Find where a variable is over-written with a different value

trace_variable_changes.rb

class Abc
  def initialize
    @thing = {"foo" => "bar"}
  end
end

$stack = [{:config => {}}]
set_trace_func lambda { |event, file, line, id, binding, classname|
  printf("%8s %s:%-2d %10s %8s\n", event, file, line, id, classname)

  if binding.eval("local_variables").include?(:config)
    _new = binding.eval("config")

    if _new && ($stack.last[:config][:value] != _new.inspect)
      $stack << {
        :config => {
          :self => binding.eval("self"),
          :source => "#{file}:#{line}",
          :value => _new.inspect
        }
      }
    end
  end
}


config = Abc.new
config.instance_variable_set(:@thing, 123)
config = "foo"


set_trace_func nil
puts $stack