infer_clone/infer/src/backend/symExec.ml

(*
 * Copyright (c) 2009 - 2013 Monoidics ltd.
 * Copyright (c) 2013 - present Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *)

(** Symbolic Execution *)

module L = Logging
module F = Format
open Utils

let rec idlist_assoc id = function
  | [] -> raise Not_found
  | (i, x):: l -> if Ident.equal i id then x else idlist_assoc id l

let rec fldlist_assoc fld = function
  | [] -> raise Not_found
  | (fld', x, a):: l -> if Sil.fld_equal fld fld' then x else fldlist_assoc fld l

let rec explist_assoc e = function
  | [] -> raise Not_found
  | (e', x):: l -> if Sil.exp_equal e e' then x else explist_assoc e l

let append_list_op list_op1 list_op2 =
  match list_op1, list_op2 with
  | None, _ -> list_op2
  | _, None -> list_op1
  | Some list1, Some list2 -> Some (list1@list2)

let reverse_list_op list_op =
  match list_op with
  | None -> None
  | Some list -> Some (IList.rev list)

let rec unroll_type tenv typ off =
  match (typ, off) with
  | Sil.Tvar _, _ ->
      let typ' = Sil.expand_type tenv typ in
      unroll_type tenv typ' off
  | Sil.Tstruct (ftal, sftal, _, _, _, _, _), Sil.Off_fld (fld, _) ->
      begin
        try fldlist_assoc fld (ftal @ sftal)
        with Not_found ->
          L.d_strln ".... Invalid Field Access ....";
          L.d_strln ("Fld : " ^ Ident.fieldname_to_string fld);
          L.d_str "Type : "; Sil.d_typ_full typ; L.d_ln ();
          raise (Exceptions.Bad_footprint (try assert false with Assert_failure x -> x))
      end
  | Sil.Tarray (typ', _), Sil.Off_index _ ->
      typ'
  | _, Sil.Off_index (Sil.Const (Sil.Cint i)) when Sil.Int.iszero i ->
      typ
  | _ ->
      L.d_strln ".... Invalid Field Access ....";
      L.d_str "Fld : "; Sil.d_offset off; L.d_ln ();
      L.d_str "Type : "; Sil.d_typ_full typ; L.d_ln ();
      assert false

(* Given a node, returns a list of pvar of blocks that have been nullified in the block *)
let get_nullified_block node =
  let null_blocks = IList.flatten(IList.map (fun i -> match i with
      | Sil.Nullify(pvar, _, true) when Sil.is_block_pvar pvar -> [pvar]
      | _ -> []) (Cfg.Node.get_instrs node)) in
  null_blocks

(* Given a proposition and an objc block checks whether by existentially quantifying *)
(* captured variables in the block we obtain a leak *)
let check_block_retain_cycle cfg tenv pname _prop block_nullified =
  let mblock = Sil.pvar_get_name block_nullified in
  let block_captured = (match Cfg.get_block_pdesc cfg mblock with
      | Some pd -> fst (IList.split (Cfg.Procdesc.get_captured pd))
      | None -> []) in
  let _prop' = Cfg.remove_seed_captured_vars_block block_captured _prop in
  let _prop'' = Prop.prop_rename_fav_with_existentials _prop' in
  let _ = Abs.abstract_junk ~original_prop: _prop pname tenv _prop'' in
  ()

(** Apply function [f] to the expression at position [offlist] in [strexp].
    If not found, expand [strexp] and apply [f] to [None].
    The routine should maintain the invariant that strexp and typ correspond to
    each other exactly, without involving any re - interpretation of some type t
    as the t array. The [fp_root] parameter indicates whether the kind of the
    root expression of the corresponding pointsto predicate is a footprint identifier.
    The function can expand a list of higher - order [hpara_psto] predicates, if
    the list is stored at [offlist] in [strexp] initially. The expanded list
    is returned as a part of the result. All these happen under [p], so that it
    is sound to call the prover with [p]. Finally, before running this function,
    the tool should run strexp_extend_value in rearrange.ml for the same strexp
    and offlist, so that all the necessary extensions of strexp are done before
    this function. If the tool follows this protocol, it will never hit the assert
    false cases for field and array accesses. *)
let rec apply_offlist
    footprint_part pdesc tenv p fp_root nullify_struct
    (root_lexp, strexp, typ) offlist (f: Sil.exp option -> Sil.exp) inst lookup_inst =
  let pname = Cfg.Procdesc.get_proc_name pdesc in
  let pp_error () =
    L.d_strln ".... Invalid Field ....";
    L.d_str "strexp : "; Sil.d_sexp strexp; L.d_ln ();
    L.d_str "offlist : "; Sil.d_offset_list offlist; L.d_ln ();
    L.d_str "type : "; Sil.d_typ_full typ; L.d_ln ();
    L.d_str "prop : "; Prop.d_prop p; L.d_ln (); L.d_ln () in
  match offlist, strexp with
  | [], Sil.Eexp (e, inst_curr) ->
      let inst_is_uninitialized = function
        | Sil.Ialloc ->
            (* java allocation initializes with default values *)
            !Config.curr_language <> Config.Java
        | Sil.Iinitial -> true
        | _ -> false in
      let is_hidden_field () =
        match State.get_instr () with
        | Some (Sil.Letderef (_, Sil.Lfield (_, fieldname, _), _, _)) ->
            Ident.fieldname_is_hidden fieldname
        | _ -> false in
      let inst_new = match inst with
        | Sil.Ilookup when inst_is_uninitialized inst_curr && not (is_hidden_field()) -> (* we are in a lookup of an uninitialized value *)
            lookup_inst := Some inst_curr;
            let alloc_attribute_opt =
              if inst_curr = Sil.Iinitial then None
              else Prop.get_undef_attribute p root_lexp in
            let deref_str = Localise.deref_str_uninitialized alloc_attribute_opt in
            let err_desc = Errdesc.explain_memory_access deref_str p (State.get_loc ()) in
            let exn = (Exceptions.Uninitialized_value (err_desc, try assert false with Assert_failure x -> x)) in
            let pre_opt = State.get_normalized_pre (Abs.abstract_no_symop pname) in
            Reporting.log_warning pname ~pre: pre_opt exn;
            Sil.update_inst inst_curr inst
        | Sil.Ilookup -> (* a lookup does not change an inst unless it is inst_initial *)
            lookup_inst := Some inst_curr;
            inst_curr
        | _ -> Sil.update_inst inst_curr inst in
      let e' = f (Some e) in
      (e', Sil.Eexp (e', inst_new), typ, None)
  | [], Sil.Estruct (fesl, inst') ->
      if not nullify_struct then (f None, Sil.Estruct (fesl, inst'), typ, None)
      else if fp_root then (pp_error(); assert false)
      else
        begin
          L.d_strln "WARNING: struct assignment treated as nondeterministic assignment";
          (f None, Prop.create_strexp_of_type (Some tenv) Prop.Fld_init typ inst, typ, None)
        end
  | [], Sil.Earray _ ->
      let offlist' = (Sil.Off_index Sil.exp_zero):: offlist in
      apply_offlist
        footprint_part pdesc tenv p fp_root nullify_struct
        (root_lexp, strexp, typ) offlist' f inst lookup_inst
  | (Sil.Off_fld (fld, _)):: offlist', Sil.Earray _ ->
      let offlist_new = Sil.Off_index(Sil.exp_zero) :: offlist in
      apply_offlist
        footprint_part pdesc tenv p fp_root nullify_struct
        (root_lexp, strexp, typ) offlist_new f inst lookup_inst
  | (Sil.Off_fld (fld, fld_typ)):: offlist', Sil.Estruct (fsel, inst') ->
      begin
        let typ' = Sil.expand_type tenv typ in
        let ftal, sftal, csu, nameo, supers, def_mthds, iann =
          match typ' with
          | Sil.Tstruct (ftal, sftal, csu, nameo, supers, def_mthds, iann) ->
              ftal, sftal, csu, nameo, supers, def_mthds, iann
          | _ -> assert false in
        let t' = unroll_type tenv typ (Sil.Off_fld (fld, fld_typ)) in
        try
          let _, se' = IList.find (fun fse -> Ident.fieldname_equal fld (fst fse)) fsel in
          let res_e', res_se', res_t', res_pred_insts_op' =
            apply_offlist
              footprint_part pdesc tenv p fp_root nullify_struct
              (root_lexp, se', t') offlist' f inst lookup_inst in
          let replace_fse fse = if Sil.fld_equal fld (fst fse) then (fld, res_se') else fse in
          let res_se = Sil.Estruct (IList.map replace_fse fsel, inst') in
          let replace_fta (f, t, a) = if Sil.fld_equal fld f then (fld, res_t', a) else (f, t, a) in
          let res_t =
            Sil.Tstruct
              (IList.map replace_fta ftal, sftal, csu, nameo, supers, def_mthds, iann) in
          (res_e', res_se, res_t, res_pred_insts_op')
        with Not_found ->
          pp_error();
          assert false
          (* This case should not happen. The rearrangement should
             have materialized all the accessed cells. *)
      end
  | (Sil.Off_fld _):: _, _ ->
      pp_error();
      assert false

  | (Sil.Off_index idx):: offlist', Sil.Earray (size, esel, inst1) ->
      let nidx = Prop.exp_normalize_prop p idx in
      begin
        let typ' = Sil.expand_type tenv typ in
        let t', size' = match typ' with Sil.Tarray (t', size') -> (t', size') | _ -> assert false in
        try
          let idx_ese', se' = IList.find (fun ese -> Prover.check_equal p nidx (fst ese)) esel in
          let res_e', res_se', res_t', res_pred_insts_op' =
            apply_offlist
              footprint_part pdesc tenv p fp_root nullify_struct
              (root_lexp, se', t') offlist' f inst lookup_inst in
          let replace_ese ese = if Sil.exp_equal idx_ese' (fst ese) then (idx_ese', res_se') else ese in
          let res_se = Sil.Earray(size, IList.map replace_ese esel, inst1) in
          let res_t = Sil.Tarray(res_t', size') in
          (res_e', res_se, res_t, res_pred_insts_op')
        with Not_found -> (* return a nondeterministic value if the index is not found after rearrangement *)
          L.d_str "apply_offlist: index "; Sil.d_exp idx; L.d_strln " not materialized -- returning nondeterministic value";
          let res_e' = Sil.Var (Ident.create_fresh Ident.kprimed) in
          (res_e', strexp, typ, None)
      end
  | (Sil.Off_index idx):: offlist', _ ->
      pp_error();
      raise (Exceptions.Internal_error (Localise.verbatim_desc "Array out of bounds in Symexec"))
(* This case should not happen. The rearrangement should
   have materialized all the accessed cells. *)

(** Given [lexp |-> se: typ], if the location [offlist] exists in [se],
    function [ptsto_lookup p (lexp, se, typ) offlist id] returns a tuple.
    The first component of the tuple is an expression at position [offlist] in [se].
    The second component is an expansion of the predicate [lexp |-> se: typ],
    where the entity at [offlist] in [se] is expanded if the entity is a list of
    higher - order parameters [hpara_psto]. If this expansion happens,
    the last component of the tuple is a list of pi - sigma pairs obtained
    by instantiating the [hpara_psto] list. Otherwise, the last component is None.
    All these steps happen under [p]. So, we can call a prover with [p].
    Finally, before running this function, the tool should run strexp_extend_value
    in rearrange.ml for the same se and offlist, so that all the necessary
    extensions of se are done before this function. *)
let ptsto_lookup footprint_part pdesc tenv p (lexp, se, typ, st) offlist id =
  let f =
    function Some exp -> exp | None -> Sil.Var id in
  let fp_root =
    match lexp with Sil.Var id -> Ident.is_footprint id | _ -> false in
  let lookup_inst = ref None in
  let e', se', typ', pred_insts_op' =
    apply_offlist
      footprint_part pdesc tenv p fp_root false
      (lexp, se, typ) offlist f Sil.inst_lookup lookup_inst in
  let lookup_uninitialized = (* true if we have looked up an uninitialized value *)
    match !lookup_inst with
    | Some (Sil.Iinitial | Sil.Ialloc | Sil.Ilookup) -> true
    | _ -> false in
  let ptsto' = Prop.mk_ptsto lexp se' (Sil.Sizeof (typ', st)) in
  (e', ptsto', pred_insts_op', lookup_uninitialized)

