+#if __has_builtin(__builtin_add_overflow) || (defined(__GNUC__) && __GNUC__ >= 5)
+#define add_overflow(a, b, r) __builtin_add_overflow(a, b, &(r))
+#define sub_overflow(a, b, r) __builtin_sub_overflow(a, b, &(r))
+#else
+#define add_overflow(a, b, r) ({r = (u32)a + (u32)b; (a ^ ~b) & (a ^ r) & (1u<<31);})
+#define sub_overflow(a, b, r) ({r = (u32)a - (u32)b; (a ^ b) & (a ^ r) & (1u<<31);})
+#endif
+