[racket] Freeing FFI resources

9 minutes ago, Neil Toronto wrote:
> Eli Barzilay wrote:
> > But of course if the problem is the original one in this thread, where
> > each C string eventually needs to be converted to a Racket string,
> > then there's little point in holding on to a pointer instead of
> > converting it immediately (and freeing the C pointer).
> 
> True, dat.
> 
> > With this code:
> > 
> >   #lang racket
> >   (require ffi/unsafe)
> >   (define bytes/free
> >     (make-ctype _bytes
> >                 #f ; a Racket bytes can be used as a pointer
> >                 (lambda (b)
> >                   (register-finalizer b free)
> >                   b)))
> >   (define strdup
> >     (get-ffi-obj 'strdup #f (_fun _bytes -> bytes/free)))
> >   (for ([i (in-range 1000000000)]) (strdup #"bleh"))
> > 
> > I get memory at around 200mb; with a `free' instead of the
> > finalizer, it's around 130mb.
> 
> That tracks well with my experience. As I made a ctype for them, I
> found there were two allocations for each Racket-managed struct,
> each about the same size as the Racket-managed one. So yeah, it's
> easy to triple Racket's memory consumption without it knowing.

(Having your memory full by just these things is not something that
should happen in practical programs.)

-- 
          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                    http://barzilay.org/                   Maze is Life!