(** ** Semantics of dynamic memory allocation (malloc) *)
Inductive extcall_malloc_sem (ge: Senv.t):
list val -> mem -> trace -> val -> mem -> Prop :=
| extcall_malloc_sem_intro: forall sz m m' b m'',
Mem.alloc m (- size_chunk Mptr) (Ptrofs.unsigned sz) = (m', b) ->
Mem.store Mptr m' b (- size_chunk Mptr) (Vptrofs sz) = Some m'' ->
extcall_malloc_sem ge (Vptrofs sz :: nil) m E0 (Vptr b Ptrofs.zero) m''.

Lemma extcall_malloc_ok:
extcall_properties extcall_malloc_sem
(mksignature (Tptr :: nil) (Some Tptr) cc_default).