qom: Use return values to check for error where that's simpler

When using the Error object to check for error, we need to receive it
into a local variable, then propagate() it to @errp.

Using the return value permits allows receiving it straight to @errp.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20200707160613.848843-26-armbru@redhat.com>

qom/object.c

@@ -549,8 +549,7 @@ void object_initialize_child_with_propsv(Object *parentobj,
     object_initialize(childobj, size, type);
     obj = OBJECT(childobj);
 
-    object_set_propv(obj, &local_err, vargs);
-    if (local_err) {
+    if (object_set_propv(obj, errp, vargs) < 0) {
         goto out;
     }
 
@@ -743,7 +742,7 @@ Object *object_new_with_propv(const char *typename,
     }
     obj = object_new_with_type(klass->type);
 
-    if (object_set_propv(obj, &local_err, vargs) < 0) {
+    if (object_set_propv(obj, errp, vargs) < 0) {
         goto error;
     }
 
@@ -1777,20 +1776,24 @@ static void object_set_link_property(Object *obj, Visitor *v,
     LinkProperty *prop = opaque;
     Object **targetp = object_link_get_targetp(obj, prop);
     Object *old_target = *targetp;
-    Object *new_target = NULL;
+    Object *new_target;
     char *path = NULL;
 
-    visit_type_str(v, name, &path, &local_err);
+    if (!visit_type_str(v, name, &path, errp)) {
+        return;
+    }
 
-    if (!local_err && strcmp(path, "") != 0) {
-        new_target = object_resolve_link(obj, name, path, &local_err);
+    if (*path) {
+        new_target = object_resolve_link(obj, name, path, errp);
+        if (!new_target) {
+            g_free(path);
+            return;
+        }
+    } else {
+        new_target = NULL;
     }
 
     g_free(path);
-    if (local_err) {
-        error_propagate(errp, local_err);
-        return;
-    }
 
     prop->check(obj, name, new_target, &local_err);
     if (local_err) {