Unexpect behaviour with pointer array - c

Question

im currently implementing a basic linked list structure on C.
Basically im parsing a txt file, and I buffer each line into a Node which contains a pointer to an array of integers. The problem is, that my data (the array of integers) doesn't save correctly / i don't know how to iterate through it correctly.
These are the structures that I use:
typedef struct Node
{
struct Node* next;
struct Node* prev;
int* data;
int len;
} Node;
typedef struct LinkedList
{
Node* head;
Node* tail;
} LinkedList;
and I use this method to create a new node from a buffered string:
int nodeManager(FILE* filePointer, char* buffer, char* token, LinkedList* linkedList)
{
token = strtok(buffer, DELIMITER);
int* data = (int*)malloc(sizeof(int));
int dataIndex = 0;
if (data == NULL)
{
fprintf(stderr, DATA_ALLOCATION_ERROR);
freeLinkedList(linkedList);
fclose(filePointer);
return EXIT_FAILURE;
}
const char* insertPosition = token;
while ((token = strtok(NULL, DELIMITER)))
{
data = realloc(data, dataIndex + 1);
if (data == NULL) {
fprintf(stderr, DATA_ALLOCATION_ERROR);
freeLinkedList(linkedList);
fclose(filePointer);
return EXIT_FAILURE;
}
char *res;
int num = (int) strtol(token, &res, 10);
data[dataIndex] = num;
dataIndex++;
}
Node* newNode = (Node*)malloc(sizeof(Node));
if (newNode == NULL)
{
freeLinkedList(linkedList);
free(data);
fclose(filePointer);
return EXIT_FAILURE;
}
newNode -> prev = NULL; newNode -> next = NULL;
newNode -> len = dataIndex; newNode -> data = data;
if(strcmp(insertPosition, INSERT_TO_START) == 0)
{
addToStartLinkedList(linkedList, newNode);
}
else
{
addToEndLinkedList(linkedList, newNode);
}
return EXIT_SUCCESS; // TODO - Change
}
A line of input looks like this:
start,1,2,3,4,5,6,7,10,22,44,55,66,66,77
for some reason, node -> data doesn't get all the values that I assign in this method and I can't really tell why.
I tried to print the values like this:
for (int i = 0; i < newNode -> len; i++)
{
printf("%d,", (newNode -> data)[i]);
}
However, as I said, something quite doesn't work with my assigment, or I just don't know how to access the values correctly.
Would love to get some insight - thanks.

Answer 1

This part is wrong:
data = realloc(data, dataIndex + 1);
You have forgotten to multiply with sizeof(int) or better sizeof *p
BTW: Be careful about doing realloc directly into data. On failure realloc may return NULL and then you have a memory leak. You should use a temporary pointer like:
int * temp = realloc(data, SOME_SIZE);
if (temp == NULL)
{
// oh dear, add error handling here - maybe a return or whatever fits
}
else
{
// All good
data = temp;
}
OT: Passing the file pointer to the function in order to be able to close the file is (IMO) a rather strange design. Instead, the caller should check the return value and close the file (if desired).