tracing: avoid warnings from zero-arg tracepoints

Tracepoints with no arguments can issue two warnings:

	"field" defined by not used
	"ret" is uninitialized in this function

Mark field as being OK to leave unused, and initialize ret.

[ Impact: fix false positive compiler warnings. ]

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: mathieu.desnoyers@polymtl.ca
LKML-Reference: <1239950139-1119-5-git-send-email-jeremy@goop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h
index 60c5323..39a3351 100644
--- a/include/trace/ftrace.h
+++ b/include/trace/ftrace.h
@@ -160,8 +160,8 @@
 static int								\
 ftrace_format_##call(struct trace_seq *s)				\
 {									\
-	struct ftrace_raw_##call field;					\
-	int ret;							\
+	struct ftrace_raw_##call field __attribute__((unused));		\
+	int ret = 0;							\
 									\
 	tstruct;							\
 									\