Is there a mistake in my insert at beginning(head) code in a doubly Linked List in C?-CodePudding

Please point out the mistake in the logic of my code(if any). It is a function attempting to insert an element at the beginning of a Doubly Linked List in C language.

struct DLL *insertAthead(struct DLL *head, int newData)
{
struct DLL *p = (struct DLL *)malloc(sizeof(struct DLL *));
p->prev = NULL;
p->next = head;
head->prev = p;
p->data = newData;
head = p;
return head;
}

CodePudding user response：

struct DLL *p = (struct DLL *)malloc(sizeof(struct DLL *));

should be:

struct DLL *p = malloc(sizeof(struct DLL));
                       ^^^^^^^^^^^^^^^^^^

Currently you are only allocating the size of a pointer (struct DLL *), rather than whatever size is needed for a struct DLL.

Note that some people prefer to write the above like this:

struct DLL *p = malloc(sizeof(*p));

which is arguably more robust.

Note that I've also removed the redundant cast, which is not a bug as such, but it's just unnecessary clutter and can in some cases be dangerous.