Re: [XEN PATCH v2 09/13] xen/public: fix violations of MISRA C:2012 Rule 7.2

[Jan Beulich <jbeulich@xxxxxxxx>]

On 05.07.2023 17:33, Juergen Gross wrote:
> On 05.07.23 17:26, Simone Ballarin wrote:
>> From: Gianluca Luparini <gianluca.luparini@xxxxxxxxxxx>
>>
>> The xen sources contains violations of MISRA C:2012 Rule 7.2 whose
>> headline states:
>> "A 'u' or 'U' suffix shall be applied to all integer constants
>> that are represented in an unsigned type".
>>
>> Add the 'U' suffix to integers literals with unsigned type and also to other
>> literals used in the same contexts or near violations, when their positive
>> nature is immediately clear. The latter changes are done for the sake of
>> uniformity.
>>
>> Signed-off-by: Simone Ballarin <simone.ballarin@xxxxxxxxxxx>
>> Signed-off-by: Gianluca Luparini <gianluca.luparini@xxxxxxxxxxx>
>> ---
>> Changes in v2:
>> - minor change to commit title
>> - change commit message
>> - correct macros code style
>> ---
>>   xen/include/public/io/ring.h | 10 +++++-----
>>   1 file changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/xen/include/public/io/ring.h b/xen/include/public/io/ring.h
>> index 025939278b..0cae4367be 100644
>> --- a/xen/include/public/io/ring.h
>> +++ b/xen/include/public/io/ring.h
>> @@ -36,11 +36,11 @@
>>   typedef unsigned int RING_IDX;
>>   
>>   /* Round a 32-bit unsigned constant down to the nearest power of two. */
>> -#define __RD2(_x)  (((_x) & 0x00000002) ? 0x2                  : ((_x) & 
>> 0x1))
>> -#define __RD4(_x)  (((_x) & 0x0000000c) ? __RD2((_x)>>2)<<2    : __RD2(_x))
>> -#define __RD8(_x)  (((_x) & 0x000000f0) ? __RD4((_x)>>4)<<4    : __RD4(_x))
>> -#define __RD16(_x) (((_x) & 0x0000ff00) ? __RD8((_x)>>8)<<8    : __RD8(_x))
>> -#define __RD32(_x) (((_x) & 0xffff0000) ? __RD16((_x)>>16)<<16 : __RD16(_x))
>> +#define __RD2(x)  (((x) & 0x00000002U) ? 0x2                     : ((x) & 
>> 0x1))
> 
> Shouldn't this be rather:
> 
> +#define __RD2(x)  (((x) & 0x00000002U) ? 0x2U                   : ((x) & 
> 0x1U))

I don't think it matters much (as the comment says, the input is expected
to be unsigned anyway), and I expect even the one U that was added here
was only added for consistency. The sole one that really matter is imo ...

>> +#define __RD4(x)  (((x) & 0x0000000cU) ? __RD2((x) >> 2) << 2    : __RD2(x))
>> +#define __RD8(x)  (((x) & 0x000000f0U) ? __RD4((x) >> 4) << 4    : __RD4(x))
>> +#define __RD16(x) (((x) & 0x0000ff00U) ? __RD8((x) >> 8) << 8    : __RD8(x))
>> +#define __RD32(x) (((x) & 0xffff0000U) ? __RD16((x) >> 16) << 16 : 
>> __RD16(x))

... this single one.

Jan