Re: [Gnash-dev] GC and refcount

[strk]

Ehm.... for the record, the case to think about is the unreachable
chain of GcResources circularly referencing each-other trouh this
"smart pointer".
The GC would delete the resources, so the "smart pointers" would
NOT be able to access the actual referee object w/out memory violations.

We'd then need a way from the GC to signal all smart pointers about
this condition. Chances are weak pointers would help here, but I've no
experience with that (will do some research).

--strk;

On Mon, Dec 21, 2009 at 06:32:12PM +0100, strk wrote:
> I've created a new shared branch for the GC work:
>  bzr branch http://bzr.savannah.gnu.org/r/gnash/branches/gc
> 
> The GC version in the branch allows "manual" deletion of GcResource
> objects by having GcResource destructor remove self from the GC-managed
> list. Cost of this is + sizeof(std::list::iterator) per GcResource.
> Removal from the std::list runs in constant time.
> 
> Now that we have that possibility, adding a ref-count in GcResource
> would let us remove earlier any object not containing circular refs.
> Only trouble would be making sure intrusive_ptrs for GcResource
> are properly used within the whole codebase. 
> The SafeStack implementation would need to stop keeping as_value
> alive in order for memory reduction to be noticeable.
> 
> --strk;
> 
> 
> On Sat, Dec 19, 2009 at 12:17:43PM +0100, strk wrote:
> > Here's another idea to reduce memory use.
> > We could mix refcount and gc for the GcResources
> > so that in absence of circular refs we'll release
> > them sooner.
> > 
> > The additional overhead would be:
> >     - refcount management  (per reference)
> >     - GC list  management (per object)
> > 
> > Implementation:
> >     - manage GcResources with intrusive_ptr<>
> >       like others.
> >     - Tweak add/drop refs for GcResource in libbase/smart_ptr.h
> >     - Tweak GcResource to add refcount and signal GC
> >       about being removed.
> > 
> > --strk;
> > 
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