How to tell if a field in c struct is initialized?

Hi, I come across this code: http://elixir.free-electrons.com/linux/latest/source/drivers/scsi/scsi_netli... other fields such as .cbmutex, .bind, etc are not initialized. Since the object =cfg= is of automatic storage, I wonder how the kernel tells if a field is initialized or its value is just some random bits on the stack? -- Best, Shiyao