linux-kernel - Re: linux-next: build warnings after merge of the akpm tree

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Message-Id: <20121026011645.5a4e6adac51cf0bdc44e48bc@canb.auug.org.au>
Date:	Fri, 26 Oct 2012 01:16:45 +1100
From:	Stephen Rothwell <sfr@...b.auug.org.au>
To:	Richard Yang <weiyang@...ux.vnet.ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: linux-next: build warnings after merge of the akpm tree

Hi Richard,

On Thu, 25 Oct 2012 22:12:32 +0800 Richard Yang <weiyang@...ux.vnet.ibm.com> wrote:
>
> I did a quick check. 
> 
> The root reason is, 
> 1. kfifo_in() second parameter should be type "const void *"
> 2. kfifo_out_locked() second parameter should be type "void *"
> 3. kfifo_in_locked() second parameter should be type "const void *"
> 
> And I am curious about why the original code couldn't detect this type
> mismatch.  
> 
> The reason is: the original code use = not ==. 
> so when a const void * is assigned another pointer type, there is no warning.
> 
> While I write this test code, there is still no warning. 
> int   main()
> {
> 	int *a; 
> 	void* b;
> 	b = a;  // this should be ok.
> 	a = b;  // this should need the type transfer, but still no warning.
> 	return 0;
> } 
> 
> Hmm... not understand. Any error in my test code?

Yes, any pointer can be assigned to a void pointer and a void pointer can
be assigned to any pointer, so neither of the above should complain.

-- 
Cheers,
Stephen Rothwell                    sfr@...b.auug.org.au

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