lttng-sessiond: remove goto in ust_metadata_channel_statedump

A follow-up patch uses an std::vector declared in the middle of
ust_metadata_channel_statedump. This isn't compatible with the
goto-based error handling, since gotos should not jump over object
initialization (otherwise, the object gets destroyed without having been
constructed).

Moving the std::vector declaration to the beginning of the function
would work, but it would be a pessimization: we would construct an
object that we may not need, depending on the code path taken. We
therefore want to declare (and construct) the std::vector just before
we need it.

Fix this by replacing gotos with return statements.

Also, add a `ret` check after the last lttng_metadata_printf call. If
this call failed, for some reason, we would return an error, but still
set chan->metadata_dumped. That makes this case different than the other
error paths in the function, where chan->metadata_dumped doesn't get
set. Adding the check makes this case like the other ones.

Change-Id: Iba81422a7c3bac96a8d209bba6b4d53ad26b3e4e
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/src/bin/lttng-sessiond/ust-metadata.cpp b/src/bin/lttng-sessiond/ust-metadata.cpp
index b507f7870e687841abe139c17b1a805b42c97612..d08cb40ae7f10ade8a8add223997a2e7aa884bed 100644 (file)
--- a/src/bin/lttng-sessiond/ust-metadata.cpp
+++ b/src/bin/lttng-sessiond/ust-metadata.cpp
@@ -899,7 +899,7 @@ end:
 int ust_metadata_channel_statedump(struct ust_registry_session *session,
                struct ust_registry_channel *chan)
 {
-       int ret = 0;
+       int ret;
 
        /* Don't dump metadata events */
        if (chan->chan_id == -1U)
@@ -918,37 +918,40 @@ int ust_metadata_channel_statedump(struct ust_registry_session *session,
                        "struct event_header_compact" :
                        "struct event_header_large");
        if (ret) {
-               goto end;
+               return ret;
        }
 
        if (chan->ctx_fields) {
                ret = lttng_metadata_printf(session,
                        "       event.context := struct {\n");
                if (ret) {
-                       goto end;
+                       return ret;
                }
        }
        ret = _lttng_context_metadata_statedump(session,
                chan->nr_ctx_fields,
                chan->ctx_fields);
        if (ret) {
-               goto end;
+               return ret;
        }
        if (chan->ctx_fields) {
                ret = lttng_metadata_printf(session,
                        "       };\n");
                if (ret) {
-                       goto end;
+                       return ret;
                }
        }
 
        ret = lttng_metadata_printf(session,
                "};\n\n");
+       if (ret) {
+               return ret;
+       }
+
        /* Flag success of metadata dump. */
        chan->metadata_dumped = 1;
 
-end:
-       return ret;
+       return 0;
 }
 
 static