CODEWITHSUNDEEP
cmemorylinked-list
Clayton D
Clayton D

Reputation: 37

Deleting the first node in a linked list

I am trying to delete the first node in my linked list and I'm not sure how to go about it. My linked list looks like this

typedef struct availableForRent{
   int milage;
   char plateNum[8];
   struct availableForRent * next;
} availablreForRent;

The initial node of my linked list is hard coded exactly like this

struct availableForRent * head = NULL;
head = malloc(sizeof(struct availableForRent));
head->milage = 190000;
fillString(head->plateNum);
head->next = NULL;

fillString just gets a user input and places it in an array

I add a member to my list through a push function like this

void pushAvailable(struct availableForRent * head) {
   struct availableForRent * current = head;
   while (current->next != NULL) {
      current = current->next;
   }

   current->next = malloc(sizeof(struct availableForRent));
   printf("Enter a milage amount: ");
   scanf("%d", &current->next->milage);
   fillString(current->next->plateNum);
   current->next->next = NULL;
}

and my function to remove the first member looks like this

struct availableForRent * next_node = *head;

if (next_node->next == NULL) {
   printf("Cannot remove member as it is the only data in the list!\n");
   return;
}

next_node = next_node->next;
free(*head);
*head = next_node;

When I run my program I get this error message,

rentalQ1(2799,0x7fff9d09b380) malloc: *** error for object 0x7ffee8f62a08: pointer being freed was not allocated
*** set a breakpoint in malloc_error_break to debug
Abort trap: 6

Does this mean that the node I am trying to free doesn't exist or something else?

Upvotes: 0

Views: 63

Answers (1)

Clayton D
Clayton D

Reputation: 37

It appears that not mallocing the next_node was my problem. 

next_node = malloc(sizeof(struct availableForRent));

Upvotes: 0

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