[libcxx-commits] [libcxx] [libc++] Introduce implicit and explicit ABI annotations (PR #193045)

[Louis Dionne via libcxx-commits]

https://github.com/ldionne commented:

I like this patch a lot. I think it will allow really simplifying the code and it might even catch a few bugs where we don't have the necessary annotations and our clang-tidy check misses them.

However, because this patch touches essentially everything in the codebase, it has the perfect profile for finding stuff that we should be testing but aren't. Specifically, I think it would be generally beneficial to split up our CI to represent the two axis that actually exist in reality:
1. The configuration used to build libc++.dylib (exceptions? RTTI? hardening mode?)
2. The configuration when *using* libc++ (aka how the developer builds their own code)

By being able to properly test cross-variations of the configuration modes we support, we might find additional issues. I don't really want to block this patch landing on that project since it might be major, but I did want to at least leave a note for posterity since I think this is worth doing.

For now, let's get all the existing CI happy and I can have another look -- but I don't see a fundamental problem with this change, other than I think it's possible it will show us blind spots in our testing.

https://github.com/llvm/llvm-project/pull/193045