Problems with nested structs and the newer cffi

[Liam Healy]

On Thu, Apr 25, 2013 at 4:33 AM, Chris Bagley <chris.bagley at gmail.com>wrote:

> I ran into similar issues to Willem and have taken to using the following
> macro:
>
> (defmacro with-foreign-slots* ((vars ptr type) &body body)
>   "Create local symbol macros for each var in VARS to reference
> foreign slots in PTR of TYPE. Similar to WITH-SLOTS.
> Each var can be of the form: slot-name - in which case slot-name will
> be bound to the value of the slot or: (:pointer slot-name) - in which
> case slot-name will be bound to the pointer to that slot."
>   (let ((ptr-var (gensym "PTR")))
>     `(let ((,ptr-var ,ptr))
>        (symbol-macrolet
>            ,(loop :for var :in vars :collect
>                  (if (listp var)
>                      (if (eq (first var) :pointer)
>                          `(,(second var) (foreign-slot-pointer
>                                           ,ptr-var ',type ',(second var)))
>                          (error "Malformed var names must be:~%name~% -or-
> ~%(:pointer name)"))
>                      `(,var (foreign-slot-value
>                              ,ptr-var ',type ',var))))
>          , at body))))
>
> This, for me, balances the needs quite nicely and feels in line with the
> style of cffi. Thoughts or  modifications?
>

I had thought about doing something like this when looking into Willem's
problems. I like it, but I think the "*" in the name is unnecessary. It is
upwardly compatible with the current with-foreign-slots, isn't it? That is,
if it were to replace with-foreign-slots, it would expand correctly for
current usage (to values).  I think we should replace that macro with this.

Liam
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