Re: Strict aliasing problem with rte_eth_linkstatus_set()

[Tyler Retzlaff <roretzla@linux.microsoft.com>]

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.
> 
> 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.