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

[Lucas Mellone via libcxx-commits]

lknknm wrote:

> The issue is that Clang doesn't make the C overloads `constexpr`, i.e. the `copysign`/`copysignf` etc. I'm quite certain that everything would work just fine if we change that.

But what should be changed specifically? I tried changing `Builtins.td` and checking `InterpBuiltin` but nothing has changed. Moreover the same issue happened when compiling with GCC unless I changed the overloads (you can see I also flipped the tests for it).

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