linux-kernel - Re: [HELP]Problem with exit(0) and

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Message-id: <479530BF.10606@shaw.ca>
Date:	Mon, 21 Jan 2008 17:54:39 -0600
From:	Robert Hancock <hancockr@...w.ca>
To:	Li Xiaodong <lixd@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [HELP]Problem with exit(0) and _exit(0) on RHEL x86

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@...pamshaw.ca
Home Page: http://www.roberthancock.com/

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