shared_ptr causing segfault

I am trying to use shared_ptr with my class but for some reason I get segfault. Maybe I am doing something stupid.

#include <tr1/memory>
#include <iostream>
class Dataset ;
typedef int DataClass;
class Dataset_Impl{
    friend class Dataset ;
    DataClass *dc;
    Dataset_Impl(){dc = new DataClass[10];}
    public:
    void getSubset(Dataset_Impl* &dObj){
        dObj = new Dataset_Impl();  //Causing segfault when using shared_ptr
        /*copy subset of 'dc' to dObj->dc and return*/std::cout<<"Copied subset";
    }
};
class Dataset{
    Dataset_Impl *d;
    public:
        Dataset (){};
        inline void const getSubset(Dataset &dObj) const{d->getSubset(dObj.d);}
};
int main(){
    Dataset m1,subset1;std::shared_ptr<Dataset> subset2;
    m1.getSubset(su开发者_如何学运维bset1);
    m1.getSubset((*subset2)); //Causing segfault
}

You haven't created an object; subset2 is a null pointer. You need to create an object for it to manage:

std::shared_ptr<Dataset> subset2(new Dataset);

For information there is a dedicated function to create a shared_ptr on a new allocated object , in your case:

std::make_shared<Dataset>()

This will call Dataset() constructor. If you have a second constructor, let's say Dataset(int), you may write std::make_shared<Dataset>(i) with an integer i.

Your shared_ptr is empty. It does not store a pointer to a Dataset. Use e.g.

 std::shared_ptr<Dataset> subset2(new Dataset) ;

you are not creating an object for the shared_ptr variable and trying to access a member variable of pointer. try

std::shared_ptr<Dataset> subset2(new Dataset())