Program Comprehension in Preprocessor-Based Software

To adapt to heterogeneous hardware, software of embedded systems provides customization capacities. Typically, this customization is achieved using conditional compilation with preprocessors. However, preprocessor usage can lead to obfuscated source code that can be difficult to comprehend, which in turn cause increased maintenance costs, bugs, and security vulnerabilities. To profit from the benefit of preprocessors usage, we need to improve their comprehensibility. In this paper, we describe how program comprehension can be improved and, to that end, measured. We show that reliably measuring program comprehension requires considerably effort. However, the benefit is that we can apply concepts that have proven to improve program comprehension, and thus can e.g. improve maintainability, reliability, and security of source code.