Why my linked list isn't ouputting anything?

Question

I have created a very basic link list and it's not outputting anything. I am unable to output anything. What went wrong? I am not getting any kind of error on the console. I am trying C after learning node and react on JS. C is extremely different than JS.

typedef struct node {
    int data;
    struct node *next;
} node;

//Creates new node
node *createNewNode(int data){
    node *tmp = malloc(sizeof(node));
    tmp->data = data;
    tmp->next = NULL;

    return tmp;
}

//adds node at the end
void addNodeAtEnd(node *head, node *nodeToInsert){

    node *tmp = head;

    //If head is null, make first node your head
    if (head==NULL)
    {
        head=nodeToInsert;
        return;
    }
    
    //Insert new node at the end
    //traverse through whole node to reach the end
    while (tmp->next != NULL)
    {
        tmp=tmp->next;
    }
    
    //Finally insert at the last nodes
    tmp->next = nodeToInsert;
}

//views all nodes
void viewAllNodes(node *head){
    node *tmp = head;

    while(tmp->next != NULL){
        printf("%d - ", tmp->data);
        tmp=tmp->next;
    }
}

int main(){

    node *head = NULL;

    addNodeAtEnd(head,createNewNode(1));
    addNodeAtEnd(head,createNewNode(2));
    addNodeAtEnd(head,createNewNode(3));

    viewAllNodes(head);
}

Answer 1

The function addNodeAtEnd declared like

void addNodeAtEnd(node *head, node *nodeToInsert);

accepts the pointer head declared in main by value. It means that the function deals with a copy of the value of the pointer. Changing the copy does not reflect on the original pointer.

You need to pass the pointer by reference.

In C passing by reference means passing an object indirectly through a pointer to it. Dereferencing the pointer you can get a direct access to the original object.

The function can be declared and defined the following way

//Creates new node
node * createNewNode(int data)
{
    node *tmp = malloc(sizeof(node));

    if ( tmp != NULL )
    {
        tmp->data = data;
        tmp->next = NULL;
    }

    return tmp;
}

//adds node at the end
int addNodeAtEnd(node **head, node *nodeToInsert )
{
    int success = nodeToInsert != NULL;

    if ( success )
    {
        while ( *head != NULL ) head = &( *head )->next;

        *head = nodeToInsert;
    }

    return success;
}

And in main the function is called like

addNodeAtEnd( &head, createNewNode(1));

Though it would be much better to declare and define the function the following way

//adds node at the end
int addNodeAtEnd(node **head, int data )
{
    node *nodeToInsert = createNewNode( data );

    int success = nodeToInsert != NULL;

    if ( success )
    {
        while ( *head != NULL ) head = &( *head )->next;

        *head = nodeToInsert;
    }

    return success;
}

And call it like

addNodeAtEnd( &head, 1 );