I’m getting this error building racket7

Are you using racket7/racket/bin/racket to build racket/src/cs, and if so, did you run make at the repo’s top-level directory to update it?

Yeah I am, and I didn’t run make at the top level. thanks!

for the record, why is it necessary to run make at the top level in this case?

The racket that you’re trying to run just doesn’t work, because the executable is out of sync with racket/unsafe/ops