Ensure we don't dereference fields_obj as Qundef

We rely on the GC to clear this when the GC is run on another EC than
the cache.

1 files changed, 16 insertions, 0 deletions

diff --git a/test/ruby/test_variable.rb b/test/ruby/test_variable.rb
index d4ba0f9fc7..13b8a7905f 100644
--- a/test/ruby/test_variable.rb
+++ b/test/ruby/test_variable.rb
@@ -529,6 +529,22 @@ class TestVariable < Test::Unit::TestCase
     assert_equal :new_value, str.instance_variable_get(:@x)
   end
 
+  def test_genivar_cache_invalidated_by_gc
+    str = +"hello"
+    str.instance_variable_set(:@x, :old_value)
+
+    str.instance_variable_get(:@x) # populate cache
+
+    Fiber.new {
+      str.remove_instance_variable(:@x)
+      str.instance_variable_set(:@x, :new_value)
+    }.resume
+
+    GC.start
+
+    assert_equal :new_value, str.instance_variable_get(:@x)
+  end
+
   private
   def with_kwargs_11(v1:, v2:, v3:, v4:, v5:, v6:, v7:, v8:, v9:, v10:, v11:)
     local_variables