ecify the length [n].
However, if the result contains null codes, which is usual for structs,
the length of the foreign-string should be explicitly given.
Whether you should use (:string n) or (:foreign-string n) is not
only the matter of speed, but the matter of structure sharing.
The difference is whether the result is copied or not.

<P>
Fortran users should note that every argument to a Fortran function or a
subroutine is passed by call-by-reference.
Therefore, even a simple integer or float type argume