linux-kernel - Re: [PATCH] staging: comedi: serial2002: quiet NULL pointer sparse noise

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Message-ID: <4FD1C0D2.8060704@mev.co.uk>
Date:	Fri, 8 Jun 2012 10:07:30 +0100
From:	Ian Abbott <abbotti@....co.uk>
To:	Dan Carpenter <dan.carpenter@...cle.com>
CC:	Ian Abbott <ian.abbott@....co.uk>,
	H Hartley Sweeten <hartleys@...ionengravers.com>,
	"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
	"fmhess@...rs.sourceforge.net" <fmhess@...rs.sourceforge.net>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] staging: comedi: serial2002: quiet NULL pointer sparse
 noise

On 2012/06/08 07:51 AM, Dan Carpenter wrote:
> On Fri, Jun 08, 2012 at 07:46:19AM +0100, Ian Abbott wrote:
>> On 08/06/12 01:14, H Hartley Sweeten wrote:
>>> Quiet a number of sparse warnings in this file:
>>>
>>> warning: Using plain integer as NULL pointer
>>
>> I wonder why sparse warns about that for a literal, unadorned 0?  I
>> suppose NULL is more explicit, but a plain 0 means the same as NULL
>> in a pointer context (unlike a zero from some random expression).
> 
> http://lwn.net/Articles/93574/

Thanks for the link.  I understand the intent to make null pointer
constants easier to recognize.  Still, the text of the sparse warning
message "Using plain integer as NULL pointer" is technically incorrect
since 0 is not an integer (plain or otherwise) in a pointer context,
it's a null pointer constant.

I wonder if it also issues that warning for a struct initializer such as
{0} where the first member of the struct is a pointer, or would it
expect you to use {NULL} which is more confusing when the struct
contains a mixture of pointer and non-pointer members?

-- 
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@....co.uk>             )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587              )=-
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