gistfile1.c

typedef unsigned __int128 TaggedPointer;

#define TP_GET_PTR(ptr)         ((Node *)((ptr) >> 64))
#define TP_GET_VERSION(ptr)     ((uint64_t)(ptr))


TaggedPointer pack_tagged_pointer(void *ptr, uint64_t version) {
        printf("args of %p, %lu\n", ptr, version);
        unsigned __int128 result = (intptr_t)ptr;
        result = result << 64;

        result |= version;
        return result;
}

TaggedPointer tp = pack_tagged_pointer(&foo, 1);
printf("res = %d, version = %lu, ptr = %p\n", res, TP_GET_VERSION(tp), TP_GET_PTR(tp));