Record extcall_properties (sem: extcall_sem) (sg: signature) : Prop :=
  mk_extcall_properties {

(** The return value of an external call must agree with its signature. *)
  ec_well_typed:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Val.has_type vres (proj_sig_res sg);

(** The semantics is invariant under change of global environment that preserves symbols. *)
  ec_symbols_preserved:
    forall ge1 ge2 vargs m1 t vres m2,
    Senv.equiv ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    sem ge2 vargs m1 t vres m2;

(** External calls cannot invalidate memory blocks.  (Remember that
  freeing a block does not invalidate its block identifier.) *)
  ec_valid_block:
    forall ge vargs m1 t vres m2 b,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.valid_block m2 b;

(** External calls cannot increase the max permissions of a valid block.
    They can decrease the max permissions, e.g. by freeing. *)
  ec_max_perm:
    forall ge vargs m1 t vres m2 b ofs p,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.perm m2 b ofs Max p -> Mem.perm m1 b ofs Max p;

(** External call cannot modify memory unless they have [Max, Writable]
   permissions. *)
  ec_readonly:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Mem.unchanged_on (loc_not_writable m1) m1 m2;

(** External calls must commute with memory extensions, in the
  following sense. *)
  ec_mem_extends:
    forall ge vargs m1 t vres m2 m1' vargs',
    sem ge vargs m1 t vres m2 ->
    Mem.extends m1 m1' ->
    Val.lessdef_list vargs vargs' ->
    exists vres', exists m2',
       sem ge vargs' m1' t vres' m2'
    /\ Val.lessdef vres vres'
    /\ Mem.extends m2 m2'
    /\ Mem.unchanged_on (loc_out_of_bounds m1) m1' m2';

(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject:
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    injection_full f m1 ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t'
    /\ injection_full f' m2;
  
(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject':
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t';

(** External calls produce at most one event. *)
  ec_trace_length:
    forall ge vargs m t vres m',
    sem ge vargs m t vres m' -> (length t <= 1)%nat;

(** External calls must be receptive to changes of traces by another, matching trace. *)
  ec_receptive:
    forall ge vargs m t1 vres1 m1 t2,
    sem ge vargs m t1 vres1 m1 -> match_traces ge t1 t2 ->
    exists vres2, exists m2, sem ge vargs m t2 vres2 m2;

(** External calls must be deterministic up to matching between traces. *)
  ec_determ:
    forall ge vargs m t1 vres1 m1 t2 vres2 m2,
    sem ge vargs m t1 vres1 m1 -> sem ge vargs m t2 vres2 m2 ->
    match_traces ge t1 t2 /\ (t1 = t2 -> vres1 = vres2 /\ m1 = m2)
}.Record extcall_properties (sem: extcall_sem) (sg: signature) : Prop :=
  mk_extcall_properties {

(** The return value of an external call must agree with its signature. *)
  ec_well_typed:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Val.has_type vres (proj_sig_res sg);

(** The semantics is invariant under change of global environment that preserves symbols. *)
  ec_symbols_preserved:
    forall ge1 ge2 vargs m1 t vres m2,
    Senv.equiv ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    sem ge2 vargs m1 t vres m2;

(** External calls cannot invalidate memory blocks.  (Remember that
  freeing a block does not invalidate its block identifier.) *)
  ec_valid_block:
    forall ge vargs m1 t vres m2 b,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.valid_block m2 b;

(** External calls cannot increase the max permissions of a valid block.
    They can decrease the max permissions, e.g. by freeing. *)
  ec_max_perm:
    forall ge vargs m1 t vres m2 b ofs p,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.perm m2 b ofs Max p -> Mem.perm m1 b ofs Max p;

(** External call cannot modify memory unless they have [Max, Writable]
   permissions. *)
  ec_readonly:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Mem.unchanged_on (loc_not_writable m1) m1 m2;

(** External calls must commute with memory extensions, in the
  following sense. *)
  ec_mem_extends:
    forall ge vargs m1 t vres m2 m1' vargs',
    sem ge vargs m1 t vres m2 ->
    Mem.extends m1 m1' ->
    Val.lessdef_list vargs vargs' ->
    exists vres', exists m2',
       sem ge vargs' m1' t vres' m2'
    /\ Val.lessdef vres vres'
    /\ Mem.extends m2 m2'
    /\ Mem.unchanged_on (loc_out_of_bounds m1) m1' m2';

(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject:
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    injection_full f m1 ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t'
    /\ injection_full f' m2;
  
(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject':
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t';

(** External calls produce at most one event. *)
  ec_trace_length:
    forall ge vargs m t vres m',
    sem ge vargs m t vres m' -> (length t <= 1)%nat;

