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

[Shreyansh Jain]

On Wednesday 14 December 2016 03:54 AM, Jan Blunck wrote:
> 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.

I too thought something similar was discussed. I tried searching the 
archives but couldn't find anything - thus, I thought probably I was 
hallucinating :P

So, you want me to revert back the '()' change? Does it impact the 
expansion of this macro?

>
>
>> +#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
>>
>