Question

I have the following snippet of code:

struct Node
{
    Node* left;
    Node* right;
    string data;
};    

void test()
    {
        Node thing;
        thing.data = "h";
        thing.left = NULL;
        thing.right = NULL;

        cout<< "Thing data = " << thing.data << endl;

        Node* thing2;
        thing2->data = "f";
        thing2->left = NULL;
        thing2->right = NULL;

        cout<< "Thing2 data = " << thing2->data << endl;

    }

The problem I’m having is that thing2->data = “f” is producing a segmentation fault during runtime. I’ve run the program through GDB and get this error, but I can’t figure out what it means:

Reading symbols for shared libraries ++. done
Thing data = h

Program received signal
EXC_BAD_ACCESS, Could not access
memory. Reason: 13 at address:
0x0000000000000000 0x00007fff874d59a3
in std::string::assign ()

Any help would be great. Thanks!

Answer 1

thing2 is a non initialized pointer.
It doesn’t point to a valid Node object.

You should allocate it:

thing2 = new Node;

or make it point to a valid Node object:

thing2 = & thing;