bufdemo.c

8：bufdemo.c
这个函数是要让我们输入一个字符串，放入长度为4的数组中，然后再将数组里面的数据挨个输出，但如果输入的字符串长度超过4，那么就会发生错误。
代码为：

#include <stdio.h>
#include <stdlib.h>

char *gets(char *dest)
{
  int c = getchar();
  char *p = dest;
  while (c != EOF && c != '\n') {
    *p++ = c;
    c = getchar();
  }
  *p = '\0';
  return dest;
}

/* Read input line and write it back */
void echo()
{
    char buf[4];  /* Way too small! */
    gets(buf);
    puts(buf);
}

void call_echo() 
{
    echo();
}

/*void smash() 
{
    printf("I've been smashed!\n");
    exit(0);
}
*/

int main()
{
    printf("Type a string:");
    call_echo();
    return 0;
}

/*gcc -S bufdemo.c的时候会有警告
bufdemo.c: In function ‘echo’:
bufdemo.c:22:5: warning: ‘gets’ is deprecated (declared at /usr/include/stdio.h:638) [-Wdeprecated-declarations]
     gets(buf);
     ^
	 
运行结果：
 ***@ubuntu:/mnt/hgfs/share/csapp_code$ ./a.out
Type a string:0123
0123
***@ubuntu:/mnt/hgfs/share/csapp_code$ ./a.out
Type a string:012345
012345
*** stack smashing detected ***: ./a.out terminated
已放弃 (核心已转储)