From: "shyouhei (Shyouhei Urabe)" <shyouhei@...>
Date: 2012-06-27T18:33:00+09:00
Subject: [ruby-core:45912] [ruby-trunk - Bug #6614] GC doesn't collect objects bound to (collectable) proc


Issue #6614 has been updated by shyouhei (Shyouhei Urabe).


cjheath (Clifford Heath) wrote:
> On 27/06/2012, at 4:35 PM, nobu (Nobuyoshi Nakada) wrote:
>  > headius (Charles Nutter) wrote:
>  >> Finalizers in JRuby are stored on a reference from the object itself, so they don't actually prevent the object from collecting.
>  > 
>  > You're missing the point.
>  
>  Is he? Surely somewhere in that loop{finalized_puts []} the GC will activate,
>  and that will find collectable objects (with finalisers attached in JRuby). In
>  MRI, they might be found but they won't be finalised, if I understand the
>  behaviour right.

When a proc that touches an object is attatched to that object's finalizer, that finalizer can "escape" that object.

  ObjectSpace.define_finalizer(obj) { $escaped = obj } # Woo!

This would break the whole concept of finalizing.  Nobu's point is that how JRuby prevents this situation.
----------------------------------------
Bug #6614: GC doesn't collect objects bound to (collectable) proc
https://bugs.ruby-lang.org/issues/6614#change-27518

Author: rogerdpack (Roger Pack)
Status: Rejected
Priority: Normal
Assignee: 
Category: 
Target version: 
ruby -v: tcs-ruby 1.9.3p28 (2012-01-28, TCS patched 2012-01-30) [i386-mingw32]


Hello all.
Previously discussed here: http://www.ruby-forum.com/topic/4402823

I would expect the following code to eventually run the finalizers mentioned:

def finalized_puts bad
    ObjectSpace.define_finalizer(bad) { print 'collector run', bad }
end

loop { finalized_puts [] }

This works in jruby as expected, but not in MRI.  This has the unfortunate side effect of making define_finalizer *very* difficult to actually use right http://www.mikeperham.com/2010/02/24/the-trouble-with-ruby-finalizers/

Cheers!



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