Re: [Qemu-devel] [PATCH 1/4] rtc: fix 12-hour mode

[Avi Kivity]

On 11/21/2011 08:00 PM, Paolo Bonzini wrote:
> Hours in 12-hour mode are in the 1-12 range, not 0-11.
>
> @@ -320,7 +324,8 @@ static void rtc_copy_date(RTCState *s)
>          s->cmos_data[RTC_HOURS] = rtc_to_bcd(s, tm->tm_hour);
>      } else {
>          /* 12 hour format */
> -        s->cmos_data[RTC_HOURS] = rtc_to_bcd(s, tm->tm_hour % 12);
> +        int h = (tm->tm_hour % 12) ? tm->tm_hour % 12 : 12;
> +        s->cmos_data[RTC_HOURS] = rtc_to_bcd(s, h);
>          if (tm->tm_hour >= 12)
>              s->cmos_data[RTC_HOURS] |= 0x80;
>      }

Nitpick, don't update patch on this account:

I dislike seeing int-to-bool conversion on anything that is not a
true/false or count value.  Things like if (has_some_property) or if
(!nr_items) read well and are easily understood.  But here, you're not
checking for "are there any tm_hours, if yes, use them, if not, use
12".  You're testing against the value 0 which has a special encoding in
12 hour mode.

The is usually manifested in

   if (!strcmp(a, b)) ...

strcmp() does not return a bool or a count, and in fact it reads exactly
the opposite of the intent: "if not string compare".  strcmp() returns
an enumeration, or perhaps a mapping of string trichotomy to integer
trichotomy.

Sorry about the pontification, back to the regularly scheduled
whitespace discussion.

-- 
error compiling committee.c: too many arguments to function