linked list implemetation from scratch, segmentation fault

Question

I want to implement linked list from scratch. I programmed it, but when I run it gives me a Segmentation fault in my node_adder(int data) function. I don't know what caused this.

struct linked_list
{
    int value;
    struct linked_list *next;
};

struct linked_list *head = NULL;
struct linked_list *tail = NULL;

void node_adder(int data)
{
    struct linked_list *new = NULL;

    new->value = data;
    new->next = NULL;

    if (head == NULL)
    {
        head = new;
        tail = new;
        printf("head added\n");
    }
    else
    {
        tail->next = new;
        tail = new;
        printf("tail added\n");
    }
}

Answer 1

In node_adder(), you are not allocating any memory for the new node before accessing its members.

Try this instead:

struct linked_list
{
    int value;
    struct linked_list *next;
};
    
struct linked_list *head = NULL;
struct linked_list *tail = NULL;

void node_adder(int data)
{
    struct linked_list *newNode;

    // ADD THIS!!!
    // in C:
    newNode = malloc(sizeof(struct linked_list));
    // in C++:
    newNode = new linked_list;
    //

    newNode->value = data;
    newNode->next = NULL;

    if (head == NULL)
    {
        head = tail = newNode;
        printf("head added\n");
    }
    else
    {
        tail->next = newNode;
        tail = newNode;
        printf("tail added\n");
    }
}