[dpdk-dev] [PATCH v2 01/12] eal: define container_of macro

Jan Blunck jblunck at infradead.org
Tue Dec 13 23:24:33 CET 2016


On Tue, Dec 13, 2016 at 2:37 PM, Shreyansh Jain <shreyansh.jain at nxp.com> wrote:
> From: Jan Blunck <jblunck at infradead.org>
>
> This macro is based on Jan Viktorin's original patch but also checks the
> type of the passed pointer against the type of the member.
>
> Signed-off-by: Jan Viktorin <viktorin at rehivetech.com>
> [shreyansh.jain at nxp.com: Fix checkpatch error]
> Signed-off-by: Shreyansh Jain <shreyansh.jain at nxp.com>
> [jblunck at infradead.org: add type checking and __extension__]
> Signed-off-by: Jan Blunck <jblunck at infradead.org>
>
> --
> v2:
>  - fix checkpatch error
> ---
>  lib/librte_eal/common/include/rte_common.h | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
>
> diff --git a/lib/librte_eal/common/include/rte_common.h b/lib/librte_eal/common/include/rte_common.h
> index db5ac91..3eb8d11 100644
> --- a/lib/librte_eal/common/include/rte_common.h
> +++ b/lib/librte_eal/common/include/rte_common.h
> @@ -331,6 +331,27 @@ rte_bsf32(uint32_t v)
>  #define offsetof(TYPE, MEMBER)  __builtin_offsetof (TYPE, MEMBER)
>  #endif
>
> +/**
> + * Return pointer to the wrapping struct instance.
> + *
> + * Example:
> + *
> + *  struct wrapper {
> + *      ...
> + *      struct child c;
> + *      ...
> + *  };
> + *
> + *  struct child *x = obtain(...);
> + *  struct wrapper *w = container_of(x, struct wrapper, c);
> + */
> +#ifndef container_of
> +#define container_of(ptr, type, member)        (__extension__  ({              \
> +                       typeof(((type *)0)->member) * _ptr = (ptr);     \
> +                       (type *)(((char *)_ptr) - offsetof(type, member));\
> +                       }))

This is a checkpatch false positive. It should be fine to ignore this.
IIRC we already discussed this before.


> +#endif
> +
>  #define _RTE_STR(x) #x
>  /** Take a macro value and get a string version of it */
>  #define RTE_STR(x) _RTE_STR(x)
> --
> 2.7.4
>


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