Section STABILITY.
Variables env env': composite_env.
Hypothesis extends: forall id co, env!id = Some co -> env'!id = Some co.

Lemma Cop_Sem_add_ptr_long_stable ty u v (H:complete_type env ty = true):
Cop.sem_add_ptr_long env ty u v =
Cop.sem_add_ptr_long env' ty u v.