[Cffi-devel] readded broken link from last post

[Willem Rein Oudshoorn]

Joeish W <joeish80829 at yahoo.com> writes:

> Lisp code is here https://gist.github.com/W-Net-AI/11205892
>  ...
> LCV> (dotimes (ic (vector-rect-size faces)) 
>             (setf n (%vector-rect-to-c-array faces))
>             (rect-x (mem-aref n :pointer ic)))
>
> this is where it fails, rect-x, my Lisp wrapper for C wrapper for the
> c++ Rect class member x in this statement isn't getting a Rect* so it
> outputs error: Unhandled ;memory fault at #xC9000000D5.  The
> %vector-rect-to-c-array function is a wrapper for the c function in
> the posted c/c++ code. It works as expected on everything else but the
> vector<Rect> output of detectMultiScale.

This fails because `n` is a pointer the data of vector<Rect>.  
So it points to an array of Rect structures, NOT an array of Rect*
(pointers to Rect).

What would work (but I am advising against this), is:

(rect-x (inc-pointer n (* ic SIZE_OF_RECT)))

Where SIZE_OF_RECT is the size of the Rect struct.

What you should do is look into `defcstruct` to properly wrap the Rect
struct and start from there.

Wim Oudshoorn.