共享指针的向量，清除向量后出现内存问题 [英] Vector of shared pointers , memory problems after clearing the vector

问题描述

我意识到，调用包含共享指针的vector.clear()之后，shared_ptr拥有的对象的析构函数不会被释放.

I realized that after calling vector.clear() which hold shared pointers, the destructors of the object which own by shared_ptr is not being released.

代码示例可以在下面看到.甚至vector.clear()被调用，共享指针之后的析构函数调用也超出了范围.我的问题是-我是否必须通过重置手动删除向量中的所有智能指针?有什么更简单的建议方法吗?

Code example can be seen below . Even vector.clear() being called, destructor called after shared pointer goes beyond the scope.My question is - do I have to delete all smart pointers inside the vector manually by resetting them? Is there any easier way that you can advice ?

Output :   

constructor
I am here
destructor

Code:

#include <vector>
#include <iostream>
#include <memory>

using namespace std;

class A
{
public:
    A(){cout << "constructor" << endl;};
    ~A(){cout << "destructor"  << endl;};
};

int main( )
{
    shared_ptr<A> sharedptr (new A);
    std::vector<shared_ptr<A> > test;
    test.push_back(sharedptr);

    test.clear();
    cout << "I am here" << endl;
}

推荐答案

在这种情况下，您有两个shared_ptr<A>副本，一个是sharedptr变量，另一个是向量中的元素.

you have two copies of shared_ptr<A> in this case, one is the sharedptr variable and the other as an element in the vector.

改为执行此操作

test.push_back(std::move(sharedptr));

现在请注意原始的sharedptr已在内部移动并且不再可用.另一件事是什么也不做，这是shared_ptr的完全有效用法，sharedptr在超出范围后会自行清理.

note now the original sharedptr has it's internal moved and no longer usable. The other thing is don't do anything at all, this is a perfectly valid usage of of shared_ptr and sharedptr will clean up itself after it goes out of scope.

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