#include <stdio.h>

static int stack_direction = 0;

static void FindStackDirection()
{
  static char *addr = NULL;
  auto char dummy;
  if (NULL == addr) {
    addr = &dummy;
    FindStackDirection();  //遞歸調用，讓dummy兩次被定義，并一先一后入棧
  } else {
    if (&dummy > addr) {  //兩次地址相比較，后入棧的dummy地址大于先前的地址則說明是往高地址增長
      stack_direction = 1;
    } else {
      stack_direction = -1;
    }
  }
}

int main(int argc, char const *argv[])
{
  FindStackDirection();
  if (1 == stack_direction) {
    puts("stack grew upward");
  } else {
    puts("stack grew downward");
  }

  return 0;
}