CONFIGEN: A tool for managing configuration options

A good way to build secure systems is the top-down approach, where each step refines the softwaretowards the final implementation. The result is well-integrated, but quite monolithic. Consequently,further extensions often lead to an overuse of preprocessor conditionals and some code duplication. It isthen important to refactor and modularize the code, with the goal of increasing maintainability and codereuse.We are trying to apply this process to the implementation of the OASIS [9] kernel, an execution sup-port for hard real-time safety critical applications. Modularizing this software has specific requirements.First, the configuration has to be chosen at compile-time (in particular, qualification for use in safety-critical environments requires that no dead code remains in the system). Second, modularity should notimpact the degree of performance, in terms of execution time and memory footprint (for instance, mod-ularity should not imply new indirections, like C++ virtual method tables). Thus, the tool should allowthe static selection of a subset of the code in order to implement a specific behavior.C