Clarify empty string/NULL filter errors

[lttng-tools.git] / src / lib / lttng-ctl / lttng-ctl.c

diff --git a/src/lib/lttng-ctl/lttng-ctl.c b/src/lib/lttng-ctl/lttng-ctl.c
index 6238d9a00749865e23e390c2ac87b9e8799a09af..96351bdcf25b81318e8af78bcd1a5fc742a21a22 100644 (file)
--- a/src/lib/lttng-ctl/lttng-ctl.c
+++ b/src/lib/lttng-ctl/lttng-ctl.c
@@ -841,8 +841,20 @@ int lttng_enable_event_with_filter(struct lttng_handle *handle,
        FILE *fmem;
        int ret = 0;
 
-       /* Safety check. */
-       if (handle == NULL || !filter_expression) {
+       if (!filter_expression) {
+               /*
+                * Fall back to normal event enabling if no filter
+                * specified.
+                */
+               return lttng_enable_event(handle, event, channel_name);
+       }
+
+       /*
+        * Empty filter string will always be rejected by the parser
+        * anyway, so treat this corner-case early to eliminate
+        * lttng_fmemopen error for 0-byte allocation.
+        */
+       if (handle == NULL || filter_expression[0] == '\0') {
                return -LTTNG_ERR_INVALID;
        }