(** External calls must be receptive to changes of traces by another, matching trace. *)
  ec_receptive:
    forall ge vargs m t1 vres1 m1 t2,
    sem ge vargs m t1 vres1 m1 -> match_traces ge t1 t2 ->
    exists vres2, exists m2, sem ge vargs m t2 vres2 m2;

(** External calls must be deterministic up to matching between traces. *)
  ec_determ:
    forall ge vargs m t1 vres1 m1 t2 vres2 m2,
    sem ge vargs m t1 vres1 m1 -> sem ge vargs m t2 vres2 m2 ->
    match_traces ge t1 t2 /\ (t1 = t2 -> vres1 = vres2 /\ m1 = m2)
}.Record extcall_properties (sem: extcall_sem) (sg: signature) : Prop :=
  mk_extcall_properties {

(** The return value of an external call must agree with its signature. *)
  ec_well_typed:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Val.has_type vres (proj_sig_res sg);

(** The semantics is invariant under change of global environment that preserves symbols. *)
  ec_symbols_preserved:
    forall ge1 ge2 vargs m1 t vres m2,
    Senv.equiv ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    sem ge2 vargs m1 t vres m2;

(** External calls cannot invalidate memory blocks.  (Remember that
  freeing a block does not invalidate its block identifier.) *)
  ec_valid_block:
    forall ge vargs m1 t vres m2 b,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.valid_block m2 b;

(** External calls cannot increase the max permissions of a valid block.
    They can decrease the max permissions, e.g. by freeing. *)
  ec_max_perm:
    forall ge vargs m1 t vres m2 b ofs p,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.perm m2 b ofs Max p -> Mem.perm m1 b ofs Max p;

(** External call cannot modify memory unless they have [Max, Writable]
   permissions. *)
  ec_readonly:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Mem.unchanged_on (loc_not_writable m1) m1 m2;

(** External calls must commute with memory extensions, in the
  following sense. *)
  ec_mem_extends:
    forall ge vargs m1 t vres m2 m1' vargs',
    sem ge vargs m1 t vres m2 ->
    Mem.extends m1 m1' ->
    Val.lessdef_list vargs vargs' ->
    exists vres', exists m2',
       sem ge vargs' m1' t vres' m2'
    /\ Val.lessdef vres vres'
    /\ Mem.extends m2 m2'
    /\ Mem.unchanged_on (loc_out_of_bounds m1) m1' m2';

(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject:
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    injection_full f m1 ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t'
    /\ injection_full f' m2;
  
(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject':
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t';

(** External calls produce at most one event. *)
  ec_trace_length:
    forall ge vargs m t vres m',
    sem ge vargs m t vres m' -> (length t <= 1)%nat;

(** External calls must be receptive to changes of traces by another, matching trace. *)
  ec_receptive:
    forall ge vargs m t1 vres1 m1 t2,
    sem ge vargs m t1 vres1 m1 -> match_traces ge t1 t2 ->
    exists vres2, exists m2, sem ge vargs m t2 vres2 m2;

(** External calls must be deterministic up to matching between traces. *)
  ec_determ:
    forall ge vargs m t1 vres1 m1 t2 vres2 m2,
    sem ge vargs m t1 vres1 m1 -> sem ge vargs m t2 vres2 m2 ->
    match_traces ge t1 t2 /\ (t1 = t2 -> vres1 = vres2 /\ m1 = m2)
}.Record extcall_properties (sem: extcall_sem) (sg: signature) : Prop :=
  mk_extcall_properties {

(** The return value of an external call must agree with its signature. *)
  ec_well_typed:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Val.has_type vres (proj_sig_res sg);

(** The semantics is invariant under change of global environment that preserves symbols. *)
  ec_symbols_preserved:
    forall ge1 ge2 vargs m1 t vres m2,
    Senv.equiv ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    sem ge2 vargs m1 t vres m2;

(** External calls cannot invalidate memory blocks.  (Remember that
  freeing a block does not invalidate its block identifier.) *)
  ec_valid_block:
    forall ge vargs m1 t vres m2 b,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.valid_block m2 b;

(** External calls cannot increase the max permissions of a valid block.
    They can decrease the max permissions, e.g. by freeing. *)
  ec_max_perm:
    forall ge vargs m1 t vres m2 b ofs p,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.perm m2 b ofs Max p -> Mem.perm m1 b ofs Max p;

(** External call cannot modify memory unless they have [Max, Writable]
   permissions. *)
  ec_readonly:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Mem.unchanged_on (loc_not_writable m1) m1 m2;

