Not able to push when implementing linked list in C - c

Question

here's part of my code for the linked list:
struct node {
float data;
int key;
struct node* next;
};
typedef struct{
struct node *head;
struct node *current;
int length;
} linked_list;
linked_list *init_list(){
linked_list *out = malloc(sizeof(linked_list));
struct node *head = NULL;
struct node *current = NULL;
out->head = head;
out->current = current;
out->length = 0;
return out;
}
void push_core(struct node *head, int key, float data){
struct node *link = malloc(sizeof(struct node));
link->data = data;
link->key = key;
link->next = head;
// readjust to point at the new first node
head = link;
printf("%f; ", head->data);
}
void push(linked_list *list, int key, float data){
push_core(list->head, key, data);
list->length ++;
}
void print_list_core(struct node *head){
struct node* ptr = head;
printf("\n[");
while(ptr != NULL){
printf("(%d,%f)", ptr->key, ptr->data);
ptr = ptr->next;
}
}
void print_list(linked_list *list){
print_list_core(list->head);
}
But in the main, after I initialized the linked list structure, I wasn't able to use push() to link new pointers, why is that?
linked_list *S = init_list();
for (int i = 0; i < n; i++)
{
push(S,i,0);
print_list(S);
printf("%d;", S->length);
}
To clarify, the length of the list does update correctly. But when I try to print the list it doesn't work. Also, it's interesting that in another file when I initially just worked with the node struct and defined global variables for head and current, the code works fine. But when I try to wrap them up inside this linked_list struct, things aren't quite working as expected.

Answer 1

The problem occurred because you passed the pointer value of list->head to your push_code function as a parameter. This is a function call-by-value. So, when you change the head pointer inside the push_core function, it actually do not change the list->head pointer that you are expecting to. One quick fix would be returning the newly created link pointer from the push_core function and save it as list->head. The following code should fix your problem.
struct node * push_core(struct node *head, int key, float data){
struct node *link = malloc(sizeof(struct node));
link->data = data;
link->key = key;
link->next = head;
return link;
}
void push(linked_list *list, int key, float data){
list->head = push_core(list->head, key, data);
list->length ++;
}