This is related but separate to Clang 16. Clang 15+ started warning on this but it's not fatal right now. -Werror=deprecated-non-prototype issues are forbidden in C23 (C2x) so at the latest, this will become a problem for us when compilers switch in ~2025/2026/2027 to C23 as default, but it might become a problem sooner if Clang decides to change.