentation of
> finalizer
> in "trivial-garbage" package)!!
>
> Any help and feedback is very much appreciated!
IMHO, attempting to transparently wrap a foreign object with a CLOS object is
not a good design.
Using a finalizer is dangerous because it is difficult to guarantee that the
Lisp wrapper object is retained for the correct lifetime.
For example, consider
(defstruct table
foreign-pointer)
(defun allocate-table ()
(make-table :foreign-pointer (foreign-allocate-table)))
(defun allocate-and-munge-table ()
(let ((table (allocate-table)))
(foreign-munge-table (table-foreign-pointer table))))
The compiler might not keep the variable "table" alive during the call to the
foreign function foreign-munge-table. As a result, the Lisp table object
might be gc'ed in another thread while the foreign code is accessing it.
--
Martin Simmons
LispWorks Ltd
http://www.lispworks.com/
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