Input of integers' array of unknown size - c

Question

I'm trying to create an array of integers of an unknown size.
Every time I input a positive element I use realloc to increase the size of the array and store that element
The thing is that when I run this code, I get a run-time error after 2 iterations of the while of the function create1DArray, so it's probably due to a realloc failure.
Can anybody tell me what I did wrong and how to fix it?
Thanks in advance,
#include <stdio.h>
#include <stdlib.h>
void create1DArray(int** perArray, int* size);
int main()
{
int *perArray, size=0, i;
create1DArray(&perArray, &size );
for(i=0; i<size; i++)
printf("%d ",perArray[i]);
free(perArray);
return 0;
}
void create1DArray(int** perArray, int* size)
{
int flag=0, i=0, x;
*perArray=(int*)malloc(sizeof(int) );
if(*perArray==NULL)
{
printf("Allocation failed!");
exit(1);
}
while(!flag)
{
if( scanf("%d", &x)<1 || (x<0) )
{
printf("Invalid input!");
free(perArray);
exit(1);
}
if(!x)
{
if( !(*size) )
{
printf("The first element of the array must not be 0");
free(perArray);
exit(1);
}
flag++;
}
else
{
*perArray=(int*)realloc(*perArray, (++(*size))*sizeof(int) );
if(*perArray==NULL)
{
printf("Reallocation failed!");
free(perArray);
exit(1);
}
*perArray[i++]=x;
}
}
}

Answer 1

I think I see two problems (and M Oehm spotted one more):
1) Your handling of size is wrong (or at least strange). Normally you'll do something like:
*perArray=(int*)malloc(sizeof(int) );
*size = 1;
Perhaps even better - you should drop the malloc and just initialize the pointer in main to NULL. realloc works like malloc when called with NULL.
This would also allow you to call the function several times - something you current code doesn't allow.
2) There is a problem with your realloc
*perArray=(int*)realloc(perArray, (++(*size))*sizeof(int) );
^^^^
Should be *perArray
3) You need to dereference the pointer before indexing (noticed by M Oehm - thanks).
*perArray[i++]=x; ---> (*perArray)[i++]=x;

Answer 2

May not be exactly what you want, but take a look at how it can be done concisely (although doing realloc at each iteration is inefficient). It should be compiled with the flag std=c11.
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
int main()
{
int size = 0;
int input = 0;
int * perArray = NULL;
while(scanf("%d", &input) && input > 0)
{
++size;
perArray = (int *) realloc(perArray, sizeof(int) * (long unsigned) size);
assert(perArray);
perArray[size - 1] = input;
}
if(perArray)
{
for(int i = 0; i < size; ++i) printf("%d ", perArray[i]);
printf("\n");
free(perArray);
}
return 0;
}