# File lib/ruote/util/treechecker.rb, line 40
    def initialize (context)

      (context['use_ruby_treechecker'] == false) and return

      require 'rufus/treechecker' # gem 'rufus-treechecker'
        # load only when needed

      @checker = Rufus::TreeChecker.new do

        exclude_fvccall :abort, :exit, :exit!
        exclude_fvccall :system, :fork, :syscall, :trap, :require, :load

        #exclude_call_to :class
        exclude_fvcall :private, :public, :protected

        #exclude_def               # no method definition
        exclude_eval              # no eval, module_eval or instance_eval
        exclude_backquotes        # no `rm -fR the/kitchen/sink`
        exclude_alias             # no alias or aliast_method
        exclude_global_vars       # $vars are off limits
        exclude_module_tinkering  # no module opening
        exclude_raise             # no raise or throw

        exclude_rebinding Kernel # no 'k = Kernel'

        exclude_access_to(
          IO, File, FileUtils, Process, Signal, Thread, ThreadGroup)

        #exclude_class_tinkering :except => Ruote::ProcessDefinition
          #
          # excludes defining/opening any class except
          # Ruote::ProcessDefinition

        exclude_call_to :instance_variable_get, :instance_variable_set
      end

      @cchecker = @checker.clone # and not dup
      @cchecker.add_rules do
        at_root do
          exclude_head [ :block ] # preventing 'a < b; do_sthing_evil()'
          exclude_head [ :lasgn ] # preventing 'a = 3'
        end
      end

      @checker.freeze
      @cchecker.freeze
      freeze
        #
        # preventing further modifications
    end