marshal.c: check instance variable count

* marshal.c (w_ivar_each): ensure that no instance variable was
  removed while dumping other instance variables.  [Bug #15968]

1 files changed, 13 insertions, 1 deletions

diff --git a/test/ruby/test_marshal.rb b/test/ruby/test_marshal.rb
index 0565a1c04f..f6d84d181a 100644
--- a/test/ruby/test_marshal.rb
+++ b/test/ruby/test_marshal.rb
@@ -795,7 +795,11 @@ class TestMarshal < Test::Unit::TestCase
       end
 
       def marshal_dump
-        self.foo.baz = :problem
+        if self.foo.baz
+          self.foo.remove_instance_variable(:@baz)
+        else
+          self.foo.baz = :problem
+        end
         {foo: self.foo}
       end
 
@@ -811,4 +815,12 @@ class TestMarshal < Test::Unit::TestCase
       Marshal.dump(obj)
     end
   end
+
+  def test_marshal_dump_removing_instance_variable
+    obj = Bug15968.new
+    obj.baz = :Bug15968
+    assert_raise_with_message(RuntimeError, /instance variable removed/) do
+      Marshal.dump(obj)
+    end
+  end
 end