Weak References

[PJP]

Jason House Wrote:

> Bill Baxter Wrote:
> 
> > On Thu, Aug 7, 2008 at 8:12 AM, Jason House <jason.james.house at gmail.com> wrote:
> > > A weak reference library exists but doesn't always work...
> > 
> > By doesn't always work you mean that it seems to you that sometimes it
> > prevents the target object from being collected, right?
> 
> It causes crashes under the right circumstances. I posted test cases to reproduce the behavior when I was experimenting with it...
> 
> 
> 
> 
> > 
> > But I think you said your only test case for this was something that
> > is not reproducible, correct?
> > 
> > Very frustrating to not be able to say for sure.  It would be a huge
> > help if the GC exposed some API for querying where a particular
> > pointer is being referenced.  Without that it's really hard to say
> > where the reference actually is coming from.
> > 
> > One possible gotcha that just crossed my mind:  I think the current GC
> > allocates chunks in an all or nothing manner -- hasPointers is just a
> > single bit.  So could it be that the fact that all Objects have a
> > vtable pointer mean that everything in an Object is always treated as
> > having pointers?
> > 
> > --bb
> > 
> > > PJP Wrote:
> > >
> > >> Is there any plan to add support for weak references to the D garbage collector?
> > >>
> > >> Weak references are references which don't prevent the object from being garbage collected.  If it has been garbage collected then the weak reference returns null.
> > >>
> > >> This is useful for things like resource caches, maintaining references to all instances of a specific class (ex: to implement an operation such as Window.minimizeAllWindows()), or to register a callback/listener with an object such that the registration won't prevent that object from being garbage collected.
>