How to delete node in double-linked-list by C programming?

Question

struct someEvent
{
    int id;
    struct someEvent *prev;
    struct someEvent *next;
} * someEvent;

struct someEvent *someEventQueue = NULL;

int main(){

//There is some conditions. If passing all of conditions then It is inserted to someEventQueue.

struct someEvent **curr = &someEventQueue;

if ((*curr) != NULL)
{
    while ((*curr) != NULL)
    {
        //After some processes, I want to delete (*curr)

            if ((*curr)->prev == NULL && (*curr)->next == NULL)
            {
                //I don't know how to do this........................
            }
            if ((*curr)->prev != NULL)
            {
                (*curr)->next->prev = (*curr)->prev;
            }
            if ((*curr)->next != NULL)
            {
                (*curr)->prev->next = (*curr)->next;
            }
    
        curr = &(*curr)->next;
    }
}
}

I want to delete node which is presenting in someEventQueue. someEventQueue is double-linked-list. I tried to make a deleting node code. But, I failed. I don't know why but it returns segmentation fault. How to solve this problem?

Please provide a minimal reproducible example. Also, deleting a node from a list is not a new problem. Try to see if there isn't any questions about this you can use to solve your problem. — klutt
– klutt, Commented Oct 13, 2020 at 14:16

DipStax · Accepted Answer · 2020-10-13 14:30:08Z

1

To simply delete a node you can do this:

// dnode is the node to delete
if ((*dnode)->prev != NULL) {      // checking if this is the first
    (*dnode)->prev->next = (*dnode)->next;
    if ((*dnode)->next != NULL) {  // checking if this is the last
        (*dnode)->next->prev = (*dnode)->prev;
    }
} else {                           // here the node is the first
    (*dnode) = (*dnode)->next;
    if ((*dnode) != NULL) {        // checking if he was the last
        (*dnode)->prev = NULL;
    }
}

Now your node is delete from the linked list, but take care to the positionnement of your cursor on the list and to free dnode.

edited Oct 13, 2020 at 14:30

answered Oct 13, 2020 at 14:23

DipStax

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