linux-kernel - Re: [PATCH 2/2] mdadm.c: fix compile error "switch condition has boolean value"

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Message-ID: <1f82bdbf-6b69-ce77-d989-6f375a9ff61b@gmail.com>
Date:   Thu, 30 Mar 2017 11:53:54 -0400
From:   Jes Sorensen <jes.sorensen@...il.com>
To:     Gioh Kim <gi-oh.kim@...fitbricks.com>, NeilBrown <neilb@...e.com>
Cc:     linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
        Wol <anthony@...ngman.org.uk>
Subject: Re: [PATCH 2/2] mdadm.c: fix compile error "switch condition has
 boolean value"

On 03/30/2017 03:52 AM, Gioh Kim wrote:
> On Thu, Mar 30, 2017 at 08:38:35AM +1100, NeilBrown wrote:
>> On Thu, Mar 30 2017, jes.sorensen@...il.com wrote:
>>
>>> Gioh Kim <gi-oh.kim@...fitbricks.com> writes:
>>>> Remove a boolean expression in switch condition
>>>> to prevent compile error of some compilers.
>>>
>>> Please be specific, which compile is unable to handle this?
>>>
>>>> Signed-off-by: Gioh Kim <gi-oh.kim@...fitbricks.com>
>>>> ---
>>>>  mdadm.c | 6 +++---
>>>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/mdadm.c b/mdadm.c
>>>> index 08ddcab..a98a051 100644
>>>> --- a/mdadm.c
>>>> +++ b/mdadm.c
>>>> @@ -1905,11 +1905,11 @@ static int misc_list(struct mddev_dev *devlist,
>>>>  			rv |= SetAction(dv->devname, c->action);
>>>>  			continue;
>>>>  		}
>>>> -		switch(dv->devname[0] == '/') {
>>>> -			case 0:
>>>> +		switch(dv->devname[0]) {
>>>> +			default:
>>>>  				mdfd = open_dev(dv->devname);
>>>>  				if (mdfd >= 0) break;
>>>> -			case 1:
>>>> +			case '/':
>>>>  				mdfd = open_mddev(dv->devname, 1);
>>>>  		}
>>>>  		if (mdfd>=0) {
>>>
>>> While I agree the original code is ugly, I am not convinced your
>>> replacement is a lot prettier.
>>>
>>
>> Maybe
>>
>> 		if (dv->devname[0] == '/' ||
>> 		    (mdfd = open_dev(dv->devname)) < 0)
>> 				mdfd = open_mddev(dv->devname, 1);
>>
>> ??
>> NeilBrown
>
> Yes, the initial version I thought was:
>
> if (dev->devname[0] != '/')
>     mdfd = open_dev(dv->devname);
> if (dev->devname[0] == '/' || mdfd < 0)
>     mdfd = open_mddev(dv->devname, 1);
>
> But I thought you have a reason to use switch-case expression,
> so I kept switch-case.
> If you agree, I'll send v2 patch using if-expression.
>

I like this solution better, I much favor code that is more explicit in 
what it does. Request less brain capacity for me to read :)

Cheers,
Jes