(** [ptsto_update p (lexp,se,typ) offlist exp] takes
    [lexp |-> se: typ], and updates [se] by replacing the
    expression at [offlist] with [exp]. Then, it returns
    the updated pointsto predicate. If [lexp |-> se: typ] gets
    expanded during this update, the generated pi - sigma list from
    the expansion gets returned, and otherwise, None is returned.
    All these happen under the proposition [p], so it is ok call
    prover with [p]. Finally, before running this function,
    the tool should run strexp_extend_value in rearrange.ml for the same
    se and offlist, so that all the necessary extensions of se are done
    before this function. *)
let ptsto_update footprint_part pdesc tenv p (lexp, se, typ, st) offlist exp =
  let f _ = exp in
  let fp_root =
    match lexp with Sil.Var id -> Ident.is_footprint id | _ -> false in
  let lookup_inst = ref None in
  let _, se', typ', pred_insts_op' =
    let pos = State.get_path_pos () in
    apply_offlist
      footprint_part pdesc tenv p fp_root true (lexp, se, typ)
      offlist f (State.get_inst_update pos) lookup_inst in
  let ptsto' = Prop.mk_ptsto lexp se' (Sil.Sizeof (typ', st)) in
  (ptsto', pred_insts_op')

let update_iter iter pi sigma =
  let iter' = Prop.prop_iter_update_current_by_list iter sigma in
  IList.fold_left (Prop.prop_iter_add_atom false) iter' pi

(** Module for builtin functions with their symbolic execution handler *)
module Builtin = struct
  type ret_typ = (Prop.normal Prop.t * Paths.Path.t) list
  type sym_exe_builtin =
    Cfg.cfg -> Cfg.Procdesc.t -> Sil.instr -> Sil.tenv -> Prop.normal Prop.t -> Paths.Path.t ->
    Ident.t list -> (Sil.exp * Sil.typ) list -> Procname.t -> Location.t -> ret_typ

  (* builtin function names for which we do symbolic execution *)
  let builtin_functions = Procname.Hash.create 4
  (* builtin plain function names: they match all the function names whose plain name is the given string *)
  let builtin_plain_functions = Hashtbl.create 4

  (* Check if the function is a builtin *)
  let is_registered name =
    Procname.Hash.mem builtin_functions name
    ||
    Hashtbl.mem builtin_plain_functions (Procname.to_string name)

  (* get the symbolic execution handler associated to the builtin function name *)
  let get_sym_exe_builtin name : sym_exe_builtin =
    try Procname.Hash.find builtin_functions name
    with Not_found ->
    try Hashtbl.find builtin_plain_functions (Procname.to_string name)
    with Not_found -> assert false

  (* register a builtin function name and symbolic execution handler *)
  let register proc_name_str (sym_exe_fun: sym_exe_builtin) =
    let proc_name = Procname.from_string_c_fun proc_name_str in
    Procname.Hash.replace builtin_functions proc_name sym_exe_fun;
    proc_name

  (* register a builtin plain function name and symbolic execution handler *)
  let register_plain proc_name_str (sym_exe_fun: sym_exe_builtin) =
    let proc_name = Procname.from_string_c_fun proc_name_str in
    Hashtbl.replace builtin_plain_functions proc_name_str sym_exe_fun;
    proc_name

  (* register a builtin [Procname.t] and symbolic execution handler *)
  let register_procname proc_name (sym_exe_fun: sym_exe_builtin) =
    Procname.Hash.replace builtin_functions proc_name sym_exe_fun

  (* register a builtin plain [Procname.t] and symbolic execution handler *)
  let register_plain_procname proc_name (sym_exe_fun: sym_exe_builtin) =
    Hashtbl.replace builtin_plain_functions (Procname.to_string proc_name) sym_exe_fun

  (** print the functions registered *)
  let pp_registered fmt () =
    let builtin_names = ref [] in
    Procname.Hash.iter (fun name _ -> builtin_names := name :: !builtin_names) builtin_functions;
    builtin_names := IList.sort Procname.compare !builtin_names;
    let pp pname = Format.fprintf fmt "%a@\n" Procname.pp pname in
    Format.fprintf fmt "Registered builtins:@\n  @[";
    IList.iter pp !builtin_names;
    Format.fprintf fmt "@]@."
end

(** print the builtin functions and exit *)
let print_builtins () =
  Builtin.pp_registered Format.std_formatter ();
  exit 0

(** Check if the function is a builtin *)
let function_is_builtin = Builtin.is_registered

(** Precondition: se should not include hpara_psto
    that could mean nonempty heaps. *)
let rec execute_nullify_se = function
  | Sil.Eexp _ ->
      Sil.Eexp (Sil.exp_zero, Sil.inst_nullify)
  | Sil.Estruct (fsel, _) ->
      let fsel' = IList.map (fun (fld, se) -> (fld, execute_nullify_se se)) fsel in
      Sil.Estruct (fsel', Sil.inst_nullify)
  | Sil.Earray (size, esel, inst) ->
      let esel' = IList.map (fun (idx, se) -> (idx, execute_nullify_se se)) esel in
      Sil.Earray (size, esel', Sil.inst_nullify)

(** Do pruning for conditional [if (e1 != e2) ] if [positive] is true
    and [(if (e1 == e2)] if [positive] is false *)
let prune_ne tenv positive e1 e2 prop =
  let is_inconsistent =
    if positive then Prover.check_equal prop e1 e2
    else Prover.check_disequal prop e1 e2 in
  if is_inconsistent then Propset.empty
  else
    let conjoin = if positive then Prop.conjoin_neq else Prop.conjoin_eq in
    let new_prop = conjoin ~footprint: (!Config.footprint) e1 e2 prop in
    if Prover.check_inconsistency new_prop then Propset.empty
    else Propset.singleton new_prop

(** Do pruning for conditional "if ([e1] CMP [e2])" if [positive] is
    true and "if (!([e1] CMP [e2]))" if [positive] is false, where CMP
    is "<" if [is_strict] is true and "<=" if [is_strict] is false.
*)
let prune_ineq ~is_strict positive prop e1 e2 =
  if Sil.exp_equal e1 e2 then
    if (positive && not is_strict) || (not positive && is_strict) then
      Propset.singleton prop
    else Propset.empty
  else
    (* build the pruning condition and its negation, as explained in
       the comment above *)
    (* build [e1] CMP [e2] *)
    let cmp = if is_strict then Sil.Lt else Sil.Le in
    let e1_cmp_e2 = Sil.BinOp (cmp, e1, e2) in
    (* build !([e1] CMP [e2]) *)
    let dual_cmp = if is_strict then Sil.Le else Sil.Lt in
    let not_e1_cmp_e2 = Sil.BinOp (dual_cmp, e2, e1) in
    (* take polarity into account *)
    let (prune_cond, not_prune_cond) =
      if positive then (e1_cmp_e2, not_e1_cmp_e2)
      else (not_e1_cmp_e2, e1_cmp_e2) in
    let is_inconsistent = Prover.check_atom prop (Prop.mk_inequality not_prune_cond) in
    if is_inconsistent then Propset.empty
    else
      let footprint = !Config.footprint in
      let prop_with_ineq = Prop.conjoin_eq ~footprint prune_cond Sil.exp_one prop in
      Propset.singleton prop_with_ineq

let rec prune_polarity tenv positive condition prop =
  match condition with
  | Sil.Var _ | Sil.Lvar _ ->
      prune_ne tenv positive condition Sil.exp_zero prop
  | Sil.Const (Sil.Cint i) when Sil.Int.iszero i ->
      if positive then Propset.empty else Propset.singleton prop
  | Sil.Const (Sil.Cint _) | Sil.Sizeof _ | Sil.Const (Sil.Cstr _) | Sil.Const (Sil.Cclass _) ->
      if positive then Propset.singleton prop else Propset.empty
  | Sil.Const _ ->
      assert false
  | Sil.Cast (_, condition') ->
      prune_polarity tenv positive condition' prop
  | Sil.UnOp (Sil.LNot, condition', _) ->
      prune_polarity tenv (not positive) condition' prop
  | Sil.UnOp _ ->
      assert false
  | Sil.BinOp (Sil.Eq, e, Sil.Const (Sil.Cint i))
  | Sil.BinOp (Sil.Eq, Sil.Const (Sil.Cint i), e) when Sil.Int.iszero i && not (Sil.Int.isnull i) ->
      prune_polarity tenv (not positive) e prop
  | Sil.BinOp (Sil.Eq, e1, e2) ->
      prune_ne tenv (not positive) e1 e2 prop
  | Sil.BinOp (Sil.Ne, e, Sil.Const (Sil.Cint i))
  | Sil.BinOp (Sil.Ne, Sil.Const (Sil.Cint i), e) when Sil.Int.iszero i && not (Sil.Int.isnull i) ->
      prune_polarity tenv positive e prop
  | Sil.BinOp (Sil.Ne, e1, e2) ->
      prune_ne tenv positive e1 e2 prop
  | Sil.BinOp (Sil.Ge, e2, e1) | Sil.BinOp (Sil.Le, e1, e2) ->
      prune_ineq ~is_strict:false positive prop e1 e2
  | Sil.BinOp (Sil.Gt, e2, e1) | Sil.BinOp (Sil.Lt, e1, e2) ->
      prune_ineq ~is_strict:true positive prop e1 e2
  | Sil.BinOp (Sil.LAnd, condition1, condition2) ->
      let pruner = if positive then prune_polarity_inter else prune_polarity_union in
      pruner tenv positive condition1 condition2 prop
  | Sil.BinOp (Sil.LOr, condition1, condition2) ->
      let pruner = if positive then prune_polarity_union else prune_polarity_inter in
      pruner tenv positive condition1 condition2 prop
  | Sil.BinOp _ | Sil.Lfield _ | Sil.Lindex _ ->
      prune_ne tenv positive condition Sil.exp_zero prop

and prune_polarity_inter tenv positive condition1 condition2 prop =
  let res = ref Propset.empty in
  let pset1 = prune_polarity tenv positive condition1 prop in
  let do_p p =
    res := Propset.union (prune_polarity tenv positive condition2 p) !res in
  Propset.iter do_p pset1;
  !res

and prune_polarity_union tenv positive condition1 condition2 prop =
  let pset1 = prune_polarity tenv positive condition1 prop in
  let pset2 = prune_polarity tenv positive condition2 prop in
  Propset.union pset1 pset2

let prune_prop tenv condition prop =
  match condition with
  | Sil.Const (Sil.Cint i) when Sil.Int.iszero i -> Propset.empty
  | Sil.Const (Sil.Cint _) -> Propset.singleton prop
  | _ -> prune_polarity tenv true condition prop

let dangerous_functions =
  let dangerous_list = ["gets"] in
  ref ((IList.map Procname.from_string_c_fun) dangerous_list)

let check_inherently_dangerous_function caller_pname callee_pname =
  if IList.exists (Procname.equal callee_pname) !dangerous_functions then
    let exn = Exceptions.Inherently_dangerous_function (Localise.desc_inherently_dangerous_function callee_pname) in
    let pre_opt = State.get_normalized_pre (Abs.abstract_no_symop caller_pname) in
    Reporting.log_warning caller_pname ~pre: pre_opt exn

let is_defined cfg pname =
  match Cfg.Procdesc.find_from_name cfg pname with
  | None -> false
  | Some pdesc -> Cfg.Procdesc.is_defined pdesc

let call_should_be_skipped callee_pname summary =
  (* skip all procedures in intra-precedural mode *)
  !Config.intraprocedural
  (* check skip flag *)
  || Specs.get_flag callee_pname proc_flag_skip <> None
  (* skip abstract methods *)
  || summary.Specs.attributes.ProcAttributes.is_abstract
  (* treat calls with no specs as skip functions in angelic mode *)
  || (!Config.angelic_execution && Specs.get_specs_from_payload summary == [])

let report_raise_memory_leak tenv msg hpred prop =
  L.d_strln msg;
  L.d_increase_indent 1;
  L.d_strln "PROP:";
  Prop.d_prop prop; L.d_ln ();
  L.d_strln "PREDICATE:";
  Prop.d_sigma [hpred];
  L.d_decrease_indent 1;
  L.d_ln ();
  let footprint_part = false in
  let resource = match Errdesc.hpred_is_open_resource prop hpred with
    | Some res -> res
    | None -> Sil.Rmemory Sil.Mmalloc in
  raise (Exceptions.Leak (footprint_part, prop, hpred, Errdesc.explain_leak tenv hpred prop None None, false, resource, try assert false with Assert_failure x -> x))

