C++ smart pointers for objects containing raw pointers

I have a class having an element which contains a raw pointer of another object as following. Note that the example I simplified from my actual work may probably work, but I am trying to get conceptual mistake if I am doing here, because in the perfectly same structure and scenario I am getting segmentation fault error.

/*This doesn't have a raw pointer of another object*/
class H1
private:
int x, y;
public:
constructors;
copy_constructor;

/*This has a h1_ptr element which is a raw pointer of H1*/
class G1
private:
int count;
H1* h1_ptr;
public:
G1(int c, H1* lst)
count = 0;
h1_ptr = lst;

G1(const G1& g)
count = g.count;
h1_ptr = g.h1_ptr;

G1& operator=(const G1& g)

count = g.count;
h1_ptr = g.h1_ptr;


/*The class that I create unique_ptr from*/
class H3
private:
H1 h1, h2;
G1 g1;
public:
H3(H1 _h1, H1 _h2, G1 _g1)
h1 = _h1; h2 = _h2; g1 = _g1;




I create a unique_ptr from the class H3 in a function and return it to another function:

unique_ptr

H3

unique_ptr<H3> create_ptr()
H1 h1(5, 10);
H1 h2(50, 100);

H1* h1_lst = new H1[20];
H1 ls;
for (int i=0;i<20;i++)

H1 ls(i, i*2);
h1_lst[i] = ls;

G1 g1(200, h1_lst);
unique_ptr<H3> p_h3(new H3(h1, h2, g1));
return p_h3;

int main()
unique_ptr<H3> p_h3 = create_ptr();
H3* h_3 = p_h3.get();//to get the raw pointer
G1 g1(h_3->g1);//corrected
H1* h1_lst = g1.h1_ptr;
for (int i=0;i< 5; i++)
//I just want 5 of them even if there is more
H1 ls = h1_lst[i];
cout << ls.x << ":" << ls.y << endl;

return 0;



This will just write 1 or 2 lines, then it will crash with segmentation fault. If I didn't return the unique pointer, but get the raw pointer and write the result in the create_ptr function instead, it would work perfectly fine.

create_ptr

constructors

copy_constructors

2 Answers
2

The problem was in destructor of foreign class like (G1 in this example) which was trying to delete raw pointer objects. When I remove those delete processes it works fine, but I believe this is still a bad idea.

You cannot copy assign the std::unique_ptr from another unique pointer. Its not CopyConstructible or CopyAssignable.

std::unique_ptr

However, you can transfer ownership using std::move:

std::move

std::unique_ptr iptr1new int1;
std::unique_ptr iptr2 = std::move(iptr1); // iptr1 now null


If you whish to have multiple owners of the pointer use std::shared_ptr instead.

std::shared_ptr

Read more about it on the cppreference page std::unique_ptr

std::unique_ptr

unique_ptr

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