trace: print a warning if user tries to enable an unknown trace event

There was no warning if a bad trace event name was given to
'trace-event' command, thus the user could think that the command
was successful even if this was not the case.

Print a warning if the user tries to enable a trace event which is not
known.

Acked-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/simpletrace.c b/simpletrace.c
index f849e42914..deb1e0742e 100644
--- a/simpletrace.c
+++ b/simpletrace.c
@@ -246,12 +246,14 @@ static TraceEvent* find_trace_event_by_name(const char *tname)
     return NULL; /* indicates end of list reached without a match */
 }
 
-void st_change_trace_event_state(const char *tname, bool tstate)
+bool st_change_trace_event_state(const char *tname, bool tstate)
 {
     TraceEvent *tp;
 
     tp = find_trace_event_by_name(tname);
     if (tp) {
         tp->state = tstate;
+        return true;
     }
+    return false;
 }