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

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

[Li Xiaodong]

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.

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

[Robert Hancock]

Li Xiaodong wrote:
> 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.

Why do you expect a different result? Also, calling exit from a vforked 
child is explicitly not allowed. The only things you can do are execve 
or _exit.

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/