嵌套的共享指针不符合我的预期

Question

问题

我想修改变量th。但是，当我修改th时，变量k也会被修改。我不清楚变量th和k是如何相关的，因此，为什么修改变量会影响另一个变量。

代码段

#include <memory>
#include <vector>
#include <iostream>
#include <string>
#include <cstring>

using sptrVec = std::shared_ptr< std::vector< int > >;

int main()
{
    std::vector< int > b = {4, 6, 8 ,20};
    sptrVec k = std::make_shared< std::vector< int > >(b.begin(), b.end());
    auto th = std::make_shared< std::vector< sptrVec > >();
    th->push_back( k );

    std::cout << "Org: " << k->at(0) << std::endl;
    std::cout << "Copy: " << th->at(0)->at(0) << std::endl;
    std::cout << "Corrupt!" << std::endl;

    uint8_t* merkle_ptr = (uint8_t*)&(th->at(0)->at(0));
    memfrob(merkle_ptr, sizeof(int));

    std::cout << "Org: " << k->at(0) << std::endl;
    std::cout << "Copy: " << th->at(0)->at(0) << std::endl;
}

输出

Org: 4
Copy: 4
Corrupt!
Org: 707406382
Copy: 707406382