Issue #10191 has been updated by Usaku NAKAMURA.

Backport changed from 2.0.0: REQUIRED, 2.1: DONE to 2.0.0: DONE, 2.1: DONE

backported into `ruby_2_0_0` at r47548.

In my environment, I don't have to change the limit of assert_no_memory_leak.
I may change it if CIs report some problems.

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Bug #10191: Possible memory leak using dup and setting an unassigned instance variable (Windows)
https://bugs.ruby-lang.org/issues/10191#change-48860

* Author: Ben Hellerstein
* Status: Closed
* Priority: Normal
* Assignee: 
* Category: 
* Target version: 
* ruby -v: 1.9.3p327 (2012-11-10) [i386-mingw32] (also present in 2.0.0p481 [i386-mingw32] from rubyinstaller.org)
* Backport: 2.0.0: DONE, 2.1: DONE
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Steps:

1. Run the following code (tested on Window 7):

  ~~~ruby
  class Leaky
    attr_accessor :v
    def leak; d = dup; d.v = nil; end
  end

  l = Leaky.new
  while true; l.leak; end
  ~~~

2. Watch the memory usage in Task Manager or equivalent
  Expected result:
  Infinite loop, memory usage fairly stable (as GC cleans up)

  Actual result:
  Interpreter consumes more and more memory, and eventually throws the following exception: "in `dup': failed to allocate memory (NoMemoryError)."  Presumably, this is a memory leak.  

  Workaround:
  If you manually set the instance variable before dup-ing, memory usage is stable.  Accordingly, this code does not appear to leak memory:

  ~~~ruby
  class NonLeaky
    attr_accessor :v
    def leak; @v ||= nil; d = dup; d.v = nil; end
  end

  l = NonLeaky.new
  while true; l.leak; end
  ~~~





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