objspace: Hide identhash containing internal objs

Inside ObjectSpace.reachable_objects_from we keep an internal identhash
in order to de-duplicate reachable objects when wrapping them as
InternalObject. Previously this hash was not hidden, making it possible
to leak references to those internal objects to Ruby if using
ObjectSpace.each_object.

This commit solves this by hiding the hash. To simplify collection of
values, we instead now just use the hash as a set of visited objects,
and collect an Array (not hidden) of values to be returned.

1 files changed, 12 insertions, 0 deletions

diff --git a/test/objspace/test_objspace.rb b/test/objspace/test_objspace.rb
index 34d9dd76ec..781fb5b3c2 100644
--- a/test/objspace/test_objspace.rb
+++ b/test/objspace/test_objspace.rb
@@ -140,6 +140,18 @@ class TestObjSpace < Test::Unit::TestCase
     end;
   end
 
+  def test_reachable_objects_during_iteration
+    opts = %w[--disable-gem --disable=frozen-string-literal -robjspace]
+    assert_separately opts, "#{<<-"begin;"}\n#{<<-'end;'}"
+    begin;
+      ObjectSpace.each_object{|o|
+        o.inspect
+        ObjectSpace.reachable_objects_from(Class)
+      }
+    end;
+  end
+
+
   def test_reachable_objects_from_root
     root_objects = ObjectSpace.reachable_objects_from_root