gettimeodday()函数问题？

源函数：
#include <time.h>
#include <stdio.h>
#include <sys/time.h>
int main( void)
{

struct tm *local;
struct timeval *tv1,*tv2;//这样不对吗？

time_t t;
t=time(NULL);
local=localtime(&t);
printf("local hour is: %d \n",local->tm_hour);
local=gmtime(&t);
printf("utc hour is: %d \n",local->tm_hour);
printf("time is %s \n",asctime (local));
printf("time is %s \n",ctime(&t));
gettimeofday(tv1,NULL);
printf("interval time is %ld \n",tv1->tv_sec);
sleep(10);
gettimeofday(tv2,NULL);
printf("interval time is %ld \n",tv2->tv_sec);
return 0;
}
第一次运行：
local hour is: 9
utc hour is: 1
time is Fri Jun 8 01:20:53 2012

time is Fri Jun 8 09:20:53 2012

interval time is 430687105
interval time is 1547644
第二次运行：
local hour is: 9
utc hour is: 1
time is Fri Jun 8 01:20:53 2012

time is Fri Jun 8 09:20:53 2012

interval time is 430687105
interval time is 1547644
为什么，两次运行的结果一样呢？
并且这个结果好像不对把？
我把
struct timeval *tv1,*tv2;改为struct timeval tv1,tv2;
后
运行
#include <time.h>
#include <stdio.h>
#include <sys/time.h>
int main( void)
{

struct tm *local;
struct timeval tv1,tv2;

time_t t;
t=time(NULL);
local=localtime(&t);
printf("local hour is: %d \n",local->tm_hour);
local=gmtime(&t);
printf("utc hour is: %d \n",local->tm_hour);
printf("time is %s \n",asctime (local));
printf("time is %s \n",ctime(&t));
gettimeofday(&tv1,NULL);
printf("interval time is %ld \n",tv1.tv_sec);
sleep(10);
gettimeofday(&tv2,NULL);
printf("interval time is %ld \n",tv2.tv_sec);
return 0;
}
运行：
local hour is: 9
utc hour is: 1
time is Fri Jun 8 01:39:43 2012

time is Fri Jun 8 09:39:43 2012

interval time is 1339119583
interval time is 1339119593
这样貌似正确了，这是为什么啊？？
谢谢大家！！

[解决办法]
前面的程序是错的，后面的是正确的
[解决办法]
没内存啊,哥.

C语言和没学过一样,说实话.
[解决办法]
第一程序只给了指针地址，没有内存确保，就是两个野指针啊。
[解决办法]
前者，野指针，需要先分配内存