bedrock.lang.cpp.semantics.values
(*
* Copyright (c) 2020-2024 BedRock Systems, Inc.
* This software is distributed under the terms of the BedRock Open-Source License.
* See the LICENSE-BedRock file in the repository root for details.
*)
* Copyright (c) 2020-2024 BedRock Systems, Inc.
* This software is distributed under the terms of the BedRock Open-Source License.
* See the LICENSE-BedRock file in the repository root for details.
*)
The "operational" style definitions about C++ values.
Require Import Stdlib.Strings.Ascii.
Require Import stdpp.gmap.
Require Import bedrock.prelude.base.
Require Import bedrock.prelude.option.
Require Import bedrock.prelude.numbers.
Require Import bedrock.lang.cpp.reserved_notation. (* TODO *)
Require Import bedrock.lang.cpp.arith.operator.
Require Import bedrock.lang.cpp.arith.builtins.
Require Import bedrock.lang.cpp.syntax.
Require Export bedrock.lang.cpp.semantics.types.
Require Export bedrock.lang.cpp.semantics.sub_module.
Require Export bedrock.lang.cpp.semantics.genv.
Require Export bedrock.lang.cpp.semantics.ptrs.
Require Export bedrock.lang.cpp.semantics.heap_types.
#[local] Set Printing Coercions.
#[local] Close Scope nat_scope.
#[local] Open Scope Z_scope.
Implicit Types (σ : genv).
(* TODO: improve our axiomatic support for raw values - including "shattering"
non-raw values into their constituent raw pieces - to enable deriving
tptsto_ptr_congP_transport from tptsto_raw_ptr_congP_transport.
*)
Module Type RAW_BYTES.
Require Import stdpp.gmap.
Require Import bedrock.prelude.base.
Require Import bedrock.prelude.option.
Require Import bedrock.prelude.numbers.
Require Import bedrock.lang.cpp.reserved_notation. (* TODO *)
Require Import bedrock.lang.cpp.arith.operator.
Require Import bedrock.lang.cpp.arith.builtins.
Require Import bedrock.lang.cpp.syntax.
Require Export bedrock.lang.cpp.semantics.types.
Require Export bedrock.lang.cpp.semantics.sub_module.
Require Export bedrock.lang.cpp.semantics.genv.
Require Export bedrock.lang.cpp.semantics.ptrs.
Require Export bedrock.lang.cpp.semantics.heap_types.
#[local] Set Printing Coercions.
#[local] Close Scope nat_scope.
#[local] Open Scope Z_scope.
Implicit Types (σ : genv).
(* TODO: improve our axiomatic support for raw values - including "shattering"
non-raw values into their constituent raw pieces - to enable deriving
tptsto_ptr_congP_transport from tptsto_raw_ptr_congP_transport.
*)
Module Type RAW_BYTES.
Raw bytes
Raw bytes represent the low-level view of data. raw_byte abstracts over the internal structure of this low-level view of data. E.g. in the simple_pred model, raw_byte would be instantiated with runtime_val.
Parameter raw_byte : Set.
Parameter raw_byte_eq_dec : EqDecision raw_byte.
#[global] Existing Instance raw_byte_eq_dec.
Axiom raw_int_byte : N -> raw_byte.
(* TODO: refine our treatment of `raw_bytes` s.t. we respect
the size constraints imposed by the physical hardware.
The following might help but will likely require other
axioms which reflect boundedness or round-trip properties.
Parameter of_raw_byte : raw_byte -> N.
Axiom inj_of_raw_byte : Inj (=) (=) of_raw_byte.
#[global] Existing Instance inj_of_raw_byte.
*)
End RAW_BYTES.
Module Type VAL_MIXIN (Import P : PTRS) (Import R : RAW_BYTES).
Parameter raw_byte_eq_dec : EqDecision raw_byte.
#[global] Existing Instance raw_byte_eq_dec.
Axiom raw_int_byte : N -> raw_byte.
(* TODO: refine our treatment of `raw_bytes` s.t. we respect
the size constraints imposed by the physical hardware.
The following might help but will likely require other
axioms which reflect boundedness or round-trip properties.
Parameter of_raw_byte : raw_byte -> N.
Axiom inj_of_raw_byte : Inj (=) (=) of_raw_byte.
#[global] Existing Instance inj_of_raw_byte.
End RAW_BYTES.
Module Type VAL_MIXIN (Import P : PTRS) (Import R : RAW_BYTES).
Values
Primitive abstract C++ runtime values come in two flavors.- pointers (also used for references)
- integers (used for everything else)
Variant val : Set :=
| Vint (_ : Z)
| Vchar (_ : N)
(* ^ value used for non-integral character types, e.g.
char, wchar, etc, but *not* unsigned char and signed char
The values here are *always* unsigned. When arithmetic is performed
the semantics will convert the unsigned value into the appropriate
equivalent on the target platform based on the signedness of the type.
*)
| Vptr (_ : ptr)
| Vraw (_ : raw_byte)
| Vundef
| Vmember_ptr (_ : name) (_ : option atomic_name).
#[global] Notation Vref := Vptr (only parsing).
(* TODO Maybe this should be removed *)
#[global] Coercion Vint : Z >-> val.
Definition val_dec : forall a b : val, {a = b} + {a <> b}.
Proof. solve_decision. Defined.
#[global] Instance val_eq_dec : EqDecision val := val_dec.
#[global] Instance val_inhabited : Inhabited val := populate (Vint 0).
| Vint (_ : Z)
| Vchar (_ : N)
(* ^ value used for non-integral character types, e.g.
char, wchar, etc, but *not* unsigned char and signed char
The values here are *always* unsigned. When arithmetic is performed
the semantics will convert the unsigned value into the appropriate
equivalent on the target platform based on the signedness of the type.
