A test to prove Symbol can't be GC in both Ruby 1.9 and Ruby 1.8

gistfile1.rb

MAX_LENGTH = 10

def generate(base_str)
  [('a'..'z'), ('A'..'Z'), ('0'..'9')].map(&:to_a).flatten.each do |char|
    str = base_str + char
    str.to_sym # You can comment this statement and compare the result
    generate(str) if str.size <= MAX_LENGTH
  end
end

main = Thread.start { 
  generate('')
  Thread.kill(counter)
  puts 'generating is over ...'
}

counter = Thread.start {
  loop do
    GC.start # GC here to free memery
    puts "Current number of Objects: " + ObjectSpace.each_object(Object).count.to_s
    sleep 1
  end
}

counter.join
main.join