devel/cil 1.7.3p7 OpenBSD

CIL (C Intermediate Language) is a high-level representation along with a set of tools that permit easy analysis and source-to-source transformation of C programs.

CIL is both lower-level than abstract-syntax trees, by clarifying ambiguous constructs and removing redundant ones, and also higher-level than typical intermediate languages designed for compilation, by maintaining types and a close relationship with the source program. The main advantage of CIL is that it compiles all valid C programs into a few core constructs with a very clean semantics. Also CIL has a syntax-directed type system that makes it easy to analyze and manipulate C programs. Furthermore, the CIL front-end is able to process not only ANSI-C programs but also those using Microsoft C or GNU C extensions. If you do not use CIL and want instead to use just a C parser and analyze programs expressed as abstract-syntax trees then your analysis will have to handle a lot of ugly corners of the language (let alone the fact that parsing C itself is not a trivial task).