[PATCH] building libtraceevent with clang

[Arnaldo Carvalho de Melo]

Hi Steven,

        I tried building perf (and thus libtraceevent) with clang and
got this one:

kbuffer-parse.c:312:7: warning: variable 'length' is used uninitialized 
whenever switch case is taken [-Wsometimes-uninitialized]
        case OLD_RINGBUF_TYPE_TIME_EXTEND:
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
kbuffer-parse.c:339:29: note: uninitialized use occurs here
        kbuf->next = kbuf->index + length;
                                   ^~~~~~
kbuffer-parse.c:297:21: note: initialize the variable 'length' to silence this 
warning
        unsigned int length;
                           ^
                            = 0
1 warning generated.


Please take a look if the following is what should be done:

diff --git a/tools/lib/traceevent/kbuffer-parse.c 
b/tools/lib/traceevent/kbuffer-parse.c
index 65984f1c2974..3f717294cb82 100644
--- a/tools/lib/traceevent/kbuffer-parse.c
+++ b/tools/lib/traceevent/kbuffer-parse.c
@@ -309,20 +309,20 @@ static unsigned int old_update_pointers(struct kbuffer 
*kbuf)
                kbuf->next = kbuf->size;
                return 0;
 
-       case OLD_RINGBUF_TYPE_TIME_EXTEND:
-               extend = read_4(kbuf, ptr);
-               extend <<= TS_SHIFT;
-               extend += delta;
-               delta = extend;
-               ptr += 4;
-               break;
-
        case OLD_RINGBUF_TYPE_TIME_STAMP:
                /* should never happen! */
                kbuf->curr = kbuf->size;
                kbuf->next = kbuf->size;
                kbuf->index = kbuf->size;
                return -1;
+
+       case OLD_RINGBUF_TYPE_TIME_EXTEND:
+               extend = read_4(kbuf, ptr);
+               extend <<= TS_SHIFT;
+               extend += delta;
+               delta = extend;
+               ptr += 4;
+               /* Fall through */
        default:
                if (len)
                        length = len * 4;