c why realloc isn't working - c

Question

I have the following code
void getPariceArray(Board board, treeNode *tn, Position *dst, int **prices, int *counter, int total)
{
if (tn == NULL)
return NULL;
if (tn->position[0] == dst[0][0] && tn->position[1] == dst[0][1])
{
prices = (int **)realloc(prices, sizeof(prices) *4);
prices[*counter] = (int *)malloc(sizeof(int));
printf("%d", sizeof(prices));
*prices[*counter] = total;
*counter = *counter + 1;
}
int x = tn->position[1] - '1';
int y = tn->position[0] - 'A';
int cellPrice = board[x][y] - '0';
total += cellPrice;
getPariceArray(board, tn->up, dst, prices, counter, total);
getPariceArray(board, tn->down, dst, prices, counter, total);
getPariceArray(board, tn->right, dst, prices, counter, total);
getPariceArray(board, tn->left, dst, prices, counter, total);
}
prices is array of pointers and every step in recursion I'm casting realloc to increase the prices size.
I got many error bugs and I had a feeling it related to allocation,
I printed the sizeof(prices) and I saw that it stayed 4 and not increase
Can someone please tell me where I went wrong?
thanks in advance
P.S
Edit
I have another function that princt the **prices
void printPricesArray(int **arr, int length)
{
for (int i = 0; i < length; i++)
{
printf("place:%d Price:%d\n", i, *arr[i]);
}
}
This is the error I'm getting when prices = realloc(prices, sizeof(prices) *4);
but when I'm changing the line to this prices = realloc(prices, sizeof(prices) * 150); everything goes well without errors because I know that in my example size isn't going passed 130, but I need dynamic increasing incase in different example size will be over 150.

Answer 1

I suppose that during code writing and correcting (compiler) errors the code evolved into a wrong direction.
I feel that you actually do not want to handle an array of pointers to integers but a (dynamically growing) array of integer values (not pointers to them). Yet the circumstance, that the function has to rewrite the pointer to the array, which led to introduce one more '*' in the interface, took you into the dilemma, and statement prices[*counter] = (int *)malloc(sizeof(int)) indicates to me that this is the basic misunderstanding.
Let me explain what I mean it on the following short example.
Suppose that we want to have a function dynamicPriceListAlloc, which allocates an array of integers for nrOfItems integers.
Let's start with the caller, i.e. function main: Therein, as we want to have a dynamically allocated integer array, we will hold a variable of type int *, i.e. a pointer to this array. As we want to have the array allocated in a function, we have to pass a pointer to this pointer, because otherwise the function could not assign the newly allocated memory address to this pointer. Hence, dynamicPriceListAlloc must take a pointer to a pointer to ints, i.e. int **.
But - now the misleading thing - the intent of dynamicPriceListAlloc is not to allocate a pointer with 10 pointers to ints, but to allocate an array of 10 integers and assigning this memory block to the pointer passed (by reference) as argument:
int main(){
int *priceList;
dynamicPriceListAlloc(&priceList, 10);
for (int i=0; i<10; i++)
printf("%d\n", priceList[i]);
}
void dynamicPriceListAlloc(int **prices, int nrOfItems) {
*prices = (int*)malloc(nrOfItems * sizeof(int));
for (int i=0; i<nrOfItems; i++)
// *prices[i] = i; // Wrong: takes prices[i] and then dereferences it
(*prices)[i] = i; // OK: derefernces prices (yielding a pointer an int-array) and then setting the i'th element
}
I suppose that you missed to correct the dereference-precedence thing in *prices[i] = i, and instead of correcting this to (*prices)[i] = i, you "solved" the problem by actually allocating storage for the pointer you dereference. And that's what I meant with "the code evolved in the wrong direction".
If I am right with this assumption, then your code would change as follows:
void getPariceArray(Board board, treeNode *tn, Position *dst, int **prices, int *counter, int total)
{
if (tn == NULL)
return;
if (tn->position[0] == dst[0][0] && tn->position[1] == dst[0][1])
{
size_t sizeOfPrices = (*counter) * sizeof(int);
*prices = (int*)realloc(*prices, sizeOfPrices);
printf("size of prices: %ld", sizeOfPrices);
(*prices)[*counter] = total;
*counter = *counter + 1;
}
int x = tn->position[1] - '1';
int y = tn->position[0] - 'A';
int cellPrice = board[x][y] - '0';
total += cellPrice;
getPariceArray(board, tn->up, dst, prices, counter, total);
getPariceArray(board, tn->down, dst, prices, counter, total);
getPariceArray(board, tn->right, dst, prices, counter, total);
getPariceArray(board, tn->left, dst, prices, counter, total);
}
And printPricesArray would be adapted as follows:
void printPricesArray(int *arr, int length)
{
for (int i = 0; i < length; i++)
{
printf("place:%d Price:%d\n", i, arr[i]);
}
}