[libcxx-commits] [libcxx] [libc++] Ensure that `std::expected` has no tail padding (PR #69673)

[Jan Kokemüller via libcxx-commits]

jiixyj wrote:


> In terms of next steps, please address remaining comments (which are nitpicks), and then I'll "squash and merge" this on Friday after my 1:1 with @huixie90, or earlier if Hui has time to have a final look. I'll then handle the communication with vendors and summarize the state of things (for both this and `__movable_box`) in #70820 , but that's easy since we have release notes.

I think I addressed all comments. Please let me know if I missed anything! I also did another rebase on `main`. Regarding the CI, I noticed that the "libcxx/utilities/expected/expected.void/transform_error.mandates.verify.cpp" test still fails on Windows clang-cl builds. Does anyone know why `XFAIL: msvc` does not seem to work?

> @jiixyj I want to thank you for taking the lead on this important fix. This has been one of the trickiest bugs (and fix) I've ever seen in the library and you stepped up with a comprehensive fix and diligent testing. Please know that this provides great value to the project and that the quality of this contribution is recognized and appreciated.

Thank you @ldionne and everyone for your comments and suggestions! I really enjoyed working on this PR with you all, and learned a lot.

https://github.com/llvm/llvm-project/pull/69673