Hi, I have implemented the separate preprocess and compile setup in build2. For GCC it is using -fdirectives-only (thanks to everyone's suggestions in the earlier thread). I've also done some benchmarking:
https://build2.org/article/preprocess-compile-performance.xhtml TL;DR for GCC: Surprisingly, a separate preprocessor run is about 1% faster (probably because of the time-localization of filesystem access). Overall, a preprocessor run costs about 5% of a non-optimized C++ build. Boris