(** External calls must commute with memory extensions, in the
  following sense. *)
  ec_mem_extends:
    forall ge vargs m1 t vres m2 m1' vargs',
    sem ge vargs m1 t vres m2 ->
    Mem.extends m1 m1' ->
    Val.lessdef_list vargs vargs' ->
    exists vres', exists m2',
       sem ge vargs' m1' t vres' m2'
    /\ Val.lessdef vres vres'
    /\ Mem.extends m2 m2'
    /\ Mem.unchanged_on (loc_out_of_bounds m1) m1' m2';

(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject:
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    injection_full f m1 ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t'
    /\ injection_full f' m2;
  
(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject':
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t';

(** External calls produce at most one event. *)
  ec_trace_length:
    forall ge vargs m t vres m',
    sem ge vargs m t vres m' -> (length t <= 1)%nat;

(** External calls must be receptive to changes of traces by another, matching trace. *)
  ec_receptive:
    forall ge vargs m t1 vres1 m1 t2,
    sem ge vargs m t1 vres1 m1 -> match_traces ge t1 t2 ->
    exists vres2, exists m2, sem ge vargs m t2 vres2 m2;

(** External calls must be deterministic up to matching between traces. *)
  ec_determ:
    forall ge vargs m t1 vres1 m1 t2 vres2 m2,
    sem ge vargs m t1 vres1 m1 -> sem ge vargs m t2 vres2 m2 ->
    match_traces ge t1 t2 /\ (t1 = t2 -> vres1 = vres2 /\ m1 = m2)
}.Record extcall_properties (sem: extcall_sem) (sg: signature) : Prop :=
  mk_extcall_properties {

(** The return value of an external call must agree with its signature. *)
  ec_well_typed:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Val.has_type vres (proj_sig_res sg);

(** The semantics is invariant under change of global environment that preserves symbols. *)
  ec_symbols_preserved:
    forall ge1 ge2 vargs m1 t vres m2,
    Senv.equiv ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    sem ge2 vargs m1 t vres m2;

(** External calls cannot invalidate memory blocks.  (Remember that
  freeing a block does not invalidate its block identifier.) *)
  ec_valid_block:
    forall ge vargs m1 t vres m2 b,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.valid_block m2 b;

(** External calls cannot increase the max permissions of a valid block.
    They can decrease the max permissions, e.g. by freeing. *)
  ec_max_perm:
    forall ge vargs m1 t vres m2 b ofs p,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.perm m2 b ofs Max p -> Mem.perm m1 b ofs Max p;

(** External call cannot modify memory unless they have [Max, Writable]
   permissions. *)
  ec_readonly:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Mem.unchanged_on (loc_not_writable m1) m1 m2;

(** External calls must commute with memory extensions, in the
  following sense. *)
  ec_mem_extends:
    forall ge vargs m1 t vres m2 m1' vargs',
    sem ge vargs m1 t vres m2 ->
    Mem.extends m1 m1' ->
    Val.lessdef_list vargs vargs' ->
    exists vres', exists m2',
       sem ge vargs' m1' t vres' m2'
    /\ Val.lessdef vres vres'
    /\ Mem.extends m2 m2'
    /\ Mem.unchanged_on (loc_out_of_bounds m1) m1' m2';

(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject:
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    injection_full f m1 ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t'
    /\ injection_full f' m2;
  
(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject':
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t';

(** External calls produce at most one event. *)
  ec_trace_length:
    forall ge vargs m t vres m',
    sem ge vargs m t vres m' -> (length t <= 1)%nat;

(** External calls must be receptive to changes of traces by another, matching trace. *)
  ec_receptive:
    forall ge vargs m t1 vres1 m1 t2,
    sem ge vargs m t1 vres1 m1 -> match_traces ge t1 t2 ->
    exists vres2, exists m2, sem ge vargs m t2 vres2 m2;

(** External calls must be deterministic up to matching between traces. *)
  ec_determ:
    forall ge vargs m t1 vres1 m1 t2 vres2 m2,
    sem ge vargs m t1 vres1 m1 -> sem ge vargs m t2 vres2 m2 ->
    match_traces ge t1 t2 /\ (t1 = t2 -> vres1 = vres2 /\ m1 = m2)
}.Record extcall_properties (sem: extcall_sem) (sg: signature) : Prop :=
  mk_extcall_properties {

(** The return value of an external call must agree with its signature. *)
  ec_well_typed:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Val.has_type vres (proj_sig_res sg);

(** The semantics is invariant under change of global environment that preserves symbols. *)
  ec_symbols_preserved:
    forall ge1 ge2 vargs m1 t vres m2,
    Senv.equiv ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    sem ge2 vargs m1 t vres m2;

