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

[Lai Jiangshan]

On Saturday, December 8, 2012, Mathieu Desnoyers wrote:

> * Lai Jiangshan (laijs at cn.fujitsu.com <javascript:;>) 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 <javascript:;>>
> > ---
> >  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
> >
> >
> > _______________________________________________
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> > lttng-dev at lists.lttng.org <javascript:;>
> > http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>
>
> --
> Mathieu Desnoyers
> Operating System Efficiency R&D Consultant
> EfficiOS Inc.
> http://www.efficios.com
>
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