Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754840AbbLJRrO (ORCPT ); Thu, 10 Dec 2015 12:47:14 -0500 Received: from mail-lf0-f43.google.com ([209.85.215.43]:33920 "EHLO mail-lf0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754603AbbLJRrJ (ORCPT ); Thu, 10 Dec 2015 12:47:09 -0500 Subject: Re: [PATCH 4/9v2] usb: host: ehci.h: fix single statement macros To: "Geyslan G. Bem" 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> Cc: Peter Senna Tschudin , Alan Stern , Greg Kroah-Hartman , linux-usb@vger.kernel.org, LKML From: Sergei Shtylyov Organization: Cogent Embedded Message-ID: <5669BA99.3000909@cogentembedded.com> Date: Thu, 10 Dec 2015 20:47:05 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2552 Lines: 77 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. > Sending v2 soon. MBR, Sergei -- 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/