From: "Florian G. Pflug" <fgp@...>
Date: 2001-08-14T13:38:05+09:00
Subject: [ruby-talk:19672] Re: Forced garbage collection

On Mon, Aug 13, 2001 at 12:34:09PM +0900, jweirich@one.net wrote:
>     Florian> Well.. but on the other hand, why isn't the block
>     Florian> collected, and then the object? Because the block is
>     Florian> needed, when the object is destructed. This seems to be a
>     Florian> kind of "circular dependency" - or in other words a
>     Florian> deadlock.
> 
> The block is referenced by the ObjectSpace data structures (whatever
> they are) that tracks finalizers.  This prevents the block from being
> GC'ed.  The block references the object, so the object can't be GC'ed
> either.  The object has no reference back to the block (AFAIK), so
> there are no cycles in the object graph.

I saw "block is references by the ObjectSpace data structures, to be called
when object is dead" as similar to "object has reference to block" - just
as an explaination for why I said "deadlock" - but I can easily be than this
defines "has reference to" to widely.

Howevery, would it be easy to print a warning when this happens? I needed
quite I while to figure out why my finalizer was not called, and it seems as
I was not the only one bitten by this.

greetings, Florian Pflug