Re: [Caml-list] Why is struct caml_ba_proxy allocated outside the GC heap and why doesn't it have a finalizer?

[Goswin von Brederlow <goswin-v-b@web.de>]

On Sat, Feb 01, 2014 at 09:06:54PM -0500, Markus Mottl wrote:
> On Sat, Feb 1, 2014 at 8:38 PM, Goswin von Brederlow <goswin-v-b@web.de> wrote:
> > The GC knows which pointers point inside the GC heap and which point
> > outside. So there is no problem there. The pointer must just not exist
> > after the destination has been freed or it might accidentaly point to
> > inside the next GC heap. Can't happen in this use case.
> 
> Exactly.  Though the GC checks whether a pointer actually points into
> the OCaml heap before following it, it does require some care to
> guarantee that the pointer, if still reachable by the GC, is
> invalidated (e.g. set to NULL) before associated memory is freed.
> This may indeed not be that hard to achieve for the bigarray module.
> I still prefer 2), which would also be easier to add to the current
> implementation without breaking existing code.
> 
> Regards,
> Markus
> 
> -- 
> Markus Mottl        http://www.ocaml.info        markus.mottl@gmail.com

Time to try out that new ocaml program to use git-hub for patches to
the compiler. I will go with option 2 because it will not change
anything in the compiler and the optimizations for bigarrays itself.
It will only affect the C code fo allocation and dinalization. So
should be far easier.

I think I will add a new flag to the Bigarray structure that says when
a "free" function was added to the proxy object. That way even if some
software creates the proxy object themself (and won't have the free_fn
pointer) this will work.

MfG
	Goswin