(** External calls cannot invalidate memory blocks.  (Remember that
  freeing a block does not invalidate its block identifier.) *)
  ec_valid_block:
    forall ge vargs m1 t vres m2 b,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.valid_block m2 b;

(** External calls cannot increase the max permissions of a valid block.
    They can decrease the max permissions, e.g. by freeing. *)
  ec_max_perm:
    forall ge vargs m1 t vres m2 b ofs p,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.perm m2 b ofs Max p -> Mem.perm m1 b ofs Max p;

(** External call cannot modify memory unless they have [Max, Writable]
   permissions. *)
  ec_readonly:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Mem.unchanged_on (loc_not_writable m1) m1 m2;

(** External calls must commute with memory extensions, in the
  following sense. *)
  ec_mem_extends:
    forall ge vargs m1 t vres m2 m1' vargs',
    sem ge vargs m1 t vres m2 ->
    Mem.extends m1 m1' ->
    Val.lessdef_list vargs vargs' ->
    exists vres', exists m2',
       sem ge vargs' m1' t vres' m2'
    /\ Val.lessdef vres vres'
    /\ Mem.extends m2 m2'
    /\ Mem.unchanged_on (loc_out_of_bounds m1) m1' m2';

(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject:
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    injection_full f m1 ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t'
    /\ injection_full f' m2;
  
(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject':
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t';

(** External calls produce at most one event. *)
  ec_trace_length:
    forall ge vargs m t vres m',
    sem ge vargs m t vres m' -> (length t <= 1)%nat;

(** External calls must be receptive to changes of traces by another, matching trace. *)
  ec_receptive:
    forall ge vargs m t1 vres1 m1 t2,
    sem ge vargs m t1 vres1 m1 -> match_traces ge t1 t2 ->
    exists vres2, exists m2, sem ge vargs m t2 vres2 m2;

(** External calls must be deterministic up to matching between traces. *)
  ec_determ:
    forall ge vargs m t1 vres1 m1 t2 vres2 m2,
    sem ge vargs m t1 vres1 m1 -> sem ge vargs m t2 vres2 m2 ->
    match_traces ge t1 t2 /\ (t1 = t2 -> vres1 = vres2 /\ m1 = m2)
}.Record extcall_properties (sem: extcall_sem) (sg: signature) : Prop :=
  mk_extcall_properties {

(** The return value of an external call must agree with its signature. *)
  ec_well_typed:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Val.has_type vres (proj_sig_res sg);

(** The semantics is invariant under change of global environment that preserves symbols. *)
  ec_symbols_preserved:
    forall ge1 ge2 vargs m1 t vres m2,
    Senv.equiv ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    sem ge2 vargs m1 t vres m2;

(** External calls cannot invalidate memory blocks.  (Remember that
  freeing a block does not invalidate its block identifier.) *)
  ec_valid_block:
    forall ge vargs m1 t vres m2 b,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.valid_block m2 b;

(** External calls cannot increase the max permissions of a valid block.
    They can decrease the max permissions, e.g. by freeing. *)
  ec_max_perm:
    forall ge vargs m1 t vres m2 b ofs p,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.perm m2 b ofs Max p -> Mem.perm m1 b ofs Max p;

(** External call cannot modify memory unless they have [Max, Writable]
   permissions. *)
  ec_readonly:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Mem.unchanged_on (loc_not_writable m1) m1 m2;

(** External calls must commute with memory extensions, in the
  following sense. *)
  ec_mem_extends:
    forall ge vargs m1 t vres m2 m1' vargs',
    sem ge vargs m1 t vres m2 ->
    Mem.extends m1 m1' ->
    Val.lessdef_list vargs vargs' ->
    exists vres', exists m2',
       sem ge vargs' m1' t vres' m2'
    /\ Val.lessdef vres vres'
    /\ Mem.extends m2 m2'
    /\ Mem.unchanged_on (loc_out_of_bounds m1) m1' m2';

(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject:
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    injection_full f m1 ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t'
    /\ injection_full f' m2;
  
(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject':
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t';

(** External calls produce at most one event. *)
  ec_trace_length:
    forall ge vargs m t vres m',
    sem ge vargs m t vres m' -> (length t <= 1)%nat;

(** External calls must be receptive to changes of traces by another, matching trace. *)
  ec_receptive:
    forall ge vargs m t1 vres1 m1 t2,
    sem ge vargs m t1 vres1 m1 -> match_traces ge t1 t2 ->
    exists vres2, exists m2, sem ge vargs m t2 vres2 m2;

