C++: iterator rbegin不变性

int main(){
    map<int, int> mp{ {-2,-2},{2,2} };
    auto iter = mp.rbegin();
    cout << iter->first <<iter->second << endl;
    mp[3] = 4;
    cout << iter->first << iter->second << endl;
    auto iter1 = mp.begin();
    cout << iter1->first << iter1->second << endl;
    mp[-3] = -4;
    cout << iter1->first << iter1->second << endl;
    auto iter2 = mp.begin();
    cout << iter2->first << iter2->second << endl;
}

输出

22
34
-2-2
-2-2
-3-4