does gcc gives a false warning in kernel/trace/trace_events_filter.c ?

Toralf Förster
2012-09-02T09:04:56Z

The current git tree of linux gave with gcc-4.6.3 :

kernel/trace/trace_events_filter.c: In function ‘ftrace_function_set_filter_cb’:
kernel/trace/trace_events_filter.c:2074:8: warning: ‘ret’ may be used uninitialized in this function [-Wuninitialized]

which refers to this piece of code:

2061 static int ftrace_function_set_filter_cb(enum move_type move,
2062 struct filter_pred *pred,
2063 int *err, void *data)
2064 {
2065 /* Checking the node is valid for function trace. */
2066 if ((move != MOVE_DOWN) ||
2067 (pred->left != FILTER_PRED_INVALID)) {
2068 *err = ftrace_function_check_pred(pred, 0);
2069 } else {
2070 *err = ftrace_function_check_pred(pred, 1);
2071 if (*err)
2072 return WALK_PRED_ABORT;
2073
2074 *err = __ftrace_function_set_filter(pred->op == OP_EQ,
2075 pred->regex.pattern,
2076 pred->regex.len,
2077 data);
2078 }
2079
2080 return (*err) ? WALK_PRED_ABORT : WALK_PRED_DEFAULT;
2081 }
2082

>From a Gentoo forum user I got a hint :

"Maybe it's some kind of a weird inlining issue? I think it's referring to the ret in __ftrace_function_set_filter(), which would be uninitialized if the for-loop does not run (re_cnt ≤ 0)"

Now I'm wondering if re_cnt can become zero or if gcc is wrong here ?