For information about calling C libraries from Common Lisp code, see FFI.
To compile C code to Common Lisp, look at Vacietis.
However, the poor soul obliged to program in C may benefit from: ILFIVE library.
All pages in the C topic:
- c-amplify - c-amplify is an s-exp syntax for writing C code
- CLiCC - CLiCC is a Common Lisp to C Compiler, last released 1995
- cparse - cparse is a parser for C header files and building FFIs
- SC Language - SC is an s-exp syntax (Scheme-like) for writing C code, implemented in Common Lisp
- ThinLisp - ThinLisp is a Common Lisp implementation that translates a subset of Common Lisp to very efficient C code
- Vacietis - Vacietis is a C compiler for Common Lisp systems