+/**
+ * member_address_is_nonnull - check whether the member address is not NULL
+ * @ptr: the object pointer (struct type * that contains the llist_node)
+ * @member: the name of the llist_node within the struct.
+ *
+ * This macro is conceptually the same as
+ * &ptr->member != NULL
+ * but it works around the fact that compilers can decide that taking a member
+ * address is never a NULL pointer.
+ *
+ * Real objects that start at a high address and have a member at NULL are
+ * unlikely to exist, but such pointers may be returned e.g. by the
+ * container_of() macro.
+ */
+#define member_address_is_nonnull(ptr, member) \
+ ((uintptr_t)(ptr) + offsetof(typeof(*(ptr)), member) != 0)
+