程序代码：

struct MyINT64
{
    int int32high;
    unsigned uint32low;
};

MyINT64 operator+( const MyINT64& a, const MyINT64& b )
{
    MyINT64 r;
    r.uint32low = a.uint32low + b.uint32low;
    r.int32high = a.int32high + b.int32high + (r.uint32low<a.uint32low || r.uint32low<b.uint32low);
    return r;
}