linux-kernel - Re: [PATCH net-next] net: can: Fix compiling warning

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Message-ID: <20190807105042.GK1974@kadam>
Date:   Wed, 7 Aug 2019 13:50:42 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Oliver Hartkopp <socketcan@...tkopp.net>,
        Patrick Bellasi <patrick.bellasi@....com>,
        linux-sparse@...r.kernel.org
Cc:     Mao Wenan <maowenan@...wei.com>, davem@...emloft.net,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH net-next] net: can: Fix compiling warning

On Tue, Aug 06, 2019 at 06:41:44PM +0200, Oliver Hartkopp wrote:
> I compiled the code (the original version), but I do not get that "Should it
> be static?" warning:
> 
> user@box:~/net-next$ make C=1
>   CALL    scripts/checksyscalls.sh
>   CALL    scripts/atomic/check-atomics.sh
>   DESCEND  objtool
>   CHK     include/generated/compile.h
>   CHECK   net/can/af_can.c
> ./include/linux/sched.h:609:43: error: bad integer constant expression
> ./include/linux/sched.h:609:73: error: invalid named zero-width bitfield
> `value'
> ./include/linux/sched.h:610:43: error: bad integer constant expression
> ./include/linux/sched.h:610:67: error: invalid named zero-width bitfield
> `bucket_id'
>   CC [M]  net/can/af_can.o

The sched.h errors suppress Sparse warnings so it's broken/useless now.
The code looks like this:

include/linux/sched.h
   613  struct uclamp_se {
   614          unsigned int value              : bits_per(SCHED_CAPACITY_SCALE);
   615          unsigned int bucket_id          : bits_per(UCLAMP_BUCKETS);
   616          unsigned int active             : 1;
   617          unsigned int user_defined       : 1;
   618  };

bits_per() is zero and Sparse doesn't like zero sized bitfields.

regards,
dan carpenter