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

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Date:   Mon, 23 Apr 2018 21:31:34 +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 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.

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