Avoiding Some Common Preprocessing Pitfalls with Feature Queries

Preprocessors (e.g., cpp) provide simple means to manage software product variants by including/excluding required feature code to/from base program. Feature-related customizations occur at variation points in base program marked with preprocessing directives. Problems emerge when the number of inter-dependent features grows, and each feature maps to many variation points in many base program components. Component-based and architecture-centric techniques promoted by a Software Product Line approach to reuse help us contain the impact of some features in small number of base components. Still, accommodating other features into product variants requires fine granular code changes in many components, at many variation points. Fine granular code level changes are often handled by preprocessors, which becomes a source of well-known complications during component customization for reuse. In this paper, we show how some of the common preprocessing problems can be alleviated with a query-based environment that assists programmers in analysis of features handled with preprocessor's directives. We describe problems of preprocessing that can be aided by tool like ours, and problems that we believe are inherent in approaches that attempt to manage features in the base code.