> ruby lib/compiler/mri_compile.rb -frbx-kernel clone.rb clone.rbc
./lib/compiler/../../vm/gen/simple_field.rb:331: warning: already initialized constant Slots
Compiling clone.rb
> vm/vm clone.rbc
Loading: clone.rbc
Runtime exception: Unable to resolve primitive
> rake vm:missing_primitives |grep object_clone
>

> cat clone.rb
s1 = "Hello"
def klone; Ruby.primitive :object_clone; end
class << s1
  def foo; p 5;end
end

s2 = s1.klone
s2.foo