linux-kernel - Re: How to fix CHECK warning: testing a 'safe expression' ?

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Message-ID: <54920529.4080007@ti.com>
Date:	Wed, 17 Dec 2014 17:35:21 -0500
From:	Murali Karicheri <m-karicheri2@...com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
CC:	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Christopher Li <sparse@...isli.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: How to fix CHECK warning: testing a 'safe expression' ?

On 12/17/2014 01:49 PM, Bjorn Helgaas wrote:
> [+cc Christopher, linux-kernel (this doesn't sound like a PCI-specific
> question)]
>
> On Wed, Dec 17, 2014 at 9:18 AM, Murali Karicheri<m-karicheri2@...com>  wrote:
>> I am trying to address CHECK warnings in my driver and wondering how to
>> resolve 'warning: testing a 'safe expression' which appears when using
>> IS_ERR_OR_NULL(foo)
>>
>> where foo is defined as
>>
>> struct foo_type *foo;
>>
>> The foo get assigned only NULL or ERR_PTR(error code). So I believe the
>> usage is correct. But then how do I make the CHECK happy of its usage?
>>
>> I have tried a grep to check on the current usage of IS_ERR_OR_NULL() and
>> found 276 of them causes this warning in the v3.18 version of the kernel
>> that I am using
>>
>> $ grep -r "warning: testing a 'safe expression" * | wc -l
>> 276
>>
>> Can someone help me undestand what this means and how to fix the same?
>>
>> I run folling for CHECK
>>
>> make C=2 CF="-D__CHECK_ENDIAN__" CHECK=sparse
>
> If you can share your actual code or point to it in the tree, you
> might get more specific help.
>
> Bjorn

For example I get

   CHECK   drivers/pci/host/pci-keystone.c
include/linux/err.h:40:16: warning: testing a 'safe expression'

Actually it is for IS_ERR_OR_NULL() call in the file which is the only
one call in the file.

-- 
Murali Karicheri
Linux Kernel, Texas Instruments
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