Re: [Xen-devel] [PATCH] fix uninitialized variable error in do_poll()

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Oct 05, 2018 at 04:12:10AM -0600, Jan Beulich wrote:
> Now that CONFIG_HVM can (and should) be turned off for the shim, gcc 8.2
> apparently is no longer sure that "port" is indeed initialized at
> 
>     if ( sched_poll->nr_ports == 1 )
>         v->poll_evtchn = port;
> 
> It doesn't look to be impossible for the compiler to prove it is not,
> but we also can't rely on that to be the case. Add an initializer.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

TBH I fail to see how CONFIG_HVM would affect do_poll. Also there is
already build test with gcc 8.2 which never discovered the issue you
described.

The code in this patch is trivially correct, but I think the commit
message should be more straightforward.

Wei.

> 
> --- a/xen/common/schedule.c
> +++ b/xen/common/schedule.c
> @@ -1014,7 +1014,7 @@ static long do_poll(struct sched_poll *s
>  {
>      struct vcpu   *v = current;
>      struct domain *d = v->domain;
> -    evtchn_port_t  port;
> +    evtchn_port_t  port = 0;
>      long           rc;
>      unsigned int   i;
>  
> 
> 

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