Em Fri, Feb 10, 2017 at 09:08:35AM -0800, Joe Perches escreveu: > gcc v7.0 can warn on missing break statements from case labels > using a special __attribute__((fallthrough))__ marker. > > Add a __fallthrough convenience macro for gcc versions >= 7 and > make the generic use of __fallthrough a no-op.
Can you state in the log message were this idea came from? Say, something like: "This was introduced in the tools/include/linux/compiler.h, where it was first noticed while buildint tools/perf/ in a Fedora Rawhide environment." BTW, I added this to my tree: https://git.kernel.org/cgit/linux/kernel/git/acme/linux.git/commit/?h=perf/core&id=e058554b1418e00864f1702c84bfa1d7cf314627 tools include: Introduce linux/compiler-gcc.h To match the kernel headers structure, setting up things that are specific to gcc or to some specific version of gcc. It gets included by linux/compiler.h when gcc is the compiler being used. Cc: Adrian Hunter <[email protected]> Cc: David Ahern <[email protected]> Cc: Jiri Olsa <[email protected]> Cc: Joe Perches <[email protected]> Cc: Namhyung Kim <[email protected]> Cc: Wang Nan <[email protected]> Link: http://lkml.kernel.org/n/[email protected] Signed-off-by: Arnaldo Carvalho de Melo <[email protected]> Thanks, - Arnaldo > Signed-off-by: Joe Perches <[email protected]> > --- > include/linux/compiler-gcc.h | 7 +++++++ > include/linux/compiler.h | 6 ++++++ > 2 files changed, 13 insertions(+) > > diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h > index d5e1fedbad24..6af8d6448f10 100644 > --- a/include/linux/compiler-gcc.h > +++ b/include/linux/compiler-gcc.h > @@ -304,6 +304,13 @@ > #define __no_sanitize_address __attribute__((no_sanitize_address)) > #endif > > +#if GCC_VERSION >= 70000 > +/* > + * Tell the compiler not to warn when a switch/case fallthrough marker exists > + */ > +#define __fallthrough __attribute__ ((fallthrough)) > +#endif > + > #endif /* gcc version >= 40000 specific checks */ > > #if !defined(__noclone) > diff --git a/include/linux/compiler.h b/include/linux/compiler.h > index 6e8e160b1e4b..16b6efc877f4 100644 > --- a/include/linux/compiler.h > +++ b/include/linux/compiler.h > @@ -477,6 +477,12 @@ static __always_inline void __write_once_size(volatile > void *p, void *res, int s > #define __assume_aligned(a, ...) > #endif > > +/* > + * switch/case fallthrough checking > + */ > +#ifndef __fallthrough > +#define __fallthrough > +#endif > > /* Are two types/vars the same type (ignoring qualifiers)? */ > #ifndef __same_type > -- > 2.10.0.rc2.1.g053435c
