When using the event notification capture API, empty strings are
represented by a NULL pointer with a size=0 in the msgpack object.
The NULL pointer is unexpected, which triggers an assertion in
lttng_event_field_value_string_create_with_size.
Fix this by duplicating an empty string ("") when a size=0 is
encountered. This ensures that users of the API don't end up with an
unexpected NULL pointer. Indeed, the sample program notif-app.c in the
LTTng website documentation does not expect a NULL pointer.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoy...@efficios.com>
Change-Id: I7c3a839dbbeeb95a1b3bf6ddc3205a2f6b4538e3
---
src/common/event-field-value.cpp | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/src/common/event-field-value.cpp b/src/common/event-field-value.cpp
index 8017fd081..fa9e97018 100644
--- a/src/common/event-field-value.cpp
+++ b/src/common/event-field-value.cpp
@@ -183,8 +183,17 @@ struct lttng_event_field_value
*lttng_event_field_value_string_create_with_size(
goto error;
}
- LTTNG_ASSERT(val);
- field_val->val = strndup(val, size);
+ if (size) {
+ LTTNG_ASSERT(val);
+ field_val->val = strndup(val, size);
+ } else {
+ /*
+ * User code (e.g. notif-app.c on lttng.org/docs) do not expect
+ * a NULL string pointer. Populate with an empty string when
+ * length is 0.
+ */
+ field_val->val = strdup("");
+ }
if (!field_val->val) {
goto error;
}
--
2.25.1
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