(** External calls must be deterministic up to matching between traces. *)
  ec_determ:
    forall ge vargs m t1 vres1 m1 t2 vres2 m2,
    sem ge vargs m t1 vres1 m1 -> sem ge vargs m t2 vres2 m2 ->
    match_traces ge t1 t2 /\ (t1 = t2 -> vres1 = vres2 /\ m1 = m2)
}.Record extcall_properties (sem: extcall_sem) (sg: signature) : Prop :=
  mk_extcall_properties {

(** The return value of an external call must agree with its signature. *)
  ec_well_typed:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Val.has_type vres (proj_sig_res sg);

(** The semantics is invariant under change of global environment that preserves symbols. *)
  ec_symbols_preserved:
    forall ge1 ge2 vargs m1 t vres m2,
    Senv.equiv ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    sem ge2 vargs m1 t vres m2;

(** External calls cannot invalidate memory blocks.  (Remember that
  freeing a block does not invalidate its block identifier.) *)
  ec_valid_block:
    forall ge vargs m1 t vres m2 b,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.valid_block m2 b;

(** External calls cannot increase the max permissions of a valid block.
    They can decrease the max permissions, e.g. by freeing. *)
  ec_max_perm:
    forall ge vargs m1 t vres m2 b ofs p,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.perm m2 b ofs Max p -> Mem.perm m1 b ofs Max p;

(** External call cannot modify memory unless they have [Max, Writable]
   permissions. *)
  ec_readonly:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Mem.unchanged_on (loc_not_writable m1) m1 m2;

(** External calls must commute with memory extensions, in the
  following sense. *)
  ec_mem_extends:
    forall ge vargs m1 t vres m2 m1' vargs',
    sem ge vargs m1 t vres m2 ->
    Mem.extends m1 m1' ->
    Val.lessdef_list vargs vargs' ->
    exists vres', exists m2',
       sem ge vargs' m1' t vres' m2'
    /\ Val.lessdef vres vres'
    /\ Mem.extends m2 m2'
    /\ Mem.unchanged_on (loc_out_of_bounds m1) m1' m2';

(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject:
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    injection_full f m1 ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t'
    /\ injection_full f' m2;
  
(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject':
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t';

(** External calls produce at most one event. *)
  ec_trace_length:
    forall ge vargs m t vres m',
    sem ge vargs m t vres m' -> (length t <= 1)%nat;

(** External calls must be receptive to changes of traces by another, matching trace. *)
  ec_receptive:
    forall ge vargs m t1 vres1 m1 t2,
    sem ge vargs m t1 vres1 m1 -> match_traces ge t1 t2 ->
    exists vres2, exists m2, sem ge vargs m t2 vres2 m2;

(** External calls must be deterministic up to matching between traces. *)
  ec_determ:
    forall ge vargs m t1 vres1 m1 t2 vres2 m2,
    sem ge vargs m t1 vres1 m1 -> sem ge vargs m t2 vres2 m2 ->
    match_traces ge t1 t2 /\ (t1 = t2 -> vres1 = vres2 /\ m1 = m2)
}.Record extcall_properties (sem: extcall_sem) (sg: signature) : Prop :=
  mk_extcall_properties {

(** The return value of an external call must agree with its signature. *)
  ec_well_typed:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Val.has_type vres (proj_sig_res sg);

(** The semantics is invariant under change of global environment that preserves symbols. *)
  ec_symbols_preserved:
    forall ge1 ge2 vargs m1 t vres m2,
    Senv.equiv ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    sem ge2 vargs m1 t vres m2;

(** External calls cannot invalidate memory blocks.  (Remember that
  freeing a block does not invalidate its block identifier.) *)
  ec_valid_block:
    forall ge vargs m1 t vres m2 b,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.valid_block m2 b;

(** External calls cannot increase the max permissions of a valid block.
    They can decrease the max permissions, e.g. by freeing. *)
  ec_max_perm:
    forall ge vargs m1 t vres m2 b ofs p,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.perm m2 b ofs Max p -> Mem.perm m1 b ofs Max p;

(** External call cannot modify memory unless they have [Max, Writable]
   permissions. *)
  ec_readonly:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Mem.unchanged_on (loc_not_writable m1) m1 m2;

(** External calls must commute with memory extensions, in the
  following sense. *)
  ec_mem_extends:
    forall ge vargs m1 t vres m2 m1' vargs',
    sem ge vargs m1 t vres m2 ->
    Mem.extends m1 m1' ->
    Val.lessdef_list vargs vargs' ->
    exists vres', exists m2',
       sem ge vargs' m1' t vres' m2'
    /\ Val.lessdef vres vres'
    /\ Mem.extends m2 m2'
    /\ Mem.unchanged_on (loc_out_of_bounds m1) m1' m2';

