Analyzing the Effect of Preprocessor Annotations on Code Clones

The C preprocessor cpp is a powerful and language-independent tool, widely used in different programming languages (C, C++, Java). One core feature of the cpp is that it allows to express variability in programs using conditional compila-tion. To this end, the code can be annotated on different levels of granularity such as functions or statements. Depending on this granularity, we differentiate between disciplined and undisciplined annotations. In this paper, we investigate whether there is a relation between code clones and pre-processor annotations. Specifically, we address the question whether the discipline of annotation has an effect on code clones. To this end, we perform a case study on fifteen different C programs and analyze them regarding code clones and #ifdef occurrences. We found only minor effects of anno-tations on code clones but a relationship between disciplined annotations (and code clones). With this work, we provide new insights on how/why code clones are created. Furthermore, the results can support the decision whether it is beneficial to remove clones or not. 1