[inferbo] Pruning collection.size in Java

Summary:
It prunes the size of collections when the size function is called in the condition expression.  The diff extended the alias domain to understand temporary variables of SIL from Java.

Depends on D16761461

Reviewed By: ezgicicek

Differential Revision: D16761611

fbshipit-source-id: 849c5c71c

infer/src/bufferoverrun/absLoc.ml

@@ -257,6 +257,8 @@ module Loc = struct
         false
 
 
+  let is_frontend_tmp = function Var x -> not (Var.appears_in_source_code x) | _ -> false
+
   let rec is_pretty = function
     | Var _ ->
         true

infer/src/bufferoverrun/bufferOverrunDomain.ml

@@ -689,6 +689,7 @@ module AliasTarget = struct
     | Size of Loc.t
     | Fgets of Loc.t
     | Nullity of Loc.t
+    | Top
   [@@deriving compare]
 
   let equal = [%compare.equal: t]
@@ -707,6 +708,8 @@ module AliasTarget = struct
         F.fprintf fmt "fgets(%a)" Loc.pp l
     | Nullity l ->
         F.fprintf fmt "nullity(%a)" Loc.pp l
+    | Top ->
+        F.fprintf fmt "T"
 
 
   let fgets l = Fgets l
@@ -715,10 +718,12 @@ module AliasTarget = struct
 
   let get_loc = function
     | Simple l | SimplePlusA (l, _) | Empty l | Size l | Fgets l | Nullity l ->
-        l
+        Some l
+    | Top ->
+        None
 
 
-  let use l x = Loc.equal l (get_loc x)
+  let use_loc l x = Option.value_map (get_loc x) ~default:false ~f:(Loc.equal l)
 
   let loc_map x ~f =
     match x with
@@ -734,18 +739,17 @@ module AliasTarget = struct
         Option.map (f l) ~f:(fun l -> Fgets l)
     | Nullity l ->
         Option.map (f l) ~f:(fun l -> Nullity l)
+    | Top ->
+        Some Top
 
 
   let ( <= ) ~lhs ~rhs = equal lhs rhs
 
-  let join x y =
+  let join x y = if equal x y then x else Top
-    assert (equal x y) ;
-    x
-
 
   let widen ~prev ~next ~num_iters:_ = join prev next
 
-  let is_unknown x = Loc.is_unknown (get_loc x)
+  let is_unknown x = Option.value_map (get_loc x) ~default:false ~f:Loc.is_unknown
 end
 
 (* Relations between values of logical variables(registers) and program variables
@@ -767,23 +771,76 @@ end
    AliasTarget.Empty relation, but is used when there is a program variable [i] for the length of
    the array. *)
 module AliasMap = struct
-  include AbstractDomain.Map (Ident) (AliasTarget)
+  module Key = struct
+    type t = IdentKey of Ident.t | JavaTmp of Loc.t [@@deriving compare]
+
+    let of_id id = IdentKey id
+
+    let of_java_tmp l = JavaTmp l
+
+    let pp f = function IdentKey id -> Ident.pp f id | JavaTmp l -> Loc.pp f l
+
+    let use_loc l = function JavaTmp l' -> Loc.equal l l' | IdentKey _ -> false
+  end
+
+  include AbstractDomain.InvertedMap (Key) (AliasTarget)
+
+  let some_non_top = function AliasTarget.Top -> None | v -> Some v
+
+  let add k v m = match some_non_top v with None -> remove k m | Some v -> add k v m
+
+  let join x y =
+    let join_v _key vx vy =
+      IOption.map2 vx vy ~f:(fun vx vy -> AliasTarget.join vx vy |> some_non_top)
+    in
+    merge join_v x y
+
+
+  let widen ~prev:x ~next:y ~num_iters =
+    let widen_v _key vx vy =
+      IOption.map2 vx vy ~f:(fun vx vy ->
+          AliasTarget.widen ~prev:vx ~next:vy ~num_iters |> some_non_top )
+    in
+    merge widen_v x y
+
 
   let pp : F.formatter -> t -> unit =
    fun fmt x ->
     if not (is_empty x) then
       let pp_sep fmt () = F.fprintf fmt ", @," in
-      let pp1 fmt (k, v) = F.fprintf fmt "%a=%a" Ident.pp k AliasTarget.pp v in
+      let pp1 fmt (k, v) = F.fprintf fmt "%a=%a" Key.pp k AliasTarget.pp v in
       F.pp_print_list ~pp_sep pp1 fmt (bindings x)
 