(** In case of constant string dereference, return the result immediately *)
let check_constant_string_dereference lexp =
  let string_lookup s n =
    let c = try Char.code (String.get s (Sil.Int.to_int n)) with Invalid_argument _ -> 0 in
    Sil.exp_int (Sil.Int.of_int c) in
  match lexp with
  | Sil.BinOp(Sil.PlusPI, Sil.Const (Sil.Cstr s), e)
  | Sil.Lindex (Sil.Const (Sil.Cstr s), e) ->
      let value = match e with
        | Sil.Const (Sil.Cint n) when Sil.Int.geq n Sil.Int.zero && Sil.Int.leq n (Sil.Int.of_int (String.length s)) ->
            string_lookup s n
        | _ -> Sil.exp_get_undefined false in
      Some value
  | Sil.Const (Sil.Cstr s) ->
      Some (string_lookup s Sil.Int.zero)
  | _ -> None

(** Normalize an expression and check for arithmetic problems *)
let exp_norm_check_arith pname prop exp =
  match Prop.find_arithmetic_problem (State.get_path_pos ()) prop exp with
  | Some (Prop.Div0 div), prop' ->
      let desc = Errdesc.explain_divide_by_zero div (State.get_node ()) (State.get_loc ()) in
      let exn = Exceptions.Divide_by_zero (desc, try assert false with Assert_failure x -> x) in
      let pre_opt = State.get_normalized_pre (Abs.abstract_no_symop pname) in
      Reporting.log_warning pname ~pre: pre_opt exn;
      Prop.exp_normalize_prop prop exp, prop'
  | Some (Prop.UminusUnsigned (e, typ)), prop' ->
      let desc = Errdesc.explain_unary_minus_applied_to_unsigned_expression e typ (State.get_node ()) (State.get_loc ()) in
      let exn = Exceptions.Unary_minus_applied_to_unsigned_expression (desc, try assert false with Assert_failure x -> x) in
      let pre_opt = State.get_normalized_pre (Abs.abstract_no_symop pname) in
      Reporting.log_warning pname ~pre: pre_opt exn;
      Prop.exp_normalize_prop prop exp, prop'
  | None, prop' -> Prop.exp_normalize_prop prop exp, prop'

(** Check if [cond] is testing for NULL a pointer already dereferenced *)
let check_already_dereferenced pname cond prop =
  let find_hpred lhs =
    try Some (IList.find (function
        | Sil.Hpointsto (e, _, _) -> Sil.exp_equal e lhs
        | _ -> false) (Prop.get_sigma prop))
    with Not_found -> None in
  let rec is_check_zero = function
    | Sil.Var id ->
        Some id
    | Sil.UnOp(Sil.LNot, e, _) ->
        is_check_zero e
    | Sil.BinOp ((Sil.Eq | Sil.Ne), Sil.Const Sil.Cint i, Sil.Var id)
    | Sil.BinOp ((Sil.Eq | Sil.Ne), Sil.Var id, Sil.Const Sil.Cint i) when Sil.Int.iszero i ->
        Some id
    | _ -> None in
  let dereferenced_line = match is_check_zero cond with
    | Some id ->
        (match find_hpred (Prop.exp_normalize_prop prop (Sil.Var id)) with
         | Some (Sil.Hpointsto (_, se, _)) ->
             (match Tabulation.find_dereference_without_null_check_in_sexp se with
              | Some n -> Some (id, n)
              | None -> None)
         | _ -> None)
    | None ->
        None in
  match dereferenced_line with
  | Some (id, (n, pos)) ->
      let desc = Errdesc.explain_null_test_after_dereference (Sil.Var id) (State.get_node ()) n (State.get_loc ()) in
      let exn = (Exceptions.Null_test_after_dereference (desc, try assert false with Assert_failure x -> x)) in
      let pre_opt = State.get_normalized_pre (Abs.abstract_no_symop pname) in
      Reporting.log_warning pname ~pre: pre_opt exn
  | None -> ()

let run_with_abs_val_eq_zero f =
  let abs_val_old = !Config.abs_val in
  Config.abs_val := 0;
  let res = try f () with
    | exn ->
        Config.abs_val := abs_val_old;
        raise exn in
  Config.abs_val := abs_val_old;
  res

(** Check whether symbolic execution de-allocated a stack variable or a constant string, raising an exception in that case *)
let check_deallocate_static_memory prop_after =
  let check_deallocated_attribute = function
    | Sil.Lvar pv, Sil.Aresource ({ Sil.ra_kind = Sil.Rrelease } as ra) when Sil.pvar_is_local pv || Sil.pvar_is_global pv ->
        let freed_desc = Errdesc.explain_deallocate_stack_var pv ra in
        raise (Exceptions.Deallocate_stack_variable freed_desc)
    | Sil.Const (Sil.Cstr s), Sil.Aresource ({ Sil.ra_kind = Sil.Rrelease } as ra) ->
        let freed_desc = Errdesc.explain_deallocate_constant_string s ra in
        raise (Exceptions.Deallocate_static_memory freed_desc)
    | _ -> () in
  let exp_att_list = Prop.get_all_attributes prop_after in
  IList.iter check_deallocated_attribute exp_att_list;
  prop_after

(** create a copy of a procdesc with a new proc name *)
let proc_desc_copy cfg pdesc pname pname' =
  if (Procname.equal pname pname') then pdesc
  else
    (match Cfg.Procdesc.find_from_name cfg pname' with
     | Some pdesc' -> pdesc'
     | None ->
         Cfg.Procdesc.create {
           Cfg.Procdesc.cfg = cfg;
           proc_attributes =
             { (ProcAttributes.copy (Cfg.Procdesc.get_attributes pdesc)) with
               ProcAttributes.proc_name = pname'; };
         })

let method_exists right_proc_name methods =
  if !Config.curr_language = Config.Java then
    IList.exists (fun meth_name -> Procname.equal right_proc_name meth_name) methods
  else (* ObjC case *)
    Specs.summary_exists right_proc_name

let resolve_method tenv class_name proc_name =
  let found_class =
    let visited = ref Typename.Set.empty in
    let rec resolve class_name =
      visited := Typename.Set.add class_name !visited;
      let right_proc_name =
        if Procname.is_java proc_name then
          Procname.java_replace_class proc_name (Typename.name class_name)
        else Procname.c_method_replace_class proc_name (Typename.name class_name) in
      match Sil.tenv_lookup tenv class_name with
      | Some (Sil.Tstruct (_, _, Csu.Class, cls, super_classes, methods, iann)) ->
          if method_exists right_proc_name methods then
            Some right_proc_name
          else
            (match super_classes with
             | super_classname:: interfaces ->
                 if not (Typename.Set.mem super_classname !visited)
                 then resolve super_classname
                 else None
             | _ -> None)
      | _ -> None in
    resolve class_name in
  match found_class with
  | None ->
      Logging.d_strln
        ("Couldn't find method in the hierarchy of type "^(Typename.name class_name));
      proc_name
  | Some proc_name -> proc_name

let resolve_typename prop arg =
  let (arg_exp, _) = arg in
  let typexp_opt =
    let rec loop = function
      | [] -> None
      | Sil.Hpointsto(e, _, typexp) :: _ when Sil.exp_equal e arg_exp -> Some typexp
      | _ :: hpreds -> loop hpreds in
    loop (Prop.get_sigma prop) in
  match typexp_opt with
  | Some (Sil.Sizeof (Sil.Tstruct (_, _, _, None, _, _, _), _)) -> None
  | Some (Sil.Sizeof (Sil.Tstruct (_, _, Csu.Class, Some name, _, _, _), _)) ->
      Some (Typename.TN_csu (Csu.Class, name))
  | _ -> None

(** If the dynamic type of the object calling a method is known, the method from the dynamic type
    is called *)
let resolve_virtual_pname cfg tenv prop args pname call_flags : Procname.t =
  if not call_flags.Sil.cf_virtual then pname
  else
    match args with
    | [] -> failwith "Expecting the first parameter to be the object expression"
    | obj_exp :: _ ->
        begin
          match resolve_typename prop obj_exp with
          | Some class_name -> resolve_method tenv class_name pname
          | None -> pname
        end

(* let resolve_procname cfg tenv prop args pname : Procname.t = *)

(** recognize calls to shared_ptr procedures and re-direct them to infer procedures for modelling *)
let redirect_shared_ptr tenv cfg pname actual_params =
  let class_shared_ptr typ =
    try match Sil.expand_type tenv typ with
      | Sil.Tstruct (_, _, Csu.Class, Some cl_name, _, _, _) ->
          let name = Mangled.to_string cl_name in
          name = "shared_ptr" || name = "__shared_ptr"
      | t -> false
    with exn when exn_not_failure exn -> false in
  (* We pattern match over some specific library function, *)
  (* so we make precise matching to distinghuis between *)
  (* references and pointers in C++ *)
  let ptr_to filter = function
    | Sil.Tptr (t, Sil.Pk_pointer)
    | Sil.Tptr (t, Sil.Pk_objc_weak)
    | Sil.Tptr (t, Sil.Pk_objc_unsafe_unretained)
    | Sil.Tptr (t, Sil.Pk_objc_autoreleasing) -> filter t
    | _ -> false in
  let ref_to filter = function
    | Sil.Tptr (t, Sil.Pk_reference) -> filter t
    | _ -> false in
  let ptr_to_shared_ptr typ = ptr_to class_shared_ptr typ in
  let ref_to_shared_ptr typ = ref_to class_shared_ptr typ in
  let ptr_to_something typ = ptr_to (fun _ -> true) typ in
  let pname' = match Procname.to_string pname, actual_params with
    | "shared_ptr", [(_, this_t); (_, t1)] when ptr_to_shared_ptr this_t && ptr_to_something t1 ->
        Procname.from_string_c_fun "__infer_shared_ptr"
    | "shared_ptr", [(_, this_t); (_, t1)] when ptr_to_shared_ptr this_t && ref_to_shared_ptr t1 ->
        Procname.from_string_c_fun "__infer_shared_ptr_ref"
    | "operator=", [(_, this_t); (_, t1)] when ptr_to_shared_ptr this_t && ref_to_shared_ptr t1 ->
        Procname.from_string_c_fun "__infer_shared_ptr_eq"
    | "operator==", [(_, t1); (_, t2)] when ref_to_shared_ptr t1 && ref_to_shared_ptr t2 ->
        Procname.from_string_c_fun "__infer_shared_ptr_eqeq"
    | ("operator->" | "operator*"),[(_, t1)] when ptr_to_shared_ptr t1 ->
        Procname.from_string_c_fun "__infer_shared_ptr_arrow"
    | "~shared_ptr",[(_, t1)] ->
        Procname.from_string_c_fun "__infer_shared_ptr_destructor"
    | _ -> pname in
  if Procname.equal pname pname' then pname
  else
    let found = Specs.summary_exists pname' in
    if found then
      match Cfg.Procdesc.find_from_name cfg pname with
      | None -> pname
      | Some pdesc ->
          let _pdesc = proc_desc_copy cfg pdesc pname pname' in
          pname'
    else pname


(** Lookup Java types by name *)
let lookup_java_typ_from_string tenv typ_str =
  let rec loop = function
    | "" | "void" -> Sil.Tvoid
    | "int" -> Sil.Tint Sil.IInt
    | "byte" -> Sil.Tint Sil.IShort
    | "short" -> Sil.Tint Sil.IShort
    | "boolean" -> Sil.Tint Sil.IBool
    | "char" -> Sil.Tint Sil.IChar
    | "long" -> Sil.Tint Sil.ILong
    | "float" -> Sil.Tfloat Sil.FFloat
    | "double" -> Sil.Tfloat Sil.FDouble
    | typ_str when String.contains typ_str '[' ->
        let stripped_typ = String.sub typ_str 0 ((String.length typ_str) - 2) in
        let array_typ_size = Sil.exp_get_undefined false in
        Sil.Tptr (Sil.Tarray (loop stripped_typ, array_typ_size), Sil.Pk_pointer)
    | typ_str ->
        (* non-primitive/non-array type--resolve it in the tenv *)
        let typename = Typename.TN_csu (Csu.Class, (Mangled.from_string typ_str)) in
        match Sil.tenv_lookup tenv typename with
        | Some (Sil.Tstruct _ as typ) -> typ
        | _ -> failwith ("Failed to look up typ " ^ typ_str) in
  loop typ_str


