C linked list incompatible pointer type

January 17, 2022

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

struct linked_list {
    int size;
    struct list_node *head;
};

void print_linked_list(struct linked_list *list){
    struct linked_list *current = list;

    while(current != NULL){
        printf("%d ", current->head->value);
        current = current->head->next;
    }
}

I have to define a function to print out a linked list, but I get an error message saying "incompatible pointer type". I know that the problem is in "current = current->head->next;" but how can I achieve that?

>Solution :

current is a struct linked_list*, but current->head->next is a struct list_node*.

struct linked_list and struct list_node are two different unrelatd structures in spite of their similarity.

You cannot assign pointers to different types, hence the error message incompatible pointer type.

You probably want this:

void print_linked_list(struct linked_list* list) {
  struct list_node* current = list->head;

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