 
+  let find_id : Ident.t -> t -> AliasTarget.t option = fun id x -> find_opt (Key.of_id id) x
+
+  let find_java_tmp : Loc.t -> t -> AliasTarget.t option =
+   fun id x -> find_opt (Key.of_java_tmp id) x
+
+
   let load : Ident.t -> AliasTarget.t -> t -> t =
-   fun id a x -> if not (AliasTarget.is_unknown a) then add id a x else x
+   fun id tgt x ->
+    if AliasTarget.is_unknown tgt then x
+    else
+      let tgt =
+        match tgt with
+        | AliasTarget.Simple loc when Language.curr_language_is Java ->
+            Option.value (find_java_tmp loc x) ~default:tgt
+        | _ ->
+            tgt
+      in
+      add (Key.of_id id) tgt x
+
 
+  let forget : Loc.t -> t -> t =
+   fun l m -> filter (fun k y -> (not (Key.use_loc l k)) && not (AliasTarget.use_loc l y)) m
 
-  let forget : Loc.t -> t -> t = fun l m -> filter (fun _ y -> not (AliasTarget.use l y)) m
 
-  let find : Ident.t -> t -> AliasTarget.t option = find_opt
+  let store : Loc.t -> Ident.t -> t -> t =
+   fun l id x ->
+    if Language.curr_language_is Java && Loc.is_frontend_tmp l then
+      Option.value_map (find_id id x) ~default:x ~f:(fun tgt -> add (Key.of_java_tmp l) tgt x)
+    else x
 end
 
 module AliasRet = struct
@@ -823,7 +880,7 @@ module Alias = struct
 
   let bind_map : (AliasMap.t -> 'a) -> t -> 'a = fun f a -> f a.map
 
-  let find : Ident.t -> t -> AliasTarget.t option = fun x -> bind_map (AliasMap.find x)
+  let find_id : Ident.t -> t -> AliasTarget.t option = fun x -> bind_map (AliasMap.find_id x)
 
   let find_ret : t -> AliasTarget.t option = fun x -> AliasRet.get x.ret
 
@@ -833,9 +890,12 @@ module Alias = struct
    fun loc e a ->
     let a = lift_map (AliasMap.forget loc) a in
     match e with
-    | Exp.Var l when Loc.is_return loc ->
+    | Exp.Var l ->
-        let update_ret retl = {a with ret= AliasRet.v retl} in
+        let a = lift_map (AliasMap.store loc l) a in
-        Option.value_map (find l a) ~default:a ~f:update_ret
+        if Loc.is_return loc then
+          let update_ret retl = {a with ret= AliasRet.v retl} in
+          Option.value_map (find_id l a) ~default:a ~f:update_ret
+        else a
     | Exp.BinOp (Binop.PlusA _, Exp.Var id, Exp.Const (Const.Cint i))
     | Exp.BinOp (Binop.PlusA _, Exp.Const (Const.Cint i), Exp.Var id) ->
         lift_map (AliasMap.load id (AliasTarget.SimplePlusA (loc, IntLit.neg i))) a
@@ -866,7 +926,8 @@ module Alias = struct
         a
 
 
-  let remove_temp : Ident.t -> t -> t = fun temp -> lift_map (AliasMap.remove temp)
+  let remove_temp : Ident.t -> t -> t =
+   fun temp -> lift_map (AliasMap.remove (AliasMap.Key.of_id temp))
 end
 
 module CoreVal = struct
@@ -1350,22 +1411,27 @@ module MemReach = struct
     PowLoc.fold find_join locs Val.bot
 
