[Libguestfs] how to clear <defunct> qemu-system-x86 processes

Hi all, I have a long term running program which call libguestfs to check VM images. but i found that each time after i call guestfs_close(), the qeum-system-x86 process which is forked by libguestfs changes to <defunct> process. as docs of guestfs_close said "This closes the connection handle and frees up all resources used.", so this is a bug or is there any other way to clear them. thanks a lot! ------------------------ Chunyang Liu