https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109049
Bug ID: 109049 Summary: std::declval gives wrong result for cv void Product: gcc Version: 12.2.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: libstdc++ Assignee: unassigned at gcc dot gnu.org Reporter: fsb4000 at yandex dot ru Target Milestone: --- A. Jiang <d...@live.cn> found that: Quote: "The return type is... cursed for cv void. It seems that decltype(std::declval<const void>) should be const void() (until C++17) / const void() noexcept (since C++17) (same for volatile void and const volatile void), but the cv-qualifiers are dropped" Code example: #include <utility> #include <type_traits> int main() { static_assert(std::is_same_v<decltype(std::declval<const void>), const void () noexcept>); static_assert(std::is_same_v<decltype(std::declval<volatile void>), volatile void () noexcept>); } https://gcc.godbolt.org/z/TMe3v9sxh I've created the same issue for libc++: https://github.com/llvm/llvm-project/issues/61232