(** recognize calls to the constructor java.net.URL and splits the argument string
    to be only the protocol.  *)
let call_constructor_url_update_args pname actual_params =
  let url_pname = Procname.mangled_java
      ((Some "java.net"), "URL") None "<init>" [(Some "java.lang"), "String"] Procname.Non_Static in
  if (Procname.equal url_pname pname) then
    (match actual_params with
     | [this; (Sil.Const (Sil.Cstr s), atype)] ->
         let parts = Str.split (Str.regexp_string "://") s in
         (match parts with
          | frst:: parts ->
              if (frst = "http") || (frst = "ftp") || (frst = "https") || (frst = "mailto") || (frst = "jar") then
                [this; (Sil.Const (Sil.Cstr frst), atype)]
              else actual_params
          | _ -> actual_params)
     | [this; _, atype] -> [this; (Sil.Const (Sil.Cstr "file"), atype)]
     | _ -> actual_params)
  else actual_params

(** Handles certain method calls in a special way *)
let handle_special_cases_call tenv cfg pname actual_params =
  if (!Config.curr_language = Config.Java) then
    pname, (call_constructor_url_update_args pname actual_params)
  else if (!Config.curr_language = Config.C_CPP) then
    (redirect_shared_ptr tenv cfg pname actual_params), actual_params
  else pname, actual_params

(* This method handles ObjC method calls, in particular the fact that calling a method with nil *)
(* returns nil. The exec_call function is either standard call execution or execution of ObjC *)
(* getters and setters using a builtin. *)
let handle_objc_method_call actual_pars actual_params pre tenv cfg ret_ids pdesc callee_pname loc
    path exec_call =
  let path_description = "Message "^(Procname.to_simplified_string callee_pname)^" with receiver nil returns nil." in
  let receiver = (match actual_pars with
      | (e, _):: _ -> e
      | _ -> raise (Exceptions.Internal_error
                      (Localise.verbatim_desc "In Objective-C instance method call there should be a receiver."))) in
  let is_receiver_null =
    match actual_pars with
    | (e, _):: _ when Sil.exp_equal e Sil.exp_zero || Option.is_some (Prop.get_objc_null_attribute pre e) -> true
    | _ -> false in
  let add_objc_null_attribute_or_nullify_result prop =
    match ret_ids with
    | [ret_id] ->
        (match Prop.find_equal_formal_path receiver prop with
         | Some info ->
             Prop.add_or_replace_exp_attribute prop (Sil.Var ret_id) (Sil.Aobjc_null info)
         | None -> Prop.conjoin_eq (Sil.Var ret_id) Sil.exp_zero prop)
    | _ -> prop in
  if is_receiver_null then  (* objective-c instance method with a null receiver just return objc_null(res) *)
    let path = Paths.Path.add_description path path_description in
    L.d_strln ("Object-C method " ^ Procname.to_string callee_pname^ " called with nil receiver. Returning 0/nil");
    (* We wish to nullify the result. However, in some cases, we want to add the attribute OBJC_NULL to it so that we *)
    (* can keep track of how this object became null, so that in a NPE we can separate it into a different error type *)
    [(add_objc_null_attribute_or_nullify_result pre, path)]
  else
    let res = exec_call tenv cfg ret_ids pdesc callee_pname loc actual_params pre path in
    let is_undef =
      Option.is_some (Prop.get_undef_attribute pre receiver) in
    if !Config.footprint && not is_undef then
      let res_null = (* returns: (objc_null(res) /\ receiver=0) or an empty list of results *)
        let pre_with_attr_or_null = add_objc_null_attribute_or_nullify_result pre in
        let propset = prune_ne tenv false receiver Sil.exp_zero pre_with_attr_or_null in
        if Propset.is_empty propset then []
        else
          let prop = IList.hd (Propset.to_proplist propset) in
          let path = Paths.Path.add_description path path_description in
          [(prop, path)] in
      res_null @ res
    else res (* Not known if receiver = 0 and not footprint. Standard tabulation *)

let normalize_params pdesc prop actual_params =
  let norm_arg (p, args) (e, t) =
    let e', p' = exp_norm_check_arith pdesc p e in
    (p', (e', t) :: args) in
  let prop, args = IList.fold_left norm_arg (prop, []) actual_params in
  (prop, IList.rev args)

let do_error_checks node_opt instr pname pdesc = match node_opt with
  | Some node ->
      if !Config.curr_language = Config.Java then
        PrintfArgs.check_printf_args_ok node instr pname pdesc
  | None ->
      ()

let add_to_footprint abducted_pv typ prop =
  let abducted_lvar = Sil.Lvar abducted_pv in
  let fresh_fp_var = Sil.Var (Ident.create_fresh Ident.kfootprint) in
  let lvar_pt_fpvar =
    let sizeof_exp = Sil.Sizeof (typ, Sil.Subtype.subtypes) in
    Prop.mk_ptsto abducted_lvar (Sil.Eexp (fresh_fp_var, Sil.Inone)) sizeof_exp in
  let sigma_fp = Prop.get_sigma_footprint prop in
  (Prop.normalize (Prop.replace_sigma_footprint (lvar_pt_fpvar :: sigma_fp) prop), fresh_fp_var)

let add_constraints_on_retval pdesc prop ret_exp typ callee_pname callee_loc =
  if Procname.is_infer_undefined callee_pname then prop
  else
    let is_rec_call pname = (* TODO: (t7147096) extend this to detect mutual recursion *)
      Procname.equal pname (Cfg.Procdesc.get_proc_name pdesc) in
    let already_has_abducted_retval p abducted_ret_pv =
      IList.exists
        (fun hpred -> match hpred with
           | Sil.Hpointsto (Sil.Lvar pv, _, _) -> Sil.pvar_equal pv abducted_ret_pv
           | _ -> false)
        (Prop.get_sigma_footprint p) in
    (* find an hpred [abducted_pvar] |-> A in [prop] and add [exp] = A to prop *)
    let bind_exp_to_abducted_val exp_to_bind abducted_pvar prop =
      let bind_exp prop = function
        | Sil.Hpointsto (Sil.Lvar pv, Sil.Eexp (rhs, _), _)
          when Sil.pvar_equal pv abducted_pvar ->
            Prop.conjoin_eq exp_to_bind rhs prop
        | _ -> prop in
      IList.fold_left bind_exp prop (Prop.get_sigma prop) in
    (* To avoid obvious false positives, assume skip functions do not return null pointers *)
    let add_ret_non_null exp typ prop =
      match typ with
      | Sil.Tptr _ -> Prop.conjoin_neq exp Sil.exp_zero prop
      | _ -> prop in
    let add_tainted_post ret_exp callee_pname prop =
      Prop.add_or_replace_exp_attribute prop ret_exp (Sil.Ataint callee_pname) in

    if !Config.angelic_execution && not (is_rec_call callee_pname) then
      (* introduce a fresh program variable to allow abduction on the return value *)
      let abducted_ret_pv = Sil.mk_pvar_abducted_ret callee_pname callee_loc in
      (* prevent introducing multiple abducted retvals for a single call site in a loop *)
      if already_has_abducted_retval prop abducted_ret_pv then prop
      else
        let prop' =
          if !Config.footprint then
            let (prop', fresh_fp_var) = add_to_footprint abducted_ret_pv typ prop in
            Prop.conjoin_eq ~footprint: true ret_exp fresh_fp_var prop'
          else
            (* bind return id to the abducted value pointed to by the pvar we introduced *)
            bind_exp_to_abducted_val ret_exp abducted_ret_pv prop in
        let prop'' = add_ret_non_null ret_exp typ prop' in
        if !Config.taint_analysis && Taint.returns_secret callee_pname then
          add_tainted_post ret_exp callee_pname prop''
        else prop''
    else add_ret_non_null ret_exp typ prop

let execute_letderef ?(report_deref_errors=true) pname pdesc tenv id rhs_exp typ loc prop_ =
  let execute_letderef_ pdesc tenv id rhs_exp loc acc_in iter =
    let iter_ren = Prop.prop_iter_make_id_primed id iter in
    let prop_ren = Prop.prop_iter_to_prop iter_ren in
    match Prop.prop_iter_current iter_ren with
    | (Sil.Hpointsto(lexp, strexp, Sil.Sizeof (typ, st)), offlist) ->
        let contents, new_ptsto, pred_insts_op, lookup_uninitialized =
          ptsto_lookup false pdesc tenv prop_ren (lexp, strexp, typ, st) offlist id in
        let update acc (pi, sigma) =
          let pi' = Sil.Aeq (Sil.Var(id), contents):: pi in
          let sigma' = new_ptsto:: sigma in
          let iter' = update_iter iter_ren pi' sigma' in
          let prop' = Prop.prop_iter_to_prop iter' in
          let prop'' =
            if lookup_uninitialized then
              Prop.add_or_replace_exp_attribute prop' (Sil.Var id) (Sil.Adangling Sil.DAuninit)
            else prop' in
          prop'' :: acc in
        begin
          match pred_insts_op with
          | None -> update acc_in ([],[])
          | Some pred_insts -> IList.rev (IList.fold_left update acc_in pred_insts)
        end
    | (Sil.Hpointsto _, _) ->
        Errdesc.warning_err loc "no offset access in execute_letderef -- treating as skip@.";
        (Prop.prop_iter_to_prop iter_ren) :: acc_in
    | _ ->
        (* The implementation of this case means that we
           ignore this dereferencing operator. When the analyzer treats
           numerical information and arrays more precisely later, we
           should change the implementation here. *)
        assert false in
  try
    let n_rhs_exp, prop = exp_norm_check_arith pname prop_ rhs_exp in
    let n_rhs_exp' = Prop.exp_collapse_consecutive_indices_prop prop typ n_rhs_exp in
    match check_constant_string_dereference n_rhs_exp' with
    | Some value ->
        [Prop.conjoin_eq (Sil.Var id) value prop]
    | None ->
        let exp_get_undef_attr exp =
          let fold_undef_pname callee_opt attr =
            if Option.is_none callee_opt && Sil.attr_is_undef attr then Some attr
            else callee_opt in
          IList.fold_left fold_undef_pname None (Prop.get_exp_attributes prop exp) in
        let prop' =
          if !Config.angelic_execution then
            (* when we try to deref an undefined value, add it to the footprint *)
            match exp_get_undef_attr n_rhs_exp' with
            | Some (Sil.Aundef (callee_pname, callee_loc, _)) ->
                add_constraints_on_retval pdesc prop n_rhs_exp' typ callee_pname callee_loc
            | _ -> prop
          else prop in
        let iter_list =
          Rearrange.rearrange ~report_deref_errors pdesc tenv n_rhs_exp' typ prop' loc in
        IList.rev (IList.fold_left (execute_letderef_ pdesc tenv id n_rhs_exp' loc) [] iter_list)
  with Rearrange.ARRAY_ACCESS ->
    if (!Config.array_level = 0) then assert false
    else
      let undef = Sil.exp_get_undefined false in
      [Prop.conjoin_eq (Sil.Var id) undef prop_]

let execute_set ?(report_deref_errors=true) pname pdesc tenv lhs_exp typ rhs_exp loc prop_ =
  let execute_set_ pdesc tenv rhs_exp acc_in iter =
    let (lexp, strexp, typ, st, offlist) =
      match Prop.prop_iter_current iter with
      | (Sil.Hpointsto(lexp, strexp, Sil.Sizeof (typ, st)), offlist) ->
          (lexp, strexp, typ, st, offlist)
      | _ -> assert false in
    let p = Prop.prop_iter_to_prop iter in
    let new_ptsto, pred_insts_op =
      ptsto_update false pdesc tenv p (lexp, strexp, typ, st) offlist rhs_exp in
    let update acc (pi, sigma) =
      let sigma' = new_ptsto:: sigma in
      let iter' = update_iter iter pi sigma' in
      let prop' = Prop.prop_iter_to_prop iter' in
      prop' :: acc in
    match pred_insts_op with
    | None -> update acc_in ([],[])
    | Some pred_insts -> IList.fold_left update acc_in pred_insts in
  try
    let n_lhs_exp, _prop' = exp_norm_check_arith pname prop_ lhs_exp in
    let n_rhs_exp, prop = exp_norm_check_arith pname _prop' rhs_exp in
    let prop = Prop.replace_objc_null prop n_lhs_exp n_rhs_exp in
    let n_lhs_exp' = Prop.exp_collapse_consecutive_indices_prop prop typ n_lhs_exp in
    let iter_list = Rearrange.rearrange ~report_deref_errors pdesc tenv n_lhs_exp' typ prop loc in
    IList.rev (IList.fold_left (execute_set_ pdesc tenv n_rhs_exp) [] iter_list)
  with Rearrange.ARRAY_ACCESS ->
    if (!Config.array_level = 0) then assert false
    else [prop_]

