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

Jan Blunck jblunck at infradead.org
Fri Dec 16 09:14:29 CET 2016


On Wed, Dec 14, 2016 at 6:12 AM, Shreyansh Jain <shreyansh.jain at nxp.com> wrote:
> 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?

We haven't added this on any other usage of the __extension__ keyword
in the existing code. From my perspective it is more consistent to
revert it.

Anyone else with an opinion here? David? Thomas?


>
>>
>>
>>> +#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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