Непонятное поведение указателя

static uint32_t * std_calculate(int16_t * data_buffer, uint16_t size)
{
  uint16_t buffer_size = size + STD_WINDOW_APERTURE - 1;
  uint8_t extender_size = (STD_WINDOW_APERTURE - 1) >> 1;
 
 
  int16_t * extended_buffer = (int16_t*)malloc(buffer_size * sizeof(int16_t));
  uint32_t * std_buffer = (uint32_t *)malloc(size * sizeof(uint32_t));
 
  for(uint16_t i = 0, j = 0; i < size; j++)
  {
    if(j < extender_size)
    {
      extended_buffer[j] = data_buffer[0];
      extended_buffer[buffer_size - j - 1] = data_buffer[size -1];
    }
    else
    {
      extended_buffer[j] = data_buffer[i];
      i++;
    }
  }
 
 
  //for(uint16_t iterator = 0; iterator < 1; iterator++)
    //extended_buffer[iterator] = extended_buffer[iterator];
 
  uint32_t sum1, sum2 = 0;
 
  for(uint16_t j = 0; j < size; j++)
  {
    if (!j)
    {
      for(uint16_t i = 0; i < STD_WINDOW_APERTURE; i++)
      {
        sum1 += extended_buffer[i] * extended_buffer[i];
        sum2 += extended_buffer[i];
      }
    }
    else
    {
      sum1 = sum1 - extended_buffer[j - 1] * extended_buffer[j - 1] +
      extended_buffer[j + STD_WINDOW_APERTURE - 1] * extended_buffer[j + STD_WINDOW_APERTURE - 1];
 
      sum2 = sum2 - extended_buffer[j - 1] + extended_buffer[j + STD_WINDOW_APERTURE - 1];
    }
    std_buffer[j] = (uint32_t)(sum1 - (sum2 * sum2)/STD_WINDOW_APERTURE)/STD_WINDOW_APERTURE;
    // std_buffer[j] = 0;
  }
  free(extended_buffer);
  return std_buffer;
}