From: Eric Hodel <drbrain@...7.net>
Date: 2007-09-30T08:46:31+09:00
Subject: Re: ObjectSpace reveals order?

On Sep 28, 2007, at 18:18 , Todd Benson wrote:

> If I do...
>
> ObjectSpace.each_object { |o| puts o; gets }
>
> will it give me the consecutive order of the loading of the objects
> (i.e. the time order that memory is allocated on the heap)?

Well, its kinda backwards*:

$ cat test.rb
items = ['a', 'b']

ObjectSpace.each_object do |o|
   p o.object_id => o
end

$ ruby test.rb | head -3
{1001920=>"b"}
{1001930=>"a"}
{1001940=>["a", "b"]}

[] was allocated first, then 'a', then 'b', not the other way around.

* This example was too small to invoke the garbage collector, so it  
will be in reverse order.  With garbage collection you aren't  
guaranteed any ordering.

> Or is it a tree structure underneath or something strange like that?

You can infer the structure of ruby's heap if you make enough  
objects.  Replace items = ['a', 'b'] with ('a'..'aaa').to_a and add  
GC.disable and you'll see something like:

{987780=>"aaa"}     # <-- end (bottom) of first heap
{987800=>"zz"}
{987820=>"zy"}
[...]
{1035860=>Kernel}
{1035900=>Class}
{1035910=>Module}
{1035920=>Object}   # <-- start (top) of first heap
{1820790=>"Object"} # <-- last used address of second heap
{1820800=>"Object"}
{1820810=>"1035920"}
{1820820=>"{1035920=>Object}"}
[...]
{1828610=>"1022660"}
{1828620=>"{1022660=>\"Errno::EREMOTE\"}"}
{1828630=>{1022660=>"Errno::EREMOTE"}} # <-- start (top) of second heap

Ruby's heaps look something like:

heaps = [
   [ ... ], # objects live in here
   ...      # more arrays of objects, as necessary
]

This was on OS X.

> Why do I get String objects right off the bat like...
>
> ' does not evaluate to a gem specification

You have RUBYOPT=-rubygems