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

Stephen Rothwell
2012-10-25T14:16:45Z

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Hi Richard,

On Thu, 25 Oct 2012 22:12:32 +0800 Richard Yang <weiyang@linux.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.