Speculatively implement LWG-4139 [time.zone.leap] recursive constraint in <=>
#4902
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
CaseyCarter
approved these changes
Aug 21, 2024
| bool _Is_positive; | ||
| seconds _Elapsed_offset; | ||
| }; | ||
| _NODISCARD friend constexpr bool operator==(const leap_second& _Left, const leap_second& _Right) noexcept { |
There was a problem hiding this comment.
No change requested: I don't think we need a comment here to indicated speculative implementation of LWG-4139, despite that this is a fairly big change and that LWG hasn't yet signed off on a proposed resolution. LWG has demonstrated approval of the "make leap_second's operators hidden friends" approach, and both libc++ and libstdc++implement it, so I have no doubt this will be the eventual resolution of the issue.
StephanTLavavej
approved these changes
Aug 21, 2024
|
I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed. |
StephanTLavavej
changed the title
<=><=>
|
Thanks for the preventative spaceship maintenance! 🔧 🛸 🪄 |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
LWG-4139 indicated constraint recursion in the current specification of the
operator<=>forleap_secondandsys_time, which is not yet revealed due to the bugs in MSVC and (old versions of) Clang.Although the proposed resolution is not shown in the LWG issue, I think the necessary changes are clear enough - just moving the operator functions from the synopsis of
<chrono>to that ofstd::chrono::leap_secondand addingfriend.This has been done in libstdc++ years ago (gcc-mirror/gcc@1736bf5), and recently in libc++ via LLVM-104713.