From: Bruce Richardson <bruce.richardson@intel.com>
To: "Qiu, Michael" <michael.qiu@intel.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>, Michael Qiu <qdy220091330@gmail.com>
Subject: Re: [dpdk-dev] [PATCH] test-pmd: Fix pointer aliasing error
Date: Wed, 3 Dec 2014 15:36:35 +0000 [thread overview]
Message-ID: <20141203153634.GA6524@bricha3-MOBL3> (raw)
In-Reply-To: <533710CFB86FA344BFBF2D6802E60286C9C5BA@SHSMSX101.ccr.corp.intel.com>
On Wed, Dec 03, 2014 at 03:19:34PM +0000, Qiu, Michael wrote:
> On 2014/12/3 22:51, Richardson, Bruce wrote:
> > On Wed, Dec 03, 2014 at 01:59:58PM +0000, Qiu, Michael wrote:
> >> On 2014/12/3 19:43, Richardson, Bruce wrote:
> >>> On Wed, Dec 03, 2014 at 07:28:19PM +0800, Michael Qiu 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 *'.
> >>>>
> >>> What compiler version is this with? Is there any other way to fix this
> >>> other than disabling the compiler warnings. Turning off strict aliasing may
> >>> affect performance as it reduces the number of optimizations that the compiler
> >>> can perform.
> >> The compile version is:
> >>
> >> $ gcc -v
> >> Using built-in specs.
> >> Target: x86_64-redhat-linux
> >> ...
> >> gcc version 4.4.7 20120313 (Red Hat 4.4.7-4) (GCC)
> >>
> >>
> >> The OS is centos6.5 x86_64
> >>
> >>
> >> Actually, another possible solution is, as gcc manual shows, use union.
> >> In function rte_raw_cksum() of lib/librte_net/rte_ip.h:
> >>
> >> static inline uint16_t
> >> rte_raw_cksum(const char *buf, size_t len){
> >> union {
> >> const char *ubuf;
> >> const uint16_t *uu16;
> >> } convert;
> >>
> >> convert.ubuf = buf;
> >> const uint16_t *u16 = convert.uu16;
> >> ...
> >> }
> >>
> >> This may be work, but not test yet.
> >>
> >> Any comments about this solution?
> > what happens if you make rte_raw_cksum take a void * (or const void *) parameter
> > instead of "const char *"?
>
> "size_t len" is for type char, it is the the array size(for char array
> is byte numbers), if we use void *, the meaning maybe confuse I think.
That shouldn't be a big issue. We can rename it to "size" instead of "len" if
needed.
> But it should work with other code change.
>
> Thanks,
> Michael
> >
> > /Bruce
> >
>
next prev parent reply other threads:[~2014-12-03 17:34 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1417606044-3432-1-git-send-email-michael.qiu@intel.com>
[not found] ` <1417606099-3489-1-git-send-email-michael.qiu@intel.com>
2014-12-03 11:42 ` Bruce Richardson
2014-12-03 13:59 ` Qiu, Michael
2014-12-03 14:51 ` Bruce Richardson
2014-12-03 15:19 ` Qiu, Michael
2014-12-03 15:36 ` Bruce Richardson [this message]
2014-12-04 2:38 ` Qiu, Michael
2014-12-04 3:28 ` [dpdk-dev] [PATCH v2] " Michael Qiu
2014-12-04 4:16 ` [dpdk-dev] [PATCH v3] " Michael Qiu
2014-12-05 5:34 ` Qiu, Michael
2014-12-05 9:24 ` Thomas Monjalon
2014-12-08 1:28 ` Qiu, Michael
2014-12-08 1:30 ` Qiu, Michael
2014-12-10 3:44 ` Qiu, Michael
2014-12-11 0:54 ` Thomas Monjalon
2014-12-11 17:51 ` r k
2014-12-12 6:49 ` Qiu, Michael
2014-12-04 12:54 ` [dpdk-dev] [PATCH v2] " Ananyev, Konstantin
2014-12-03 15:24 ` [dpdk-dev] [PATCH] " Olivier MATZ
2014-12-03 16:03 ` Dayu Qiu
2014-12-03 15:57 ` Dayu Qiu
2014-12-03 16:26 ` [dpdk-dev] [PATCH] test-pmd: Fix "__BYTE_ORDER__" not defined error Qiu, Michael
2014-12-03 19:59 ` Thomas Monjalon
2014-12-03 20:47 ` [dpdk-dev] [PATCH 0/2] fix endianness in EAL Thomas Monjalon
2014-12-03 20:47 ` [dpdk-dev] [PATCH 1/2] eal: detect endianness Thomas Monjalon
2014-12-04 2:28 ` Qiu, Michael
2014-12-04 9:00 ` Thomas Monjalon
2014-12-04 10:28 ` Qiu, Michael
2014-12-04 12:19 ` Thomas Monjalon
2014-12-04 12:50 ` Qiu, Michael
2014-12-03 20:47 ` [dpdk-dev] [PATCH 2/2] app/testpmd: fix endianness detection Thomas Monjalon
2014-12-04 9:28 ` [dpdk-dev] [PATCH 0/2] fix endianness in EAL Chao Zhu
2014-12-05 16:01 ` Thomas Monjalon
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