An empirical study of build system migrations in practice: Case studies on KDE and the Linux kernel

As the build system, i.e. the infrastructure that constructs executable deliverables out of source code and other resources, tries to catch up with the ever-evolving source code base, its size and already significant complexity keep on growing. Recently, this has forced some major software projects to migrate their build systems towards more powerful build system technologies. Since at all times software developers, testers and QA personnel rely on a functional build system to do their job, a build system migration is a risky and possibly costly undertaking, yet no methodology, nor best practices have been devised for it. In order to understand the build system migration process, we empirically studied two failed and two successful attempts of build system migration in two major open source projects, i.e. Linux and KDE, by mining source code repositories and tens of thousands of developer mailing list messages. The major contributions of this paper are: (a) isolating the phases of a common methodology for build system migrations, which is similar to the spiral model for source code development (multiple iterations of a waterfall process); (b) identifying four of the major challenges associated with this methodology: requirements gathering, communication issues, performance vs. complexity of build system code, and effective evaluation of build system prototypes; (c) detailed analysis of the first challenge, i.e., requirements gathering for the new build system, which revealed that the failed migrations did not gather requirements rigorously. Based on our findings, practitioners will be able to make more informed decisions about migrating their build system, potentially saving them time and money.