DPDK patches and discussions
 help / color / mirror / Atom feed
From: "Qiu, Michael" <michael.qiu@intel.com>
To: "Wodkowski, PawelX" <pawelx.wodkowski@intel.com>,
	"dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] error: value computed is not used
Date: Mon, 8 Dec 2014 15:23:34 +0000	[thread overview]
Message-ID: <533710CFB86FA344BFBF2D6802E60286C9DB8B@SHSMSX101.ccr.corp.intel.com> (raw)
In-Reply-To: <F6F2A6264E145F47A18AB6DF8E87425D12B675CD@IRSMSX102.ger.corp.intel.com>

On 2014/12/8 19:00, Wodkowski, PawelX wrote:
>> lib/librte_pmd_enic/enic_main.c: In function ‘enic_set_rsskey’:
>> lib/librte_pmd_enic/enic_main.c:862:2: error: value computed is not used
>>
>> I dig out that, it was ome issue of  the macros rte_memcpy()
>> #define rte_memcpy(dst, src, n)              \
>>         ((__builtin_constant_p(n)) ?          \
>>         memcpy((dst), (src), (n)) :          \
>>         rte_memcpy_func((dst), (src), (n)))
>>
>> When I use only (n) instead of (__builtin_constant_p(n), it will pass( I
>> know that it was incorrect, just a experiment).
>>
>> But I try to use inline function instead of macros:
>> static inline void * rte_memcpy(void *dst, const void *src, size_t n)
>> {
>>         return __builtin_constant_p(n) ? memcpy(dst, src, n) :
>>                                          rte_memcpy_func(dst, src, n);
>> }
>>
>> It will pass:), and works, this could be one potential workaround fix.
>>
>> Who knows why? The root cause is what?
>>
>> I've no idea about this.
>>
> I got the same issue while ago. I don't remember exactly everything
> but my conclusion was that there was some bug in compiler. I think,
> when 'n' I constant and/or small compiler is inlining memcpy and throwing
> everything else (including returned value). In that case error is not
> produced (I think this is a bug in compiler). In other case it is computing
> some value calling memcpy or rte_ memcpy and you should at least
> explicitly throw it away by casting to void. I like solution with static

Actually, I try to pass "n" as a Int value like 4, it still report this
error :)

> inline but someone else should spoke about possible side effects.

Yes, but as I know inline is better than macros.

Thanks,
Michael
>
> Pawel
>
>


  reply	other threads:[~2014-12-08 15:24 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-08  9:05 Qiu, Michael
2014-12-08 11:00 ` Wodkowski, PawelX
2014-12-08 15:23   ` Qiu, Michael [this message]
2014-12-08 15:26     ` Wodkowski, PawelX
2014-12-15 10:54       ` Thomas Monjalon
2014-12-15 11:07         ` [dpdk-dev] [PATCH] enic: fix build on SUSE 11 Thomas Monjalon
2014-12-15 11:27         ` [dpdk-dev] error: value computed is not used Wodkowski, PawelX
2014-12-15 13:26           ` Thomas Monjalon
2014-12-15 13:47             ` Wodkowski, PawelX
2014-12-15 14:16               ` Thomas Monjalon
2014-12-15 15:44                 ` Wodkowski, PawelX
2014-12-15 16:35                   ` Ananyev, Konstantin
2014-12-15 16:00                 ` Ananyev, Konstantin
2014-12-15 16:40                   ` Thomas Monjalon
2014-12-15 17:03                 ` Jastrzebski, MichalX K
2014-12-16  0:49         ` Qiu, Michael
2014-12-09  9:19 ` Qiu, Michael
2014-12-10  9:26 ` Qiu, Michael

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=533710CFB86FA344BFBF2D6802E60286C9DB8B@SHSMSX101.ccr.corp.intel.com \
    --to=michael.qiu@intel.com \
    --cc=dev@dpdk.org \
    --cc=pawelx.wodkowski@intel.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
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).