Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755022AbbLJSEM (ORCPT ); Thu, 10 Dec 2015 13:04:12 -0500 Received: from mail-vk0-f42.google.com ([209.85.213.42]:36823 "EHLO mail-vk0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754946AbbLJSEI (ORCPT ); Thu, 10 Dec 2015 13:04:08 -0500 MIME-Version: 1.0 In-Reply-To: <5669BA99.3000909@cogentembedded.com> References: <1449700359-14262-1-git-send-email-geyslan@gmail.com> <1449700359-14262-4-git-send-email-geyslan@gmail.com> <5669680E.4070304@cogentembedded.com> <56698FB3.9030705@cogentembedded.com> <5669B5BB.6060608@cogentembedded.com> <5669BA99.3000909@cogentembedded.com> Date: Thu, 10 Dec 2015 15:04:07 -0300 Message-ID: Subject: Re: [PATCH 4/9v2] usb: host: ehci.h: fix single statement macros From: "Geyslan G. Bem" To: Sergei Shtylyov Cc: Peter Senna Tschudin , Alan Stern , Greg Kroah-Hartman , linux-usb@vger.kernel.org, LKML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2851 Lines: 104 2015-12-10 14:47 GMT-03:00 Sergei Shtylyov : > On 12/10/2015 08:40 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 >>>>>>>>> --- >>>>>>>>> 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? > > >> There's nothing wrong with post-increment. The pre one would be >> necessary if using return. > > > Maybe it was intended to return the old value? :-) > >>> >>> Anyway, this talk is quite pointless since the macro didn't return >>> any >>> value anyway. >> >> You're sure, there's no use anywhere of the return of that macro indeed. > > > *do* {} *while* (0) just couldn't return any value, it's not just a > compound statement which gcc indeed allows to be evaluated. Indeed. :-) v2 in the oven. > > >> Sending v2 soon. > > > MBR, Sergei > -- Regards, Geyslan G. Bem hackingbits.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/