[HELP]Problem with exit(0) and _exit(0) on RHEL x86

["Li Xiaodong" <lixd@cn.fujitsu.com>]

I thought the effects of exit(0) and _exit(0) should be different.

----
int main(void)
{
        int var = 0;
        pid_t pid;

        printf("before vfork\n");
        if ( (pid = vfork()) < 0 )
                printf("error\n");
        else if ( pid == 0 )
        {
                var++;
                exit(0);  /* Clear parent's IO */
        }

        printf("%d\n",var);
        return 0;
}

----

int main(void)
{
        int var = 0;
        pid_t pid;

        printf("before vfork\n");
        if ( (pid = vfork()) < 0 )
                printf("error\n");
        else if ( pid == 0 )
        {
                var++;
                _exit(0);  /* Do not clear parent's IO */
        }

        printf("%d\n",var);
        return 0;
}

----

But the actual results on RHEL5 x86 were beyond my ken. The outputs of the
above two are the same. 

$./a.out
before vfork
1

Could anyone help me with this? Thanks.