c++ - 将 shared_ptr 与 vector 一起使用时出现段错误

Question

我是第一次使用 shared_ptr 如果我犯了一个非常愚蠢的错误并帮助我克服这个段错误请原谅我。

我希望有一个私有(private)的vector，即使对象被销毁，它也可以从不同的类中读取。因此我读到了 std::shared_ptr

代码在 storeCounterData 函数中出现段错误

提前感谢您的帮助!!!

主要.cpp

#include <iostream>
#include "counter.hpp"
#include "getCounter.hpp"

const int max_ports = 3;

int main()
{
  Counter *counter = new Counter(3);
  counter->age = 1;
  counter->id = 12;
  counter->pincode = 123;

  std::vector<Counter*> counterData;

  std::cout<<"inside main"<<std::endl;

  counter->storeCounterData(counter,0);
  counter->storeCounterData(counter,1);
  counter->storeCounterData(counter,2);

  std::cout<<"inside main calling getCounterData"<<std::endl;
  counter->getCounterData(counterData);

  Counter countji(3);

  countji.getCounterData(counterData);

  //getCounterData class function

   getCounter *gcount = new getCounter();

   gcount->printCounterData();

  return 0;
}

计数器.hpp

#ifndef COUNTERHPP
#define COUNTERHPP
#include <vector>
#include <memory>

class Counter
{
private:
typedef std::shared_ptr<Counter> sharedCtr; 
std::vector<sharedCtr> vecData;
public:
Counter();
Counter(int vecSize);
int age, id, pincode;
void storeCounterData(Counter *counter,int user);
void getCounterData(std::vector<Counter*> &counter);

};

#endif

计数器.cpp

#include "counter.hpp"
#include <iostream>
#include <vector>

Counter::Counter()
{

}

Counter::Counter(int vecSize):vecData(vecSize)
{

}

void Counter::storeCounterData(Counter *counter,int user)
{ 
  vecData[user]->age = counter->age;
  vecData[user]->id = counter->id;
  vecData[user]->pincode = counter->pincode;

  std::cout<<"vector size inside storeCounterData = "<<vecData.size()<<std::endl;
}

void Counter::getCounterData(std::vector<Counter*> &counter)
{

  std::cout<<"vector size inside getCounterData = "<<vecData.size()<<std::endl;

for (auto& c : vecData)
  {
    std::cout << c->age << std::endl;
    std::cout << c->id << std::endl;
    std::cout << c->pincode << std::endl;
  }
}

输出

Bazooka~/VECTOR$ ./a.out

inside main

Segmentation fault (core dumped)

Answer 1

在 Counter 的构造函数中，您正在创建一个空 shared_ptr vector ，即没有 Counter 的托管对象(see (1) here ).

只需将行更改为:

Counter(int vecSize) : vecData(vecSize, std::make_shared<Counter>()) {}

编辑: 你正在创建一个指针 vector ，所以我在这里看到两个选项来满足你希望它的工作方式:

1. 您的做法:使用 3 个 shared_ptr 实例化 vector ，但随后您需要在访问指针时检查指针是否已创建。

也许这就是要走的路。 shared_ptr 也是指针，您应该这样对待它们并始终检查其有效性。

Counter(int vecSize) : vecData(vecSize) {} // previous constructor

void storeCounterData(Counter* counter, int user) {
  if (!vecData[user]) {
    vecData[user] = std::make_shared<Counter>();
  }
  vecData[user]->age = counter->age;
  vecData[user]->id = counter->id;
  vecData[user]->pincode = counter->pincode;

  std::cout << "vector size inside storeCounterData = " << vecData.size()
            << std::endl;
}
void getCounterData(std::vector<Counter*>& counter) {
  std::cout << "vector size inside getCounterData = " << vecData.size()
            << std::endl;

  for (auto& c : vecData) {
    if (c) {
      std::cout << c->age << std::endl;
      std::cout << c->id << std::endl;
      std::cout << c->pincode << std::endl;
    }
  }
}

1. 使用 std::vector::push_back，这样您在 vector 中只有“有效”(您永远无法确定这一点)shared_ptr。<