So, you decided to play around with quicklisp but when you try to load some packages you get a CFFI:LOAD-FOREIGN-LIBRARY-ERROR ?  CFFI is a Common Lisp library for interfacing with C libraries.  So if you install a quicklisp package like SDL2 it will attempt to load the libSDL2 shared library (libSDL2.dylib on Mac OS X) so that CFFI can forward calls to the shared library.  Usually when this error arises CFFI can’t find the library at all**.  What you need to do is just tell CFFI how to find it.  CFFI has a variable cffi:*foreign-library-directories* which is a list of directories to hunt for dynamic libraries.  So you can do something like this if you library is in “/opt/local/lib”:

You could even throw this code in your init file for you lisp as well so that it always gets executed (sbcl: ~/.sbclrc  ccl:~/.ccl-init.lisp)

** You also might want to check that your architecture is correct for your lisp as well (on Mac OS X “lipo -info <library file>”)