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

Sergei Shtylyov
2015-12-10T17:26:27Z

On 12/10/2015 05:56 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@gmail.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.

It's because the literals don't need parens at all.

> 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.

Why if there was a post-increment before?

Anyway, this talk is quite pointless since the macro didn't return any
value anyway.

MBR, Sergei