From: "nagachika (Tomoyuki Chikanaga) via ruby-core" <ruby-core@...>
Date: 2023-07-17T08:27:13+00:00
Subject: [ruby-core:114215] [Ruby master Bug#19601] YJIT `try to mark T_NONE object` stemming from object shape transition on `self`

Issue #19601 has been updated by nagachika (Tomoyuki Chikanaga).

Backport changed from 3.0: DONTNEED, 3.1: DONTNEED, 3.2: REQUIRED to 3.0: DONTNEED, 3.1: DONTNEED, 3.2: DONE

ruby_3_2 5fbd72764e020c6b165604e9cdcc932a1c5d2a93 merged revision(s) 31e67a476f2262e01a0829e8ab5e6d8a97e0724e,0b95cbcbde8875effdbcbb676cb0a7f751a1d4c1.

----------------------------------------
Bug #19601: YJIT `try to mark T_NONE object` stemming from object shape transition on `self`
https://bugs.ruby-lang.org/issues/19601#change-103902

* Author: alanwu (Alan Wu)
* Status: Closed
* Priority: Normal
* ruby -v: ruby 3.2.2 (2023-03-30 revision e51014f9c0) +YJIT [arm64-darwin22]
* Backport: 3.0: DONTNEED, 3.1: DONTNEED, 3.2: DONE
----------------------------------------
We've identified a false collection bug with YJIT.
Symptoms can range from `[BUG] try to mark T_NONE object` to SEGVs.
Due to the bug requiring specific transient heap state to reproduce,
it may be hard to identify by looking at the crash-site stack trace.

`ruby --yjit-call-threshold=1` reproducer:

```ruby
class RegressionTest
  def initialize
    @a = @b = @fourth_ivar_does_shape_transition = nil
  end

  def extender
    @first_extended_ivar = [:ok]
  end
end

GC.stress = true

test = RegressionTest.new

# Used to crash due to GC run in rb_ensure_iv_list_size()
# not marking the newly allocated [:ok].
test.extender

GC.start
```

Fix: https://github.com/ruby/ruby/pull/7718



-- 
https://bugs.ruby-lang.org/
 ______________________________________________
 ruby-core mailing list -- ruby-core@ml.ruby-lang.org
 To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org
 ruby-core info -- https://ml.ruby-lang.org/mailman3/postorius/lists/ruby-core.ml.ruby-lang.org/