If pointer is a null pointer (that is, a pointer pointing to address 0) then t is returned, otherwise null-pointer-p returns nil .
The function null-pointer-p is used to determine if a pointer is a null pointer. A null pointer is a pointer pointing to address 0.
In the following example a pointer to an :int is defined, and tested with null-pointer-p . The pointer is then freed, becoming a null pointer, and is once again tested using null-pointer-p .
(setq point (fli:allocate-foreign-object :type :int)) (fli:null-pointer-p point) (fli:free-foreign-object point) (fli:null-pointer-p point)