DPDK patches and discussions
 help / color / mirror / Atom feed
From: "Qiu, Michael" <michael.qiu@intel.com>
To: "Richardson, Bruce" <bruce.richardson@intel.com>,
	Michael Qiu <qdy220091330@gmail.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH] test-pmd: Fix pointer aliasing error
Date: Wed, 3 Dec 2014 13:59:58 +0000
Message-ID: <533710CFB86FA344BFBF2D6802E60286C9C531@SHSMSX101.ccr.corp.intel.com> (raw)
In-Reply-To: <20141203114258.GA2396@bricha3-MOBL3>

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?

Thanks,
Michael
>
> /Bruce
>
>> Need to add CFLAG '-Wno-strict-aliasing' to avoid this issue.
>>
>> Signed-off-by: Michael Qiu <michael.qiu@intel.com>
>> ---
>>  app/test-pmd/Makefile | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/app/test-pmd/Makefile b/app/test-pmd/Makefile
>> index 97dc2e6..995c874 100644
>> --- a/app/test-pmd/Makefile
>> +++ b/app/test-pmd/Makefile
>> @@ -38,7 +38,7 @@ ifeq ($(CONFIG_RTE_TEST_PMD),y)
>>  #
>>  APP = testpmd
>>  
>> -CFLAGS += -O3
>> +CFLAGS += -O3 -Wno-strict-aliasing
>>  CFLAGS += $(WERROR_FLAGS)
>>  
>>  ifeq ($(CONFIG_RTE_LIBRTE_PMD_PCAP),y)
>> -- 
>> 1.9.3
>>


  reply	other threads:[~2014-12-03 21:49 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 [this message]
2014-12-03 14:51       ` Bruce Richardson
2014-12-03 15:19         ` Qiu, Michael
2014-12-03 15:36           ` Bruce Richardson
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=533710CFB86FA344BFBF2D6802E60286C9C531@SHSMSX101.ccr.corp.intel.com \
    --to=michael.qiu@intel.com \
    --cc=bruce.richardson@intel.com \
    --cc=dev@dpdk.org \
    --cc=qdy220091330@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

DPDK patches and discussions

This inbox may be cloned and mirrored by anyone:

	git clone --mirror https://inbox.dpdk.org/dev/0 dev/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 dev dev/ https://inbox.dpdk.org/dev \
		dev@dpdk.org
	public-inbox-index dev

Example config snippet for mirrors.
Newsgroup available over NNTP:
	nntp://inbox.dpdk.org/inbox.dpdk.dev


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git