netdev - Re: [PATCH] net/bonding: adjust codingstyle for bond

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Date:	Sat, 7 May 2011 12:35:17 -0700
From:	matt mooney <mfmooney@...il.com>
To:	Joe Perches <joe@...ches.com>
Cc:	aquini@...ux.com, kernel-janitors@...r.kernel.org,
	David Miller <davem@...emloft.net>,
	Jay Vosburgh <fubar@...ibm.com>,
	Andy Gospodarek <andy@...yhouse.net>, shemminger@...tta.com,
	netdev@...r.kernel.org, Nicolas Kaiser <nikai@...ai.net>
Subject: Re: [PATCH] net/bonding: adjust codingstyle for bond_3ad files

On Sat, May 7, 2011 at 11:02 AM, Joe Perches <joe@...ches.com> wrote:
> On Sat, 2011-05-07 at 14:31 -0300, Rafael Aquini wrote:
>> To exemplify my point, I'll taking that very  __ad_timer_to_ticks() as an example:
>> static u16 __ad_timer_to_ticks(u16 timer_type, u16 par)
>> {
>>         u16 retval = 0;
>>
>>         switch (timer_type) {
>>         case AD_CURRENT_WHILE_TIMER:    /* for rx machine usage */
>>                 if (par)
>>                         retval = (AD_SHORT_TIMEOUT_TIME*ad_ticks_per_sec);
>>                 else
>>                         retval = (AD_LONG_TIMEOUT_TIME*ad_ticks_per_sec);
>>                 break;
>>         case AD_ACTOR_CHURN_TIMER:      /* for local churn machine */
>>                 retval = (AD_CHURN_DETECTION_TIME*ad_ticks_per_sec);
>>                 break;
>>         case AD_PERIODIC_TIMER:         /* for periodic machine */
>>                 retval = (par*ad_ticks_per_sec);
>>                 break;
>>         case AD_PARTNER_CHURN_TIMER:    /* for remote churn machine */
>>                 retval = (AD_CHURN_DETECTION_TIME*ad_ticks_per_sec);
>>                 break;
>>         case AD_WAIT_WHILE_TIMER:       /* for selection machine */
>>                 retval = (AD_AGGREGATE_WAIT_TIME*ad_ticks_per_sec);
>>                 break;
>>         }
>>         return retval;
>> }
>>
>> If, for some unknown reason timer_type receives an 'alien' value, and
>> we were
>> using retval uninitialized, this function, as it is, would return an
>> unpredictable value to its caller. Unless we have the switch block
>> re-factored, we cannot leave retval uninitialized. So, it's not just a
>> matter of leaving the variable uninitialized, or initialize it just to
>> get rid of a compiler warning. That's why those comments are not
>> helpful anyway.
>
> I'd write this not using a retval variable at all as:

But isn't the preferred style to have a single exit point?

>        switch (timer_type) {
>        case AD_CURRENT_WHILE_TIMER:    /* for rx machine usage */
>                if (par)
>                        return AD_SHORT_TIMEOUT_TIME * ad_ticks_per_sec;
>                return AD_LONG_TIMEOUT_TIME * ad_ticks_per_sec;
>        case AD_ACTOR_CHURN_TIMER:      /* for local churn machine */
>                return AD_CHURN_DETECTION_TIME * ad_ticks_per_sec;
>        ...
>        }
>        WARN(1, "Invalid timer type: %u\n", timer_type)
>        return 0;
> }
>
>
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