Lemma extcall_malloc_sem_inv: forall g v m t res m2 (E:Events.extcall_malloc_sem g v m t res m2), exists m1 b (sz : ptrofs), v=[Vptrofs sz] /\ t= Events.E0 /\ res=Vptr b Ptrofs.zero /\ Mem.alloc m (- size_chunk Mptr) (Ptrofs.unsigned sz) = (m1, b) /\ Mem.store Mptr m1 b (- size_chunk Mptr) (Vptrofs sz) = Some m2.