[libcxx-commits] [PATCH] D120064: Fix EBO on std::optional and std::variant when targeting the MSVC ABI

Tue Mar 1 12:22:39 PST 2022

ldionne added a comment.
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In D120064#3352402 <https://reviews.llvm.org/D120064#3352402>, @rnk wrote:

> In D120064#3352256 <https://reviews.llvm.org/D120064#3352256>, @mstorsjo wrote:
>
>> @rnk @thakis @hans Is such an ABI break in libc++ for the clang-cl case tolerable for you guys?
>
> Yes, we can tolerate it, but that's not a great proxy for project policy.
>
> I think, in practice, libc++ is not the system-standard C++ library in MSVC environments. It would be reasonable for libc++ to proclaim that the MSVC libc++ ABI is unstable, for now. I expect we will discover more issues like this in the near future. We may wish to re-evaluate the placement of dllexport annotations, for example, since @smeenai informed me that they interact poorly with inlining.

Yeah, I agree with that. We could update the Windows row in https://libcxx.llvm.org/#platform-and-compiler-support to say that the ABI is unstable -- would that be reasonable?

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https://reviews.llvm.org/D120064