Re: [PATCH 5/6] zsmalloc: remove unnecessary type casting

[Minchan Kim <minchan@kernel.org>]

On 04/25/2012 10:35 PM, Nitin Gupta wrote:

> On 04/25/2012 02:23 AM, Minchan Kim wrote:
> 
>> Let's remove unnecessary type casting of (void *).
>>
>> Signed-off-by: Minchan Kim <minchan@kernel.org>
>> ---
>>  drivers/staging/zsmalloc/zsmalloc-main.c |    3 +--
>>  1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c
>> index b7d31cc..ff089f8 100644
>> --- a/drivers/staging/zsmalloc/zsmalloc-main.c
>> +++ b/drivers/staging/zsmalloc/zsmalloc-main.c
>> @@ -644,8 +644,7 @@ void zs_free(struct zs_pool *pool, void *obj)
>>  	spin_lock(&class->lock);
>>  
>>  	/* Insert this object in containing zspage's freelist */
>> -	link = (struct link_free *)((unsigned char *)kmap_atomic(f_page)
>> -							+ f_offset);
>> +	link = (struct link_free *)(kmap_atomic(f_page)	+ f_offset);
>>  	link->next = first_page->freelist;
>>  	kunmap_atomic(link);
>>  	first_page->freelist = obj;
> 
> 
> 
> Incrementing a void pointer looks weired and should not be allowed by C
> compilers though gcc and clang seem to allow this without any warnings.
> (fortunately C++ forbids incrementing void pointers)


It's a gcc extension and we have been already used lots of place so I think it's no problem
although it's non-standard.
If we compile kernel with -Wpointer-arith, we would find a ton of warning in here and there.

> 
> So, we should keep this cast to unsigned char pointer to avoid relying
> on a non-standard, compiler specific behavior.



Okay. It's a just trivial and I have no justification to do it at the cost of breaking standard.

> 
> Thanks,
> Nitin
> 
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-- 
Kind regards,
Minchan Kim

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