Bug #5077: method_missing throws NoMemoryError after inheriting from BasicObject

• Status: Rejected
• Assignee: -
• Target version: 1.9.2
• ruby -v: ruby 1.9.2p290 (2011-07-09 revision 32478) [x86_64-linux]

[madtrick (Farruco Sanjurjo)]

If a class inherits from BasicObject and then overwrites method_missing like this:

class A < BasicObject
def method_missing(*a)
puts "#{a}"
end
end

And we try it:

A.new.fooooo

The interpreter enters what looks like a loop and then crashes with this trace (in irb):

NoMemoryError: failed to allocate memory
from (irb):3:in method_missing' from (irb):3:in method_missing'
from (irb):3:in method_missing' from (irb):3:in method_missing'
from (irb):3:in method_missing' from (irb):3:in method_missing'
from (irb):3:in method_missing' from (irb):3:in method_missing'
from (irb):3:in method_missing' from (irb):3:in method_missing'
from (irb):3:in method_missing' from (irb):3:in method_missing'
from (irb):3:in method_missing' from (irb):3:in method_missing'
from (irb):3:in method_missing' from (irb):3:in method_missing'
from (irb):3:in method_missing' from (irb):3:in method_missing'
from (irb):3:in method_missing' from (irb):3:in method_missing'
from (irb):3:in method_missing' from (irb):3:in method_missing'
from (irb):3:in method_missing' from (irb):3:in method_missing'
from (irb):3:in method_missing' from (irb):3:in method_missing'
from (irb):3:in method_missing' from (irb):3:in method_missing'
from (irb):3:in method_missing' from (irb):3:in method_missing'

If we create the same class with the same method_missing but without inheriting from BasicObject it works right.

[Eregon (Benoit Daloze)]

Farruco Sanjurjo wrote:

If a class inherits from BasicObject and then overwrites method_missing like this:

class A < BasicObject
def method_missing(*a)
puts "#{a}"
end
end

And we try it:

A.new.fooooo

The interpreter enters what looks like a loop and then crashes with this trace (in irb):

method_missing is called indefinitely recursively because "puts" is not a method in BasicObject.

Only methods available in BasicObject are:
BasicObject.instance_methods # => [:==, :equal?, :!, :!=, :instance_eval, :instance_exec, :send]

"puts" is usually provided by Kernel#puts. But Kernel is not included in BasicObject.
You could solve this two ways:

• use "::Kernel::puts" instead of "puts" (the documentation about the first :: is being discussed in Bug #5067)
• include Kernel into your class A

[mrkn (Kenta Murata)]

• Status changed from Open to Rejected
• Priority changed from 5 to Normal

BasicObject doesn't include Kernel module.
It is a spec.