Make it or break it: Mining anomalies from Linux Kbuild

The Linux kernel has long been an interesting subject of study in terms of its source code. Recently, it has also been studied in terms of its variability since the Linux kernel can be configured to include or omit certain features according to the user's selection. These features are defined in the Kconfig files included in the Linux kernel code. Several articles study both the source code and Kconfig files to ensure variability is correctly implemented and to detect anomalies. However, these studies ignore the Make files which are another important component that controls the variability of the Linux kernel. The Make files are responsible for specifying what actually gets compiled and built into the final kernel. With over 1,300 Make files, more than 35,000 source code files, and over 10,000 Kconfig features, inconsistencies and anomalies are inevitable. In this paper, we explore the Linux's Make files (Kbuild) to detect anomalies. We develop three rules to identify anomalies in the Make files. Using these rules, we detect 89 anomalies in the latest release of the Linux kernel (2.6.38.6). We also perform a longitudinal analysis to study the evolution of Kbuild anomalies over time, and the solutions implemented to correct them. Our results show that many of the anomalies we detect are eventually corrected in future releases. This work is a first attempt at exploring the consistency of the variability implemented in Kbuild with the rest of the kernel. Such work opens the door for automatic anomaly detection in build systems which can save developers time in the future.