Re: [Vala] use weak and var together

[Hans Vercammen <hveso3 gmail com>]

On Sat, 2009-01-10 at 13:16 -0800, Noah Gibbs wrote:
> In addition to keeping a list of pointers to the object, you'll need
> to traverse them in some way to find cycles and free storage with
> cycles, but not pointed to by any non-cycles.  That pass should not be
> done every time you break a pointer link because it can be very
> expensive, just as garbage collection is.  You could do it
> periodically, maybe every so many allocations or so many seconds --
> but if you do that, you've basically written a garbage collector.

I agree. However, cyclic references are basically a trademark for
reference counting. It's relatively fast and easy to implement, but you
probably don't want use this in combination with a garbage collector as
the reference count other than zero is of no meaning to the collector.

>   Remember that an object can be part of more than one cycle, and you
> have to know how many of those refs are "cyclic" refs, and how many
> (if any) aren't from cycles.  That's non-local knowledge.  What I'm
> saying is that it's not an easy think to calculate, and there's a
> reason that garbage collectors tend to be slow :-)

There are actually rather fast garbage collection algorithms out there.
The main reason I can think of why they still appear to be slow is that
in most cases they have to "stop the world" to do their processing.

Hans