Semi-Automatic Refactoring to C++20 Modules: A Semi-Success Story

The component-based design of software projects is a desired property both for development and ease of code comprehension. Programming languages have long allowed component-based development (e.g., Java packages, Python modules); however, other languages, especially C and C++, had stuck to the “translation unit” model where every source file is individually compiled. The Modules system of C++20 was expected to allow cleaner encapsulation of concern. In this paper, we investigate the effort of a (semi-)automatic modularisation of existing C++ projects. Based on our investigation, upgrading existing software systems to the new Modules feature is extremely hard due to coupling issues arising from necessarily legacy design. Implementing real transition requires a significant redesign of both project-internal and user-facing programming interfaces.