*)
| Vptr (_ : ptr)
| Vraw (_ : raw_byte)
| Vundef
| Vmember_ptr (_ : name) (_ : option atomic_name).
#[global] Notation Vref := Vptr (only parsing).
(* TODO Maybe this should be removed *)
#[global] Coercion Vint : Z >-> val.
Definition val_dec : forall a b : val, {a = b} + {a <> b}.
Proof. solve_decision. Defined.
#[global] Instance val_eq_dec : EqDecision val := val_dec.
#[global] Instance val_inhabited : Inhabited val := populate (Vint 0).
Notation wrappers for val
Definition Vbool (b : bool) : val :=
Vint (if b then 1 else 0).
Definition Vnat (b : nat) : val :=
Vint (Z.of_nat b).
Definition Vn (b : N) : val :=
Vint (Z.of_N b).
Notation Vz := Vint (only parsing).
Vint (if b then 1 else 0).
Definition Vnat (b : nat) : val :=
Vint (Z.of_nat b).
Definition Vn (b : N) : val :=
Vint (Z.of_N b).
Notation Vz := Vint (only parsing).
we use Vundef as our value of type void
Definition is_raw (v : val) : bool :=
match v with
| Vraw _ => true
| _ => false
end.
Definition is_true (v : val) : option bool :=
match v with
| Vint v => Some (bool_decide (v <> 0))
| Vptr p => Some (bool_decide (p <> nullptr))
| Vchar n => Some (bool_decide (n <> 0%N))
| Vundef | Vraw _ => None
| Vmember_ptr _ p => Some (bool_decide (p <> None))
end.
#[global] Arguments is_true !_.
(* An error used to say that is_true failed on the value v *)
Record is_true_None (v : val) : Prop := {}.
Theorem is_true_int : forall i,
is_true (Vint i) = Some (bool_decide (i <> 0)).
Proof. reflexivity. Qed.
Lemma Vptr_inj p1 p2 : Vptr p1 = Vptr p2 -> p1 = p2.
Proof. by move=> []. Qed.
Lemma Vint_inj a b : Vint a = Vint b -> a = b.
Proof. by move=> []. Qed.
Lemma Vchar_inj a b : Vchar a = Vchar b -> a = b.
Proof. by move=> []. Qed.
Lemma Vbool_inj a b : Vbool a = Vbool b -> a = b.
Proof. by move: a b =>[] [] /Vint_inj. Qed.
#[global] Instance Vptr_Inj : Inj (=) (=) Vptr := Vptr_inj.
#[global] Instance Vint_Inj : Inj (=) (=) Vint := Vint_inj.
#[global] Instance Vchar_Inj : Inj (=) (=) Vchar := Vchar_inj.
#[global] Instance Vbool_Inj : Inj (=) (=) Vbool := Vbool_inj.
Definition N_to_char (t : char_type.t) (z : N) : val :=
Vchar $ trimN (char_type.bitsN t) z.
(* the default value for a type.
* this is used to initialize primitives if you do, e.g.
* int x{};
*)
Fixpoint get_default (t : type) : option val :=
match t with
| Tptr _ => Some (Vptr nullptr)
| Tnum _ _ => Some (Vint 0%Z)
| Tchar_ _ => Some (Vchar 0%N)
| Tbool => Some (Vbool false)
| Tnullptr => Some (Vptr nullptr)
| Tqualified _ t => get_default t
| _ => None
end.
End VAL_MIXIN.
Module Type RAW_BYTES_VAL
(Import P : PTRS) (Import R : RAW_BYTES)
(Import V : VAL_MIXIN P R).
match v with
| Vraw _ => true
| _ => false
end.
Definition is_true (v : val) : option bool :=
match v with
| Vint v => Some (bool_decide (v <> 0))
| Vptr p => Some (bool_decide (p <> nullptr))
| Vchar n => Some (bool_decide (n <> 0%N))
| Vundef | Vraw _ => None
| Vmember_ptr _ p => Some (bool_decide (p <> None))
end.
#[global] Arguments is_true !_.
(* An error used to say that is_true failed on the value v *)
Record is_true_None (v : val) : Prop := {}.
Theorem is_true_int : forall i,
is_true (Vint i) = Some (bool_decide (i <> 0)).
Proof. reflexivity. Qed.
Lemma Vptr_inj p1 p2 : Vptr p1 = Vptr p2 -> p1 = p2.
Proof. by move=> []. Qed.
Lemma Vint_inj a b : Vint a = Vint b -> a = b.
Proof. by move=> []. Qed.
Lemma Vchar_inj a b : Vchar a = Vchar b -> a = b.
Proof. by move=> []. Qed.
Lemma Vbool_inj a b : Vbool a = Vbool b -> a = b.
Proof. by move: a b =>[] [] /Vint_inj. Qed.
#[global] Instance Vptr_Inj : Inj (=) (=) Vptr := Vptr_inj.
#[global] Instance Vint_Inj : Inj (=) (=) Vint := Vint_inj.
#[global] Instance Vchar_Inj : Inj (=) (=) Vchar := Vchar_inj.
#[global] Instance Vbool_Inj : Inj (=) (=) Vbool := Vbool_inj.
Definition N_to_char (t : char_type.t) (z : N) : val :=
Vchar $ trimN (char_type.bitsN t) z.
(* the default value for a type.
* this is used to initialize primitives if you do, e.g.
