Accepté dans l'ACM Crossroads de printemps 2006. C-Transformers - A Framework to Write C Program Transformations A. Borghi, V. David, A. Demaille https://publis.lrde.epita.fr/200510-Crossroads Program transformation techniques have reached a maturity level that allows processing high-level language sources in new ways. Not only do they revolutionize the implementation of compilers and interpreters, but with modularity as a design philosophy, they also permit the seamless extension of the syntax and semantics of existing programming languages. The C-Transformers project provides a transformation environment for C, a language that proves to be hard to transform. We demonstrate the effectiveness of C-Transformers by extending C's instructions and control flow to support Design by Contract. C-Transformers is developed by members of the LRDE: EPITA undergraduate students.