Mark extension as Ractor-safe

[kddnewton]

@tenderlove does this look okay to you? I'm less familiar with Ractors, but wanted to make sure this was okay. From the documentation on Ractor safety, I believe this is okay?

[tenderlove]

Change makes sense to me. I guess there's some tests failing though?

[kddnewton]

Yeah, just because I forgot to check HAVE_RB_EXT_RACTOR_SAFE for Ruby 2.7.

[XrXr]

A bunch of weird test failures started happening in ruby/ruby when this landed:

  
    1) Failure:
  TestObjectSpace#test_each_object [/Users/runner/work/ruby/ruby/src/test/ruby/test_objectspace.rb:226]:
  <1> expected but was
  <0>.
  
    2) Failure:
  TestObjectSpace#test_each_object_enumerator [/Users/runner/work/ruby/ruby/src/test/ruby/test_objectspace.rb:237]:
  <1> expected but was
  <0>.
  
    3) Error:
  TestObjectSpace#test_id2ref_32:
  Test::Unit::ProxyError: "32616" is id of the unshareable object on multi-ractor
      /Users/runner/work/ruby/ruby/src/test/ruby/test_objectspace.rb:32:in 'ObjectSpace._id2ref'
      /Users/runner/work/ruby/ruby/src/test/ruby/test_objectspace.rb:32:in 'block in TestObjectSpace#deftest_id2ref'

    klass = Class.new
    new_obj = klass.new

    found = []
    count = ObjectSpace.each_object(klass) do |obj|
      found << obj
    end
#>> assert_equal(1, count)

Seems something is missing. https://github.com/ruby/ruby/actions/runs/13819663391/job/38661667031#step:14:1953

[eregon]

I suspect that's because this adds tests for Ractor in the same process, and Ractor simply isn't compatible enough (e.g. it changes the semantics of ObjectSpace.each_object: https://bugs.ruby-lang.org/issues/21149), and so no Ractor must be created in the main test process in CRuby test-all.