* int x{};
*)
Fixpoint get_default (t : type) : option val :=
match t with
| Tptr _ => Some (Vptr nullptr)
| Tnum _ _ => Some (Vint 0%Z)
| Tchar_ _ => Some (Vchar 0%N)
| Tbool => Some (Vbool false)
| Tnullptr => Some (Vptr nullptr)
| Tqualified _ t => get_default t
| _ => None
end.
End VAL_MIXIN.
Module Type RAW_BYTES_VAL
(Import P : PTRS) (Import R : RAW_BYTES)
(Import V : VAL_MIXIN P R).
raw_bytes_of_val σ ty v rs states that the value v of type
ty is represented by the raw bytes in rs. What this means
depends on the type ty.
Parameter raw_bytes_of_val : genv -> Rtype -> val -> list raw_byte -> Prop.
#[local] Notation PROPER R1 R2 := (
Proper (R1 ==> eq ==> eq ==> eq ==> R2) raw_bytes_of_val
) (only parsing).
#[global] Declare Instance raw_bytes_of_val_mono : PROPER genv_leq impl.
#[global] Instance raw_bytes_of_val_flip_mono : PROPER (flip genv_leq) (flip impl).
Proof. repeat intro. exact: raw_bytes_of_val_mono. Qed.
#[global] Instance raw_bytes_of_val_flip_proper : PROPER genv_eq iff.
Proof. intros σ1 σ2 [??]; repeat intro. split; exact: raw_bytes_of_val_mono. Qed.
Axiom raw_bytes_of_val_unique_encoding : forall {σ ty v rs rs'},
raw_bytes_of_val σ ty v rs -> raw_bytes_of_val σ ty v rs' -> rs = rs'.
Axiom raw_bytes_of_val_int_unique_val : forall {σ sz sgn z z' rs},
raw_bytes_of_val σ (Tnum sz sgn) (Vint z) rs ->
raw_bytes_of_val σ (Tnum sz sgn) (Vint z') rs ->
z = z'.
Axiom raw_bytes_of_val_int_bound : forall {σ sz sgn z rs},
#[local] Notation PROPER R1 R2 := (
Proper (R1 ==> eq ==> eq ==> eq ==> R2) raw_bytes_of_val
) (only parsing).
#[global] Declare Instance raw_bytes_of_val_mono : PROPER genv_leq impl.
#[global] Instance raw_bytes_of_val_flip_mono : PROPER (flip genv_leq) (flip impl).
Proof. repeat intro. exact: raw_bytes_of_val_mono. Qed.
#[global] Instance raw_bytes_of_val_flip_proper : PROPER genv_eq iff.
Proof. intros σ1 σ2 [??]; repeat intro. split; exact: raw_bytes_of_val_mono. Qed.
Axiom raw_bytes_of_val_unique_encoding : forall {σ ty v rs rs'},
raw_bytes_of_val σ ty v rs -> raw_bytes_of_val σ ty v rs' -> rs = rs'.
Axiom raw_bytes_of_val_int_unique_val : forall {σ sz sgn z z' rs},
raw_bytes_of_val σ (Tnum sz sgn) (Vint z) rs ->
raw_bytes_of_val σ (Tnum sz sgn) (Vint z') rs ->
z = z'.
Axiom raw_bytes_of_val_int_bound : forall {σ sz sgn z rs},
raw_bytes_of_val σ (Tnum sz sgn) (Vint z) rs ->
int_rank.bound sz sgn z.
Axiom raw_bytes_of_val_sizeof : forall {σ ty v rs},
raw_bytes_of_val σ ty v rs -> size_of σ ty = Some (N.of_nat $ length rs).
(* TODO Maybe add?
Axiom raw_bytes_of_val_int : forall σ sz z rs,
raw_bytes_of_val σ (Tnum sz Unsigned) (Vint z) rs <->
exists l,
(_Z_from_bytes (genv_byte_order σ) Unsigned l = z) /\
rs = raw_int_byte <*)
Module FieldOrBase.
(* type for representing direct subobjects
*Always* qualify this name, e.g. FieldOrBase.t
*)
Variant t : Set :=
| Field (_ : atomic_name)
| Base (_ : globname).
#[global] Instance t_eq_dec : EqDecision t := ltac:(solve_decision).
#[global] Declare Instance t_countable : Countable t. (*
{ encode x := encode match x with
| Field a => inl a
| Base b => inr b
end
; decode x := (fun x => match x with
| inl a => Field a
| inr b => Base b
end) <*) (* TODO NAMES *)
End FieldOrBase.
int_rank.bound sz sgn z.
Axiom raw_bytes_of_val_sizeof : forall {σ ty v rs},
raw_bytes_of_val σ ty v rs -> size_of σ ty = Some (N.of_nat $ length rs).
(* TODO Maybe add?
Axiom raw_bytes_of_val_int : forall σ sz z rs,
raw_bytes_of_val σ (Tnum sz Unsigned) (Vint z) rs <->
exists l,
(_Z_from_bytes (genv_byte_order σ) Unsigned l = z) /\
rs = raw_int_byte <*)
Module FieldOrBase.
(* type for representing direct subobjects
*Always* qualify this name, e.g. FieldOrBase.t
*)
Variant t : Set :=
| Field (_ : atomic_name)
| Base (_ : globname).
#[global] Instance t_eq_dec : EqDecision t := ltac:(solve_decision).
#[global] Declare Instance t_countable : Countable t. (*
{ encode x := encode match x with
| Field a => inl a
| Base b => inr b
end
; decode x := (fun x => match x with
| inl a => Field a
| inr b => Base b
end) <*) (* TODO NAMES *)
End FieldOrBase.
raw_bytes_of_struct σ cls rss rs states that the struct
consisting of fields of the raw bytes rss is represented by the
raw bytes in rs.
rs should agree with rss on the offsets of the fields.
