coredump_repro.rb

require 'rexml/parsers/pullparser'

def look_at_record(parser)
  # While this first 'if' condition will never be triggered, it is somehow
  # neccesary as is to trigger the core dump.
  if Module.constants.index('FooBarBazNoSuchThing') && parser.is_a?(String)
  else
    while parser.has_next?
      event = parser.pull
      if event.end_element?
        if event[0] == "record"
          return "foo"
        end
      end
    end
  end
end


  sample_xml = <<EOF
<record>
  <leader>foo</leader>
</record>
EOF


parser = REXML::Parsers::PullParser.new(StringIO.new(sample_xml))
while parser.has_next?
  event = parser.pull
  # if it's the start of a record element
  if event.start_element? and event[0] == 'record'
    puts look_at_record(parser)
  end
end