Open Source Summit Europe + ELC Europe 2017

The Linux kernel is the canonical example of highly configurable infrastructure software. In principle, any line of code can be included or excluded from the compiled kernel based on complex configuration operations that are not locally apparent. This poses a challenge for new developers who want to contribute to the code. How to tell if their code is actually being compiled? To address this issue, we propose JMake, a lightweight mutation-based tool for giving immediate feedback on whether each changed line has been subjected to the compiler. We illustrate the use of JMake on the commits between Linux v4.3 and v4.4, and find that JMake completes in most cases in under 30 seconds. We then characterize the situations in which changed code is not subjected to compilation in practice.

JMake is available at http://jmake-release.gforge.inria.fr/