let init_cfg kf =
let env = new_cfg_env kf in
let start = add_node env (Vstart) in
let fct_in = add_node env (VfctIn) in
let _ = add_edge env start Enone fct_in in
let fct_out = add_node env (VfctOut) in
let nexit = add_node env (Vexit) in
let nend = add_node env (Vend) in
let _ = add_edge env fct_out Enone nend in
let _ = add_edge env nexit Enone nend in
env, fct_in, fct_out