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Re: [PATCH-for-5.0 v2 10/11] hw/timer/pxa2xx_timer: Add assertion to sil


From: Alistair Francis
Subject: Re: [PATCH-for-5.0 v2 10/11] hw/timer/pxa2xx_timer: Add assertion to silent static analyzer warning
Date: Mon, 23 Mar 2020 08:55:08 -0700

On Sat, Mar 21, 2020 at 7:50 AM Philippe Mathieu-Daudé
<address@hidden> wrote:
>
> pxa2xx_timer_tick4() takes an opaque pointer, then calls
> pxa2xx_timer_update4(), so the static analyzer can not
> verify that the 'n < 8':
>
>   425 static void pxa2xx_timer_tick4(void *opaque)
>   426 {
>   427     PXA2xxTimer4 *t = (PXA2xxTimer4 *) opaque;
>   428     PXA2xxTimerInfo *i = (PXA2xxTimerInfo *) t->tm.info;
>   429
>   430     pxa2xx_timer_tick(&t->tm);
>   433     if (t->control & (1 << 6))
>   434         pxa2xx_timer_update4(i, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL), 
> t->tm.num - 4);
>
>   135 static void pxa2xx_timer_update4(void *opaque, uint64_t now_qemu, int n)
>   136 {
>   137     PXA2xxTimerInfo *s = (PXA2xxTimerInfo *) opaque;
>   140     static const int counters[8] = { 0, 0, 0, 0, 4, 4, 6, 6 };
>   142
>   143     if (s->tm4[n].control & (1 << 7))
>   144         counter = n;
>   145     else
>   146         counter = counters[n];
>
> Add an assert() to give the static analyzer a hint, this fixes a
> warning reported by Clang static code analyzer:
>
>     CC      hw/timer/pxa2xx_timer.o
>   hw/timer/pxa2xx_timer.c:146:17: warning: Assigned value is garbage or 
> undefined
>           counter = counters[n];
>                   ^ ~~~~~~~~~~~
>
> Reported-by: Clang Static Analyzer
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>

Reviewed-by: Alistair Francis <address@hidden>

Alistair

> ---
>  hw/timer/pxa2xx_timer.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/hw/timer/pxa2xx_timer.c b/hw/timer/pxa2xx_timer.c
> index cd172cc1e9..944c165889 100644
> --- a/hw/timer/pxa2xx_timer.c
> +++ b/hw/timer/pxa2xx_timer.c
> @@ -140,6 +140,7 @@ static void pxa2xx_timer_update4(void *opaque, uint64_t 
> now_qemu, int n)
>      static const int counters[8] = { 0, 0, 0, 0, 4, 4, 6, 6 };
>      int counter;
>
> +    assert(n < ARRAY_SIZE(counters));
>      if (s->tm4[n].control & (1 << 7))
>          counter = n;
>      else
> --
> 2.21.1
>
>



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