> Under MIT Scheme, what I do is evaluate (pp (lambda ()
> <macro-definition>)).  That pretty prints the expanded form without
> executing it.

This works in Gambit too. But it only works in cases where the macro
expands to something that's fine to have inside a (lambda () ...). For
example, it doesn't work for macros that expand to FFI definitions,
since those require the compiler (not interpreter) and cannot appear
inside a lambda.