(** Execute [instr] with a symbolic heap [prop].*)
let rec sym_exec cfg tenv pdesc _instr (_prop: Prop.normal Prop.t) path
  : (Prop.normal Prop.t * Paths.Path.t) list =
  let pname = Cfg.Procdesc.get_proc_name pdesc in
  State.set_instr _instr; (* mark instruction last seen *)
  State.set_prop_tenv_pdesc _prop tenv pdesc; (* mark prop,tenv,pdesc last seen *)
  SymOp.pay(); (* pay one symop *)
  let ret_old_path pl = (* return the old path unchanged *)
    IList.map (fun p -> (p, path)) pl in
  let skip_call prop path callee_pname loc ret_ids ret_typ_opt actual_args =
    let exn = Exceptions.Skip_function (Localise.desc_skip_function callee_pname) in
    Reporting.log_info pname exn;
    L.d_strln
      ("Undefined function " ^ Procname.to_string callee_pname
       ^ ", returning undefined value.");
    (match Specs.get_summary pname with
     | None -> ()
     | Some summary ->
         Specs.CallStats.trace
           summary.Specs.stats.Specs.call_stats callee_pname loc
           (Specs.CallStats.CR_skip) !Config.footprint);
    call_unknown_or_scan
      false cfg pdesc tenv prop path
      ret_ids ret_typ_opt actual_args callee_pname loc in
  let instr = match _instr with
    | Sil.Call (ret, exp, par, loc, call_flags) ->
        let exp' = Prop.exp_normalize_prop _prop exp in
        let instr' = match exp' with
          | Sil.Const (Sil.Ctuple (e1 :: el)) -> (* closure: combine arguments to call *)
              let e1' = Prop.exp_normalize_prop _prop e1 in
              let par' = IList.map (fun e -> (e, Sil.Tvoid)) el in
              Sil.Call (ret, e1', par' @ par, loc, call_flags)
          | _ ->
              Sil.Call (ret, exp', par, loc, call_flags) in
        instr'
    | _ -> _instr in
  match instr with
  | Sil.Letderef (id, rhs_exp, typ, loc) ->
      execute_letderef pname pdesc tenv id rhs_exp typ loc _prop
      |> ret_old_path
  | Sil.Set (lhs_exp, typ, rhs_exp, loc) ->
      execute_set pname pdesc tenv lhs_exp typ rhs_exp loc _prop
      |> ret_old_path
  | Sil.Prune (cond, loc, true_branch, ik) ->
      let _prop = Prop.nullify_exp_with_objc_null _prop cond in
      let check_condition_always_true_false () =
        let report_condition_always_true_false i =
          let skip_loop = match ik with
            | Sil.Ik_while | Sil.Ik_for -> not (Sil.Int.iszero i) (* skip wile(1) and for (;1;) *)
            | Sil.Ik_dowhile -> true (* skip do..while *)
            | Sil.Ik_land_lor -> true (* skip subpart of a condition obtained from compilation of && and || *)
            | _ -> false in
          true_branch && not skip_loop in
        (* in comparisons, nil is translated as (void * ) 0 rather than 0 *)
        let is_comparison_to_nil = function
          | Sil.Cast ((Sil.Tptr (Sil.Tvoid, _)), exp) ->
              !Config.curr_language = Config.C_CPP && Sil.exp_is_zero exp
          | _ -> false in
        match Prop.exp_normalize_prop Prop.prop_emp cond with
        | Sil.Const (Sil.Cint i) when report_condition_always_true_false i ->
            let node = State.get_node () in
            let desc = Errdesc.explain_condition_always_true_false i cond node loc in
            let exn = Exceptions.Condition_always_true_false (desc, not (Sil.Int.iszero i), try assert false with Assert_failure x -> x) in
            let pre_opt = State.get_normalized_pre (Abs.abstract_no_symop pname) in
            Reporting.log_warning pname ~pre: pre_opt exn
        | Sil.BinOp ((Sil.Eq | Sil.Ne), lhs, rhs)
          when true_branch && !Config.footprint && not (is_comparison_to_nil rhs) ->
            (* iOS: check that NSNumber *'s are not used in conditionals without comparing to nil *)
            let lhs_normal = Prop.exp_normalize_prop _prop lhs in
            let is_nsnumber = function
              | Sil.Tvar (Typename.TN_csu (Csu.Class, name)) ->
                  Mangled.to_string name = "NSNumber"
              | _ -> false in
            let lhs_is_ns_ptr () =
              IList.exists
                (function
                  | Sil.Hpointsto (_, Sil.Eexp (exp, _), Sil.Sizeof (Sil.Tptr (typ, _), _)) ->
                      Sil.exp_equal exp lhs_normal && is_nsnumber typ
                  | _ -> false)
                (Prop.get_sigma _prop) in
            if not (Sil.exp_is_zero lhs_normal) && lhs_is_ns_ptr () then
              let node = State.get_node () in
              let desc = Errdesc.explain_bad_pointer_comparison lhs node loc in
              let fail = try assert false with Assert_failure x -> x in
              let exn = Exceptions.Bad_pointer_comparison (desc, fail) in
              Reporting.log_warning pname exn
        | _ -> () in
      check_already_dereferenced pname cond _prop;
      check_condition_always_true_false ();
      let n_cond, prop = exp_norm_check_arith pname _prop cond in
      ret_old_path (Propset.to_proplist (prune_prop tenv n_cond prop))
  | Sil.Call (ret_ids, Sil.Const (Sil.Cfun callee_pname), args, loc, call_flags)
    when function_is_builtin callee_pname ->
      let sym_exe_builtin = Builtin.get_sym_exe_builtin callee_pname in
      sym_exe_builtin cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
  | Sil.Call (ret_ids, Sil.Const (Sil.Cfun callee_pname), actual_params, loc, call_flags)
    when !Config.curr_language = Config.Java ->
      do_error_checks (Paths.Path.curr_node path) instr pname pdesc;
      let norm_prop, norm_args = normalize_params pname _prop actual_params in
      let url_handled_args =
        call_constructor_url_update_args callee_pname norm_args in
      let resolved_pname =
        resolve_virtual_pname cfg tenv norm_prop url_handled_args callee_pname call_flags in
      if !Config.ondemand_enabled then
        Ondemand.do_analysis pdesc resolved_pname;
      let exec_skip_call ret_type =
        skip_call norm_prop path resolved_pname loc ret_ids (Some ret_type) url_handled_args in
      begin
        match Specs.get_summary resolved_pname with
        | None ->
            let ret_typ_str = Procname.java_get_return_type resolved_pname in
            let ret_typ =
              match lookup_java_typ_from_string tenv ret_typ_str with
              | Sil.Tstruct _ as typ -> Sil.Tptr (typ, Sil.Pk_pointer)
              | typ -> typ in
            exec_skip_call ret_typ
        | Some summary when call_should_be_skipped resolved_pname summary ->
            exec_skip_call summary.Specs.attributes.ProcAttributes.ret_type
        | Some summary ->
            sym_exec_call cfg pdesc tenv norm_prop path ret_ids url_handled_args summary loc
      end

  | Sil.Call (ret_ids, Sil.Const (Sil.Cfun callee_pname), actual_params, loc, call_flags) ->
      (** Generic fun call with known name *)
      let (prop_r, _n_actual_params) = normalize_params pname _prop actual_params in
      let fn, n_actual_params = handle_special_cases_call tenv cfg callee_pname _n_actual_params in
      let resolved_pname =
        resolve_virtual_pname cfg tenv prop_r n_actual_params fn call_flags in
      if !Config.ondemand_enabled then
        Ondemand.do_analysis pdesc resolved_pname;

      let callee_pdesc_opt = Cfg.Procdesc.find_from_name cfg resolved_pname in
      let ret_typ_opt = Option.map Cfg.Procdesc.get_ret_type callee_pdesc_opt in
      let sentinel_result =
        if !Config.curr_language = Config.C_CPP then
          sym_exe_check_variadic_sentinel_if_present
            cfg pdesc tenv prop_r path actual_params callee_pname loc
        else [(prop_r, path)] in
      let do_call (prop, path) =
        let attrs_opt = Option.map Cfg.Procdesc.get_attributes callee_pdesc_opt in
        let objc_property_accessor =
          match attrs_opt with
          | Some attrs -> attrs.ProcAttributes.objc_accessor
          | None -> None in
        let summary = Specs.get_summary resolved_pname in
        let should_skip resolved_pname summary =
          match summary with
          | None -> true
          | Some summary -> call_should_be_skipped resolved_pname summary in
        if should_skip resolved_pname summary then
          (* If it's an ObjC getter or setter, call the builtin rather than skipping *)
          match objc_property_accessor with
          | Some objc_property_accessor ->
              handle_objc_method_call
                n_actual_params n_actual_params prop tenv cfg ret_ids pdesc callee_pname loc path
                (sym_exec_objc_accessor objc_property_accessor ret_typ_opt)
          | None ->
              skip_call prop path resolved_pname loc ret_ids ret_typ_opt n_actual_params
        else
          sym_exec_call cfg pdesc tenv prop path ret_ids n_actual_params (Option.get summary) loc in
      IList.flatten (IList.map do_call sentinel_result)
  | Sil.Call (ret_ids, fun_exp, actual_params, loc, call_flags) -> (** Call via function pointer *)
      let (prop_r, n_actual_params) = normalize_params pname _prop actual_params in
      if call_flags.Sil.cf_is_objc_block then
        Rearrange.check_call_to_objc_block_error pdesc prop_r fun_exp loc;
      Rearrange.check_dereference_error pdesc prop_r fun_exp loc;
      if call_flags.Sil.cf_noreturn then begin
        L.d_str "Unknown function pointer with noreturn attribute "; Sil.d_exp fun_exp; L.d_strln ", diverging.";
        execute_diverge prop_r path
      end else begin
        L.d_str "Unknown function pointer "; Sil.d_exp fun_exp; L.d_strln ", returning undefined value.";
        let callee_pname = Procname.from_string_c_fun "__function_pointer__" in
        call_unknown_or_scan
          false cfg pdesc tenv prop_r path ret_ids None n_actual_params callee_pname loc
      end
  | Sil.Nullify (pvar, loc, deallocate) ->
      begin
        let eprop = Prop.expose _prop in
        match IList.partition
                (function
                  | Sil.Hpointsto (Sil.Lvar pvar', _, _) -> Sil.pvar_equal pvar pvar'
                  | _ -> false) (Prop.get_sigma eprop) with
        | [Sil.Hpointsto(e, se, typ)], sigma' ->
            let sigma'' = match deallocate with
              | false ->
                  let se' = execute_nullify_se se in
                  Sil.Hpointsto(e, se', typ):: sigma'
              | true -> sigma' in
            let eprop_res = Prop.replace_sigma sigma'' eprop in
            ret_old_path [Prop.normalize eprop_res]
        | _ -> assert false
      end
  | Sil.Abstract loc ->
      let node = State.get_node () in
      let blocks_nullified = get_nullified_block node in
      IList.iter (check_block_retain_cycle cfg tenv pname _prop) blocks_nullified;
      if Prover.check_inconsistency _prop
      then
        ret_old_path []
      else
        ret_old_path [Abs.remove_redundant_array_elements pname tenv
                        (Abs.abstract pname tenv _prop)]
  | Sil.Remove_temps (temps, loc) ->
      ret_old_path [Prop.exist_quantify (Sil.fav_from_list temps) _prop]
  | Sil.Declare_locals (ptl, loc) ->
      let sigma_locals =
        let add_None (x, y) = (x, Sil.Sizeof (y, Sil.Subtype.exact), None) in
        let fp_mode = !Config.footprint in
        Config.footprint := false; (* no footprint vars for locals *)
        let sigma_locals =
          IList.map
            (Prop.mk_ptsto_lvar (Some tenv) Prop.Fld_init Sil.inst_initial)
            (IList.map add_None ptl) in
        Config.footprint := fp_mode;
        sigma_locals in
      let sigma' = Prop.get_sigma _prop @ sigma_locals in
      let prop' = Prop.normalize (Prop.replace_sigma sigma' _prop) in
      ret_old_path [prop']
  | Sil.Stackop _ -> (* this should be handled at the propset level *)
      assert false
  | Sil.Goto_node (node_e, loc) ->
      let n_node_e, prop = exp_norm_check_arith pname _prop node_e in
      begin
        match n_node_e with
        | Sil.Const (Sil.Cint i) ->
            let node_id = Sil.Int.to_int i in
            State.set_goto_node node_id;
            [(prop, path)]
        | _ -> (* target not known, do nothing as the next nodes are set to the possible targets by the front-end *)
            [(prop, path)]
      end
and execute_diverge prop path =
  State.add_diverging_states (Paths.PathSet.from_renamed_list [(prop, path)]); (* diverge *)
  []

