Ruby

Don't ask how or why I wrote this code, but suppose you have a class like this:

class BrokenNumber def initialize(num) @num = num end def method_missing(m, *a, &b) @num.send(m, *a, &b) end def coerce(other) [self, self] end end 

Then you require this code in IRB, and you create a new instance (x) and you then call 2+x.

The first call will raise a SystemStackError. The second will cause a segmentation fault.

>> require "./broken" => true >> x = BrokenNumber.new(2) => #<BrokenNumber:0x007f8b5a84c190 @num=2> >> 2 + x SystemStackError: stack level too deep	from /Users/gtb/broken.rb:7:in `+'	from /Users/gtb/broken.rb:7:in `method_missing'	from /Users/gtb/broken.rb:7:in `+'	from /Users/gtb/broken.rb:7:in `method_missing'	from /Users/gtb/broken.rb:7:in `+'	from /Users/gtb/broken.rb:7:in `method_missing'	from /Users/gtb/broken.rb:7:in `+'	from /Users/gtb/broken.rb:7:in `method_missing'	from /Users/gtb/broken.rb:7:in `+'	from /Users/gtb/broken.rb:7:in `method_missing'	from /Users/gtb/broken.rb:7:in `+'	from /Users/gtb/broken.rb:7:in `method_missing'	from /Users/gtb/broken.rb:7:in `+'	from /Users/gtb/broken.rb:7:in `method_missing'	from /Users/gtb/broken.rb:7:in `+'	from /Users/gtb/broken.rb:7:in `method_missing' ... 7559 levels...	from /Users/gtb/broken.rb:7:in `method_missing'	from /Users/gtb/broken.rb:7:in `+'	from /Users/gtb/broken.rb:7:in `method_missing'	from /Users/gtb/broken.rb:7:in `+'	from /Users/gtb/broken.rb:7:in `method_missing'	from /Users/gtb/broken.rb:7:in `+'	from /Users/gtb/broken.rb:7:in `method_missing'	from /Users/gtb/broken.rb:7:in `+'	from /Users/gtb/broken.rb:7:in `method_missing'	from /Users/gtb/broken.rb:7:in `+'	from /Users/gtb/broken.rb:7:in `method_missing'	from /Users/gtb/broken.rb:7:in `+'	from /Users/gtb/broken.rb:7:in `method_missing'	from (irb):3:in `+'	from (irb):3	from /Users/gtb/.rubies/ruby-2.3.1/bin/irb:11:in `<main>' >> 2 + x Segmentation fault: 11 MacBook-Pro:~ gtb$ ruby -v ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-darwin15] 

I've asked multiple people to confirm this and they've reproduced the error. I have no clue how to debug it, but thought it may be worth mentioning... even though it's a strange corner case and invalid code.