C - How can I free dynamically allocated memory?

问题:

Have a look at this piece of codes, it's part of a linked list.

int main()

{
    List* head1 = NULL;

    insertFront(&head1, 1);
    insertFront(&head1, 2);

    print(head1);

    free(head1);

    return 0;
}

another function is:

void insertFront(List** head, int value)

{
    List* node = (List*)malloc(sizeof(List));
    node->data = value;
    node->next = NULL;

    node->next = *head;
    *head = node;

   //free(node); essentially I am not freeing node
}

My questions are:

1. Is my code going to cause memory leak problem?

2. Should I need to free the allocated memory (dynamically) for node (Which is inside a function)?

3. If I free head1, will the memory allocated for node also be freed? If yes, then how?

回答1:

You have a memory leak because you are only freeing the first node in the list. You don't want to free in the insertNode function otherwise you're immediately throwing away memory you just allocated.

At the end of your program, you need to traverse the list and free each element.

while (head1) {
    List *temp = head1;
    head1 = head1->next;
    free(temp);
}