(** Like sym_exec but for generated instructions.
    If errors occur and [mask_errors] is false, just treat as skip.*)
and sym_exec_generated mask_errors cfg tenv pdesc instrs ppl =
  let exe_instr instr (p, path) =
    L.d_str "Executing Generated Instruction "; Sil.d_instr instr; L.d_ln ();
    try sym_exec cfg tenv pdesc instr p path
    with exn when exn_not_failure exn && mask_errors ->
      let err_name, _, ml_source, _ , _, _, _ = Exceptions.recognize_exception exn in
      let loc = (match ml_source with
          | Some (src, l, c) -> "at "^(src^" "^(string_of_int l))
          | None -> "") in
      L.d_warning ("Generated Instruction Failed with: " ^ (Localise.to_string err_name)^loc ); L.d_ln();
      [(p, path)] in
  let f plist instr = IList.flatten (IList.map (exe_instr instr) plist) in
  IList.fold_left f ppl instrs

and add_constraints_on_actuals_by_ref prop actuals_by_ref callee_pname callee_loc =
  (* replace an hpred of the form actual_var |-> _ with new_hpred in prop *)
  let replace_actual_hpred actual_var new_hpred prop =
    let sigma' =
      IList.map
        (function
          | Sil.Hpointsto (lhs, _, _) when Sil.exp_equal lhs actual_var -> new_hpred
          | hpred -> hpred)
        (Prop.get_sigma prop) in
    Prop.normalize (Prop.replace_sigma sigma' prop) in
  if !Config.angelic_execution then
    let add_actual_by_ref_to_footprint prop (actual, actual_typ) =
      match actual with
      | Sil.Lvar actual_pv ->
          (* introduce a fresh program variable to allow abduction on the return value *)
          let abducted_ref_pv =
            Sil.mk_pvar_abducted_ref_param callee_pname actual_pv callee_loc in
          let already_has_abducted_retval p =
            IList.exists
              (fun hpred -> match hpred with
                 | Sil.Hpointsto (Sil.Lvar pv, _, _) -> Sil.pvar_equal pv abducted_ref_pv
                 | _ -> false)
              (Prop.get_sigma_footprint p) in
          (* prevent introducing multiple abducted retvals for a single call site in a loop *)
          if already_has_abducted_retval prop then prop
          else
          if !Config.footprint then
            let (prop', fresh_fp_var) =
              add_to_footprint abducted_ref_pv (Sil.typ_strip_ptr actual_typ) prop in
            (* replace [actual] |-> _ with [actual] |-> [fresh_fp_var] *)
            let filtered_sigma =
              IList.map
                (function
                  | Sil.Hpointsto (lhs, _, typ_exp) when Sil.exp_equal lhs actual ->
                      Sil.Hpointsto (lhs, Sil.Eexp (fresh_fp_var, Sil.Inone), typ_exp)
                  | hpred -> hpred)
                (Prop.get_sigma prop') in
            Prop.normalize (Prop.replace_sigma filtered_sigma prop')
          else
            (* bind actual passed by ref to the abducted value pointed to by the synthetic pvar *)
            let prop' =
              let filtered_sigma =
                IList.filter
                  (function
                    | Sil.Hpointsto (lhs, _, typ_exp) when Sil.exp_equal lhs actual ->
                        false
                    | _ -> true)
                  (Prop.get_sigma prop) in
              Prop.normalize (Prop.replace_sigma filtered_sigma prop) in
            IList.fold_left
              (fun p hpred ->
                 match hpred with
                 | Sil.Hpointsto (Sil.Lvar pv, rhs, texp) when Sil.pvar_equal pv abducted_ref_pv ->
                     let new_hpred = Sil.Hpointsto (actual, rhs, texp) in
                     Prop.normalize (Prop.replace_sigma (new_hpred :: (Prop.get_sigma prop')) p)
                 | _ -> p)
              prop'
              (Prop.get_sigma prop')
      | _ -> assert false in
    IList.fold_left add_actual_by_ref_to_footprint prop actuals_by_ref
  else
    (* non-angelic mode; havoc each var passed by reference by assigning it to a fresh id *)
    let havoc_actual_by_ref (actual, actual_typ) prop =
      let actual_pt_havocd_var =
        let havocd_var = Sil.Var (Ident.create_fresh Ident.kprimed) in
        let sizeof_exp = Sil.Sizeof (Sil.typ_strip_ptr actual_typ, Sil.Subtype.subtypes) in
        Prop.mk_ptsto actual (Sil.Eexp (havocd_var, Sil.Inone)) sizeof_exp in
      replace_actual_hpred actual actual_pt_havocd_var prop in
    IList.fold_left (fun p var -> havoc_actual_by_ref var p) prop actuals_by_ref

and check_untainted exp caller_pname callee_pname prop =
  match Prop.get_taint_attribute prop exp with
  | Some (Sil.Ataint source_pname) ->
      let err_desc =
        Errdesc.explain_tainted_value_reaching_sensitive_function exp source_pname
          callee_pname (State.get_loc ()) in
      let exn =
        Exceptions.Tainted_value_reaching_sensitive_function
          (err_desc, try assert false with Assert_failure x -> x) in
      Reporting.log_warning caller_pname exn;
      Prop.add_or_replace_exp_attribute prop exp (Sil.Auntaint)
  | _ ->
      if !Config.footprint then
        let untaint_attr = Sil.Const (Sil.Cattribute (Sil.Auntaint)) in
        (* add untained(n_lexp) to the footprint *)
        Prop.conjoin_neq ~footprint:true exp untaint_attr prop
      else prop

(** execute a call for an unknown or scan function *)
and call_unknown_or_scan is_scan cfg pdesc tenv pre path
    ret_ids ret_type_option actual_pars callee_pname loc =
  let remove_file_attribute prop =
    let do_exp p (e, t) =
      let do_attribute q = function
        | Sil.Aresource res_action as res
          when res_action.Sil.ra_res = Sil.Rfile ->
            Prop.remove_attribute res q
        | _ -> q in
      IList.fold_left do_attribute p (Prop.get_exp_attributes p e) in
    IList.fold_left do_exp prop actual_pars in
  let add_tainted_pre prop actuals caller_pname callee_pname =
    if !Config.taint_analysis then
      match Taint.accepts_sensitive_params callee_pname with
      | [] -> prop
      | param_nums ->
          let check_taint_if_nums_match (prop_acc, param_num) (actual_exp, _actual_typ) =
            let prop_acc' =
              if IList.exists (fun num -> num = param_num) param_nums
              then check_untainted actual_exp caller_pname callee_pname prop_acc
              else prop_acc in
            prop_acc', param_num + 1 in
          IList.fold_left
            check_taint_if_nums_match
            (prop, 0)
            actuals
          |> fst
    else prop in
  let actuals_by_ref =
    IList.filter
      (function
        | Sil.Lvar _, _ -> true
        | _ -> false)
      actual_pars in
  let pre_final =
    (* in Java, assume that skip functions close resources passed as params *)
    let pre_1 = if !Config.curr_language = Config.Java then remove_file_attribute pre else pre in
    let pre_2 = match ret_ids, ret_type_option with
      | [ret_id], Some ret_typ ->
          add_constraints_on_retval pdesc pre_1 (Sil.Var ret_id) ret_typ callee_pname loc
      | _ -> pre_1 in
    let pre_3 = add_constraints_on_actuals_by_ref pre_2 actuals_by_ref callee_pname loc in
    let caller_pname = Cfg.Procdesc.get_proc_name pdesc in
    add_tainted_pre pre_3 actual_pars caller_pname callee_pname in
  if is_scan (* if scan function, don't mark anything with undef attributes *)
  then [(Tabulation.remove_constant_string_class pre_final, path)]
  else
    (* otherwise, add undefined attribute to retvals and actuals passed by ref *)
    let exps_to_mark =
      let ret_exps = IList.map (fun ret_id -> Sil.Var ret_id) ret_ids in
      IList.fold_left
        (fun exps_to_mark (exp, _) -> exp :: exps_to_mark) ret_exps actuals_by_ref in
    let path_pos = State.get_path_pos () in
    [(Prop.mark_vars_as_undefined pre_final exps_to_mark callee_pname loc path_pos, path)]

and sym_exe_check_variadic_sentinel ?(fails_on_nil = false) cfg pdesc tenv prop path n_formals actual_params (sentinel, null_pos) callee_pname loc =
  (* from clang's lib/Sema/SemaExpr.cpp: *)
  (* "nullPos" is the number of formal parameters at the end which *)
  (* effectively count as part of the variadic arguments.  This is *)
  (* useful if you would prefer to not have *any* formal parameters, *)
  (* but the language forces you to have at least one. *)
  let first_var_arg_pos = if null_pos > n_formals then 0 else n_formals - null_pos in
  let nargs = IList.length actual_params in
  (* sentinels start counting from the last argument to the function *)
  let sentinel_pos = nargs - sentinel - 1 in
  let mk_non_terminal_argsi (acc, i) a =
    if i < first_var_arg_pos || i >= sentinel_pos then (acc, i +1)
    else ((a, i):: acc, i +1) in
  (* IList.fold_left reverses the arguments *)
  let non_terminal_argsi = fst (IList.fold_left mk_non_terminal_argsi ([], 0) actual_params) in
  let check_allocated result ((lexp, typ), i) =
    (* simulate a Letderef for [lexp] *)
    let tmp_id_deref = Ident.create_fresh Ident.kprimed in
    let letderef = Sil.Letderef (tmp_id_deref, lexp, typ, loc) in
    try
      sym_exec_generated false cfg tenv pdesc [letderef] result
    with e when exn_not_failure e ->
      if not fails_on_nil then
        let deref_str = Localise.deref_str_nil_argument_in_variadic_method callee_pname nargs i in
        let err_desc =
          Errdesc.explain_dereference ~use_buckets: true ~is_premature_nil: true
            deref_str prop loc in
        raise (Exceptions.Premature_nil_termination
                 (err_desc, try assert false with Assert_failure x -> x))
      else
        raise e in
  (* IList.fold_left reverses the arguments back so that we report an *)
  (* error on the first premature nil argument *)
  IList.fold_left check_allocated [(prop, path)] non_terminal_argsi

and sym_exe_check_variadic_sentinel_if_present
    cfg pdesc tenv prop path actual_params callee_pname loc =
  match Specs.proc_resolve_attributes callee_pname with
  | None ->
      [(prop, path)]
  | Some callee_attributes ->
      match Sil.get_sentinel_func_attribute_value
              callee_attributes.ProcAttributes.func_attributes with
      | None -> [(prop, path)]
      | Some sentinel_arg ->
          let formals = callee_attributes.ProcAttributes.formals in
          sym_exe_check_variadic_sentinel
            cfg pdesc tenv prop path (IList.length formals)
            actual_params sentinel_arg callee_pname loc

