测试栈的增长方向的程序

static:
用在函数这一级，表示该函数只对本文件可见
用在函数内部，表示该变量的值在各个调用间一直保持延续性

#include <stdio.h>

int flag = 0;

void find_stack_direction(void)
{
        static char *addr = NULL;
        char dummy;

        if(addr == NULL){
                addr = &dummy;
                find_stack_direction();
        }
        else{
                (addr > &dummy) ? (flag = -1) : (flag = 1);
        }
}

int main(int argc, char **argv)
{
        find_stack_direction();
        if(flag == 1){
                printf("stack grew upward\n");
        }
        else{
                printf("stack grew downward\n");
        }

        return 0;
}