This is captured by raw_offsets.
It might be possible to make some assumptions about the
parts of rs that represent padding based on the ABI.
Parameter raw_bytes_of_struct :
genv -> globname -> gmap FieldOrBase.t (list raw_byte) -> list raw_byte -> Prop.
genv -> globname -> gmap FieldOrBase.t (list raw_byte) -> list raw_byte -> Prop.
TODO: introduction rules for raw_bytes_of_struct
The size of the raw bytes of an object is the size of the object
Elimination rules for raw_bytes_of_struct
Axiom raw_bytes_of_struct_wf_size : forall σ cls flds rs,
raw_bytes_of_struct σ cls flds rs ->
Some (length rs) = N.to_nat <$> (size_of σ (Tnamed cls)).
raw_bytes_of_struct σ cls flds rs ->
Some (length rs) = N.to_nat <$> (size_of σ (Tnamed cls)).
The raw bytes in each field is the size of the field
(* TODO: type_of_field
Axiom raw_bytes_of_struct_wf_field : forall σ cls flds rs,
raw_bytes_of_struct σ cls flds rs ->
(forall m mty,
type_of_field cls m = Some mty ->
exists bytes, flds !! FieldOrBase.Field m = Some bytes /\
Some (length bytes) = N.to_nat <*)
Axiom raw_bytes_of_struct_wf_field : forall σ cls flds rs,
raw_bytes_of_struct σ cls flds rs ->
(forall m mty,
type_of_field cls m = Some mty ->
exists bytes, flds !! FieldOrBase.Field m = Some bytes /\
Some (length bytes) = N.to_nat <*)
The raw bytes in each base is the size of the base
Axiom raw_bytes_of_struct_wf_base : forall σ cls flds rs base bytes,
raw_bytes_of_struct σ cls flds rs ->
flds !! FieldOrBase.Base base = Some bytes ->
Some (length bytes) = N.to_nat <$> (size_of σ $ Tnamed base).
raw_bytes_of_struct σ cls flds rs ->
flds !! FieldOrBase.Base base = Some bytes ->
Some (length bytes) = N.to_nat <$> (size_of σ $ Tnamed base).
The bytes at the offset are the ones that are referenced by the field
Axiom raw_bytes_of_struct_offset : forall σ cls flds rs m bytes off,
raw_bytes_of_struct σ cls flds rs ->
flds !! FieldOrBase.Field m = Some bytes ->
offset_of σ cls m = Some off ->
firstn (length bytes) (skipn (Z.to_nat off) rs) = bytes.
End RAW_BYTES_VAL.
Module Type RAW_BYTES_MIXIN
(Import P : PTRS) (Import R : RAW_BYTES)
(Import V : VAL_MIXIN P R)
(Import RD : RAW_BYTES_VAL P R V).
raw_bytes_of_struct σ cls flds rs ->
flds !! FieldOrBase.Field m = Some bytes ->
offset_of σ cls m = Some off ->
firstn (length bytes) (skipn (Z.to_nat off) rs) = bytes.
End RAW_BYTES_VAL.
Module Type RAW_BYTES_MIXIN
(Import P : PTRS) (Import R : RAW_BYTES)
(Import V : VAL_MIXIN P R)
(Import RD : RAW_BYTES_VAL P R V).
The relation val_related ty is, for most types ty, equality on
values. For type Tu8, it also includes the relation between Vint
and Vraw induced by raw_bytes_of_val.
NOTE: Should we need it, we can show val_related to be compatible
with qualifier normalization (qual_norm', qual_norm,
decompose_type, drop_qualifiers) and erasure
(erase_qualifiers) up to iff. The following, for example, is
provable.
∀ {σ} ty v1 v2,
val_related ty v1 v2 <->
qual_norm (fun _ ty => val_related ty v1 v2) ty
>>
We have the option to strengthen that <-> to =
∀ {σ} ty,
val_related ty =
qual_norm (fun _ => val_related_unqualified) ty
>>
by defining val_related using qual_norm and an auxiliary
type-indexed family of relations val_related_unqualified, rather
than directly as an inductive.
Inductive {σ : genv} : Rtype -> val -> val -> Prop :=
| Veq_refl ty v : val_related ty v v
| Vqual t ty v1 v2 :
val_related ty v1 v2 ->
val_related (Tqualified t ty) v1 v2
| Vraw_uint8 raw z (Hraw : raw_bytes_of_val σ Tbyte (Vint z) [raw]) :
val_related Tbyte (Vraw raw) (Vint z)
| Vuint8_raw z raw (Hraw : raw_bytes_of_val σ Tbyte (Vint z) [raw]) :
val_related Tbyte (Vint z) (Vraw raw).
#[local] Hint Constructors val_related : core.
Lemma val_related_not_raw {σ} v1 v2 ty :
~~ is_raw v1 -> ~~ is_raw v2 ->
val_related ty v1 v2 -> v1 = v2.
Proof. intros ??. induction 1; naive_solver. Qed.
Lemma val_related_Vint' {σ} ty v1 v2 :
val_related ty v1 v2 ->
forall z1 z2, v1 = Vint z1 -> v2 = Vint z2 -> z1 = z2.
Proof.
induction 1; simpl; intros; subst; eauto; try congruence.
Qed.
Lemma val_related_Vint {σ} ty z1 z2 :
val_related ty (Vint z1) (Vint z2) -> z1 = z2.
Proof. intros. exact: val_related_Vint'. Qed.
Lemma val_related_Vchar' {σ} ty v1 v2 :
val_related ty v1 v2 ->
forall z1 z2, v1 = Vchar z1 -> v2 = Vchar z2 -> z1 = z2.
