[libcxx-commits] [PATCH] D127570: [libc++][format] Use forwarding references.

Wed Jul 13 08:34:24 PDT 2022

Mordante added a comment.

In D127570#3647884 <https://reviews.llvm.org/D127570#3647884>, @h-vetinari wrote:

> This PR didn't update the format status page. Is the warning from C++20 status still current?
>
>> P0645: The paper is implemented but still marked as an incomplete feature (the feature-test macro is not set and the libary is only available when built with LIBCXX_ENABLE_INCOMPLETE_FEATURES). Not yet implemented LWG-issues will cause API and ABI breakage.
>
> I would have though that the chrono-integration is orthogonal to the ABI issues.

I'm quite sure I indeed can do chono without an ABI break. But https://wg21.link/p2572r0 will be ABI breaking for at least `char`.  If I really wanted, I probably can work around it. But since the paper hasn't been seen by LEWG I don't know how it will be received there. I also intend to look at some other improvements, this will be a lot easier when we're not ABI frozen.

However when we have `-fexperimental-library` I can set the feature-test macro to the value for P2418 <https://reviews.llvm.org/P2418>. That's already on my todo list. Having it in experimental will make it a lot easier to use format, so I'm quite happy about that.

Repository:
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https://reviews.llvm.org/D127570