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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, "Jiri Olsa" <jolsa@kernel.org>,
        "William Cohen" <wcohen@redhat.com>,
        "David Ahern" <dsahern@gmail.com>,
        "Arnaldo Carvalho de Melo" <acme@redhat.com>,
        "Namhyung Kim" <namhyung@kernel.org>,
        "Wang Nan" <wangnan0@huawei.com>,
        "Adrian Hunter" <adrian.hunter@intel.com>
Date:   Sun, 11 Nov 2018 19:49:05 +0000
Message-ID: <lsq.1541965745.540187054@decadent.org.uk>
Subject: [PATCH 3.16 358/366] tools include: Add a __fallthrough statement
In-Reply-To: <lsq.1541965744.387173642@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

3.16.61-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Arnaldo Carvalho de Melo <acme@redhat.com>

commit b5bf1733d6a391c4e90ea8f8468d83023be74a2a upstream.

For cases where implicit fall through case labels are intended,
to let us inform that to gcc >= 7:

    CC       /tmp/build/perf/util/string.o
  util/string.c: In function 'perf_atoll':
  util/string.c:22:7: error: this statement may fall through [-Werror=implicit-fallthrough=]
      if (*p)
         ^
  util/string.c:24:3: note: here
     case '\0':
     ^~~~

So we introduce:

  #define __fallthrough __attribute__ ((fallthrough))

And use it in such cases.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: William Cohen <wcohen@redhat.com>
Link: http://lkml.kernel.org/n/tip-qnpig0xfop4hwv6k4mv1wts5@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 tools/include/linux/compiler.h | 9 +++++++++
 1 file changed, 9 insertions(+)

--- a/tools/include/linux/compiler.h
+++ b/tools/include/linux/compiler.h
@@ -37,4 +37,13 @@
 
 #define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
 
+
+#ifndef __fallthrough
+# if defined(__GNUC__) && __GNUC__ >= 7
+#  define __fallthrough __attribute__ ((fallthrough))
+# else
+#  define __fallthrough
+# endif
+#endif
+
 #endif /* _TOOLS_LINUX_COMPILER_H */