and sym_exec_objc_getter field_name ret_typ_opt tenv cfg ret_ids pdesc pname loc args prop =
  L.d_strln ("No custom getter found. Executing the ObjC builtin getter with ivar "^
             (Ident.fieldname_to_string field_name)^".");
  let ret_id =
    match ret_ids with
    | [ret_id] -> ret_id
    | _ -> assert false in
  let ret_typ =
    match ret_typ_opt with
    | Some ret_typ -> ret_typ
    | None -> assert false in
  match args with
  | [(lexp, typ)] ->
      let typ' = (match Sil.expand_type tenv typ with
          | Sil.Tstruct _ as s -> s
          | Sil.Tptr (t, _) -> Sil.expand_type tenv t
          | _ -> assert false) in
      let field_access_exp = Sil.Lfield (lexp, field_name, typ') in
      execute_letderef
        ~report_deref_errors:false pname pdesc tenv ret_id field_access_exp ret_typ loc prop
  | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

and sym_exec_objc_setter field_name ret_typ_opt tenv cfg ret_ids pdesc pname loc args prop =
  L.d_strln ("No custom setter found. Executing the ObjC builtin setter with ivar "^
             (Ident.fieldname_to_string field_name)^".");
  match args with
  | (lexp1, typ1) :: (lexp2, typ2)::_ ->
      let typ1' = (match Sil.expand_type tenv typ1 with
          | Sil.Tstruct _ as s -> s
          | Sil.Tptr (t, _) -> Sil.expand_type tenv t
          | _ -> assert false) in
      let field_access_exp = Sil.Lfield (lexp1, field_name, typ1') in
      execute_set ~report_deref_errors:false pname pdesc tenv field_access_exp typ2 lexp2 loc prop
  | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

and sym_exec_objc_accessor property_accesor ret_typ_opt tenv cfg ret_ids pdesc callee_pname loc args
    prop path : Builtin.ret_typ =
  let f_accessor =
    match property_accesor with
    | ProcAttributes.Objc_getter field_name -> sym_exec_objc_getter field_name
    | ProcAttributes.Objc_setter field_name -> sym_exec_objc_setter field_name in
  (* we want to execute in the context of the current procedure, not in the context of callee_pname,
     since this is the procname of the setter/getter method *)
  let cur_pname = Cfg.Procdesc.get_proc_name pdesc in
  f_accessor ret_typ_opt tenv cfg ret_ids pdesc cur_pname loc args prop
  |> IList.map (fun p -> (p, path))

(** Perform symbolic execution for a function call *)
and sym_exec_call cfg pdesc tenv pre path ret_ids actual_pars summary loc =
  let caller_pname = Cfg.Procdesc.get_proc_name pdesc in
  let callee_pname = Specs.get_proc_name summary in
  let ret_typ = Specs.get_ret_type summary in
  let check_return_value_ignored () = (* check if the return value of the call is ignored, and issue a warning *)
    let is_ignored = match ret_typ, ret_ids with
      | Sil.Tvoid, _ -> false
      | Sil.Tint _, _ when not (is_defined cfg callee_pname) ->
          (* if the proc returns Tint and is not defined, *)
          (* don't report ignored return value *)
          false
      | _, [] -> true
      | _, [id] -> Errdesc.id_is_assigned_then_dead (State.get_node ()) id
      | _ -> false in
    if is_ignored
       && Specs.get_flag callee_pname proc_flag_ignore_return = None then
      let err_desc = Localise.desc_return_value_ignored callee_pname loc in
      let exn = (Exceptions.Return_value_ignored (err_desc, try assert false with Assert_failure x -> x)) in
      let pre_opt = State.get_normalized_pre (Abs.abstract_no_symop caller_pname) in
      Reporting.log_warning caller_pname ~pre: pre_opt exn in
  check_inherently_dangerous_function caller_pname callee_pname;
  begin
    let formal_types = IList.map (fun (_, typ) -> typ) (Specs.get_formals summary) in
    let rec comb actual_pars formal_types =
      match actual_pars, formal_types with
      | [], [] -> actual_pars
      | (e, t_e):: etl', t:: tl' ->
          (e,
           if
             (!Config.Experiment.activate_subtyping_in_cpp ||
              !Config.curr_language = Config.Java)
           then t_e else t) :: comb etl' tl'
      | _,[] ->
          Errdesc.warning_err
            (State.get_loc ())
            "likely use of variable-arguments function, or function prototype missing@.";
          L.d_warning "likely use of variable-arguments function, or function prototype missing"; L.d_ln();
          L.d_str "actual parameters: "; Sil.d_exp_list (IList.map fst actual_pars); L.d_ln ();
          L.d_str "formal parameters: "; Sil.d_typ_list formal_types; L.d_ln ();
          actual_pars
      | [], _ ->
          L.d_str ("**** ERROR: Procedure " ^ Procname.to_string callee_pname);
          L.d_strln (" mismatch in the number of parameters ****");
          L.d_str "actual parameters: "; Sil.d_exp_list (IList.map fst actual_pars); L.d_ln ();
          L.d_str "formal parameters: "; Sil.d_typ_list formal_types; L.d_ln ();
          raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x)) in
    let actual_params = comb actual_pars formal_types in
    (* Actual parameters are associated to their formal
       parameter type if there are enough formal parameters, and
       to their actual type otherwise. The latter case happens
       with variable - arguments functions *)
    check_return_value_ignored ();
    (* In case we call an objc instance method we add and extra spec *)
    (* were the receiver is null and the semantics of the call is nop*)
    if (!Config.curr_language <> Config.Java) && !Config.objc_method_call_semantics &&
       (Specs.get_attributes summary).ProcAttributes.is_objc_instance_method then
      handle_objc_method_call actual_pars actual_params pre tenv cfg ret_ids pdesc callee_pname loc
        path Tabulation.exe_function_call
    else  (* non-objective-c method call. Standard tabulation *)
      Tabulation.exe_function_call
        tenv cfg ret_ids pdesc callee_pname loc actual_params pre path
  end

(** perform symbolic execution for a single prop, and check for junk *)
and sym_exec_wrapper handle_exn cfg tenv pdesc instr ((prop: Prop.normal Prop.t), path)
  : Paths.PathSet.t =
  let pname = Cfg.Procdesc.get_proc_name pdesc in
  let prop_primed_to_normal p = (** Rename primed vars with fresh normal vars, and return them *)
    let fav = Prop.prop_fav p in
    Sil.fav_filter_ident fav Ident.is_primed;
    let ids_primed = Sil.fav_to_list fav in
    let ids_primed_normal =
      IList.map (fun id -> (id, Ident.create_fresh Ident.knormal)) ids_primed in
    let ren_sub = Sil.sub_of_list (IList.map (fun (id1, id2) -> (id1, Sil.Var id2)) ids_primed_normal) in
    let p' = Prop.normalize (Prop.prop_sub ren_sub p) in
    let fav_normal = Sil.fav_from_list (IList.map snd ids_primed_normal) in
    p', fav_normal in
  let prop_normal_to_primed fav_normal p = (* rename given normal vars to fresh primed *)
    if Sil.fav_to_list fav_normal = [] then p
    else Prop.exist_quantify fav_normal p in
  try
    let pre_process_prop p =
      let p', fav =
        if Sil.instr_is_auxiliary instr
        then p, Sil.fav_new ()
        else prop_primed_to_normal p in
      let p'' =
        let map_res_action e ra = (* update the vpath in resource attributes *)
          let vpath, _ = Errdesc.vpath_find p' e in
          { ra with Sil.ra_vpath = vpath } in
        Prop.attribute_map_resource p' map_res_action in
      p'', fav in
    let post_process_result fav_normal p path =
      let p' = prop_normal_to_primed fav_normal p in
      State.set_path path None;
      let node_has_abstraction node =
        let instr_is_abstraction = function
          | Sil.Abstract _ -> true
          | _ -> false in
        IList.exists instr_is_abstraction (Cfg.Node.get_instrs node) in
      let curr_node = State.get_node () in
      match Cfg.Node.get_kind curr_node with
      | Cfg.Node.Prune_node _ when not (node_has_abstraction curr_node) ->
          (* don't check for leaks in prune nodes, unless there is abstraction anyway, but force them into either branch *)
          p'
      | _ ->
          check_deallocate_static_memory (Abs.abstract_junk ~original_prop: p pname tenv p') in
    L.d_str "Instruction "; Sil.d_instr instr; L.d_ln ();
    let prop', fav_normal = pre_process_prop prop in
    let res_list = run_with_abs_val_eq_zero (* no exp abstraction during sym exe *)
        (fun () ->
           sym_exec cfg tenv pdesc instr prop' path) in
    let res_list_nojunk = IList.map (fun (p, path) -> (post_process_result fav_normal p path, path)) res_list in
    let results = IList.map (fun (p, path) -> (Prop.prop_rename_primed_footprint_vars p, path)) res_list_nojunk in
    L.d_strln "Instruction Returns";
    Propgraph.d_proplist prop (IList.map fst results); L.d_ln ();
    State.mark_instr_ok ();
    Paths.PathSet.from_renamed_list results
  with exn when Exceptions.handle_exception exn && !Config.footprint ->
    handle_exn exn; (* calls State.mark_instr_fail *)
    if !Config.nonstop
    then (Paths.PathSet.from_renamed_list [(prop, path)]) (* in nonstop mode treat the instruction as skip *)
    else Paths.PathSet.empty

(** {2 Lifted Abstract Transfer Functions} *)

let lifted_sym_exec
    handle_exn cfg tenv pdesc (pset : Paths.PathSet.t) node (instrs : Sil.instr list)
  : Paths.PathSet.t =
  let pname = Cfg.Procdesc.get_proc_name pdesc in
  let exe_instr_prop instr p tr (pset1: Paths.PathSet.t) =
    let pset2 =
      if Tabulation.prop_is_exn pname p && not (Sil.instr_is_auxiliary instr)
         && Cfg.Node.get_kind node <> Cfg.Node.exn_handler_kind
         (* skip normal instructions if an exception was thrown, unless this is an exception handler node *)
      then
        begin
          L.d_str "Skipping instr "; Sil.d_instr instr; L.d_strln " due to exception";
          Paths.PathSet.from_renamed_list [(p, tr)]
        end
      else sym_exec_wrapper handle_exn cfg tenv pdesc instr (p, tr) in
    Paths.PathSet.union pset2 pset1 in
  let exe_instr_pset (pset, stack) instr = (** handle a single instruction at the set level *)
    let pp_stack_instr pset' =
      L.d_str "Stack Instruction "; Sil.d_instr instr; L.d_ln ();
      L.d_strln "Stack Instruction Returns";
      Propset.d Prop.prop_emp (Paths.PathSet.to_propset pset'); L.d_ln () in
    match instr, stack with
    | Sil.Stackop (Sil.Push, _), _ ->
        pp_stack_instr pset;
        (pset, pset :: stack)
    | Sil.Stackop (Sil.Swap, _), (pset':: stack') ->
        pp_stack_instr pset';
        (pset', pset:: stack')
    | Sil.Stackop (Sil.Pop, _), (pset':: stack') ->
        let pset'' = Paths.PathSet.union pset pset' in
        pp_stack_instr pset'';
        (pset'', stack')
    | Sil.Stackop _, _ -> (* should not happen *)
        assert false
    | _ ->
        let pset' = Paths.PathSet.fold (exe_instr_prop instr) pset Paths.PathSet.empty in
        (pset', stack) in
  let stack = [] in
  let pset', stack' = IList.fold_left exe_instr_pset (pset, stack) instrs in
  if stack' != [] then assert false; (* final stack must be empty *)
  pset'

(* ============== START of ModelBuiltins ============== *)
module ModelBuiltins = struct
  (** This module contains models for the builtin functions supported *)

  let execute___no_op prop path: Builtin.ret_typ =
    [(prop, path)]

  (** model va_arg as always returning 0 *)
  let execute___builtin_va_arg cfg pdesc instr tenv prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args, ret_ids with
    | [(lexp1, typ1); (lexp2, typ2); (lexp3, typ3)], _ ->
        let instr' = Sil.Set (lexp3, typ3, Sil.exp_zero, loc) in
        sym_exec_generated true cfg tenv pdesc [instr'] [(prop, path)]
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  let mk_empty_array size =
    Sil.Earray (size, [], Sil.inst_none)

  let extract_array_type typ =
    if (!Config.curr_language = Config.Java) then
      match typ with
      | Sil.Tptr ( Sil.Tarray (typ', _), _) -> Some typ'
      | _ -> None
    else
      match typ with
      | Sil.Tptr (typ', _) | Sil.Tarray (typ', _) ->
          Some typ'
      | _ -> None

