Luís Oliveira wrote:
>> If I follow correctly, this can be more generally solved with a
>> cross-platform setf-expander for POINTER-ADDRESS that requires its PTR
>> arg to be a place, whereupon things like (incf (pointer-address
>> *ptr*)) and any other place-modifier should work.
>
> Hmm. I find that a bit confusing. (incf (pointer-address foo)) really
> makes it look look that foo's address is mutable.
No more than (incf (ldb (byte 2 1) foo)) makes it look as if the
integer itself at FOO is mutable, unless you must take into account
the prevalence of 1-arg slot accessors.
> So, I propose incf-pointer again, this time without the double
> evaluation bug:
>
> (define-modify-macro incf-pointer (&optional (offset 1)) inc-pointer)
Simple enough for anyone to duplicate for future modifiers, too. I
should spend more time expanding my symbology.
For posterity, here is a setf-expander:
(define-setf-expander pointer-address (ptr &environment env)
(multiple-value-bind (temp-vars value-forms store-vars
store-form access-form)
(get-setf-expansion ptr env)
(destructuring-bind (ptr-store-var) store-vars
(with-unique-names (store-var)
(values temp-vars value-forms
(list store-var)
`(let ((,ptr-store-var (make-pointer ,store-var)))
,store-form
,store-var)
`(pointer-address ,access-form))))))
--
Stephen Compall
http://scompall.nocandysw.com/blog
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