The g:strv-t type specifier represents and performs automatic conversion between a list of Lisp strings and an array of C strings of the CFFI :string type.

(setq str (cffi:convert-to-foreign (list "Hello" "World") 'g:strv-t))
=> #.(SB-SYS:INT-SAP #X01541998)
(cffi:convert-from-foreign str 'g:strv-t)
=> ("Hello" "World")