Please add cffi-libffi, it is another system of the CFFI master branch: https://github.com/cffi/cffi
It adds passing and returning structures by value.
From what I read from this: http://lhealy.livejournal.com/15049.html?nojs=1
The old FSBV library "did what cffi-libffi does but in a clumsier way, is now obsolete and will not work with this version of CFFI. "
The next Quicklisp update will include cffi 0.11.0, which fixes this issue.