[ruby/json] JSON::Ext::Parser mark the name cache entries when not on the heap

This is somewhat dead code as unless you are using `JSON::Parser.new`
direcltly we never allocate `JSON::Ext::Parser` anymore.

But still, we should mark all its reference in case some code out there
uses that.

Followup: #675

https://github.com/ruby/json/commit/8bf74a977b

2 files changed, 38 insertions, 0 deletions

diff --git a/test/json/json_ext_parser_test.rb b/test/json/json_ext_parser_test.rb
index ff6598f490..9db8ae772f 100644
--- a/test/json/json_ext_parser_test.rb
+++ b/test/json/json_ext_parser_test.rb
@@ -27,6 +27,26 @@ class JSONExtParserTest < Test::Unit::TestCase
       assert_equal "unexpected token at 'NaN'", ex.message
     end
 
+    if GC.respond_to?(:stress=)
+      def test_gc_stress_parser_new
+        payload = JSON.dump([{ foo: 1, bar: 2, baz: 3, egg: { spam: 4 } }] * 10)
+
+        previous_stress = GC.stress
+        JSON::Parser.new(payload).parse
+      ensure
+        GC.stress = previous_stress
+      end
+
+      def test_gc_stress
+        payload = JSON.dump([{ foo: 1, bar: 2, baz: 3, egg: { spam: 4 } }] * 10)
+
+        previous_stress = GC.stress
+        JSON.parse(payload)
+      ensure
+        GC.stress = previous_stress
+      end
+    end
+
     def parse(json)
       JSON::Ext::Parser.new(json).parse
     end
diff --git a/test/json/test_helper.rb b/test/json/test_helper.rb
index 7bff9b3391..6fcb76edf8 100644
--- a/test/json/test_helper.rb
+++ b/test/json/test_helper.rb
@@ -19,6 +19,24 @@ begin
 rescue LoadError
 end
 
+if GC.respond_to?(:verify_compaction_references)
+  # This method was added in Ruby 3.0.0. Calling it this way asks the GC to
+  # move objects around, helping to find object movement bugs.
+  begin
+    GC.verify_compaction_references(double_heap: true, toward: :empty)
+  rescue NotImplementedError
+    # Some platforms don't support compaction
+  end
+end
+
+if GC.respond_to?(:auto_compact=)
+  begin
+    GC.auto_compact = true
+  rescue NotImplementedError
+    # Some platforms don't support compaction
+  end
+end
+
 unless defined?(Test::Unit::CoreAssertions)
   require "core_assertions"
   Test::Unit::TestCase.include Test::Unit::CoreAssertions