On Fri, Dec 16, 2016 at 10:23 AM, Adrien Mazarguil
<adrien.mazarg...@6wind.com> wrote:
> On Fri, Dec 16, 2016 at 09:14:29AM +0100, Jan Blunck wrote:
>> On Wed, Dec 14, 2016 at 6:12 AM, Shreyansh Jain <shreyansh.j...@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.j...@nxp.com>
>> >> wrote:
>> >>>
>> >>> From: Jan Blunck <jblu...@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 <vikto...@rehivetech.com>
>> >>> [shreyansh.j...@nxp.com: Fix checkpatch error]
>> >>> Signed-off-by: Shreyansh Jain <shreyansh.j...@nxp.com>
>> >>> [jblu...@infradead.org: add type checking and __extension__]
>> >>> Signed-off-by: Jan Blunck <jblu...@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?
>
> As an exported header, rte_common.h must pass check-includes.sh. Both
> typeof() and the ({ ... }) construct are non-standard GCC extensions and
> would fail to compile with pedantic options.
>
Thanks Adrien. These extensions are already in use by rte_common.h and
other headers. I don't believe we can remove the usage of typeof()
that easily without making the code really ugly.
