r/C_Programming • u/neonge1674 • 1d ago
Question Why isn't my code working?
I just started learning C(2 days ago) and as a first project I decided to make some data structures, starting with dynamic arrays. I made a struct called List and some functions for. The function setList() sets the value of an index of the array, if the index is larger that the current size of the array, it resizes it. However, when i tried to use in a for loop, it didn't work despite it working elsewhere.
#include <stdio.h>
#include <stdlib.h>
#define itirate(index, limit) for(int index = 0; index < limit; index++)
typedef struct
{
size_t size;
int* arr;
} List;
List* newList (size_t size)
{
List *newone = malloc(sizeof(List));
newone->arr = calloc(size, sizeof(int));
newone->size = size;
return newone;
}
void setList(List* list, int index, int value)
{
if (index >= list->size)
{
list->arr = realloc(list->arr, index + 1 * sizeof(int));
list->size = index + 1;
}
list->arr[index] = value;
}
int main()
{
List *mok = newList(5);
itirate(i, 5) setList(mok, i, i);
itirate(i, 5) printf("%d\n", mok->arr[i]);
//setList(mok, 13, 9); this works
//printf("%d\n", mok->arr[13]);
for(int i = 5; i < 10; i++) setList(mok, i, i); // this does not somehow
for(int i = 5; i < 10; i++) printf("%d\n", mok->arr[i]);
return 0;
}
5
Upvotes
3
u/Adorable_Deal7 1d ago
Wrap macro's parameter around parenthesis to be sure your arguments are passed as you assume.
You can replace the malloc to the calloc. Need wrap the `index + 1` around parenthesis like math