[libcxx-commits] [libcxx] [libc++][math] Add constexpr for std::abs() and relatives (PR #202985)

[Nikolas Klauser via libcxx-commits]

https://github.com/philnik777 requested changes to this pull request.

This will break GCC, since they don't have `__attribute__((enable_if))`.

https://github.com/llvm/llvm-project/pull/202985