 
-  let find_alias : Ident.t -> _ t0 -> AliasTarget.t option = fun k m -> Alias.find k m.alias
+  let find_alias : Ident.t -> _ t0 -> AliasTarget.t option = fun k m -> Alias.find_id k m.alias
 
   let find_simple_alias : Ident.t -> _ t0 -> (Loc.t * IntLit.t option) option =
    fun k m ->
-    match Alias.find k m.alias with
+    match Alias.find_id k m.alias with
     | Some (AliasTarget.Simple l) ->
         Some (l, None)
     | Some (AliasTarget.SimplePlusA (l, i)) ->
         Some (l, Some i)
-    | Some (AliasTarget.Empty _ | AliasTarget.Size _ | AliasTarget.Fgets _ | AliasTarget.Nullity _)
+    | Some
+        ( AliasTarget.Empty _
+        | AliasTarget.Size _
+        | AliasTarget.Fgets _
+        | AliasTarget.Nullity _
+        | AliasTarget.Top )
     | None ->
         None
 
 
   let find_size_alias : Ident.t -> _ t0 -> Loc.t option =
-   fun k m -> match Alias.find k m.alias with Some (AliasTarget.Size l) -> Some l | _ -> None
+   fun k m -> match Alias.find_id k m.alias with Some (AliasTarget.Size l) -> Some l | _ -> None
 
 
   let find_ret_alias : _ t0 -> AliasTarget.t option = fun m -> Alias.find_ret m.alias

infer/src/bufferoverrun/bufferOverrunModels.ml

@@ -892,7 +892,12 @@ module Collection = struct
   let size coll_exp =
     let exec _ ~ret:(ret_id, _) mem =
       let result = eval_collection_length coll_exp mem in
-      model_by_value result ret_id mem
+      let mem = model_by_value result ret_id mem in
+      match PowLoc.is_singleton_or_more (eval_collection_internal_array_locs coll_exp mem) with
+      | IContainer.Singleton loc ->
+          Dom.Mem.load_size_alias ret_id loc mem
+      | IContainer.Empty | IContainer.More ->
+          mem
     in
     {exec; check= no_check}
 

infer/src/bufferoverrun/bufferOverrunSemantics.ml

@@ -30,7 +30,9 @@ let rec must_alias : Exp.t -> Exp.t -> Mem.t -> bool =
   | Exp.Var x1, Exp.Var x2 -> (
     match (Mem.find_alias x1 m, Mem.find_alias x2 m) with
     | Some x1', Some x2' ->
-        AliasTarget.equal x1' x2' && not (Mem.is_rep_multi_loc (AliasTarget.get_loc x1') m)
+        AliasTarget.equal x1' x2'
+        && Option.value_map (AliasTarget.get_loc x1') ~default:false ~f:(fun l ->
+               not (Mem.is_rep_multi_loc l m) )
     | _, _ ->
         false )
   | Exp.UnOp (uop1, e1', _), Exp.UnOp (uop2, e2', _) ->
@@ -313,7 +315,8 @@ let rec eval_arr : Typ.IntegerWidths.t -> Exp.t -> Mem.t -> Val.t =
         | AliasTarget.Size _
         | AliasTarget.Empty _
         | AliasTarget.Fgets _
-        | AliasTarget.Nullity _ )
+        | AliasTarget.Nullity _
+        | Top )
     | None ->
         Val.bot )
   | Exp.Lvar pvar ->
@@ -513,7 +516,7 @@ module Prune = struct
           let v = Mem.find lv mem in
           let v' = Val.prune_eq_zero v in
           update_mem_in_prune lv v' astate
-      | Some (AliasTarget.SimplePlusA _ | AliasTarget.Size _) | None ->
+      | Some (AliasTarget.SimplePlusA _ | AliasTarget.Size _ | Top) | None ->
           astate )
     | Exp.UnOp (Unop.LNot, Exp.Var x, _) -> (
       match Mem.find_alias x mem with
@@ -530,7 +533,7 @@ module Prune = struct
           let itv_v = Itv.prune_comp Binop.Ge (Val.get_itv v) Itv.one in
           let v' = Val.modify_itv itv_v v in
           update_mem_in_prune lv v' astate
-      | Some (AliasTarget.SimplePlusA _ | AliasTarget.Size _ | AliasTarget.Fgets _) | None ->
+      | Some (AliasTarget.SimplePlusA _ | AliasTarget.Size _ | AliasTarget.Fgets _ | Top) | None ->
           astate )
     | _ ->
         astate

