Re: [dpdk-dev] [PATCH v2] librte_eal/common: Fix cast from pointer to integer of different size

["Qiu, Michael" <michael.qiu@intel.com>]

On 3/3/2015 9:38 PM, Wodkowski, PawelX wrote:
>> -----Original Message-----
>> From: Qiu, Michael
>> Sent: Tuesday, March 03, 2015 11:00 AM
>> To: Wodkowski, PawelX; dev@dpdk.org
>> Subject: Re: [dpdk-dev] [PATCH v2] librte_eal/common: Fix cast from pointer to
>> integer of different size
>>
>> On 3/3/2015 4:25 PM, Wodkowski, PawelX wrote:
>>> On 2015-03-03 03:20, Michael Qiu wrote:
>>>> /i686-native-linuxapp-gcc/include/rte_memcpy.h:592:23: error:
>>>> cast from pointer to integer of different size
>>>> [-Werror=pointer-to-int-cast]
>>>>
>>>>    dstofss = 16 - (int)((long long)(void *)dst & 0x0F) + 16;
>>>>
>>>> Type 'long long' is 64-bit in i686 platform while 'void *'
>>>> is 32-bit.
>>>>
>>>> Signed-off-by: Michael Qiu <michael.qiu@intel.com>
>>>> ---
>>>> v2 --> v1:
>>>> 	Remove unnecessary casting (void *)
>>>>
>>>>   lib/librte_eal/common/include/arch/x86/rte_memcpy.h | 4 ++--
>>>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/lib/librte_eal/common/include/arch/x86/rte_memcpy.h
>> b/lib/librte_eal/common/include/arch/x86/rte_memcpy.h
>>>> index 7b2d382..85a5f4d 100644
>>>> --- a/lib/librte_eal/common/include/arch/x86/rte_memcpy.h
>>>> +++ b/lib/librte_eal/common/include/arch/x86/rte_memcpy.h
>>>> @@ -589,12 +589,12 @@ COPY_BLOCK_64_BACK15:
>>>>   	 * unaligned copy functions require up to 15 bytes
>>>>   	 * backwards access.
>>>>   	 */
>>>> -	dstofss = 16 - (int)((long long)(void *)dst & 0x0F) + 16;
>>>> +	dstofss = 16 - (int)((long)dst & 0x0F) + 16;
>>>>   	n -= dstofss;
>>>>   	rte_mov32((uint8_t *)dst, (const uint8_t *)src);
>>>>   	src = (const uint8_t *)src + dstofss;
>>>>   	dst = (uint8_t *)dst + dstofss;
>>>> -	srcofs = (int)((long long)(const void *)src & 0x0F);
>>>> +	srcofs = (int)((long)src & 0x0F);
>>>>
>>>>   	/**
>>>>   	 * For aligned copy
>>>>
>>> I think you should use here size_t, (u)ptrdiff_t or (u)intptr_t as this
>> Yes, but 'long' is enough, does it limit anything, or has any issue with
>> multiple platforms?
>>
> Those types ((u)ptrdiff_t, (u)intptr_t) exists specially for 
> pointer-to-int and int-to-pointer casts. Using integer primitives might 
> produce further warnings/error in the future and need further patches 
> fixing the same place.

OK, I will send out the v3 patch.

> Also why make offset variables signed and different type? This introduce 
> a lot of unnecessary explicit and implicit casts or type promotions.

But Is it suitable to make offset (u)ptrdiff_t or (u)intptr_t?

Thanks,
Michael

>>> will be more portable.
>>> Also type of dstofss and srcofs should be changed accordingly.
>> No, I think, it should be offset.
>>
>> Thanks,
>> Michael
>