foreign function interface

[dxs@evolving.com (Dan Stanger)]

is is possible to use the following construct?
(defconstant _SYS_NMLN           32)
(def-c-struct utsname 
  (sysname (c-array char _SYS_NMLN))
...
when i try it i get the following error
*** - Invalid FFI type: (C-ARRAY CHAR _SYS_NMLN)
but this works
(sysname (c-array char 32 ))

also, is there a way to pass c code directly through the compilation process?
via a special comment (for example)

thanks,
dan stanger