XCode 下编译简单C程序产生了一个怎么也想不通的问题

#include <stdio.h>
unsigned char fun(int);
int main()
{
    unsigned char a;
    a =fun(1);
    printf("2nd returned:%d\n",a);
    return 0;
}
unsigned char fun(int s)
{
    unsigned char t;
    switch(s)
    {
        case 1:printf("1st the value is:%d\n",t); return t;

        case 2:printf("???\n"); return t;
    }
    
    return 0;
}


在我的XCode 3.0 (MAC 10.5.8)中新建一个"Standard Tool" of "Command Line Utility"工程, 将如上文件内容替换掉main.c,运行程序看到的结果为:


[Session started at 2009-11-25 16:34:56 +0800.]
1st the value is:1
2nd returned:0

The Debugger has exited with status 0.

但是用gcc单独编译,打印的结果是:

1st the value is:143
2nd returned:143


t自然是一个随机值.

暂时还没有搞明白是怎么回事.