The FLI provides two foreign types to interface Lisp and C strings, :ef-wc-string and :ef-mb-string.
The :ef-mb-string converts between a Lisp string and an external format C multi-byte string. A maximum number of bytes must be given as a limit for the string size.
The :ef-wc-string converts between a Lisp string and an external format C wide character string. A maximum number of characters must be given as a limit for the string size.
For more information on converting Lisp strings to foreign language strings see the string types :ef-mb-string, :ef-wc-string, and the string functions convert-from-foreign-string, convert-to-foreign-string, and with-foreign-string.