[lttng-dev] [PATCH 1/3] urcu: avoid "expression result unused" from clang

[Lai Jiangshan]

How about the one in yy.diff?

xx.diff fixes the one what I had sent in 1/3 patch, but it may still
cause warning in future if the complier become more strict.

On Sat, Dec 8, 2012 at 1:27 AM, Lai Jiangshan <eag0628 at gmail.com> wrote:
>
>
> On Saturday, December 8, 2012, Mathieu Desnoyers wrote:
>>
>> * Lai Jiangshan (laijs at cn.fujitsu.com) wrote:
>> > The last expression result is unused and clang will complain.
>> > The trick in the patch supresses the complaint
>>
>> Hrm, but with this patch, gcc complains:
>>
>> rculfhash.c:1921:3: warning: variable '_w' set but not used
>> [-Wunused-but-set-variable]
>>
>> using
>>
>> gcc version 4.7.2 (Debian 4.7.2-4)
>
>
> Ouch, my gcc is too old
>
>
>>
>>
>> Thoughts ?
>>
>> Thanks,
>>
>> Mathieu
>>
>> >
>> > Signed-off-by: Lai Jiangshan <laijs at cn.fujitsu.com>
>> > ---
>> >  urcu/system.h        |    5 ++++-
>> >  2 files changed, 4 insertions(+), 1 deletions(-)
>> >
>> > diff --git a/urcu/system.h b/urcu/system.h
>> > index 2a45f22..6b7b0af 100644
>> > --- a/urcu/system.h
>> > +++ b/urcu/system.h
>> > @@ -46,12 +46,15 @@
>> >  /*
>> >   * Store v into x, where x is located in shared memory. Performs the
>> >   * required cache flush after writing. Returns v.
>> > + * "_w" here avoids the warning from clang:
>> > + *   warning: expression result unused [-Wunused-value]
>> >   */
>> >  #define CMM_STORE_SHARED(x, v)               \
>> >       ({                              \
>> >               __typeof__(x) _v = _CMM_STORE_SHARED(x, v);     \
>> > +             __typeof__(x) _w;       \
>> >               cmm_smp_wmc();          \
>> > -             _v;                     \
>> > +             _w = _v;                \
>> >       })
>> >
>> >  #endif /* _URCU_SYSTEM_H */
>> > --
>> > 1.7.4.4
>> >
>> >
>> > _______________________________________________
>> > lttng-dev mailing list
>> > lttng-dev at lists.lttng.org
>> > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>>
>>
>> --
>> Mathieu Desnoyers
>> Operating System Efficiency R&D Consultant
>> EfficiOS Inc.
>> http://www.efficios.com
>>
>> _______________________________________________
>> lttng-dev mailing list
>> lttng-dev at lists.lttng.org
>> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
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