When used incorrectly, container_get() can silently create containers even if the caller may not intend to do so. Add a rich document describing the helper, as container_get() should only be used in path lookups.
Add one object_dynamic_cast() check to make sure whatever objects the helper walks will be a container object (including the one to be returned). It is a programming error otherwise, hence assert that. It may make container_get() tiny slower than before, but the hope is the change is neglictable, as object_class_dynamic_cast() has a fast path just for similar leaf use case. Link: https://lore.kernel.org/r/87pln6ds8q....@pond.sub.org Suggested-by: Markus Armbruster <arm...@redhat.com> Signed-off-by: Peter Xu <pet...@redhat.com> --- qom/container.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/qom/container.c b/qom/container.c index cfec92a944..ff6e35f837 100644 --- a/qom/container.c +++ b/qom/container.c @@ -24,6 +24,20 @@ static void container_register_types(void) type_register_static(&container_info); } +/** + * container_get(): Get the container object under specific path + * + * @root: The root path object to start walking from. When starting from + * root, one can pass in object_get_root(). + * @path: The sub-path to lookup, must be an non-empty string starts with "/". + * + * Returns: The container object specified by @path. + * + * NOTE: the function may impplicitly create internal containers when the + * whole path is not yet created. It's the caller's responsibility to make + * sure the path specified is always used as object containers, rather than + * any other type of objects. + */ Object *container_get(Object *root, const char *path) { Object *obj, *child; @@ -31,6 +45,7 @@ Object *container_get(Object *root, const char *path) int i; parts = g_strsplit(path, "/", 0); + /* "path" must be an non-empty string starting with "/" */ assert(parts != NULL && parts[0] != NULL && !parts[0][0]); obj = root; @@ -40,6 +55,12 @@ Object *container_get(Object *root, const char *path) child = object_new(TYPE_CONTAINER); object_property_add_child(obj, parts[i], child); object_unref(child); + } else { + /* + * Each object within the path must be a container object + * itself, including the object to be returned. + */ + assert(object_dynamic_cast(child, TYPE_CONTAINER)); } } -- 2.45.0
