[llvm-branch-commits] [libcxx] [libc++] Add tests for the ABI break introduced by switching to _LIBCPP_COMPRESSED_PAIR (#154559) (PR #154961)

[Louis Dionne via llvm-branch-commits]

ldionne wrote:

Closing since we aren't targeting LLVM 20 anymore. Vendors who want to cherry-pick this fix are encouraged to do so on their own.

https://github.com/llvm/llvm-project/pull/154961