(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject:
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    injection_full f m1 ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t'
    /\ injection_full f' m2;
  
(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject':
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t';

(** External calls produce at most one event. *)
  ec_trace_length:
    forall ge vargs m t vres m',
    sem ge vargs m t vres m' -> (length t <= 1)%nat;

(** External calls must be receptive to changes of traces by another, matching trace. *)
  ec_receptive:
    forall ge vargs m t1 vres1 m1 t2,
    sem ge vargs m t1 vres1 m1 -> match_traces ge t1 t2 ->
    exists vres2, exists m2, sem ge vargs m t2 vres2 m2;

(** External calls must be deterministic up to matching between traces. *)
  ec_determ:
    forall ge vargs m t1 vres1 m1 t2 vres2 m2,
    sem ge vargs m t1 vres1 m1 -> sem ge vargs m t2 vres2 m2 ->
    match_traces ge t1 t2 /\ (t1 = t2 -> vres1 = vres2 /\ m1 = m2)
}.Record extcall_properties (sem: extcall_sem) (sg: signature) : Prop :=
  mk_extcall_properties {

(** The return value of an external call must agree with its signature. *)
  ec_well_typed:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Val.has_type vres (proj_sig_res sg);

(** The semantics is invariant under change of global environment that preserves symbols. *)
  ec_symbols_preserved:
    forall ge1 ge2 vargs m1 t vres m2,
    Senv.equiv ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    sem ge2 vargs m1 t vres m2;

(** External calls cannot invalidate memory blocks.  (Remember that
  freeing a block does not invalidate its block identifier.) *)
  ec_valid_block:
    forall ge vargs m1 t vres m2 b,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.valid_block m2 b;

(** External calls cannot increase the max permissions of a valid block.
    They can decrease the max permissions, e.g. by freeing. *)
  ec_max_perm:
    forall ge vargs m1 t vres m2 b ofs p,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.perm m2 b ofs Max p -> Mem.perm m1 b ofs Max p;

(** External call cannot modify memory unless they have [Max, Writable]
   permissions. *)
  ec_readonly:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Mem.unchanged_on (loc_not_writable m1) m1 m2;

(** External calls must commute with memory extensions, in the
  following sense. *)
  ec_mem_extends:
    forall ge vargs m1 t vres m2 m1' vargs',
    sem ge vargs m1 t vres m2 ->
    Mem.extends m1 m1' ->
    Val.lessdef_list vargs vargs' ->
    exists vres', exists m2',
       sem ge vargs' m1' t vres' m2'
    /\ Val.lessdef vres vres'
    /\ Mem.extends m2 m2'
    /\ Mem.unchanged_on (loc_out_of_bounds m1) m1' m2';

(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject:
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    injection_full f m1 ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t'
    /\ injection_full f' m2;
  
(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject':
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t';

(** External calls produce at most one event. *)
  ec_trace_length:
    forall ge vargs m t vres m',
    sem ge vargs m t vres m' -> (length t <= 1)%nat;

(** External calls must be receptive to changes of traces by another, matching trace. *)
  ec_receptive:
    forall ge vargs m t1 vres1 m1 t2,
    sem ge vargs m t1 vres1 m1 -> match_traces ge t1 t2 ->
    exists vres2, exists m2, sem ge vargs m t2 vres2 m2;

(** External calls must be deterministic up to matching between traces. *)
  ec_determ:
    forall ge vargs m t1 vres1 m1 t2 vres2 m2,
    sem ge vargs m t1 vres1 m1 -> sem ge vargs m t2 vres2 m2 ->
    match_traces ge t1 t2 /\ (t1 = t2 -> vres1 = vres2 /\ m1 = m2)
}.Record extcall_properties (sem: extcall_sem) (sg: signature) : Prop :=
  mk_extcall_properties {

(** The return value of an external call must agree with its signature. *)
  ec_well_typed:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Val.has_type vres (proj_sig_res sg);

(** The semantics is invariant under change of global environment that preserves symbols. *)
  ec_symbols_preserved:
    forall ge1 ge2 vargs m1 t vres m2,
    Senv.equiv ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    sem ge2 vargs m1 t vres m2;

(** External calls cannot invalidate memory blocks.  (Remember that
  freeing a block does not invalidate its block identifier.) *)
  ec_valid_block:
    forall ge vargs m1 t vres m2 b,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.valid_block m2 b;

(** External calls cannot increase the max permissions of a valid block.
    They can decrease the max permissions, e.g. by freeing. *)
  ec_max_perm:
    forall ge vargs m1 t vres m2 b ofs p,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.perm m2 b ofs Max p -> Mem.perm m1 b ofs Max p;

