The dependency information that’s provided by Clang can be used to implement a pre-scanning phase for a build system that uses Clang modules in an explicit manner, by discovering the required modules before compiling. However, the traditional approach of preprocessing all sources to find the required modular dependencies is typically not fast enough for a pre-scanning phase that must run for every build. This talk introduces clang-scan-deps, an optimized dependency discovery service that can provide speed up of up to 10X over the regular preprocessor-based scanning. This talk goes into details of how this service is implemented and how it can be leveraged by the build system to implement a fast pre-scanning phase for explicit Clang modules.
