[libcxx-commits] [libcxx] [libc++] Fix UB in <expected> related to "has value" flag (#68552) (PR #68733)

[Jan Kokemüller via libcxx-commits]

jiixyj wrote:

I implemented the proposed (ABI changing) fix [here](<https://github.com/jiixyj/llvm-project/commit/922895055cf3e31b4f3b2b89c990cec4e30ec429>) and all tests pass! With that patch `expected` has no longer any tail padding, so `std::construct_at`/`std::destroy_at` wouldn't be able to overwrite any important data (except for `__has_value_`, but that is always restored correctly).

https://github.com/llvm/llvm-project/pull/68733