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)