linux-kernel - Re: [PATCH] remove untouched code in kfifo

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Date:	Tue, 23 Oct 2012 21:25:46 +0200
From:	richard -rw- weinberger <richard.weinberger@...il.com>
To:	Richard Yang <weiyang@...ux.vnet.ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>,
	Stefani Seibold <stefani@...bold.net>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] remove untouched code in kfifo_in

On Tue, Oct 23, 2012 at 4:27 AM, Richard Yang
<weiyang@...ux.vnet.ibm.com> wrote:
> On Mon, Oct 22, 2012 at 04:56:02PM -0700, Andrew Morton wrote:
>>On Fri, 19 Oct 2012 09:34:43 +0200 (CEST)
>>Jiri Kosina <jkosina@...e.cz> wrote:
>>
>>> On Fri, 19 Oct 2012, Stefani Seibold wrote:
>>>
>>> > > > In kfifo_in marco, one piece of code is arounded by if(0). This code in
>>> > > > introduced by Stefani Seibold <stefani@...bold.net> to suppress a compiler
>>> > > > warning. This warning is not there with the upgrade of gcc version.
>>> > > >
>>> > > > This patch just remove this code.
>>> > >
>>> > > Are you sure?
>>> > > This code fragment looks like a compiler bomb to detect type mismatch to me...
>>> >
>>> > Yes, you are great! That was the reason why i made this peace of code.
>>> > So don't remove it!
>>>
>>> As even you, the author of the code, got confused by it for a while,
>>> adding an explanatory comment seems appropriate.
>>>
>>
>>include/linux/typecheck.h?
>
> Something like this?
>
> From f20c316bf87d5db0816a01705b7869526c0b2363 Mon Sep 17 00:00:00 2001
> From: Wei Yang <weiyang@...ux.vnet.ibm.com>
> Date: Wed, 17 Oct 2012 16:45:49 +0800
> Subject: [PATCH] Replace the type check code with typecheck() in kfifo_in
>
> In kfifo_in marco, one piece of code which is arounded by if(0) will check the
> type of __tmp->ptr_const and __buf. If they are different type, there will
> output a warning during compiling. This piece of code is not self explaining
> and a little bit hard to understand.
>
> Based on Andrew Morton's suggestion, this patch replace this with typecheck()
> which will be easy to understand.
> ---
>  include/linux/kfifo.h |    5 +----
>  1 files changed, 1 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/kfifo.h b/include/linux/kfifo.h
> index 10308c6..b48fe71 100644
> --- a/include/linux/kfifo.h
> +++ b/include/linux/kfifo.h
> @@ -512,10 +512,7 @@ __kfifo_uint_must_check_helper( \
>         unsigned long __n = (n); \
>         const size_t __recsize = sizeof(*__tmp->rectype); \
>         struct __kfifo *__kfifo = &__tmp->kfifo; \
> -       if (0) { \
> -               typeof(__tmp->ptr_const) __dummy __attribute__ ((unused)); \
> -               __dummy = (typeof(__buf))NULL; \
> -       } \
> +       typecheck(typeof(__tmp->ptr_const), __buf);\
>         (__recsize) ?\
>         __kfifo_in_r(__kfifo, __buf, __n, __recsize) : \
>         __kfifo_in(__kfifo, __buf, __n); \

What about all the other open coded type checks in that file?

-- 
Thanks,
//richard
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