Template Stack Class with Data types of Linkedlist gives error of Cannot Access Memory at Address c++

Question

Here's my custom template stack class

#ifndef INC_20F_FLT_PLN_DSSTACK_H
#define INC_20F_FLT_PLN_DSSTACK_H
#include <iostream>

template <typename T>
class DSStack
{
    T* data;
    int top;
    int capacity;

public:
    DSStack()=default;
    DSStack(int size);
    DSStack(const DSStack<T>& copy);
    DSStack& operator= (DSStack<T>);
    void push(const T& data);
    T pop();
    T peek();
    bool isempty();
    bool isfull();
    int getsize();
    ~DSStack(){while ( !isempty() ) {
            pop();
        }
        isempty();};
};

template<typename T>
DSStack<T>::DSStack(int size) {
    this->capacity=size;
    this->data = new T[capacity];

    top=-1;
}

template<typename T>
void DSStack<T>::push(const T& data) {
    if(!isfull())
    {
        this->data[top+1]=data;
        top++;
    }

}

template<typename T>
T DSStack<T>::pop() {
    if(!isempty())
    {
        top--;
        return data[top+1];
    }
}

template<typename T>
T DSStack<T>::peek() {
    if(!isempty())
    {
        return data[top];
    }
}

template<typename T>
int DSStack<T>::getsize() {
    return top+1;
}

template<typename T>
bool DSStack<T>::isempty() {
    if(top==-1)
    {
        return true;
    }
    else
        return false;
}

template<typename T>
bool DSStack<T>::isfull() {
    if(top==capacity-1)
    {
        return true;
    }
    else
        return false;
}

template<typename T>
DSStack<T>::DSStack(const DSStack<T> &copy) {
    this->data = new T[copy.capacity];
    this->capacity = copy.capacity;
    for(int i =0;i<capacity;i++)
    {
        this->data[i]= copy[i];
        this->top+=1;
    }
}

template<typename T>
DSStack<T> &DSStack<T>::operator=(DSStack<T> copy) {
    this->data = new T[copy.capacity];
    this->capacity = copy.capacity;
    for(int i =0;i<capacity;i++)
    {
        this->data[i]= copy[i];
        this->top+=1;
    }
    return *this;
}


#endif //INC_20F_FLT_PLN_DSSTACK_H

And my template linked list class

#ifndef INC_20F_AUTO_IDX_DSLINKEDLIST_H
#define INC_20F_AUTO_IDX_DSLINKEDLIST_H
#include <cstddef>
#include <utility>

template <typename T>
class DSList
{
    struct DSNode
    {
        T value;
        DSNode* prev;
        DSNode* next;
        DSNode(T value, DSNode *prev = nullptr, DSNode *next = nullptr)
                : value{std::move(value)}, prev{prev}, next{next}
        {}
        DSNode(const DSNode&) = delete;
        void operator=(const DSNode&) = delete;

        friend void swap(DSNode& a, DSNode& b) {
            using std::swap;
            swap(a.value, b.value);
            swap(a.prev, b.prev);
            swap(a.next, b.next);
        }
    };

public:
    DSList() = default;
    DSList(const DSList<T>&);

    DSList& operator=(DSList<T>);
    ~DSList();

    T const& get(std::size_t pos) const;
    T& get(std::size_t pos);

    void insert(T value, std::size_t pos);
    int getsize();

    template<typename U>
    friend void swap(DSList<U>&, DSList<U>&);

private:
    std::size_t n_elements = 0;
    DSNode head = { T{}, nullptr, &tail };
    DSNode tail = { T{}, &head, nullptr };
};

template<typename T>
DSList<T>::DSList(const DSList<T>& list)
{
    for (auto i = list.n_elements;  i > 0;  --i) {
        insert(list.get(i-1), 0);
    }
}


template<typename T>
DSList<T>& DSList<T>::operator=(DSList<T> list)
{
    swap(*this, list);
    return *this;
}

