linux-kernel - Re: [PATCH 24/32] tools include: Add a _

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Date:   Fri, 10 Feb 2017 11:42:38 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Joe Perches <joe@...ches.com>
Cc:     Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        David Ahern <dsahern@...il.com>, Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Wang Nan <wangnan0@...wei.com>,
        William Cohen <wcohen@...hat.com>
Subject: Re: [PATCH 24/32] tools include: Add a __fallthrough statement

Em Thu, Feb 09, 2017 at 07:02:06PM -0800, Joe Perches escreveu:
> On Thu, 2017-02-09 at 22:39 -0300, Arnaldo Carvalho de Melo wrote:
> > From: Arnaldo Carvalho de Melo <acme@...hat.com>
> > 
> > For cases where implicit fall through case labels are intended,
> > to let us inform that to gcc >= 7:
> 
> I believe this should be added to compiler_gcc.h

We still don't have it in tools/include/linux, but yeah, its a good idea
to have the equivalent of include/linux/compiler-gcc.h.

Then, at some point, the kernel can grab the definition from tools, i.e.
when people start trying to build the kernel _and_ this specific warning
is enabled there, as it is in tools/.

- Arnaldo
 
> > diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
> []
> > @@ -126,4 +126,13 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
> >  #define WRITE_ONCE(x, val) \
> >  	({ union { typeof(x) __val; char __c[1]; } __u = { .__val = (val) }; __write_once_size(&(x), __u.__c, sizeof(x)); __u.__val; })
> >  
> > +
> > +#ifndef __fallthrough
> > +# if defined(__GNUC__) && __GNUC__ >= 7
> > +#  define __fallthrough __attribute__ ((fallthrough))
> > +# else
> > +#  define __fallthrough
> > +# endif
> > +#endif
> > +
> >  #endif /* _TOOLS_LINUX_COMPILER_H */