qobject: Change qobject_to_json()'s value to GString

qobject_to_json() and qobject_to_json_pretty() build a GString, then
covert it to QString.  Just one of the callers actually needs a
QString: qemu_rbd_parse_filename().  A few others need a string they
can modify: qmp_send_response(), qga's send_response(), to_json_str(),
and qmp_fd_vsend_fds().  The remainder just need a string.

Change qobject_to_json() and qobject_to_json_pretty() to return the
GString.

qemu_rbd_parse_filename() now has to convert to QString.  All others
save a QString temporary.  to_json_str() actually becomes a bit
simpler, because GString provides more convenient modification
functions.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20201211171152.146877-6-armbru@redhat.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/block.c b/block.c
index 8f177504d4..09d4c6bd25 100644
--- a/block.c
+++ b/block.c
@@ -6995,13 +6995,13 @@ void bdrv_refresh_filename(BlockDriverState *bs)
     if (bs->exact_filename[0]) {
         pstrcpy(bs->filename, sizeof(bs->filename), bs->exact_filename);
     } else {
-        QString *json = qobject_to_json(QOBJECT(bs->full_open_options));
+        GString *json = qobject_to_json(QOBJECT(bs->full_open_options));
         if (snprintf(bs->filename, sizeof(bs->filename), "json:%s",
-                     qstring_get_str(json)) >= sizeof(bs->filename)) {
+                     json->str) >= sizeof(bs->filename)) {
             /* Give user a hint if we truncated things. */
             strcpy(bs->filename + sizeof(bs->filename) - 4, "...");
         }
-        qobject_unref(json);
+        g_string_free(json, true);
     }
 }