template<typename T>
DSList<T>::~DSList()
{
    for (auto p = head.next;  p != &tail;  ) {
        auto next = p->next;
        delete p;
        p = next;
    }
}

template<typename T>
void swap(DSList<T>& a, DSList<T>& b)
{
    using std::swap;
    swap(a.head, b.head);
    swap(a.tail, b.tail);
    swap(a.n_elements, b.n_elements);
}

template<typename T>
const T& DSList<T>::get(std::size_t pos) const
{
    auto p = head.next;
    while (pos--)
        p = p->next;
    return p->value;
}

template<typename T>
T& DSList<T>::get(std::size_t pos)
{
    auto p = head.next;
    while (pos--)
        p = p->next;
    return p->value;
}

template<typename T>
void DSList<T>::insert(T value, std::size_t pos)
{
    auto p = &head;
    while (pos--)
        p = p->next;
    auto next = p->next;
    next->prev = p->next = new DSNode(std::move(value), p, next);
    ++n_elements;
}

template<typename T>
int DSList<T>::getsize() {
    return n_elements;
}
#endif //INC_20F_FLT_PLN_DSLINKEDLIST.H

When I am trying to create a stack of type int: DSStack<int>test (2); , it will allow me to push, pop, peek with the data and it would return correct results. But when I tried to create stack of type linked list: DSStack<DSList<int>>test2(2); , I would also create a linked list of integers, DSList<int>numList; I can put some numbers in to the linked list and it would give no error. But when I try to push the linkedlist that I created into the stack, it would give error of: Process finished with exit code -1073740940 (0xC0000374). Running with a debegger gives me the error of cannot access memory at a random location. The line points to the destructor of the linked list class, but I believe that the destructor of the linked list class does function properly. I wonder if this has to do with how I set up my stack class. I would really like some help on how to fix this issue. Thank you!

Answer 1

Ok, you got a bunch of weirdness going on in your list impl. I was able to get the following singly-linked list working

#ifndef INC_20F_AUTO_IDX_DSLINKEDLIST_H
#define INC_20F_AUTO_IDX_DSLINKEDLIST_H
#include <cstddef>
#include <utility>

template <typename T>
class DSList
{
    struct DSNode
    {
        T value;
        DSNode* next;
        DSNode(T value, DSNode *next = nullptr)
                : value{std::move(value)}, next{next}
        {}
        DSNode(const DSNode&) = delete;
        void operator=(const DSNode&) = delete;

        friend void swap(DSNode& a, DSNode& b) {
            using std::swap;
            swap(a.value, b.value);
            swap(a.prev, b.prev);
            swap(a.next, b.next);
        }
    };

public:
    DSList() = default;
    DSList(const DSList<T>&);

    DSList& operator=(DSList<T>);
    ~DSList();

    T const& get(std::size_t pos) const;
    T& get(std::size_t pos);

    void insert(T value);
    int getsize();

    template<typename U>
    friend void swap(DSList<U>&, DSList<U>&);

private:
    DSNode* head = nullptr;
};


template<typename T>
DSList<T>::~DSList()
{
    if (head == nullptr) return;
    auto current = head;
    while(current->next != nullptr){
        auto next = current->next;
        delete current;
        current = next;
    }
}


template<typename T>
void DSList<T>::insert(T value)
{
    auto new_node = new DSNode(std::move(value));
    if (head == nullptr){
        head = new_node;
        return;
    }

    auto p = head;
    while (p->next != nullptr)
        p = p->next;
    auto node = new DSNode(std::move(value));
    p->next = node;
}

#endif //INC_20F_FLT_PLN_DSLINKEDLIST.H


int main(){
    DSList<int> here;
    here.insert(1);
    std::cout << "Here";
}

Before you make a DLL, make a SLL, and make sure that it works properly. When I inserted, and when the list destructed there was something weird going on with your accesses. I trimmed out everything that wasn't needed for this specific solution. You'll be on your own to add the counting behavior and bulking insertion.