Linked list implementation segmentation fault

Question

I have done basic implementation of Linked List but its giving Segmentation fault on uncommenting the commented lines otherwise its working fine. I am not able to understand why its giving the error. Please give me some help

void insert(Node **head, Symbol sym) {
    Node *temp, *p = *head;;
    Symbol a = sym;
    temp = (Node *)malloc(sizeof(Node));
    temp->value = a;
    temp->next = NULL;

    if (p == NULL)
        *head = temp;
    else {
        while (p->next != NULL)
            p = p->next;
        p->next = temp;
    }
}

void printList(Node *head) {
    Node *p = head;
    if(p == NULL) return;
    while (p != NULL) {
        printf("%d ", p->value);
        p = p->next;
    }
    printf("\n");
}
int main() {
    Node *List, *list2;
    insert(&List, 0);
    insert(&List, 1);

    //insert(&list2, 2);
    //insert(&list2, 3);

    printList(List);
    return 0;
}

Apart from personal development or an application where the additional bytes per node and processing steps per function needs to be kept low. Should people not be using GList from the GObject library or something similar — phil
– phil, Commented Mar 18, 2015 at 15:19

Vlad from Moscow · Accepted Answer · 2015-03-18 10:12:23Z

3

You did not initialize initial pointers to nodes

Node *List, *list2;

Write

Node *List = NULL, *list2 = NULL;

Take into account that variable list2 is not used in the program you showed.

The other way to write function insert is the following

void insert( Node **head, Symbol sym ) 
{
    Node *temp = malloc( sizeof( Node ) );

    if ( temp != NULL )
    {
        temp->value = sym;
        temp->next  = NULL;

        while ( *head ) head = &( *head )->next;
        *head = temp;
    }
}

edited Mar 18, 2015 at 10:12

answered Mar 18, 2015 at 9:58

Vlad from Moscow

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3 Comments

Vlad from Moscow Over a year ago

@Paul Ogilvie Does it mean that I may not give my own answer?:)

Paul Ogilvie Over a year ago

It would have been nice if you referenced Bluepix to give him the credit of the solution.

Vlad from Moscow Over a year ago

@Paul Ogilvie Oh, I am sorry. When I was writing my post I had not seen yet the comments.:)

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