[libcxx-commits] [libcxx] [libc++] Drop support for the C++20 Synchronization Library before C++20 (PR #82008)

[Mark de Wever via libcxx-commits]

mordante wrote:

Do we really need to drop support for all versions prior to C++20? For example I've seen the `<barrier>` header used in code bases. My main concern is removing support without our typical deprecation heads-up.

If possible I would prefer the keep it in C++11 and if wanted use our 2 release deprecation.

Note this is not an objection, we have done this in the past when extensions became a maintenance issue.

If we want to do this we should create a separate patch to mention this in the LLVM-18 release, we still have time for that.

https://github.com/llvm/llvm-project/pull/82008