RE: [PATCH v5] eal: fix unaligned loads/stores in rte_memcpy_generic

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

Hi Luc,
 
> > Indeed it looks like a problem.
> > Thanks for pointing it out.
> > Was able to reproduce it with gcc 11 (clang 13 seems fine).
> > Actually, adding ' __attribute__ ((__may_alias__))' for both dst and src
> > didn't quire the problem.
> 
> __may_alias__ works if it's applied to a typedef, see the following
> for a modified version of my original example that works and uses
> __may_alias__:
> 
> https://godbolt.org/z/W83zzoePq

Interesting, I played with '__may_alias__' attribute a bit more,
and yes, as you said, it seems to wok properly only with typedefs.
If so, then we probably can add a new typedefs (in rte_common.h or so),
and use it in rte_memcpy and probably few other places, where we
think it will be necessary. 
 
> The documentation I found for __may_alias__ is quite sparse, so I'm a
> little wary of assuming it'll always work.
> I'm hoping someone with
> more experience with the attribute would be able to add more
> confidence to the assumption that it'll work in all cases.

Agree, would like to see more input too.
CC-ing to other guys, who seemed to be interested in that discussion before.

Thanks
Konstantin