From: Olivier Matz <olivier.matz@6wind.com>
To: Eli Britstein <elibr@nvidia.com>
Cc: dev@dpdk.org, Ilya Maximets <i.maximets@ovn.org>,
Gaetan Rivet <gaetanr@nvidia.com>, Majd Dibbiny <majd@nvidia.com>,
Asaf Penso <asafp@nvidia.com>,
Thomas Monjalon <thomas@monjalon.net>,
Harry Van Haaren <harry.van.haaren@intel.com>,
stable@dpdk.org
Subject: Re: [dpdk-dev] [PATCH 2/3] mbuf: avoid cast-align warning in pktmbuf mtod offset macro
Date: Wed, 28 Jul 2021 17:28:47 +0200 [thread overview]
Message-ID: <YQF3rxG8y3cEz13L@platinum> (raw)
In-Reply-To: <20210713064910.12793-3-elibr@nvidia.com>
On Tue, Jul 13, 2021 at 09:49:09AM +0300, Eli Britstein wrote:
> In rte_pktmbuf_mtod_offset macro, there is a casting from char * to type
> 't', which may cause cast-align warning when using gcc flags
> '-Werror -Wcast-align':
>
> .../include/rte_mbuf_core.h:723:3: error: cast increases required alignment
> of target type [-Werror=cast-align]
> 723 | ((t)((char *)(m)->buf_addr + (m)->data_off + (o)))
> | ^
>
> As the code assumes correct alignment, add first a (void *) casting, to
> avoid the warning.
>
> Fixes: af75078fece3 ("first public release")
> Cc: stable@dpdk.org
>
> Signed-off-by: Eli Britstein <elibr@nvidia.com>
My initial thinking was that it's the problem of the application: if
-Werror=cast-align is used, it is up to the application to cast the
return value of rte_pktmbuf_mtod_offset() to (void *) before casting it
to the network type.
But, if I understand correctly, the problem is not about the application
code itself, but about inlined code in the header files of dpdk
(i.e. compiling an empty C file that just includes the dpdk headers with
-Werror=cast-align). Is it correct? If yes I think it should be
highlighted in the commit log.
Out of curiosity, how did you find the errors? I mean, is it possible
that some casts are missing some other headers, or is this patchset
exhaustive?
Thanks,
Olivier
> ---
> lib/mbuf/rte_mbuf_core.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/mbuf/rte_mbuf_core.h b/lib/mbuf/rte_mbuf_core.h
> index bb38d7f581..dabdeee604 100644
> --- a/lib/mbuf/rte_mbuf_core.h
> +++ b/lib/mbuf/rte_mbuf_core.h
> @@ -720,7 +720,7 @@ struct rte_mbuf_ext_shared_info {
> * The type to cast the result into.
> */
> #define rte_pktmbuf_mtod_offset(m, t, o) \
> - ((t)((char *)(m)->buf_addr + (m)->data_off + (o)))
> + ((t)(void *)((char *)(m)->buf_addr + (m)->data_off + (o)))
>
> /**
> * A macro that points to the start of the data in the mbuf.
> --
> 2.28.0.2311.g225365fb51
>
next prev parent reply other threads:[~2021-07-28 15:28 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-13 6:49 [dpdk-dev] [PATCH 0/3] Avoid cast-align warnings Eli Britstein
2021-07-13 6:49 ` [dpdk-dev] [PATCH 1/3] net: avoid cast-align warning in VLAN insert function Eli Britstein
2021-07-30 10:57 ` Olivier Matz
2021-07-13 6:49 ` [dpdk-dev] [PATCH 2/3] mbuf: avoid cast-align warning in pktmbuf mtod offset macro Eli Britstein
2021-07-13 7:43 ` Thomas Monjalon
2021-07-28 15:28 ` Olivier Matz [this message]
2021-07-29 7:13 ` Eli Britstein
2021-07-30 11:10 ` Olivier Matz
2021-08-01 8:06 ` Eli Britstein
2021-10-19 6:41 ` Eli Britstein
2021-10-19 9:47 ` Olivier Matz
2021-07-13 6:49 ` [dpdk-dev] [PATCH 3/3] eal/x86: avoid cast-align warning in x86 memcpy functions Eli Britstein
2021-10-21 8:51 ` [dpdk-dev] [PATCH V2 1/3] net: avoid cast-align warning in VLAN insert function Eli Britstein
2021-10-21 8:51 ` [dpdk-dev] [PATCH V2 2/3] mbuf: avoid cast-align warning in pktmbuf mtod offset macro Eli Britstein
2021-10-21 8:51 ` [dpdk-dev] [PATCH V2 3/3] eal/x86: avoid cast-align warning in x86 memcpy functions Eli Britstein
2021-10-25 15:29 ` [dpdk-dev] [dpdk-stable] " Thomas Monjalon
2021-10-21 15:48 ` [dpdk-dev] [PATCH V2 1/3] net: avoid cast-align warning in VLAN insert function Stephen Hemminger
2021-10-21 16:16 ` Eli Britstein
2021-10-21 16:22 ` Stephen Hemminger
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