dbus_shutdown() is a debug feature which closes all global resources in the dbus library. Calling this should be done by the app, not a library, because if there are multiple users of dbus in the process then SDL could shut it down even though another part is using it.

For example, i had an issue with this in mGBA, which uses both Qt and SDL, both using libdbus. I had a session bus, but no system bus (this was in a flatpak sandbox), and when SDL_DBus_Init() failed to init the system bus it called dbus_shudown() and continued on. This caused issues for Qt when running due to its session bus connections having disappeared beneath it.