In compiled Scala, what is the bitmap$0 field?

Question

I have noticed some of my Scala classes contain a field with the name bitmap$0 of type int. What is this?

Answer 1

That's where the initialization states for lazy vals are stored. When you access a lazy val (or a nested object, which is equivalent), the compiler uses the bitmap field to determine whether it's already been evaluated.

Answer 2

When lazy vals are initialized, this field is also used for synchronization when the value is initialized.