From mboxrd@z Thu Jan  1 00:00:00 1970
From: r k <rkerur-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH v3] test-pmd: Fix pointer aliasing error
Date: Thu, 11 Dec 2014 09:51:44 -0800
Message-ID: <CAFb4SLCjnFpx0KGv3_zVG49vbhEnpS_GLhM7SQtvUs-s2Wmh3A@mail.gmail.com>
References: <1417663711-19576-1-git-send-email-michael.qiu@intel.com>
 <1417666564-19950-1-git-send-email-michael.qiu@intel.com>
 <533710CFB86FA344BFBF2D6802E60286C9D683@SHSMSX101.ccr.corp.intel.com>
 <1930269.B5nWyJ5DBl@xps13>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1
Cc: "dev-VfR2kkLFssw@public.gmane.org" <dev-VfR2kkLFssw@public.gmane.org>
To: Thomas Monjalon <thomas.monjalon-pdR9zngts4EAvxtiuMwx3w@public.gmane.org>
Return-path: <dev-bounces-VfR2kkLFssw@public.gmane.org>
In-Reply-To: <1930269.B5nWyJ5DBl@xps13>
List-Id: patches and discussions about DPDK <dev.dpdk.org>
List-Unsubscribe: <http://dpdk.org/ml/options/dev>,
 <mailto:dev-request-VfR2kkLFssw@public.gmane.org?subject=unsubscribe>
List-Archive: <http://dpdk.org/ml/archives/dev/>
List-Post: <mailto:dev-VfR2kkLFssw@public.gmane.org>
List-Help: <mailto:dev-request-VfR2kkLFssw@public.gmane.org?subject=help>
List-Subscribe: <http://dpdk.org/ml/listinfo/dev>,
 <mailto:dev-request-VfR2kkLFssw@public.gmane.org?subject=subscribe>
Errors-To: dev-bounces-VfR2kkLFssw@public.gmane.org
Sender: "dev" <dev-bounces-VfR2kkLFssw@public.gmane.org>

Thomas, Michael,

Wouldn't it cause unaligned memory access (new changes as well as the
previous code)? Wondering if get_unaligned/put_unaligned macros similar to
the ones used in kernel be ported to user-space?

Thanks,
Ravi

On Wed, Dec 10, 2014 at 4:54 PM, Thomas Monjalon <thomas.monjalon-pdR9zngts4EAvxtiuMwx3w@public.gmane.org>
wrote:
>
> > > app/test-pmd/csumonly.c: In function 'get_psd_sum':
> > > build/include/rte_ip.h:161: error: dereferencing pointer 'u16'
> > >         does break strict-aliasing rules
> > > build/include/rte_ip.h:157: note: initialized from here
> > >         ...
> > >
> > > The root cause is that, compile enable strict aliasing by default,
> > > while in function rte_raw_cksum() try to convert 'const char *'
> > > to 'const uint16_t *'.
> > >
> > > This patch is one workaround fix.
> > >
> > > Signed-off-by: Michael Qiu <michael.qiu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> > > ---
> > > v3 --> v2:
> > >     use uintptr_t instead of unsigned long to
> > >     save pointer.
> > >
> > > v2 --> v1:
> > >     Workaround solution instead of shut off the
> > >     gcc params.
> >
> > This workaround is to solve the compile issue of GCC strict-aliasing(Two
> > different type pointers should not be point to the same memory address).
> >
> > For GCC 4.4.7 it will definitely occurs if  flags "-fstrict-aliasing"
> > and "-Wall" used.
>
> Acked-by: Thomas Monjalon <thomas.monjalon-pdR9zngts4EAvxtiuMwx3w@public.gmane.org>>
>
> Applied with a comment in the code.
>
> Thanks
> --
> Thomas
>