linux-kernel - Re: [PATCH] powerpc/mm/radix: add missing braces for single statement block

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Date:   Mon, 23 Apr 2018 21:34:03 +0200
From:   Mathieu Malaterre <malat@...ian.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Joe Perches <joe@...ches.com>
Subject: Re: [PATCH] powerpc/mm/radix: add missing braces for single statement block

On Mon, Apr 23, 2018 at 9:31 PM, Mathieu Malaterre <malat@...ian.org> wrote:
> On Sun, Apr 8, 2018 at 10:34 PM, Randy Dunlap <rdunlap@...radead.org> wrote:
>> On 04/08/2018 12:44 PM, Mathieu Malaterre wrote:
>>> In commit 7a22d6321c3d ("powerpc/mm/radix: Update command line parsing for
>>> disable_radix") an `if` statement was added for a possible empty body
>>> (prom_debug).
>>>
>>> Fix the following warning, treated as error with W=1:
>>>
>>>   arch/powerpc/kernel/prom_init.c:656:46: error: suggest braces around empty body in an ‘if’ statement [-Werror=empty-body]
>>>
>>> Signed-off-by: Mathieu Malaterre <malat@...ian.org>
>>> ---
>>>  arch/powerpc/kernel/prom_init.c | 3 ++-
>>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
>>> index 5ae153b97d0a..f0e802495530 100644
>>> --- a/arch/powerpc/kernel/prom_init.c
>>> +++ b/arch/powerpc/kernel/prom_init.c
>>> @@ -652,8 +652,9 @@ static void __init early_cmdline_parse(void)
>>>               } else
>>>                       prom_radix_disable = true;
>>>       }
>>> -     if (prom_radix_disable)
>>> +     if (prom_radix_disable) {
>>>               prom_debug("Radix disabled from cmdline\n");
>>
>> Looks like the macro for #prom_debug() should be fixed instead.
>
> Well if I try instead:
>
> @@ -101,9 +101,9 @@ int of_workarounds;
>  } while (0)
>
>  #ifdef DEBUG_PROM
> -#define prom_debug(x...) prom_printf(x)
> +#define prom_debug(x...) do { prom_printf(x); } while (0)
>  #else
> -#define prom_debug(x...)
> +#define prom_debug(x...) do { } while (0)
>  #endif
>
>
> the checkpatch script returns:
>
> WARNING: Single statement macros should not use a do {} while (0) loop
> #33: FILE: arch/powerpc/kernel/prom_init.c:104:
> +#define prom_debug(x...) do { prom_printf(x); } while (0)
>
>
> So I suspect we cannot do much better than my original patch unfortunately.

Right, it seems I cannot read the correct line number for a warning.
An updated patch is coming.

>>> +     }
>>>  }
>>>
>>>  #if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_PPC_POWERNV)
>>>
>>
>>
>> --
>> ~Randy