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

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Message-ID: <CAErSpo4hwMPOYBDZTu_fgKaUDYZ4h+jVpz5EigpErOgo6xO8mQ@mail.gmail.com>
Date:	Wed, 17 Dec 2014 11:49:15 -0700
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Murali Karicheri <m-karicheri2@...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' ?

[+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
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