calling opengl extensions:

- ff-funcall might be handy since it seems to allow you to call a foreign function
  if you know the address of the function:

def-foreign-call has enhanced the macroexpansion to give useful information for users. Here is an example: 

cl-user(11): (pprint 
               (macroexpand '(ff:def-foreign-call foo (x (y (* :char))))))

Warning: A runtime with-native-string call is being generated for argument `y'
         to the foreign-function `foo'.  The with-native-string macro can be
         used for explicit string conversions around the foreign calls.  This
         warning is suppressed when :strings-convert is specified in the
         def-foreign-call.

(progn (eval-when (:compile-toplevel)
         (excl::check-lock-definitions-compile-time 'foo 'function
           'foreign-functions:def-foreign-call (fboundp 'foo))
         (push 'foo excl::.functions-defined.))
       (eval-when (compile load eval) (remprop 'foo 'system::direct-ff-call))
       (setf (fdefinition 'foo)
             (let ((excl::f
                    (named-function foo
                      (lambda (x y)
                        (excl::check-args '((:int (integer * *))
                                            ((* :char) (array character (*))))
                                          'foo x y)
                        (with-native-string (#:g34798
                                             (if*
                                              (stringp y)
                                                then y
                                                else ""))
                                            (unless
                                             (stringp y)
                                             (setq #:g34798 y))
                                            (symbol-macrolet
                                             ((y #:g34798))
                                             (system::ff-funcall
                                              (load-time-value
                                               (excl::determine-foreign-address
                                                '("foo" :language :c)
                                                2
                                                nil))
                                              '(:int (integer * *))
                                              x
                                              '((* :char)
                                                (array character (*)))
                                              y
                                              '(:int (integer * *)))))))))
               (excl::set-func_name excl::f 'foo)
               excl::f))
       (record-source-file 'foo) 'foo)
cl-user(12):