From: s.wanabe@...
Date: 2017-06-11T16:23:19+00:00
Subject: [ruby-core:81650] [Ruby trunk Bug#13605] GC bug calling	`ObjectSpace.each_object`

Issue #13605 has been updated by wanabe (_ wanabe).


It seems to be for lack of write-barrier. (as _ko1 suggested at [https://twitter.com/_ko1/status/871892183464370176](https://twitter.com/_ko1/status/871892183464370176))

The following script causes similar [BUG] about 50% of the time.

```
10000.times do |i|
  v = rand(2000)
  name = "n#{v}"
  value = Object.new
  TOPLEVEL_BINDING.local_variable_set name, value
end
```

It is helpful with "-DRGENGC_CHECK_MODE=2" build flag.
I met following output:

```
verify_internal_consistency_reachable_i: WB miss (O->Y) 0x000055f470054578 [3LM  ] T_IMEMO env -> 0x000055f4701cc770 [0    ] T_OBJECT (Object)
verify_internal_consistency_reachable_i: WB miss (O->Y) 0x000055f470054758 [3LM  ] T_IMEMO env -> 0x000055f470206920 [0    ] T_OBJECT (Object)
(snip)
a.rb:3: [BUG] gc_verify_internal_consistency: found internal inconsistency.
ruby 2.5.0dev (2017-06-11 trunk 59060) [x86_64-linux]
(snip)
```

----------------------------------------
Bug #13605: GC bug calling `ObjectSpace.each_object`
https://bugs.ruby-lang.org/issues/13605#change-65346

* Author: ryanf (Ryan Fitzgerald)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-linux]
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
----------------------------------------
This code made Ruby bail out with the message "[BUG] rb_gc_mark(): 0x000000040dc740 is T_NONE":

~~~ ruby
ObjectSpace.each_object(Module){|m|
  next if (to_ignore.include?(m) rescue true)

  if m.respond_to?(:instance_methods)
    candidates.concat m.instance_methods(false).collect(&:to_s)
  end
}
~~~

I haven't been able to repro, but it happened building Pry on Travis CI: https://travis-ci.org/pry/pry/jobs/236720971

The relevant logs are attached.

---Files--------------------------------
each_object_bug.txt (81.9 KB)
patch-for-2508d68e.patch (8.07 KB)
Dockerfile (353 Bytes)


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