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Linked List Destructor Help

bsmith (12)
When running valgrind on my program, it is not showing any memory leaks, however I am still getting the error saying an invalid read of ... .

I'm not entirely sure what it means. I think it has to do with my linked list's destructor / destroy() function.

Here's what I have so far. What am I missing? 

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#include "linkedlist.h"
#include "iostream"
using namespace std;


//Default Constructor
LinkedList::LinkedList()
{
    //initialize letters pointer to null
    letter = '\n';
    next = nullptr;
    head = nullptr;
}



LinkedList::~LinkedList()
{
        destroy(head);
}


void LinkedList::destroy(LinkedList * currHead)
{
    LinkedList *current = currHead;
    while (current != nullptr)
    {
        current = current->next;
    }
    delete current;
}


void LinkedList::add(char ch)
{
    LinkedList *current = head;
    if (current == nullptr)
    {
        LinkedList *newNode = new LinkedList();
        newNode->letter = ch;
        newNode->next = nullptr;
        head = newNode;
        return;
    }
    else if (current->next == nullptr)
    {
        LinkedList *newNode = new LinkedList();
        current->next = newNode;
        newNode->letter = ch;
        newNode->next = nullptr;
        newNode->head = newNode;
        return;
    }
    else
    {
        current = current->next;
        return current->add(ch);
    }
}



bool LinkedList::find(char ch)
{
    LinkedList *temp = head;
    if (temp == nullptr) //if list is empty, return false
    {
        return false;
    }
    else if (temp->letter == ch) //if it finds the letter, return true
    {
        return true;
    }
    else if (temp->next == nullptr) //if the next spot is empty, return false
    {
        return false;
    }
    else
    {
        return temp->next->find(ch); //recursively call find(ch) function
    }
}



bool LinkedList::del(char ch)
{
    LinkedList *current = head;
    LinkedList *previous = nullptr;

    if (current == nullptr) //if current list is empty
        return false;
    
    else if (current->letter == ch) //if it finds the letter to delete
    {
        previous = current;
        current = current->next;
        head = current;
        delete previous;
        return true;
    }
    else if (current->next == nullptr) //if next spot is blank, return false
    {
        return false;
    }
    else
    {
        return current->next->del(ch); //recursively call del(ch) function
    }
}




//overload friend << operator
std::ostream& operator<<(std::ostream& out, LinkedList& list)
{
    LinkedList *current = list.head;
    while (current != nullptr)
    {
        out << (current->letter);
        current = current->next;
    }
    out << endl;
    return out;
}



Last edited on
TheToaster (628)
Give us the header file implementation
kbw (9488)
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void LinkedList::destroy(LinkedList * currHead)
{
    LinkedList *current = currHead;
    while (current != nullptr)
    {
        LinkedList *tmp = current;
        current = current->next;
        delete tmp;
    }
}
TheToaster (628)
Ah yeah I didn't even see that ^
Last edited on
dutch (2548)
There's no point passing head into destroy.
And head should be set to nullptr at the end.

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void LinkedList::destroy()
{
    while (head)
    {
        LinkedList* to_del = head;
        head = head->next;
        delete to_del;
    }
}

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