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

[Louis Dionne via libcxx-commits]

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In-Reply-To: <llvm.org/llvm/llvm-project/pull/69673 at github.com>


ldionne wrote:

> > @jiixyj The LLVM 18 branch is happening on Tuesday January 23rd. Ideally, we'd get this patch finished and landed within a couple of days. If you think that's feasible, great, otherwise please let us know and I can pick it up to give it one last push.
> 
> I can certainly clean up the PR, add some comments, and make it pass the CI. I'm not sure if I have the cycles to do the refactoring into the "always `[[no_unique_address]]` union layout" from [this](https://github.com/llvm/llvm-project/pull/69673#discussion_r1435271088) thread. GCC [doesn't](https://github.com/llvm/llvm-project/actions/runs/7511141689/job/20450379594) really like it when tried to make the union always `[[no_unique_address]]` in [this](https://github.com/llvm/llvm-project/pull/69673/commits/fe55535db87b8de529bd43a8f45c961f5c1dfbdd) commit for testing, which would make the refactoring harder than it needs to be, I feel.

Ok, sounds good. Would it be an ABI break to make this refactoring after landing this patch? We wouldn't be changing the layout so I don't think so, right?

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