1 Introduction

CFFI, the Common Foreign Function Interface, purports to be a portable foreign function interface for Common Lisp.

This specification defines a set of low-level primitives that must be defined for each Lisp implementation supported by CFFI. These operators are defined in the CFFI-SYS package.

The CFFI package uses the CFFI-SYS interface to implement an extensible foreign type system with support for typedefs, structures, and unions, a declarative interface for defining foreign function calls, and automatic conversion of foreign function arguments to/from Lisp types.

Please note the following conventions that apply to everything in CFFI-SYS:

• Functions in CFFI-SYS that are low-level versions of functions exported from the CFFI package begin with a leading percent-sign (eg. %mem-ref).
• Where “foreign type” is mentioned as the kind of an argument, the meaning is restricted to that subset of all foreign types defined in Built-In Foreign Types. Support for higher-level types is always defined in terms of those lower-level types in CFFI proper.