5 Wrapper generators

CFFI’s interface is designed for human programmers, being aimed at aesthetic as well as technical sophistication. However, there are a few programs aimed at translating C and C++ header files, or approximations thereof, into CFFI forms constituting a foreign interface to the symbols in those files.

These wrapper generators are known to support output of CFFI forms.

Verrazano

Designed specifically for Common Lisp. Uses GCC’s parser output in XML format to discover functions, variables, and other header file data. This means you need GCC to generate forms; on the other hand, the parser employed is mostly compliant with ANSI C.

SWIG

A foreign interface generator originally designed to generate Python bindings, it has been ported to many other systems, including CFFI in version 1.3.28. Includes its own C declaration munger, not intended to be fully-compliant with ANSI C.

First, this manual does not describe use of these other programs; they have documentation of their own. If you have problems using a generated interface, please look at the output CFFI forms and verify that they are a correct CFFI interface to the library in question; if they are correct, contact CFFI developers with details, keeping in mind that they communicate in terms of those forms rather than any particular wrapper generator. Otherwise, contact the maintainers of the wrapper generator you are using, provided you can reasonably expect more accuracy from the generator.

When is more accuracy an unreasonable expectation? As described in the tutorial (see Breaking the abstraction), the information in C declarations is insufficient to completely describe every interface. In fact, it is quite common to run into an interface that cannot be handled automatically, and generators should be excused from generating a complete interface in these cases.

As further described in the tutorial, the thinnest Lisp interface to a C function is not always the most pleasant one. In many cases, you will want to manually write a Lispier interface to the C functions that interest you.

Wrapper generators should be treated as time-savers, not complete automation of the full foreign interface writing job. Reports of the amount of work done by generators vary from 30% to 90%. The incremental development style enabled by CFFI generally reduces this proportion below that for languages like Python.