[libcxx-commits] [libcxx] [libc++][math] Add `constexpr` to `copysign`, `copysignf`, `copysignl` (PR #216285)

[Shafik Yaghmour via libcxx-commits]

shafik wrote:

I am not bought into the b/c gcc does it clang should as well. There are definitely places we differ and we don't want to follow, `builtin_constant_p` being a good example here. At minimum I would like documentation and guarantee that gcc will continue this behavior along with a rationale for why it is not problematic for C++ and C standardization. 

https://github.com/llvm/llvm-project/pull/216285