Re: [PATCH] libpoke: Use uncollectable memory instead of GC roots

[Jose E. Marchesi]

Hi Mohammad!

> The comments from `gc/gc.h`:
>
> /* new object is cleared.  GC_malloc_uncollectable allocates            */
> /* an object that is scanned for pointers to collectible                */
> /* objects, but is not itself collectible.  The object is scanned even  */
> /* if it does not appear to be reachable.  GC_malloc_uncollectable and  */
> /* GC_free called on the resulting object implicitly update             */
> /* GC_non_gc_bytes appropriately.                                       */
>
>
> And also this paragraph from https://www.hboehm.info/gc/gcinterface.html:
>
>   Identical to GC_MALLOC, except that the resulting object is not
>   automatically deallocated. Unlike the system-provided malloc, the
>   collector does scan the object for pointers to garbage-collectable
>   memory, even if the block itself does not appear to be reachable.
>   (Objects allocated in this way are effectively treated as roots by
>   the collector.) 

I like this solution.  We are effectively using the reference-counting
schema of the AST to allocate/free these fields, like the rest of the
node contents.  Very good.

I wasn't aware of the fact that GC_malloc_uncollectable effectively
adds a GC root... hopefully there is not a limit of objects allocated
this way?  Because in that case we would be in exactly the same problem
than before :)

If there isn't any limit, then this is OK for both master and
maint/poke-1.

I assume this fix is fixing the hard-limit you was finding while loading
pickles?

> Georgiy Tugai (SAL9000) was correct!

Yes :)

Maybe the GC can now be activated in Windows without catastrophic
crashes...