infer/src/istd/IOption.ml

@@ -14,3 +14,5 @@ let value_default_f ~f = function None -> f () | Some v -> v
 let if_none_evalopt ~f x = match x with None -> f () | Some _ -> x
 
 let if_none_eval = value_default_f
+
+let map2 x y ~f = match (x, y) with None, _ | _, None -> None | Some x, Some y -> f x y

infer/src/istd/IOption.mli

@@ -22,3 +22,6 @@ val if_none_eval : f:(unit -> 'a) -> 'a option -> 'a
 (** [if_none_eval ~f x] evaluates to [y] if [x=Some y] else to [f ()].
     Useful for terminating chains built with [if_none_evalopt]. 
     This is exactly the same as [value_default_f] but with a better name. *)
+
+val map2 : 'a option -> 'b option -> f:('a -> 'b -> 'c option) -> 'c option
+(** Like [Option.map2] but [f] may return [None]. *)

infer/tests/codetoanalyze/java/bufferoverrun/Array.java

@@ -68,4 +68,36 @@ class Array {
   void positive_alloc_Good() {
     a = new ArrayList<>(10);
   }
+
+  void iterate_collection_Good(ArrayList<Integer> a) {
+    if (a.size() > 10) {
+      int x = a.get(9);
+    }
+  }
+
+  void call_iterate_collection_Good() {
+    ArrayList<Integer> x = new ArrayList<Integer>();
+    x.add(0);
+    x.add(0);
+    x.add(0);
+    x.add(0);
+    x.add(0);
+    this.iterate_collection_Good(x);
+  }
+
+  void iterate_collection_Bad(ArrayList<Integer> a) {
+    if (a.size() >= 5) {
+      int x = a.get(5);
+    }
+  }
+
+  void call_iterate_collection_Bad() {
+    ArrayList<Integer> x = new ArrayList<Integer>();
+    x.add(0);
+    x.add(0);
+    x.add(0);
+    x.add(0);
+    x.add(0);
+    this.iterate_collection_Bad(x);
+  }
 }

infer/tests/codetoanalyze/java/bufferoverrun/issues.exp

@@ -1,3 +1,4 @@
+codetoanalyze/java/bufferoverrun/Array.java, codetoanalyze.java.bufferoverrun.Array.call_iterate_collection_Bad():void, 7, BUFFER_OVERRUN_L1, no_bucket, ERROR, [Array declaration,Through,Through,Through,Through,Through,Call,<Length trace>,Array declaration,Array access: Offset: 5 Size: 5 by call to `void Array.iterate_collection_Bad(ArrayList)` ]
 codetoanalyze/java/bufferoverrun/Array.java, codetoanalyze.java.bufferoverrun.Array.collection_remove_from_empty_Bad():java.util.ArrayList, 2, BUFFER_OVERRUN_L1, no_bucket, ERROR, [<Length trace>,Array declaration,Array access: Offset: 0 Size: 0]
 codetoanalyze/java/bufferoverrun/Array.java, codetoanalyze.java.bufferoverrun.Array.negative_alloc_Bad():void, 1, INFERBO_ALLOC_IS_NEGATIVE, no_bucket, ERROR, [Allocation: Length: -1]
 codetoanalyze/java/bufferoverrun/Array.java, codetoanalyze.java.bufferoverrun.Array.null_pruning1_Bad():void, 2, CONDITION_ALWAYS_TRUE, no_bucket, WARNING, [Here]