Proof. induction 1; naive_solver. Qed.
Lemma val_related_Vchar {σ} ty n1 n2 :
val_related ty (Vchar n1) (Vchar n2) -> n1 = n2.
Proof. intros. exact: val_related_Vchar'. Qed.
(*
NOTE: This stronger property holds because pointers do not have a
raw representation. (That's future work.).
*)
Lemma val_related_Vptr' {σ} ty v1 v2 :
val_related ty v1 v2 ->
forall p1, v1 = Vptr p1 -> Vptr p1 = v2.
Proof. induction 1; naive_solver. Qed.
Lemma val_related_Vptr {σ} ty p1 v2 :
val_related ty (Vptr p1) v2 -> Vptr p1 = v2.
Proof. intros. exact: val_related_Vptr'. Qed.
Lemma val_related_ptr_iff {σ} ty v1 v2 :
val_related (Tptr ty) v1 v2 <-> v1 = v2.
Proof. split. by inversion 1. by intros ->. Qed.
Lemma val_related_Vundef' {σ} ty v1 v2 :
val_related ty v1 v2 ->
v1 = Vundef -> v2 = Vundef.
Proof. induction 1; naive_solver. Qed.
Lemma val_related_Vundef {σ} ty v :
val_related ty Vundef v -> v = Vundef.
Proof. intros. exact: val_related_Vundef'. Qed.
Lemma val_related_Vraw' {σ} ty v1 v2 :
val_related ty v1 v2 ->
forall r1 r2, v1 = Vraw r1 -> v2 = Vraw r2 -> r1 = r2.
Proof. induction 1; naive_solver. Qed.
Lemma val_related_Vraw {σ} ty r1 r2 :
val_related ty (Vraw r1) (Vraw r2) -> r1 = r2.
Proof. intros. exact: val_related_Vraw'. Qed.
Lemma val_related_qual {σ} q ty v1 v2 :
val_related ty v1 v2 ->
val_related (Tqualified q ty) v1 v2.
Proof. by constructor. Qed.
#[global] Instance val_related_equivalence {σ} ty : Equivalence (val_related ty).
Proof.
split; red.
{ done. }
{ induction 1; auto. }
intros v1 v2. induction 1.
{ done. }
{ inversion 1; simplify_eq; auto. }
{ inversion 1; simplify_eq; auto.
have [->] := raw_bytes_of_val_unique_encoding Hraw Hraw0. auto. }
{ inversion 1; simplify_eq; auto.
have -> := raw_bytes_of_val_int_unique_val Hraw Hraw0. auto. }
Qed.
#[local] Notation PROPER R1 R2 := (
Proper (R1 ==> eq ==> eq ==> eq ==> R2) (@val_related)
) (only parsing).
#[global] Instance val_related_mono : PROPER genv_leq impl.
Proof.
intros σ1 σ2 Hσ ty?<- v1?<- v2?<-. red. induction 1; auto.
all: rewrite Hσ in Hraw; auto.
Qed.
#[global] Instance val_related_flip_mono : PROPER (flip genv_leq) (flip impl).
Proof. repeat intro. exact: val_related_mono. Qed.
#[global] Instance val_related_flip_proper : PROPER genv_eq iff.
Proof. intros σ1 σ2 [??]; repeat intro. split; exact: val_related_mono. Qed.
TODO: Arguably misplaced
Lemma raw_bytes_of_val_uint_length {σ} v rs sz sgn :
raw_bytes_of_val σ (Tnum sz sgn) v rs ->
length rs = int_rank.bytesNat sz.
Proof.
move => /raw_bytes_of_val_sizeof/=.
rewrite /int_rank.bytesN /bitsize.bytesN.
inversion 1. lia.
Qed.
End RAW_BYTES_MIXIN.
Module Type HAS_TYPE (Import P : PTRS) (Import R : RAW_BYTES) (Import V : VAL_MIXIN P R).
raw_bytes_of_val σ (Tnum sz sgn) v rs ->
length rs = int_rank.bytesNat sz.
Proof.
move => /raw_bytes_of_val_sizeof/=.
rewrite /int_rank.bytesN /bitsize.bytesN.
inversion 1. lia.
Qed.
End RAW_BYTES_MIXIN.
Module Type HAS_TYPE (Import P : PTRS) (Import R : RAW_BYTES) (Import V : VAL_MIXIN P R).
typedness of values
note that only primitives fit into this, there is no val representation
of aggregates, except through Vptr p with p pointing to the contents.
has_type_prop v ty is an under-approximation in Prop of "v is an initialized value
of type t."
Assuming ty isn't qualified, this implies:
TODO: Currently, has_type_prop isn't the maximal pure part of has_type.
- if ty <> Tvoid, then v <> Vundef in all provable cases <-- ^---- TODO: <https://gitlab.com/bedrocksystems/cpp2v-core/-/issues/319>. See aborted lemma has_type_prop_not_vundef below.
- if ty = Tvoid, then v = Vundef.
- if ty = Tnullptr, then v = Vptr nullptr.
- if ty = Tnum sz sgn, then v fits the appropriate bounds (see has_int_type').
- if ty is a type of pointers, we only ensure that v = Vptr p.
- if ty is a type of references, we ensure that v = Vref p and that p <> nullptr; Vref is an alias for Vptr
Parameter has_type_prop : forall {σ : genv}, val -> Rtype -> Prop.
#[global] Notation "'valid<' ty > v" := (has_type_prop v ty%cpp_type)
(at level 30, ty at level 20, v at level 1, format "valid< ty > v") : type_scope.
