C++ queue inside a class, segmentation fault

Question

Can somebody tell, why I have segmentation fault in that code? I have no idea why is that. I use Code:Blocks but online compilers have the same problems. I don't know where the problem is.

#include <iostream>
#include <queue>
#include <memory>

using namespace std;

class Task {   
private:
    queue <string> q;
    public:
    string input;
    void read (int hm)
    {
        for (int i=1;i<=hm;i++)
        { 
            cin>>input;
            q.push(input);
        }
    }
    void count()
    {
        cout<<q.back();
    }
};

int main()
{
    unique_ptr <Task> ptr;

    int how_many;
    cin>>how_many;
    ptr->read(how_many);
    ptr->count();
    return 0;
}

Ron · Accepted Answer · 2017-10-09 07:35:17Z

3

The pointer ptr is being used without being initialized. Use:

std::unique_ptr<Task> ptr = std::make_unique<Task>();

That being said you should also include the <string> header explicitly.

edited Oct 9, 2017 at 7:35

answered Oct 9, 2017 at 7:26

Ron

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1 Comment

Phlox Midas Over a year ago

And your count() will return the value of the most recent element rather than the number of elements. For that, use q.size(). Example: cplusplus.com/reference/queue/queue/size

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