如何使用 C 中的指针访问结构成员？

Question

I am practicing with linklist in C . My objective is that I want to delete a node using a function outside of main.
My plan to accomplish this objective is to access the next pointer without clearing/deleting/freeing the head pointer, but I get an error:

"[Error] request for member 'nextptr' in something not a structure or union"

The code:

void del(struct node **head) {
    struct node *temp = *head;
    //this is what I believe is wrong, i need to access nextptr of head
    *head->nextptr = temp->nextptr->nextptr;
    free(temp->nextptr);
    temp->nextptr = NULL;

Answer 1

Postfix operators like -> have higher precedence than unary * , so *head->nextptr is parsed as *(head->nextptr) - you're trying to apply the -> operator to head (not *head ), which is a pointer to a pointer to a struct type, hence the error.

To fix it, you need to explicitly dereference head before applying the -> operator, so you need to write it as (*head)->nextptr .