:pointer type is part of the FLI implementation of pointers. It defines a C-style pointer to an object of type. Passing
nil instead of a pointer is treated the same as passing a null pointer (that is, a pointer to address
For more details on pointers, including examples on pointer coercion, dereferencing, making, and copying see FLI Pointers.
LispWorks Foreign Language Interface User Guide and Reference Manual - 29 Sep 2017