(** External call cannot modify memory unless they have [Max, Writable]
   permissions. *)
  ec_readonly:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Mem.unchanged_on (loc_not_writable m1) m1 m2;

(** External calls must commute with memory extensions, in the
  following sense. *)
  ec_mem_extends:
    forall ge vargs m1 t vres m2 m1' vargs',
    sem ge vargs m1 t vres m2 ->
    Mem.extends m1 m1' ->
    Val.lessdef_list vargs vargs' ->
    exists vres', exists m2',
       sem ge vargs' m1' t vres' m2'
    /\ Val.lessdef vres vres'
    /\ Mem.extends m2 m2'
    /\ Mem.unchanged_on (loc_out_of_bounds m1) m1' m2';

(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject:
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    injection_full f m1 ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t'
    /\ injection_full f' m2;
  
(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject':
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t';

(** External calls produce at most one event. *)
  ec_trace_length:
    forall ge vargs m t vres m',
    sem ge vargs m t vres m' -> (length t <= 1)%nat;

(** External calls must be receptive to changes of traces by another, matching trace. *)
  ec_receptive:
    forall ge vargs m t1 vres1 m1 t2,
    sem ge vargs m t1 vres1 m1 -> match_traces ge t1 t2 ->
    exists vres2, exists m2, sem ge vargs m t2 vres2 m2;

(** External calls must be deterministic up to matching between traces. *)
  ec_determ:
    forall ge vargs m t1 vres1 m1 t2 vres2 m2,
    sem ge vargs m t1 vres1 m1 -> sem ge vargs m t2 vres2 m2 ->
    match_traces ge t1 t2 /\ (t1 = t2 -> vres1 = vres2 /\ m1 = m2)
}.Record extcall_properties (sem: extcall_sem) (sg: signature) : Prop :=
  mk_extcall_properties {

(** The return value of an external call must agree with its signature. *)
  ec_well_typed:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Val.has_type vres (proj_sig_res sg);

(** The semantics is invariant under change of global environment that preserves symbols. *)
  ec_symbols_preserved:
    forall ge1 ge2 vargs m1 t vres m2,
    Senv.equiv ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    sem ge2 vargs m1 t vres m2;

(** External calls cannot invalidate memory blocks.  (Remember that
  freeing a block does not invalidate its block identifier.) *)
  ec_valid_block:
    forall ge vargs m1 t vres m2 b,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.valid_block m2 b;

(** External calls cannot increase the max permissions of a valid block.
    They can decrease the max permissions, e.g. by freeing. *)
  ec_max_perm:
    forall ge vargs m1 t vres m2 b ofs p,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.perm m2 b ofs Max p -> Mem.perm m1 b ofs Max p;

(** External call cannot modify memory unless they have [Max, Writable]
   permissions. *)
  ec_readonly:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Mem.unchanged_on (loc_not_writable m1) m1 m2;

(** External calls must commute with memory extensions, in the
  following sense. *)
  ec_mem_extends:
    forall ge vargs m1 t vres m2 m1' vargs',
    sem ge vargs m1 t vres m2 ->
    Mem.extends m1 m1' ->
    Val.lessdef_list vargs vargs' ->
    exists vres', exists m2',
       sem ge vargs' m1' t vres' m2'
    /\ Val.lessdef vres vres'
    /\ Mem.extends m2 m2'
    /\ Mem.unchanged_on (loc_out_of_bounds m1) m1' m2';

(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject:
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    injection_full f m1 ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t'
    /\ injection_full f' m2;
  
(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject':
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t';

(** External calls produce at most one event. *)
  ec_trace_length:
    forall ge vargs m t vres m',
    sem ge vargs m t vres m' -> (length t <= 1)%nat;

(** External calls must be receptive to changes of traces by another, matching trace. *)
  ec_receptive:
    forall ge vargs m t1 vres1 m1 t2,
    sem ge vargs m t1 vres1 m1 -> match_traces ge t1 t2 ->
    exists vres2, exists m2, sem ge vargs m t2 vres2 m2;

(** External calls must be deterministic up to matching between traces. *)
  ec_determ:
    forall ge vargs m t1 vres1 m1 t2 vres2 m2,
    sem ge vargs m t1 vres1 m1 -> sem ge vargs m t2 vres2 m2 ->
    match_traces ge t1 t2 /\ (t1 = t2 -> vres1 = vres2 /\ m1 = m2)
}.Record extcall_properties (sem: extcall_sem) (sg: signature) : Prop :=
  mk_extcall_properties {

