What is the exact use of shared_ptr in c++?

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5.00/5 (1 vote)

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Why we use shared_ptr?

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

using namespace std;
class x
{
    public:
    int i;
    x():i(12323123)
    {
        cout<<"constructor called"<<endl;
    }
    ~x()
    {
        cout<<"destructor called"<<endl;
    }
};
    vector< shared_ptr<x> > testvec;

int test()
{
        shared_ptr<x> n(new x);
            testvec.push_back((n));
}

main()

{
    test();
    vector< shared_ptr<x> > tests=((testvec));
    cout<<(*(tests.at(0))).i;
}

Posted 18-Oct-12 0:53am

ppvijeesh1

Updated 18-Oct-12 0:54am

v2

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Maximilien · Accepted Answer · 2012-10-18T01:07:00

Solution 1

It is used to remove the risk of memory leakage in an application, because you don't need to remember to manually delete the pointer when you a re done with it.

Posted 18-Oct-12 1:07am

Maximilien

Comments

ppvijeesh1 18-Oct-12 7:19am

Maximilien
Sorry. I think my question is not clear. Why we use shared_ptr instead of unique_ptr,etc?

Maximilien 18-Oct-12 7:30am

Edit the original question ...

the best answer I can give you is to read this :
http://herbsutter.com/2012/01/20/gotw-103-smart-pointers-part-1-difficulty-310/

serhiy.semenyuk · Accepted Answer · 2012-10-18T09:51:00

I assume shared_ptr is used rather than unique_ptr to be able to have copies of objects from that vector and still have correct reference count for each object.

so for code:

C++

shared_ptr<x> variable = new x;
{
    vector< shared_ptr<x> > arr;
    arr.push_back(x)
}
</x></x>

in the brackets variable will have ref count equal to 2, and equal to 1 otherwise.