Fix: Stream classes' id field is always serialized

A stream class' "id" must not be expressed in the trace metadata
if the trace's packet header does not contain a stream_id field.
Otherwise, the reader will try to ensure the packets' stream_id
corresponds to the stream class' id and will fail to do so.

The fix is to omit the serialization of the stream class' id
field entirely if the stream_id field is not found within the
trace's packet header.

It remains unclear whether or not a stream class has an actual
"id" in this case, or if some "unspecified" id state should
be implemented.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/lib/ctf-ir/stream-class.c b/lib/ctf-ir/stream-class.c
index 9b1675608e37da016117e9c9988515ab3c248923..db666c4371252a1e530ea5b290ab8afbf2a39927 100644 (file)
--- a/lib/ctf-ir/stream-class.c
+++ b/lib/ctf-ir/stream-class.c
@@ -985,6 +985,8 @@ int bt_ctf_stream_class_serialize(struct bt_ctf_stream_class *stream_class,
 {
        int ret = 0;
        size_t i;
+       struct bt_ctf_trace *trace;
+       struct bt_ctf_field_type *packet_header_type = NULL;
 
        BT_LOGD("Serializing stream class's metadata: "
                "stream-class-addr=%p, stream-class-name=\"%s\", "
@@ -999,8 +1001,38 @@ int bt_ctf_stream_class_serialize(struct bt_ctf_stream_class *stream_class,
                goto end;
        }
 
-       g_string_append_printf(context->string,
-               "stream {\n\tid = %" PRId64 ";\n", stream_class->id);
+       g_string_append(context->string, "stream {\n");
+
+       /*
+        * The reference to the trace is only borrowed since the
+        * serialization of the stream class might have been triggered
+        * by the trace's destruction. In such a case, the trace's
+        * reference count would, unexepectedly, go through the sequence
+        * 1 -> 0 -> 1 -> 0 -> ..., provoking an endless loop of destruction
+        * and serialization.
+        */
+       trace = bt_ctf_stream_class_borrow_trace(stream_class);
+       assert(trace);
+       packet_header_type = bt_ctf_trace_get_packet_header_type(trace);
+       trace = NULL;
+       if (packet_header_type) {
+               struct bt_ctf_field_type *stream_id_type;
+
+               stream_id_type =
+                       bt_ctf_field_type_structure_get_field_type_by_name(
+                               packet_header_type, "stream_id");
+               if (stream_id_type) {
+                       /*
+                        * Only set the stream's id if the trace's packet header
+                        * contains a stream_id field. This field is only
+                        * needed if the trace contains only one stream
+                        * class.
+                        */
+                       g_string_append_printf(context->string,
+                               "\tid = %" PRId64 ";\n", stream_class->id);
+               }
+               bt_put(stream_id_type);
+       }
        if (stream_class->event_header_type) {
                BT_LOGD_STR("Serializing stream class's event header field type's metadata.");
                g_string_append(context->string, "\tevent.header := ");
@@ -1059,6 +1091,7 @@ int bt_ctf_stream_class_serialize(struct bt_ctf_stream_class *stream_class,
                }
        }
 end:
+       bt_put(packet_header_type);
        context->current_indentation_level = 0;
        return ret;
 }