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From: Luc Pelletier <lucp.at.work@gmail.com>
To: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
Cc: "Richardson, Bruce" <bruce.richardson@intel.com>,
	"dev@dpdk.org" <dev@dpdk.org>,
	 "Li, Xiaoyun" <xiaoyun.li@intel.com>,
	"stable@dpdk.org" <stable@dpdk.org>
Subject: Re: [PATCH v5] eal: fix unaligned loads/stores in rte_memcpy_generic
Date: Sun, 13 Feb 2022 17:31:19 -0500	[thread overview]
Message-ID: <CAFeRdtDcSEKwtzPcpHGtCy_Q93z7whGF9zFBZa5QiDbBSwmnMw@mail.gmail.com> (raw)
In-Reply-To: <DM6PR11MB4491CBFE784DD7E9F9B067899A309@DM6PR11MB4491.namprd11.prod.outlook.com>

Hi Konstantin,

> 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

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.

  reply	other threads:[~2022-02-13 22:31 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-15 19:41 [PATCH] " Luc Pelletier
2022-01-15 21:39 ` [PATCH v2] " Luc Pelletier
2022-01-15 22:13   ` Stephen Hemminger
2022-01-16 14:09     ` Luc Pelletier
2022-01-16 16:32       ` Stephen Hemminger
2022-01-24 23:21         ` Georg Sauthoff
2022-01-25  7:59           ` Morten Brørup
2022-01-25 19:57           ` Luc Pelletier
2022-01-16 14:13 ` [PATCH v3] " Luc Pelletier
2022-01-16 14:33   ` Luc Pelletier
2022-01-16 16:34     ` Stephen Hemminger
2022-01-16 17:59       ` Morten Brørup
2022-01-16 20:33 ` [PATCH v4] " Luc Pelletier
2022-01-17 15:37 ` [PATCH v5] " Luc Pelletier
2022-02-04 16:42   ` Luc Pelletier
2022-02-04 17:16   ` Ananyev, Konstantin
2022-02-08 16:53     ` Thomas Monjalon
2022-02-09 15:05     ` Luc Pelletier
2022-02-10 14:04       ` Ananyev, Konstantin
2022-02-10 16:56         ` Luc Pelletier
2022-02-11 15:51           ` Ananyev, Konstantin
2022-02-13 22:31             ` Luc Pelletier [this message]
2022-02-14 13:41               ` Ananyev, Konstantin
2022-02-25 15:51 ` [PATCH v6] eal: fix rte_memcpy strict aliasing/alignment bugs Luc Pelletier
2022-02-25 16:38 ` [PATCH v7] " Luc Pelletier
2022-03-10 14:55   ` Ananyev, Konstantin
2022-04-07 15:24     ` David Marchand
2022-04-07 15:32       ` David Marchand
2022-04-07 15:40         ` David Marchand
2022-05-13 19:15           ` Luc Pelletier
2022-05-19 16:41             ` David Marchand
2022-04-08 13:47       ` Luc Pelletier
2022-05-19 16:47       ` David Marchand

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