"incompatible marshal file format" in TestZJIT

[wks]

We have observed several times that test cases in TestZJIT randomly fail with the following messages:

TestZJIT#test_ivar_get_with_already_multi_ractor_mode:
Test::Unit::ProxyError: incompatible marshal file format (can't be read)
	format version 4.8 required; 0.0 given
    /home/runner/work/mmtk-ruby/mmtk-ruby/git/ruby/test/ruby/test_zjit.rb:3710:in 'Marshal.load'
    /home/runner/work/mmtk-ruby/mmtk-ruby/git/ruby/test/ruby/test_zjit.rb:3710:in 'TestZJIT#assert_runs'
    /home/runner/work/mmtk-ruby/mmtk-ruby/git/ruby/test/ruby/test_zjit.rb:3686:in 'TestZJIT#assert_compiles'
    /home/runner/work/mmtk-ruby/mmtk-ruby/git/ruby/test/ruby/test_zjit.rb:3300:in 'TestZJIT#test_ivar_get_with_already_multi_ractor_mode'

So far I have only observed this failure on GitHub CI in the following pull requests:

• Move to Rust 1.92 #148
• Update mmtk-core and ruby repo revisions #149

It always fails with the Immix plan and the release build. I have never reproduced this error locally.

Here are some log files from erroneous executions: testzjit-fails.tar.gz

I temporarily disabled TestZJIT for now, and let's revisit this failure when we decide to support ZJIT.