From: Austin Ziegler <halostatue@...>
Date: 2006-02-02T03:56:19+09:00
Subject: Re: PDF::Writer running out of memory

On 01/02/06, Damphyr <damphyr@freemail.gr> wrote:
> I have a bunch of XML files containing specifications and I want to
> create a PDF file with an overview of the description element from
> those XML files. I parse the XML and convert it into a Spec object
> than I create the PDF using some attributes. Now, the following code
> runs out of memory at about 53 out of 87 of those specs. header and
> footer add a line and a bit of text (it's actually code adapted from
> the PDF::Writer Manual Techbook :) )

I have had someone else report this and provide me with a customized
SimpleTable that drastically reduces the memory usage but drops
some...recoverability; it does not surprise me that this is happening,
but I have had no time to investigate exactly what can be done. It does
not surprise me that this is happening, and there may be several ways to
solve this.

The problem is best shown with code:

  require 'transaction/simple'

  class Parent
    include Transaction::Simple

    attr_accessor :children
    def add_children(*children)
      children.each { |x|
        x.parent = self
        @children << x
      }
    end
    def initialize
      @children = []
    end
  end

  class Child
    attr_accessor :parent
  end

  def show_ids(parent)
    puts <<-EOS
  self <#{parent.object_id}> [ #{parent.children.map do |el|
    el.parent.object_id end.join(', ') } ]
    EOS
  end

  a = Parent.new
  a.add_children Child.new ; nil
  show_ids(a) # self<24875792> [ 24875792 ]
  a.start_transaction ; nil
  a.add_children Child.new, Child.new ; nil
  show_ids(a) # self<24875792> [ 24875792, 24875792, 24875792 ]
  a.rewind_transaction ; nil
  a.add_children Child.new, Child.new ; nil
  show_ids(a) # self<24875792> [ 24852044, 24875792, 24875792 ]

That last one is the source of the memory leak. It's also the source of
a much more subtle bug in the making it impossible to set certain things
"late" in the process.

-austin
--
Austin Ziegler * halostatue@gmail.com
               * Alternate: austin@halostatue.ca