__usdt_t
#define __usdt_is_signed(x) (!__usdt_is_arr(x) && __usdt_t<__typeof(x)>::is_signed)
template<typename A> struct __usdt_t<A[]> : public __usdt_t<A *> {};
template<typename A, size_t N> struct __usdt_t<A[N]> : public __usdt_t<A *> {};
template<> struct __usdt_t<T> { static const bool is_signed = true; }; \
template<> struct __usdt_t<const T> { static const bool is_signed = true; }; \
template<> struct __usdt_t<volatile T> { static const bool is_signed = true; }; \
template<> struct __usdt_t<const volatile T> { static const bool is_signed = true; }
template<> struct __usdt_t<T> { static const bool is_signed = (T)-1 < (T)1; }; \
template<> struct __usdt_t<const T> { static const bool is_signed = (T)-1 < (T)1; }; \
template<> struct __usdt_t<volatile T> { static const bool is_signed = (T)-1 < (T)1; }; \
template<> struct __usdt_t<const volatile T> { static const bool is_signed = (T)-1 < (T)1; }