In the meantime, can you tell me what the following does on your version:
CL-USER> (require :cffi) NIL CL-USER> (cffi:defctype my-double :double) MY-DOUBLE CL-USER> (defmethod cffi:translate-to-foreign (value (type (eql 'my-double))) (coerce value 'double-float)) #<STANDARD-METHOD CFFI:TRANSLATE-TO-FOREIGN (T (EQL MY-DOUBLE)) {10038378E1}> CL-USER> (cffi:translate-to-foreign 10 'my-double) 10.0d0 CL-USER> (cffi:convert-to-foreign 10 'my-double) 10
Regards, Dmitry