#[global]
Declare Instance has_type_prop_mono : Proper (genv_leq ==> eq ==> eq ==> Basics.impl) (@has_type_prop).
#[global]
Instance has_type_prop_proper : Proper (genv_eq ==> eq ==> eq ==> iff) (@has_type_prop).
Proof.
compute; split; apply has_type_prop_mono; eauto; tauto.
Qed.
Section with_genv.
Context {σ : genv}.
Axiom has_type_prop_pointer : forall v ty,
has_type_prop v (Tptr ty) <-> exists p, v = Vptr p.
Axiom has_type_prop_erase_qualifiers : forall v ty,
has_type_prop v ty <-> has_type_prop v (erase_qualifiers ty).
Axiom has_type_prop_nullptr : forall v,
has_type_prop v Tnullptr <-> v = Vptr nullptr.
Axiom has_type_prop_ref : forall v ty,
has_type_prop v (Tref ty) <-> exists p, v = Vref p /\ p <> nullptr.
Axiom has_type_prop_rv_ref : forall v ty,
has_type_prop v (Trv_ref ty) <-> exists p, v = Vref p /\ p <> nullptr.
(* TODO FM-3760: the next axioms were not used and have unclear status. *)
(*
(* - if ty is a type of arrays, we ensure that v = Vptr p and
that p <> nullptr. *)
Axiom has_type_prop_array : forall v ty n,
has_type_prop v (Tarray ty n) -> exists p, v = Vptr p /\ p <> nullptr.
Axiom has_type_prop_function : forall v cc rty args,
has_type_prop v (Tfunction (cc:=cc) rty args) -> exists p, v = Vptr p /\ p <> nullptr.
(* + NOTE: We require that - for a type Tnamed nm - the name resolves to some
GlobDecl other than Gtype in a given σ : genv. *)
*)
Axiom has_type_prop_char : forall ct v,
(exists n, v = Vchar n /\ 0 <= n < 2^(char_type.bitsN ct))%N <-> has_type_prop v (Tchar_ ct).
Axiom has_type_prop_void : forall v,
has_type_prop v Tvoid <-> v = Vvoid.
Axiom has_type_prop_bool : forall v,
has_type_prop v Tbool <-> exists b, v = Vbool b.
(* NOTE: even if an enumeration's underlying type is <<unsigned char>> (which contains
raw values), raw values are not well typed at the enumeration type. *)
Axiom has_type_prop_enum : forall v nm,
has_type_prop v (Tenum nm) <->
exists tu ty ls,
tu ⊧ σ /\ tu.(types) !! nm = Some (Genum ty ls) /\
~~ is_raw v /\ has_type_prop v (drop_qualifiers ty).
#[global] Notation "'valid<' ty > v" := (has_type_prop v ty%cpp_type)
(at level 30, ty at level 20, v at level 1, format "valid< ty > v") : type_scope.
#[global]
Declare Instance has_type_prop_mono : Proper (genv_leq ==> eq ==> eq ==> Basics.impl) (@has_type_prop).
#[global]
Instance has_type_prop_proper : Proper (genv_eq ==> eq ==> eq ==> iff) (@has_type_prop).
Proof.
compute; split; apply has_type_prop_mono; eauto; tauto.
Qed.
Section with_genv.
Context {σ : genv}.
Axiom has_type_prop_pointer : forall v ty,
has_type_prop v (Tptr ty) <-> exists p, v = Vptr p.
Axiom has_type_prop_erase_qualifiers : forall v ty,
has_type_prop v ty <-> has_type_prop v (erase_qualifiers ty).
Axiom has_type_prop_nullptr : forall v,
has_type_prop v Tnullptr <-> v = Vptr nullptr.
Axiom has_type_prop_ref : forall v ty,
has_type_prop v (Tref ty) <-> exists p, v = Vref p /\ p <> nullptr.
Axiom has_type_prop_rv_ref : forall v ty,
has_type_prop v (Trv_ref ty) <-> exists p, v = Vref p /\ p <> nullptr.
(* TODO FM-3760: the next axioms were not used and have unclear status. *)
(*
(* - if ty is a type of arrays, we ensure that v = Vptr p and
that p <> nullptr. *)
Axiom has_type_prop_array : forall v ty n,
has_type_prop v (Tarray ty n) -> exists p, v = Vptr p /\ p <> nullptr.
Axiom has_type_prop_function : forall v cc rty args,
has_type_prop v (Tfunction (cc:=cc) rty args) -> exists p, v = Vptr p /\ p <> nullptr.
(* + NOTE: We require that - for a type Tnamed nm - the name resolves to some
GlobDecl other than Gtype in a given σ : genv. *)
*)
Axiom has_type_prop_char : forall ct v,
(exists n, v = Vchar n /\ 0 <= n < 2^(char_type.bitsN ct))%N <-> has_type_prop v (Tchar_ ct).
Axiom has_type_prop_void : forall v,
has_type_prop v Tvoid <-> v = Vvoid.
Axiom has_type_prop_bool : forall v,
has_type_prop v Tbool <-> exists b, v = Vbool b.
(* NOTE: even if an enumeration's underlying type is <<unsigned char>> (which contains
raw values), raw values are not well typed at the enumeration type. *)
Axiom has_type_prop_enum : forall v nm,
has_type_prop v (Tenum nm) <->
exists tu ty ls,
tu ⊧ σ /\ tu.(types) !! nm = Some (Genum ty ls) /\
~~ is_raw v /\ has_type_prop v (drop_qualifiers ty).
Note in the case of Tuchar, the value v could be a
raw value.
