linux-kernel - Re: [PATCH 4/9v2] usb: host: ehci.h: fix single statement macros

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Message-ID: <CAGG-pUSrbuT0Kh7k16ZZR5_3ibekHCgSAGLhVnjkvOrQHY5BCg@mail.gmail.com>
Date:	Thu, 10 Dec 2015 11:56:35 -0300
From:	"Geyslan G. Bem" <geyslan@...il.com>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Cc:	Peter Senna Tschudin <peter.senna@...il.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-usb@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/9v2] usb: host: ehci.h: fix single statement macros

2015-12-10 11:44 GMT-03:00 Sergei Shtylyov <sergei.shtylyov@...entembedded.com>:
> On 12/10/2015 04:05 PM, Geyslan G. Bem wrote:
>
>>>>> Don't use the 'do {} while (0)' wrapper in a single statement macro.
>>>>>
>>>>> Caught by checkpatch: "WARNING: Single statement macros should not
>>>>> use a do {} while (0) loop"
>>>>>
>>>>> Signed-off-by: Geyslan G. Bem <geyslan@...il.com>
>>>>> ---
>>>>>    drivers/usb/host/ehci.h | 4 ++--
>>>>>    1 file changed, 2 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h
>>>>> index cfeebd8..945000a 100644
>>>>> --- a/drivers/usb/host/ehci.h
>>>>> +++ b/drivers/usb/host/ehci.h
>>>>> @@ -244,9 +244,9 @@ struct ehci_hcd {                   /* one per
>>>>> controller */
>>>>>          /* irq statistics */
>>>>>    #ifdef EHCI_STATS
>>>>>          struct ehci_stats       stats;
>>>>> -#      define COUNT(x) do { (x)++; } while (0)
>>>>> +#      define COUNT(x) ((x)++)
>>>>>    #else
>>>>> -#      define COUNT(x) do {} while (0)
>>>>> +#      define COUNT(x) ((void) 0)
>>>>
>>>>
>>>>
>>>>     Why not just empty #define?
>>>
>>>
>>> Indeed. I'll change it.
>>> Tks Sergei.
>>
>>
>> Since COUNT is not used to return the empty #define is ok. Another way
>> is to use #define COUNT(x) (0) to get a 0 when necessary to read
>> returns.
>
>
>    Just 0, no parens please.
Ok, no parens, since there's no evaluation.

Then my change is:

-#      define COUNT(x) do { (x)++; } while (0)
+#      define COUNT(x) (++(x))
 #else
-#      define COUNT(x) do {} while (0)
+#      define COUNT(x) 0

Pre-increment allowing to return the updated x.

>
> MBR, Sergei
>



-- 
Regards,

Geyslan G. Bem
hackingbits.com
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