(** The return value of an external call must agree with its signature. *)
  ec_well_typed:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Val.has_type vres (proj_sig_res sg);

(** The semantics is invariant under change of global environment that preserves symbols. *)
  ec_symbols_preserved:
    forall ge1 ge2 vargs m1 t vres m2,
    Senv.equiv ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    sem ge2 vargs m1 t vres m2;

(** External calls cannot invalidate memory blocks.  (Remember that
  freeing a block does not invalidate its block identifier.) *)
  ec_valid_block:
    forall ge vargs m1 t vres m2 b,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.valid_block m2 b;

(** External calls cannot increase the max permissions of a valid block.
    They can decrease the max permissions, e.g. by freeing. *)
  ec_max_perm:
    forall ge vargs m1 t vres m2 b ofs p,
    sem ge vargs m1 t vres m2 ->
    Mem.valid_block m1 b -> Mem.perm m2 b ofs Max p -> Mem.perm m1 b ofs Max p;

(** External call cannot modify memory unless they have [Max, Writable]
   permissions. *)
  ec_readonly:
    forall ge vargs m1 t vres m2,
    sem ge vargs m1 t vres m2 ->
    Mem.unchanged_on (loc_not_writable m1) m1 m2;

(** External calls must commute with memory extensions, in the
  following sense. *)
  ec_mem_extends:
    forall ge vargs m1 t vres m2 m1' vargs',
    sem ge vargs m1 t vres m2 ->
    Mem.extends m1 m1' ->
    Val.lessdef_list vargs vargs' ->
    exists vres', exists m2',
       sem ge vargs' m1' t vres' m2'
    /\ Val.lessdef vres vres'
    /\ Mem.extends m2 m2'
    /\ Mem.unchanged_on (loc_out_of_bounds m1) m1' m2';

(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject:
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    injection_full f m1 ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t'
    /\ injection_full f' m2;
  
(** External calls must commute with memory injections,
  in the following sense. *)
  ec_mem_inject':
    forall ge1 ge2 vargs m1 t vres m2 f m1' vargs',
    symbols_inject f ge1 ge2 ->
    sem ge1 vargs m1 t vres m2 ->
    Mem.inject f m1 m1' ->
    Val.inject_list f vargs vargs' ->
    exists f', exists vres', exists m2', exists t',
            sem ge2 vargs' m1' t' vres' m2'
    /\ Val.inject f' vres vres'
    /\ Mem.inject f' m2 m2'
    /\ Mem.unchanged_on (loc_unmapped f) m1 m2
    /\ Mem.unchanged_on (loc_out_of_reach f m1) m1' m2'
    /\ inject_incr f f'
    /\ inject_separated f f' m1 m1'
    /\ inject_trace f' t t';

(** External calls produce at most one event. *)
  ec_trace_length:
    forall ge vargs m t vres m',
    sem ge vargs m t vres m' -> (length t <= 1)%nat;

(** External calls must be receptive to changes of traces by another, matching trace. *)
  ec_receptive:
    forall ge vargs m t1 vres1 m1 t2,
    sem ge vargs m t1 vres1 m1 -> match_traces ge t1 t2 ->
    exists vres2, exists m2, sem ge vargs m t2 vres2 m2;

(** External calls must be deterministic up to matching between traces. *)
  ec_determ:
    forall ge vargs m t1 vres1 m1 t2 vres2 m2,
    sem ge vargs m t1 vres1 m1 -> sem ge vargs m t2 vres2 m2 ->
    match_traces ge t1 t2 /\ (t1 = t2 -> vres1 = vres2 /\ m1 = m2)
}.(** ** Semantics of volatile loads *)

Inductive volatile_load_sem (chunk: memory_chunk) (ge: Senv.t):
              list val -> mem -> trace -> val -> mem -> Prop :=
  | volatile_load_sem_intro: forall b ofs m t v,
      volatile_load ge chunk m b ofs t v ->
      volatile_load_sem chunk ge (Vptr b ofs :: nil) m t v m.(** ** Semantics of volatile loads *)

Inductive volatile_load_sem (chunk: memory_chunk) (ge: Senv.t):
              list val -> mem -> trace -> val -> mem -> Prop :=
  | volatile_load_sem_intro: forall b ofs m t v,
      volatile_load ge chunk m b ofs t v ->
      volatile_load_sem chunk ge (Vptr b ofs :: nil) m t v m.

Lemma volatile_load_extends: forall ge chunk m b ofs t v m', volatile_load ge chunk m b ofs t v -> Mem.extends m m' -> exists v', volatile_load ge chunk m' b ofs t v' /\ Val.lessdef v v'.