[dpdk-dev] [PATCH v2 1/8] eal: define container_of macro
Shreyansh Jain
shreyansh.jain at nxp.com
Thu Dec 8 08:01:57 CET 2016
Hello Jan,
Need your help in resolving the checkpatch issue for this patch.
I have used this in EAL Bus series [1].
[1] http://dpdk.org/ml/archives/dev/2016-December/051350.html
On Monday 21 November 2016 10:25 PM, Jan Blunck wrote:
> 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>
> 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>
> ---
> lib/librte_eal/common/include/rte_common.h | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/lib/librte_eal/common/include/rte_common.h b/lib/librte_eal/common/include/rte_common.h
> index db5ac91..8dda3e2 100644
> --- a/lib/librte_eal/common/include/rte_common.h
> +++ b/lib/librte_eal/common/include/rte_common.h
> @@ -331,6 +331,26 @@ 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)); })
> +#endif
(I think there was discussion in ML about this but where, I couldn't
find it).
Above code snippet doesn't go down well with the checkpatch script. It
reports:
---->8----
ERROR:COMPLEX_MACRO: Macros with complex values should be enclosed in
parentheses
#40: FILE: lib/librte_eal/common/include/rte_common.h:349:
+#define container_of(ptr, type, member) __extension__ ({
\
+ typeof(((type *)0)->member) *_ptr = (ptr); \
+ (type *)(((char *)_ptr) - offsetof(type,
member)); })
ERROR:SPACING: need consistent spacing around '*' (ctx:WxV)
#41: FILE: lib/librte_eal/common/include/rte_common.h:350:
+ typeof(((type *)0)->member) *_ptr = (ptr); \
---->8----
Second error is primarily because of '*<space>_ptr' rather than '*_ptr'.
Is do{ ... }while(0) the fix for the first one?
This:
---->8----
#ifndef container_of
#define container_of(ptr, type, member) do { \
__extension__ \
typeof(((type *)0)->member) * _ptr = (ptr); \
(type *)(((char *)_ptr) - offsetof(type, member));\
} while (0)
#endif
---->8----
Seems to be ok with checkpatch. Do you see any technical/compiler issue
with this?
> +
> #define _RTE_STR(x) #x
> /** Take a macro value and get a string version of it */
> #define RTE_STR(x) _RTE_STR(x)
>
-
Shreyansh
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