rev dyn arr

#include <stdio.h>
#include <stdlib.h>
#define STEP 256

void checkAlloc(void *p) {
  if (p == NULL) {
    perror(NULL);
    exit(-1);
  }
}

typedef struct {
  int len, mem, *at;
} DynArr;

void addToArr(DynArr *arr, int x) {
  if (arr->len == arr->mem) {
    arr->mem += STEP;
    arr->at = realloc(arr->at, sizeof(int) * arr->mem);
  }
  arr->at[arr->len++] = x;
}

void revArr(DynArr *arr) {
  int len = arr->len;
  for (int i = 0; i < len / 2; i++) {
    int aux = arr->at[i];
    arr->at[i] = arr->at[len - i - 1];
    arr->at[len - i - 1] = aux;
  }
}

void printArr(const DynArr *const arr) {
  for (int i = 0; i < arr->len; i++) {
    printf("%d ", arr->at[i]);
  }
  puts("");
}

int main(void) {
  DynArr arr = {0, 0, NULL};
  for (int x; scanf("%d", &x) && x;) {
    addToArr(&arr, x);
  }
  revArr(&arr);
  printArr(&arr);
  free(arr.at);
  return 0;
}