Axiom has_int_type' : forall sz sgn v,
has_type_prop v (Tnum sz sgn) <->
(exists z, v = Vint z /\ bitsize.bound (int_rank.bitsize sz) sgn z) \/
(exists r, v = Vraw r /\ Tnum (lang:=lang.cpp) sz sgn = Tuchar).
End with_genv.
End HAS_TYPE.
Module Type HAS_TYPE_MIXIN (Import P : PTRS) (Import R : RAW_BYTES) (Import V : VAL_MIXIN P R)
(Import HT : HAS_TYPE P R V).
Section with_env.
Context {σ : genv}.
Lemma has_type_prop_qual_iff t q x :
has_type_prop x t <-> has_type_prop x (Tqualified q t).
Proof.
by rewrite (has_type_prop_erase_qualifiers _ (Tqualified _ _))
(has_type_prop_erase_qualifiers _ t).
Qed.
Lemma has_nullptr_type ty :
has_type_prop (Vptr nullptr) (Tptr ty).
Proof. by rewrite has_type_prop_pointer; eexists. Qed.
Lemma has_bool_type : forall z,
0 <= z < 2 <-> has_type_prop (Vint z) Tbool.
Proof.
intros z. rewrite has_type_prop_bool. split=>Hz.
- destruct (decide (z = 0)); simplify_eq; first by exists false.
destruct (decide (z = 1)); simplify_eq; first by exists true. lia.
- unfold Vbool in Hz. destruct Hz as [b Hb].
destruct b; simplify_eq; lia.
Qed.
Lemma has_int_type : forall sz (sgn : signed) z,
bitsize.bound (int_rank.bitsize sz) sgn z <-> has_type_prop (Vint z) (Tnum sz sgn).
Proof. move => *. rewrite has_int_type'. naive_solver. Qed.
Lemma has_type_prop_char' (n : N) ct : (0 <= n < 2 ^ char_type.bitsN ct)%N <-> has_type_prop (Vchar n) (Tchar_ ct).
Proof. rewrite -has_type_prop_char. naive_solver. Qed.
Lemma has_type_prop_char_255 (n : N) ct : (0 <= n < 256)%N -> has_type_prop (Vchar n) (Tchar_ ct).
Proof. intros. rewrite -has_type_prop_char'. destruct ct; simpl; lia. Qed.
Lemma has_type_prop_char_0 ct : has_type_prop (Vchar 0) (Tchar_ ct).
Proof. intros. apply has_type_prop_char_255. lia. Qed.
Lemma has_type_prop_drop_qualifiers :
forall v ty, has_type_prop v ty <-> has_type_prop v (drop_qualifiers ty).
Proof.
induction ty; simpl; eauto.
by rewrite -has_type_prop_qual_iff -IHty.
Qed.
(* TODO fix naming convention *)
Lemma has_type_prop_qual t q x :
has_type_prop x (drop_qualifiers t) ->
has_type_prop x (Tqualified q t).
Proof.
intros. by apply has_type_prop_drop_qualifiers.
Qed.
(* Not provable yet because our rules are incomplete. *)
Lemma has_type_prop_not_vundef v ty :
has_type_prop v ty ->
drop_qualifiers ty = Tvoid <-> v = Vundef.
Proof.
intros Ht%has_type_prop_drop_qualifiers; split; intros E. {
by rewrite E has_type_prop_void in Ht.
}
apply dec_stable => G.
induction ty; move: Ht => //=. (*
rewrite has_type_prop_pointer; naive_solver.
rewrite has_type_prop_ref; naive_solver.
rewrite has_type_prop_rv_ref; naive_solver.
rewrite has_int_type'; naive_solver.
rewrite -has_type_prop_char; naive_solver.
{ (* Needs well-founded induction on types and genv! *)
rewrite has_type_prop_enum => -? ? ?. }
rewrite has_type_prop_bool; naive_solver.
{ simpl in G. tauto. }
rewrite has_type_prop_nullptr; naive_solver.
all: fail. *)
Abort.
End with_env.
#[global] Hint Resolve has_type_prop_qual : has_type_prop.
Arguments Z.add _ _ : simpl never.
Arguments Z.sub _ _ : simpl never.
Arguments Z.mul _ _ : simpl never.
Arguments Z.pow _ _ : simpl never.
Arguments Z.opp _ : simpl never.
Arguments Z.pow_pos _ _ : simpl never.
End HAS_TYPE_MIXIN.
(* Collect all the axioms. *)
Module Type VALUES_DEFS (P : PTRS_INTF) := RAW_BYTES <+ VAL_MIXIN P <+ RAW_BYTES_VAL P <+ HAS_TYPE P.
(* Plug mixins. *)
Module Type VALUES_INTF_FUNCTOR (P : PTRS_INTF) := VALUES_DEFS P <+ RAW_BYTES_MIXIN P <+ HAS_TYPE_MIXIN P.
Declare Module Export PTRS_INTF_AXIOM : PTRS_INTF.
(* Interface for other modules. *)
Module Export VALUES_INTF_AXIOM <: VALUES_INTF_FUNCTOR PTRS_INTF_AXIOM.
Include VALUES_INTF_FUNCTOR PTRS_INTF_AXIOM.
End VALUES_INTF_AXIOM.
has_type_prop v (Tnum sz sgn) <->
(exists z, v = Vint z /\ bitsize.bound (int_rank.bitsize sz) sgn z) \/
(exists r, v = Vraw r /\ Tnum (lang:=lang.cpp) sz sgn = Tuchar).
End with_genv.
End HAS_TYPE.
Module Type HAS_TYPE_MIXIN (Import P : PTRS) (Import R : RAW_BYTES) (Import V : VAL_MIXIN P R)
(Import HT : HAS_TYPE P R V).
