[PATCH libevdev 2/2] tools: print an error if we don't have any matching events in the dpi tool

[Peter Hutterer]

Beats crashing by dereferencing a null-pointer (when we access
m->frequencies[idx])

Signed-off-by: Peter Hutterer <peter.hutterer at who-t.net>
---
 tools/mouse-dpi-tool.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/tools/mouse-dpi-tool.c b/tools/mouse-dpi-tool.c
index 13cefbc..b472ad0 100644
--- a/tools/mouse-dpi-tool.c
+++ b/tools/mouse-dpi-tool.c
@@ -215,8 +215,15 @@ static void
 print_summary(struct libevdev *dev, struct measurements *m)
 {
 	int res;
-	int max_freq = (int)m->max_frequency,
-	    mean_freq = (int)mean_frequency(m);
+	int max_freq, mean_freq;
+
+	if (m->nfrequencies == 0) {
+		fprintf(stderr, "Error: no matching events received.\n");
+		return;
+	}
+
+	max_freq = (int)m->max_frequency;
+	mean_freq = (int)mean_frequency(m);
 
 	printf("Estimated sampling frequency: %dHz (mean %dHz)\n",
 	       max_freq, mean_freq);
-- 
2.9.3