CFFI supports various free and commercial Lisp implementations: Allegro CL, Corman CL, clisp, CMUCL, ECL, LispWorks, Clozure CL, SBCL and the Scieneer CL.
In general, you should work with the latest versions of each implementation since those will usually be tested against recent versions of CFFI more often and might include necessary features or bug fixes. Reasonable patches for compatibility with earlier versions are welcome nevertheless.
Some features are not supported in all implementations.
:dffiis not present in
cffi:load-foreign-librarydoes not work and you must use ECL's own
ffi:load-foreign-librarywith a constant string argument.
:long-longtype natively in 32-bit platforms.