Section with_env.
Context {σ : genv}.
Lemma has_type_prop_qual_iff t q x :
has_type_prop x t <-> has_type_prop x (Tqualified q t).
Proof.
by rewrite (has_type_prop_erase_qualifiers _ (Tqualified _ _))
(has_type_prop_erase_qualifiers _ t).
Qed.
Lemma has_nullptr_type ty :
has_type_prop (Vptr nullptr) (Tptr ty).
Proof. by rewrite has_type_prop_pointer; eexists. Qed.
Lemma has_bool_type : forall z,
0 <= z < 2 <-> has_type_prop (Vint z) Tbool.
Proof.
intros z. rewrite has_type_prop_bool. split=>Hz.
- destruct (decide (z = 0)); simplify_eq; first by exists false.
destruct (decide (z = 1)); simplify_eq; first by exists true. lia.
- unfold Vbool in Hz. destruct Hz as [b Hb].
destruct b; simplify_eq; lia.
Qed.
Lemma has_int_type : forall sz (sgn : signed) z,
bitsize.bound (int_rank.bitsize sz) sgn z <-> has_type_prop (Vint z) (Tnum sz sgn).
Proof. move => *. rewrite has_int_type'. naive_solver. Qed.
Lemma has_type_prop_char' (n : N) ct : (0 <= n < 2 ^ char_type.bitsN ct)%N <-> has_type_prop (Vchar n) (Tchar_ ct).
Proof. rewrite -has_type_prop_char. naive_solver. Qed.
Lemma has_type_prop_char_255 (n : N) ct : (0 <= n < 256)%N -> has_type_prop (Vchar n) (Tchar_ ct).
Proof. intros. rewrite -has_type_prop_char'. destruct ct; simpl; lia. Qed.
Lemma has_type_prop_char_0 ct : has_type_prop (Vchar 0) (Tchar_ ct).
Proof. intros. apply has_type_prop_char_255. lia. Qed.
Lemma has_type_prop_drop_qualifiers :
forall v ty, has_type_prop v ty <-> has_type_prop v (drop_qualifiers ty).
Proof.
induction ty; simpl; eauto.
by rewrite -has_type_prop_qual_iff -IHty.
Qed.
(* TODO fix naming convention *)
Lemma has_type_prop_qual t q x :
has_type_prop x (drop_qualifiers t) ->
has_type_prop x (Tqualified q t).
Proof.
intros. by apply has_type_prop_drop_qualifiers.
Qed.
(* Not provable yet because our rules are incomplete. *)
Lemma has_type_prop_not_vundef v ty :
has_type_prop v ty ->
drop_qualifiers ty = Tvoid <-> v = Vundef.
Proof.
intros Ht%has_type_prop_drop_qualifiers; split; intros E. {
by rewrite E has_type_prop_void in Ht.
}
apply dec_stable => G.
induction ty; move: Ht => //=. (*
rewrite has_type_prop_pointer; naive_solver.
rewrite has_type_prop_ref; naive_solver.
rewrite has_type_prop_rv_ref; naive_solver.
rewrite has_int_type'; naive_solver.
rewrite -has_type_prop_char; naive_solver.
{ (* Needs well-founded induction on types and genv! *)
rewrite has_type_prop_enum => -? ? ?. }
rewrite has_type_prop_bool; naive_solver.
{ simpl in G. tauto. }
rewrite has_type_prop_nullptr; naive_solver.
all: fail. *)
Abort.
End with_env.
#[global] Hint Resolve has_type_prop_qual : has_type_prop.
Arguments Z.add _ _ : simpl never.
Arguments Z.sub _ _ : simpl never.
Arguments Z.mul _ _ : simpl never.
Arguments Z.pow _ _ : simpl never.
Arguments Z.opp _ : simpl never.
Arguments Z.pow_pos _ _ : simpl never.
End HAS_TYPE_MIXIN.
(* Collect all the axioms. *)
Module Type VALUES_DEFS (P : PTRS_INTF) := RAW_BYTES <+ VAL_MIXIN P <+ RAW_BYTES_VAL P <+ HAS_TYPE P.
(* Plug mixins. *)
Module Type VALUES_INTF_FUNCTOR (P : PTRS_INTF) := VALUES_DEFS P <+ RAW_BYTES_MIXIN P <+ HAS_TYPE_MIXIN P.
Declare Module Export PTRS_INTF_AXIOM : PTRS_INTF.
(* Interface for other modules. *)
Module Export VALUES_INTF_AXIOM <: VALUES_INTF_FUNCTOR PTRS_INTF_AXIOM.
Include VALUES_INTF_FUNCTOR PTRS_INTF_AXIOM.
End VALUES_INTF_AXIOM.
Derived
Lemma has_type_prop_raw_bytes_of_val {σ} z raw :
raw_bytes_of_val σ Tuchar (Vint z) [raw] ->
has_type_prop (Vraw raw) Tbyte <-> has_type_prop (Vint z) Tbyte.
Proof.
rewrite !has_int_type'. split.
{ intros [(? & ? & _)|(? & ? & _)]; first done.
left. eexists; split; first done. exact: raw_bytes_of_val_int_bound. }
{ intros [(? & ? & _)|(? & ? & _)]; last done. right. by eexists. }
Qed.
Lemma has_type_prop_val_related {σ} ty v1 v2 :
val_related ty v1 v2 ->
has_type_prop v1 ty <-> has_type_prop v2 ty.
Proof.
induction 1.
{ done. }
{ by rewrite -!has_type_prop_qual_iff. }
all: by rewrite has_type_prop_raw_bytes_of_val.
Qed.