tools include: Add a __fallthrough statement

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 <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Wang Nan <[email protected]>
Cc: William Cohen <[email protected]>
Link: http://lkml.kernel.org/n/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

1 files changed, 9 insertions, 0 deletions

diff --git a/tools/include/linux/compiler.h b/tools/include/linux/compiler.h
index e33fc1df3935..d94179f94caa 100644
--- 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 */