Re: [PATCH v2] drbd: change one-bit bitfield to be an unsigned int

From: Martin Kepplinger
Date: Wed Jun 18 2014 - 01:51:05 EST


Am 2014-06-17 21:46, schrieb David Rientjes:
> On Tue, 17 Jun 2014, Martin Kepplinger wrote:
>
>> The one-bit bitfields are assigned true (1) or false (0) and checked
>> for them respectively. While it should work either way and -1 is true
>> as well it is more clear to see what's going on when using an unsigned int
>> because 1 doesn't silently become -1 behind the label true.
>>
>
> Nothing is silently becoming anything, I have no idea what you're trying
> to address. Is there something in drivers/block/drbd that needs this
> change?

nope.

>
>> Signed-off-by: Martin Kepplinger <martink@xxxxxxxxx>
>> ---
>> Thanks for looking at it. This is more of a question: Does this make sense
>> to you now? I can be mistaken. It just wasn't totally clear to me at first
>> sight and even though it should be, why not try to improve it.
>>
>
> There's no improvement here, you realize that the sign of one-bit
> bitfields are implementation defined, correct? On what implementation
> does this patch make a difference?
>
> If you are trying to convert these to unsigned for consistency, then just
> say so in the changelog and don't talk about silent changes or comparisons
> to true and false that obfuscate the fact that this is just a trivial
> cleanup that is based on the author's own preference rather than anything
> else.

learning learning learning. in this case, why sparse calls this dubious.
This would be more appropriate on kernelnewbies or the like, sorry.

>
>> sparse called it 'dubious' before the change.
>>
>> (built but untested)
>>
>> drivers/block/drbd/drbd_interval.h | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/block/drbd/drbd_interval.h b/drivers/block/drbd/drbd_interval.h
>> index f38fcb0..8d670e6 100644
>> --- a/drivers/block/drbd/drbd_interval.h
>> +++ b/drivers/block/drbd/drbd_interval.h
>> @@ -9,8 +9,8 @@ struct drbd_interval {
>> sector_t sector; /* start sector of the interval */
>> unsigned int size; /* size in bytes */
>> sector_t end; /* highest interval end in subtree */
>> - int local:1 /* local or remote request? */;
>> - int waiting:1;
>> + unsigned int local:1; /* local or remote request? */
>> + unsigned int waiting:1;
>> };
>>
>> static inline void drbd_clear_interval(struct drbd_interval *i)
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