xDDD

#include <stdio.h>
#include <stdlib.h>

typedef struct {
    int size;
    int* arr;
} S;

int main(void) {
    S foo;
    int new_size = 5;
    foo.size = new_size;
    foo.arr = malloc(new_size * sizeof(int));

    free(foo.arr);
    return 0;
}