system_stack_error.rb

class Foo         
  def foo
    puts "ok!"
  end 
end 
 
Foo.prepend(Module.new do
  def foo
    puts "prepend!"
    super
  end
end)
 
Foo.class_eval {
  alias_method :old_foo, :foo
  
  def foo
    puts "class_eval!"
    old_foo() 
  end 
} 
 
Foo.new.foo

# prepend!
# class_eval!
# prepend!
# class_eval!
# prepend!
# class_eval!
# ...
# prepend!
# class_eval!
# prepend!
# class_eval!
# prepend!
# class_eval!
# prepend!
# class_eval!
# Traceback (most recent call last):
#       11913: from system_stack_error.rb:24:in `<main>'
#       11912: from system_stack_error.rb:10:in `foo'
#       11911: from system_stack_error.rb:20:in `foo'
#       11910: from system_stack_error.rb:10:in `foo'
#       11909: from system_stack_error.rb:20:in `foo'
#       11908: from system_stack_error.rb:10:in `foo'
#       11907: from system_stack_error.rb:20:in `foo'
#       11906: from system_stack_error.rb:10:in `foo'
#        ... 11901 levels...
#           4: from system_stack_error.rb:10:in `foo'
#           3: from system_stack_error.rb:20:in `foo'
#           2: from system_stack_error.rb:9:in `foo'
#           1: from system_stack_error.rb:9:in `puts'
# system_stack_error.rb:9:in `puts': system_stack_error level too deep (SystemStackError)