CODEWITHSUNDEEP
c
Ahmed Hamoudi
Ahmed Hamoudi

Reputation: 1

Freeing memory after returning from a function

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

//defined a data structure "node" which stores an int and a pointer to a node
typedef struct node
{
    int number;
    struct node *next;
}
node;

//defining functions
node* create(int number);
node* insert(node *new_linked_list, int number);
void print(node *new_linked_list);
void delete_list(node *new_linked_list);

int main(void)
{
    //create new linked list with function
    node *new_linked_list = NULL;
    
    //get input to update list
    for (int i = 0; i < 10; i++)
    {
        int temp;
        if (i == 0)
        {
            scanf(" %i", &temp);
            printf("\n");
            new_linked_list = create(temp);
            continue;
        }
        
        //will insert new nodes in the linked lists
        scanf(" %i", &temp);
        printf("\n");
        new_linked_list = insert(new_linked_list, temp);
    }
    
    //prints node number values out
    print(new_linked_list);
    
    //delete/free list
    delete_list(new_linked_list);
    
    
    
}

//function will return a pointer to the first node in the list
node* create(int number)
{
    node *firstnode = malloc(sizeof(node));
    firstnode -> number = number;
    firstnode -> next = NULL;
    
    return firstnode;
}

//function that will update the linked list and return a pointer to the new head of the linked list
node* insert(node *new_linked_list, int number)
{
    node* new_node = malloc(sizeof(node));
    if (new_node == NULL)
    {
        return new_linked_list;
    }
    
    //new node will point to the old first node and updates new_nodes number
    new_node -> number = number;
    new_node -> next = new_linked_list;
    
    //returns a pointer to the new first node
    return new_node;

}

void print(node *new_linked_list)
{
    //temporary node for reversal
    node *trav = new_linked_list;
    
    for (int i = 0; i < 10; i++)
    {
        printf("%i   ",trav -> number);
        trav =  trav -> next;
        
        if (i == 9)
        {
            printf("\n");
        }
    }
}

void delete_list(node *new_linked_list)
{
    //base case: at null pointer
    if (new_linked_list -> next == NULL)
    {
        //frees memory previously allocated to a pointer
        free(new_linked_list);
        return;
    }
    
    //else delete the rest of the list
    else
    {
        delete_list(new_linked_list -> next);
    }
    
}

Hi so I was experimenting with a linked list and came across a problem. My program leaks memory because I am not freeing the "new node". However, I'm confused on how to free it as it is being return to be used in main. How would I go about freeing "new node" while still being able to use it in the main function. Thank you for any help in advance.

Upvotes: 0

Views: 48

Answers (1)

Erik
Erik

Reputation: 11

The issue seems to be related to the recursive behaviour of 'delete_list'

It could be implemented like the following:

void delete_list(node *new_linked_list)
{
    node *next;
    while(new_linked_list != NULL)
    {
        next = new_linked_list->next;
        free(new_linked_list);
        new_linked_list = next;
    }
}

Upvotes: 1

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