ThinLisp is a Common Lisp implementation that translates a subset of Common Lisp to very efficient C code.

Note: ThinLisp is not actively developed. ECL is an active and supported Common Lisp to C compiler.

CLiCC is a similar system.

Authors: Jim Allard and Ben Hyde

Thinlisp is meant to allow deployment of Common Lisp applications as efficient C-compiled code, and thus includes notable restrictions as compared to full Common Lisp semantics. Most notably, Thinlisp does not have a garbage collector.

Thinlisp is licensed under an Apache 1.0 style license. The Apache 1.0 license is incompatible with the GPL.

The most up-to-date version of Thinlisp is available from This version contains patches by Vladimir Sedach that fix build problems on SBCL and CLISP.

The original Thinlisp project page can still be found on SourceForge at:

Tip: If the executables generated by ThinLisp are too large, try using strip. This shrinks the lecho demo binary from 555,893 to 119,020 bytes on a Red Hat Linux 6.2 system. If you compile it with make opt to use the C optimizer and then strip it, then the lecho binary size drops to 71,340.

On modern GCC, it may be necessary to add -DNO_ADDRESS_CONSTANTS to generated makefiles -- Dmitri Hrapof, 2020

On modern SBCL, it may be necessary to use CMUCL (due to constant "redefinition") -- Dmitri Hrapof, 2020