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: sta...@dpdk.org
>
> Signed-off-by: Eli Britstein <el...@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
>
