Bug #18232: Ractor.make_shareable is broken in code loaded with RubyVM::InstructionSequence.load_from_binary

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 3.0.2p107, ruby 3.1.0dev
• Backport: 3.0: DONE

[byroot (Jean Boussier)]

This was first reported as a Bootsnap bug: https://github.com/Shopify/bootsnap/issues/376

But I reduced it to:

source = <<~RUBY
  x = :foo
  pr = Proc.new { p x }
  Ractor.make_shareable(pr)
  pr.call
RUBY
RubyVM::InstructionSequence.compile(source).eval # :foo
RubyVM::InstructionSequence.load_from_binary(RubyVM::InstructionSequence.compile(source).to_binary).eval # false

The bug is present on both 3.0.2 and 3.1.0-dev. I have no idea what might cause this.

[byroot (Jean Boussier)]

Because OpenStruct was recently changed to use make_shareable, this bug suddenly became much more problematic. We actually hit it in production.

[Eregon (Benoit Daloze)]

FYI the way it currently works for OpenStruct seems buggy on the Ractor side: #18243

[Eregon (Benoit Daloze)]

• Related to Bug #18243: Ractor.make_shareable does not freeze the receiver of a Proc but allows accessing ivars of it added

[Eregon (Benoit Daloze)]

(this comment was moved to https://bugs.ruby-lang.org/issues/18243, replied to the wrong issue)

[tenderlovemaking (Aaron Patterson)]

It looks like the outer variables list is being lost when we dump the iseq to binary. AFAICT, that list is only created at compile time. I'll try to make a patch that reconstructs the list on iseq load as well.

[tenderlovemaking (Aaron Patterson)]

• File 0001-Dump-outer-variables-tables-when-dumping-an-iseq-to-.patch 0001-Dump-outer-variables-tables-when-dumping-an-iseq-to-.patch added

I've attached a patch that fixes this (for me) along with a test. I had to change the information that we dump when dumping an ISeq, so maybe we need to change the binary format version number or something? I'm not sure. Anyway there is also a PR here

[tenderlovemaking (Aaron Patterson)]

• Status changed from Open to Closed

Applied in changeset git|217df51f0e5d9824ed712a4d175f555d932e44d8.

---

Dump outer variables tables when dumping an iseq to binary

This commit dumps the outer variables table when dumping an iseq to
binary. This fixes a case where Ractors aren't able to tell what outer
variables belong to a lambda after the lambda is loaded via ISeq.load_from_binary

[Bug #18232] [ruby-core:105504]

[byroot (Jean Boussier)]

• Backport changed from 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN to 3.0: REQUIRED

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 3.0: REQUIRED to 3.0: DONE

ruby_3_0 a2fe4b75e4b236ad15778c59ace63006ace53889 merged revision(s) 217df51f0e5d9824ed712a4d175f555d932e44d8.