From: Eric Mahurin <eric_mahurin@...>
Date: 2005-06-19T06:32:44+09:00
Subject: GC.disable not working?

From what I can tell, GC.disable doesn't work.  I'm wanting to
use GC.disable/GC.enable around code using objects that I get
from ObjectSpace._id2ref to make sure that the id doesn't
become invalid because of GC.  Here is a piece of code that
demonstrates the problem:


#!/bin/env ruby

def finalizer(id)
    print("<")
    GC.enable and
        printf("GC disabled while finalizing %x!!!",id)
    @ids.delete(id)
    print(">")
end

$stdout.sync=true
@ids = {}
1000.times { |i|
    print("[")
    obj = "X"*i
    id = obj.object_id
    @ids[id] = true
    ObjectSpace.define_finalizer(obj,method(:finalizer))
    GC.disable
    print("{")
    @ids.each_key { |id|
        # go make sure all objects seem valid (test size)
        ObjectSpace._id2ref(id).size
    }
    print("}")
    GC.enable
    print("]")
}


I tried this on 1.8.2 and a 1.9 CVS version.  In both it calls
the finalizer when GC is disabled (GC.enable==true).  I thought
this would be impossible.  I also get a recycled object error. 
In the 1.9 version I'm using, it hangs while trying to finalize
one of the objects (@ids.delete(id) is where it hangs).

Any clues to what is going on with this GC stuff.  If I can't
get this to work, I don't see how anybody reliably use
ObjectSpace._id2ref.  BTW, I found this problem in my code
after running tens of thousands of random tests.  If you don't
do enough testing, you may not find problems related to garbage
collection.




		
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