Question re. Call-by-value for foreign structs

Using CFFI, do I need to specify translation methods when performing call-by-value to C? I am assuming (possibly incorrectly?) that cffi:defcstruct will create the translations for a C struct for me, then pass that struct by value to a Go foreign routine. Specifically, I am trying to call routines in Go from Lisp using a Lisp string. A Go string is a C struct { pointer-to-string , integer-length-of-string } Simple test code is in https://github.com/guitarvydas/lisp-go/blob/master/string-example/lisp-clien.... (see function "my-log", run "make" which should build and run the example, causing a NO-APPLICABLE-METHOD-ERROR). thanks pt