The main implementation of Racket today is built on top of Chez Scheme, which uses the techniques described by Dybvig that I linked to. In the earlier implemen

The main implementation of Racket today is built on top of Chez Scheme, which uses the techniques described by Dybvig that I linked to. In the earlier implementation of Racket, indeed it doesn't convert to CPS but does use something like A-normal form. There, continuations are implemented by actually copying the C stack.