Bug #13144: prettyprint doesn't detect cycles when wrapped inside Delegators

• Status: Open
• Priority: Normal
• Assignee: -
• Target version: -
• ruby -v: 2.4.0
• Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN

[richardviney (Richard Viney)]

The line count of the pretty print output for the following class grows factorially with the number of self-referencing SimpleDelegator instances created by the initializer. With an n of 8 the line count of the pretty print output is almost one million! This occurs because the cycle detection in lib/pp.rb doesn't detect the already printed object due to it being wrapped inside a Delegator instance. The same problem occurs with pretty printing cycles wrapped inside WeakRef because it is a subclass of Delegator.

class Foo
def initialize(n)
n.times { |i| instance_variable_set "@a#{i}", SimpleDelegator.new(self) }
end
end

[richardviney (Richard Viney)]

Pull request with my fix and new test case: https://github.com/ruby/ruby/pull/1518