I am trying to add a node to the end of a singly linked list but am getting a segmentation fault (core dumped error)
void slist_add_back(struct slist *l, char *str) {
struct snode *temp;
do {
l->front = l->front->next;
l->counter++;
} while (l->front !=NULL);
l->counter++;
temp = (struct snode *)malloc(sizeof(struct snode));
l->back = l->front;
l->back->next = temp;
l->back = temp;
}
When you write:
do{
l->front = l->front->next;
l->counter++;
}while(l->front !=NULL);
At the end l->front is null. Now l->back = l->front; implies l->back is also null. So this assignment is wrong:
l->back->next = temp; // causing segfault
One of your problems lies here:
do
{
l->front = l->front->next;
l->counter++;
} while(l->front !=NULL);
You are modifying the list instead of iterating it. It should be something like this:
snode* curr = l->front;
if (curr == NULL) // first element
{
front = new snode(str);
return;
}
while (curr->next != NULL)
{
++curr;
}
curr->next = new snode(str); // or the malloc version if you want to stay in C
new.
I guess this is something what you want? I dont really understand what your code is doing, sorry.
void slist_add_back(struct slist *l, char *str)
{
struct snode *currentNode = l->front;
if(currentNode!=NULL)
{
struct snode *temp = (struct snode *)malloc(sizeof(struct snode));
while(currentNode->next!=NULL)
{
l->counter++;//although i dont know why
currentNode = currentNode->next;
}
l->counter++;//again
currentNode->next = temp;
l->back = temp;
temp->next = NULL;
}
}
Here's how your code roughly should look like:
void slist_add_back(struct slist *l, char *str)
{
struct snode *temp = malloc(sizeof(struct snode));
temp->next = NULL;
//note: store str... (strdup?)
if (! l->back) {
l->front = temp;
} else {
l->back->next = temp;
}
l->back = temp;
l->counter++;
}
Note: Based on your code I would be really surprised if the rest wouldn't be full of bugs, so except crashes even if this part is fixed...
Pick a debugger, and check what your code really does.
frontrepresent the front of your list? If so, you don't want to be changing it just because you're adding another element here.