aaronmondal added a comment. @ChuanqiXu Thanks a lot for this!
We are currently implementing this module logic in the Bazel ruleset rules_ll <https://github.com/eomii/rules_ll>. This page helps clarify the differences between clang modules and C++ modules a lot. If I knew about this earlier we'd probably have saved a lot of time 😅 After reading this doc, a few things came to my mind. I can add a patch for this as a follow-up diff when I better understand how things work. - The path logic that references the source files in BMIs is very important. When precompiling a module in one directory and then moving a header included in the global module fragment from the source file, things will break. - As a result of this, some unintuitive things can happen when using sandboxed compilation. E.g. precompile BMI in sandbox, move BMI out of that sandbox, then start another sandbox that loads the previously built BMI. If the BMI used headers in a global module fragment, and those headers were in the original sandboxe, the header in the new sandbox will be in a different location (because the new sandbox is at a new location) and things will break. - Clang modulemaps are cool, but for build systems that have to declare every output, implicit modulemaps seem like a bad idea. Clang's caching system, even with custom cache paths seems like a bad idea as well. It is probably helpful to mention caveats of implicit modules and how to disable them (or link to the Clang Module docs for this). - The doc describes how to build e.g. an `iostream` module using the C++ semantics, but doesn't mention that AFAIK there is no "native" C++ Module build for libcxx yet. One would currently actually use Clang modules with implicit modulemaps. It may be helpful to mention this to avoid confusion. - Issue https://github.com/llvm/llvm-project/issues/56770 and seems-to-be-a-consequence-issue https://github.com/llvm/llvm-project/issues/57293 may be relevant apart from the already mentioned issue about clang-scan-deps. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D131388/new/ https://reviews.llvm.org/D131388 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
