I like using pointer-to-array types for this purpose as (like an array in struct) the array's length is encoded in the type, and thus likewise allows the compiler to warn if an incompatible array is provided.
e.g.
void f(char (*n)[255]);
char array[6];
f(&array);
warns of "incompatible pointer types passing 'char (* )[6]' to parameter of type 'char (* )[255]'"
This won't produce a diagnostic for f(NULL) like "static" does, but does have two properties that might be considered benefits:
1) The length is exact rather than a minimum.
2) The type of "* n" is still char[255], whereas a char[static 255] parameter is still a decayed pointer-to-char. Thus with the former sizeof(* n) behaves as expected inside of "f", yielding 255.
These are true of the array-in-struct method as well.
This won't produce a diagnostic for f(NULL) like "static" does, but does have two properties that might be considered benefits:
1) The length is exact rather than a minimum.
2) The type of "* n" is still char[255], whereas a char[static 255] parameter is still a decayed pointer-to-char. Thus with the former sizeof(* n) behaves as expected inside of "f", yielding 255.
These are true of the array-in-struct method as well.