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Date: Wed, 11 Jun 2014 16:11:46 +0300
From: Dan Carpenter <dan.carpenter@oracle.com>
To: Jeff Layton <jlayton@poochiereds.net>
Cc: linux-kernel@vger.kernel.org, linux-sparse@vger.kernel.org,
        Jeff Layton <jlayton@primarydata.com>
Subject: Re: [PATCH][RFC] err.h: silence sparse warning: dereference of
 noderef expression
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On Wed, Jun 11, 2014 at 07:06:32AM -0400, Jeff Layton wrote:
> $ rpm -q sparse
> sparse-0.5.0-1.fc20.x86_64
>
> I see it all over the tree, but an easy example is fs/locks.c:
> 
> $ make fs/locks.o C=1
> make[1]: Nothing to be done for `all'.
> make[1]: Nothing to be done for `relocs'.
>   CHK     include/config/kernel.release
>   CHK     include/generated/uapi/linux/version.h
>   CHK     include/generated/utsrelease.h
>   CALL    scripts/checksyscalls.sh
>   CHECK   fs/locks.c
> include/linux/err.h:35:16: warning: dereference of noderef expression
> include/linux/err.h:30:23: warning: dereference of noderef expression
> include/linux/err.h:35:16: warning: dereference of noderef expression
> include/linux/err.h:30:23: warning: dereference of noderef expression
>   CC      fs/locks.o
> 
> It has two IS_ERR calls and two PTR_ERR calls, and each generates the
> warning.
>

I downloaded the Fedora SRPM and built the binary but I still wasn't
able to reproduce the bug.

dcarpenter@speke:~/progs/kernel/devel$ /tmp/sparse/sparse-0.5.0/sparse --version
0.5.0
dcarpenter@speke:~/progs/kernel/devel$ make C=2 CHECK=/tmp/sparse/sparse-0.5.0/sparse fs/locks.o
  CHK     include/config/kernel.release
  CHK     include/generated/uapi/linux/version.h
  CHK     include/generated/utsrelease.h
  CALL    scripts/checksyscalls.sh
<stdin>:1226:2: warning: #warning syscall finit_module not implemented [-Wcpp]
<stdin>:1229:2: warning: #warning syscall sched_setattr not implemented [-Wcpp]
<stdin>:1232:2: warning: #warning syscall sched_getattr not implemented [-Wcpp]
<stdin>:1235:2: warning: #warning syscall renameat2 not implemented [-Wcpp]
  CHECK   scripts/mod/empty.c
  CHECK   fs/locks.c
dcarpenter@speke:~/progs/kernel/devel$

I'm on today's linux-next.  I can't think of a kernel configuration
issue which would cause this...

regards,
dan carpenter