For example, the following code leaks:

    class MyRipper < Ripper
      def initialize(src, &blk)
        super(src)
        @blk = blk
      end

      def warn(msg, *args) = @blk.call(msg)
    end

    $VERBOSE = true
    def call_parse = MyRipper.new("if true\n  end\n") { |msg| return msg }.parse

    10.times do
      500_000.times do
        call_parse
      end

      puts `ps -o rss= -p #{$$}`
    end

Before:

    37536
    53744
    70064
    86448
    102576
    119120
    135248
    151216
    167744
    183824

After:

    19280
    19696
    19728
    20336
    20448
    21408
    21616
    21616
    21824
    21840