Bug #9938: ObjectSpace::allocation_class_path does not object's class

• Status: Rejected
• Assignee: ko1 (Koichi Sasada)
• Target version: -
• ruby -v: 2.1.2
• Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN

[dunric (David Unric)]

Possible bug in ObjectSpace::allocation_class_path returning nil instead of expected class name:

require 'objspace'

class A
  def foo
    ObjectSpace::trace_object_allocations do
      obj = Object.new
      p ObjectSpace::allocation_class_path(obj)  # "A" expected, prints nil instead
      obj = Array.new
      p ObjectSpace::allocation_class_path(obj)  # "A" expected, prints nil instead
      obj = []
      p ObjectSpace::allocation_class_path(obj)  # prints "A" as expected !!
      obj = obj.dup
      p ObjectSpace::allocation_class_path(obj)  # "A" expected, prints nil instead !!
      obj = Hash.new
      p ObjectSpace::allocation_class_path(obj)  # "A" expected, prints nil instead
      obj = {}
      p ObjectSpace::allocation_class_path(obj)  # prints "A" as expected !!
    end
  end
end

A.new.foo

Very inconsistent behavior, allocation_class_path seems to works only with objects defined with literals not instantiated with class.new method.

Also discussed at StackOverflow:
http://stackoverflow.com/questions/24181789/objectspaceallocation-class-path-not-working-as-expected

[dunric (David Unric)]

I'm sorry about code formatting. Bellow is a fixed version:

require 'objspace'

class A
  def foo
    ObjectSpace::trace_object_allocations do
      obj = Object.new
      p ObjectSpace::allocation_class_path(obj) # "A" expected, prints nil instead
      obj = Array.new
      p ObjectSpace::allocation_class_path(obj) # "A" expected, prints nil instead
      obj = []
      p ObjectSpace::allocation_class_path(obj) # prints "A" as expected !!
      obj = obj.dup
      p ObjectSpace::allocation_class_path(obj) # "A" expected, prints nil instead !!
      obj = Hash.new
      p ObjectSpace::allocation_class_path(obj) # "A" expected, prints nil instead
      obj = {}
      p ObjectSpace::allocation_class_path(obj) # prints "A" as expected !!
    end
  end
end

A.new.foo

[ko1 (Koichi Sasada)]

Hi,

Thank you for your report.

Please add this magic line:
ObjectSpace.each_object(Module){|o| o.name}
at the beggining of script. It will show the correct output.

This is because of Module naming cache issue.
I want to fix this issue for 2.2.
But 2.1, please left it as a spec.
(we can acquire a class name if we had a luck)

[dunric (David Unric)]

Wow, that was fast !

I've been stuck at rb_class_path_cached from variable.c line #281 failing to look up a class_path. Glad it would be fixed in 2.2 .

Good job.

Take care.

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)

[ko1 (Koichi Sasada)]

• Status changed from Open to Rejected