Re: Strict aliasing problem with rte_eth_linkstatus_set()

[fengchengwen <fengchengwen@huawei.com>]

Hi All,

On 2024/4/11 3:58, Tyler Retzlaff wrote:
> On Wed, Apr 10, 2024 at 07:54:27PM +0200, Morten Brørup wrote:
>>> From: Stephen Hemminger [mailto:stephen@networkplumber.org]
>>> Sent: Wednesday, 10 April 2024 17.27
>>>
>>> On Wed, 10 Apr 2024 17:33:53 +0800
>>> fengchengwen <fengchengwen@huawei.com> wrote:
>>>
>>>> Last： We think there are two ways to solve this problem.
>>>> 1. Add the compilation option '-fno-strict-aliasing' for hold DPDK
>>> project.
>>>> 2. Use union to avoid such aliasing in rte_eth_linkstatus_set (please
>>> see above).
>>>> PS: We prefer first way.
>>>>
>>>
>>> Please send a patch to replace alias with union.
>>
>> +1
>>
>> Fixing this specific bug would be good.

OK for this,
and I already send a bugfix which use union.

Thanks

>>
>> Instinctively, I think we should build with -fno-strict-aliasing, so the compiler doesn't make the same mistake with similar code elsewhere in DPDK. I fear there is more than this instance.
>> I also wonder if -Wstrict-aliasing could help us instead, if we don't want -fno-strict-aliasing.
> 
> agree, union is the correct way to get defined behavior. there are
> valuable optimizatons that the compiler can make with strict aliasing
> enabled so -Wstrict-aliasing is a good suggestion as opposed to
> disabling it.
> 
> also the union won't break the abi if introduced correctly.
> .
>