  (** Return a result from a procedure call. *)
  let return_result e prop ret_ids =
    match ret_ids with
    | [ret_id] -> Prop.conjoin_eq e (Sil.Var ret_id) prop
    | _ -> prop

  let execute___get_array_size cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args with
    | [(lexp, typ)] when IList.length ret_ids <= 1 ->
        let pname = Cfg.Procdesc.get_proc_name pdesc in
        let return_result_for_array_size e prop ret_ids = return_result e prop ret_ids in
        let n_lexp, prop = exp_norm_check_arith pname _prop lexp in
        begin
          try
            let hpred = IList.find (function
                | Sil.Hpointsto(e, _, _) -> Sil.exp_equal e n_lexp
                | _ -> false) (Prop.get_sigma prop) in
            match hpred with
            | Sil.Hpointsto(e, Sil.Earray(size, _, _), _) ->
                [(return_result_for_array_size size prop ret_ids, path)]
            | _ -> []
          with Not_found ->
            let otyp' = (extract_array_type typ) in
            match otyp' with
            | Some typ' ->
                let size = Sil.Var(Ident.create_fresh Ident.kfootprint) in
                let s = mk_empty_array size in
                let hpred = Prop.mk_ptsto n_lexp s (Sil.Sizeof(Sil.Tarray(typ', size), Sil.Subtype.exact)) in
                let sigma = Prop.get_sigma prop in
                let sigma_fp = Prop.get_sigma_footprint prop in
                let prop'= Prop.replace_sigma (hpred:: sigma) prop in
                let prop''= Prop.replace_sigma_footprint (hpred:: sigma_fp) prop' in
                let prop''= Prop.normalize prop'' in
                [(return_result_for_array_size size prop'' ret_ids, path)]
            | _ -> []
        end
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  let execute___set_array_size cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args, ret_ids with
    | [(lexp, typ); (size, _)], [] ->
        let pname = Cfg.Procdesc.get_proc_name pdesc in
        let n_lexp, _prop' = exp_norm_check_arith pname _prop lexp in
        let n_size, prop = exp_norm_check_arith pname _prop' size in
        begin
          try
            let hpred, sigma' = IList.partition (function
                | Sil.Hpointsto(e, _, t) -> Sil.exp_equal e n_lexp
                | _ -> false) (Prop.get_sigma prop) in
            match hpred with
            | [Sil.Hpointsto(e, Sil.Earray(_, esel, inst), t)] ->
                let hpred' = Sil.Hpointsto (e, Sil.Earray (n_size, esel, inst), t) in
                let prop' = Prop.replace_sigma (hpred':: sigma') prop in
                [(Prop.normalize prop', path)]
            | _ -> raise Not_found
          with Not_found ->
          match typ with
          | Sil.Tptr (typ', _) ->
              let size_fp = Sil.Var(Ident.create_fresh Ident.kfootprint) in
              let se = mk_empty_array n_size in
              let se_fp = mk_empty_array size_fp in
              let hpred = Prop.mk_ptsto n_lexp se (Sil.Sizeof(Sil.Tarray(typ', size), Sil.Subtype.exact)) in
              let hpred_fp = Prop.mk_ptsto n_lexp se_fp (Sil.Sizeof(Sil.Tarray(typ', size_fp), Sil.Subtype.exact)) in
              let sigma = Prop.get_sigma prop in
              let sigma_fp = Prop.get_sigma_footprint prop in
              let prop'= Prop.replace_sigma (hpred:: sigma) prop in
              let prop''= Prop.replace_sigma_footprint (hpred_fp:: sigma_fp) prop' in
              let prop''= Prop.normalize prop'' in
              [(prop'', path)]
          | _ -> []
        end
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  let execute___print_value cfg pdesc instr tenv prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    L.err "__print_value: ";
    let pname = Cfg.Procdesc.get_proc_name pdesc in
    let do_arg (lexp, typ) =
      let n_lexp, _ = exp_norm_check_arith pname prop lexp in
      L.err "%a " (Sil.pp_exp pe_text) n_lexp in
    IList.iter do_arg args;
    L.err "@.";
    [(prop, path)]

  let is_undefined_opt prop n_lexp =
    let is_undef =
      Option.is_some (Prop.get_undef_attribute prop n_lexp) in
    is_undef && (!Config.angelic_execution || !Config.optimistic_cast)

  (** Creates an object in the heap with a given type, when the object is not known to be null or when it doesn't
      appear already in the heap. *)
  let create_type tenv n_lexp typ prop =
    let prop_type =
      try
        let _ = IList.find (function
            | Sil.Hpointsto(e, _, _) -> Sil.exp_equal e n_lexp
            | _ -> false) (Prop.get_sigma prop) in
        prop
      with Not_found ->
        let mhpred =
          match typ with
          | Sil.Tptr (typ', _) ->
              let sexp = Sil.Estruct ([], Sil.inst_none) in
              let typ'' = Sil.expand_type tenv typ' in
              let texp = Sil.Sizeof (typ'', Sil.Subtype.subtypes) in
              let hpred = Prop.mk_ptsto n_lexp sexp texp in
              Some hpred
          | Sil.Tarray (typ', _) ->
              let size = Sil.Var(Ident.create_fresh Ident.kfootprint) in
              let sexp = mk_empty_array size in
              let texp = Sil.Sizeof (typ, Sil.Subtype.subtypes) in
              let hpred = Prop.mk_ptsto n_lexp sexp texp in
              Some hpred
          | _ -> None in
        match mhpred with
        | Some hpred ->
            let sigma = Prop.get_sigma prop in
            let sigma_fp = Prop.get_sigma_footprint prop in
            let prop'= Prop.replace_sigma (hpred:: sigma) prop in
            let prop''=
              let has_normal_variables =
                Sil.fav_exists (Sil.exp_fav n_lexp) Ident.is_normal in
              if (is_undefined_opt prop n_lexp) || has_normal_variables
              then prop'
              else Prop.replace_sigma_footprint (hpred:: sigma_fp) prop' in
            let prop''= Prop.normalize prop'' in
            prop''
        | None -> prop in
    let sil_is_null = Sil.BinOp (Sil.Eq, n_lexp, Sil.exp_zero) in
    let sil_is_nonnull = Sil.UnOp (Sil.LNot, sil_is_null, None) in
    let null_case = Propset.to_proplist (prune_prop tenv sil_is_null prop) in
    let non_null_case = Propset.to_proplist (prune_prop tenv sil_is_nonnull prop_type) in
    if ((IList.length non_null_case) > 0) && (!Config.footprint) then
      non_null_case
    else if ((IList.length non_null_case) > 0) && (is_undefined_opt prop n_lexp) then
      non_null_case
    else null_case@non_null_case

  let execute___get_type_of cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args with
    | [(lexp, typ)] when IList.length ret_ids <= 1 ->
        let pname = Cfg.Procdesc.get_proc_name pdesc in
        let n_lexp, prop = exp_norm_check_arith pname _prop lexp in
        let props = create_type tenv n_lexp typ prop in
        let aux prop =
          begin
            try
              let hpred = IList.find (function
                  | Sil.Hpointsto(e, _, _) -> Sil.exp_equal e n_lexp
                  | _ -> false) (Prop.get_sigma prop) in
              match hpred with
              | Sil.Hpointsto(e, _, texp) ->
                  (return_result texp prop ret_ids), path
              | _ -> assert false
            with Not_found -> (return_result Sil.exp_zero prop ret_ids), path
          end in
        (IList.map aux props)
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  (** replace the type of the ptsto rooted at [root_e] with [texp] in [prop] *)
  let replace_ptsto_texp prop root_e texp =
    let process_sigma sigma =
      let sigma1, sigma2 =
        IList.partition (function
            | Sil.Hpointsto(e, _, _) -> Sil.exp_equal e root_e
            | _ -> false) sigma in
      match sigma1 with
      | [Sil.Hpointsto(e, se, _)] -> (Sil.Hpointsto (e, se, texp)) :: sigma2
      | _ -> sigma in
    let sigma = Prop.get_sigma prop in
    let sigma_fp = Prop.get_sigma_footprint prop in
    let prop'= Prop.replace_sigma (process_sigma sigma) prop in
    let prop''= Prop.replace_sigma_footprint (process_sigma sigma_fp) prop' in
    Prop.normalize prop''

  let execute___instanceof_cast
      cfg pdesc instr tenv _prop path ret_ids args callee_pname loc instof
    : Builtin.ret_typ =
    match args with
    | [(_val1, typ1); (_texp2, typ2)] when IList.length ret_ids <= 1 ->
        let pname = Cfg.Procdesc.get_proc_name pdesc in
        let val1, __prop = exp_norm_check_arith pname _prop _val1 in
        let texp2, prop = exp_norm_check_arith pname __prop _texp2 in
        let exe_one_prop prop =
          if Sil.exp_equal texp2 Sil.exp_zero then
            [(return_result Sil.exp_zero prop ret_ids, path)]
          else
            begin
              try
                let hpred = IList.find (function
                    | Sil.Hpointsto(e1, _, _) -> Sil.exp_equal e1 val1
                    | _ -> false) (Prop.get_sigma prop) in
                match hpred with
                | Sil.Hpointsto(_, _, texp1) ->
                    let pos_type_opt, neg_type_opt = Prover.subtype_case_analysis tenv texp1 texp2 in
                    let mk_res type_opt res_e = match type_opt with
                      | None -> []
                      | Some texp1' ->
                          let prop' =
                            if Sil.exp_equal texp1 texp1' then prop
                            else replace_ptsto_texp prop val1 texp1' in
                          [(return_result res_e prop' ret_ids, path)] in
                    if (instof) then (* instanceof *)
                      begin
                        let pos_res = mk_res pos_type_opt Sil.exp_one in
                        let neg_res = mk_res neg_type_opt Sil.exp_zero in
                        pos_res @ neg_res
                      end
                    else (* cast *)
                      begin
                        if (!Config.footprint = true) then
                          begin
                            match pos_type_opt with
                            | None ->
                                Tabulation.raise_cast_exception
                                  (try assert false with Assert_failure ml_loc -> ml_loc)
                                  None texp1 texp2 val1
                            | Some texp1' -> (mk_res pos_type_opt val1)
                          end
                        else (* !Config.footprint = false *)
                          begin
                            match neg_type_opt with
                            | Some _ ->
                                if (is_undefined_opt prop val1) then (mk_res pos_type_opt val1)
                                else
                                  Tabulation.raise_cast_exception
                                    (try assert false with Assert_failure ml_loc -> ml_loc)
                                    None texp1 texp2 val1
                            | None -> (mk_res pos_type_opt val1)
                          end
                      end
                | _ -> []
              with Not_found ->
                [(return_result val1 prop ret_ids, path)]
            end in
        let props = create_type tenv val1 typ1 prop in
        IList.flatten (IList.map exe_one_prop props)
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  let execute___instanceof cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    (execute___instanceof_cast cfg pdesc instr tenv _prop path ret_ids args callee_pname loc true)

  let execute___cast cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    (execute___instanceof_cast cfg pdesc instr tenv _prop path ret_ids args callee_pname loc false)

  let set_resource_attribute prop path n_lexp loc ra_res =
    let prop' = match Prop.get_resource_attribute prop n_lexp with
      | Some (Sil.Aresource (_ as ra)) ->
          Prop.add_or_replace_exp_attribute
            prop
            n_lexp
            (Sil.Aresource { ra with Sil.ra_res = ra_res })
      | _ ->
          ( let pname = Sil.mem_alloc_pname Sil.Mnew in
            let ra = { Sil.ra_kind = Sil.Racquire; Sil.ra_res = ra_res; Sil.ra_pname = pname; Sil.ra_loc = loc; Sil.ra_vpath = None } in
            Prop.add_or_replace_exp_attribute prop n_lexp (Sil.Aresource ra)) in
    [(prop', path)]

  (** Set the attibute of the value as file *)
  let execute___set_file_attribute cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args, ret_ids with
    | [(lexp, typ)], _ ->
        let pname = Cfg.Procdesc.get_proc_name pdesc in
        let n_lexp, prop = exp_norm_check_arith pname _prop lexp in
        set_resource_attribute prop path n_lexp loc Sil.Rfile
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  (** Set the attibute of the value as lock *)
  let execute___set_lock_attribute cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args, ret_ids with
    | [(lexp, typ)], _ ->
        let pname = Cfg.Procdesc.get_proc_name pdesc in
        let n_lexp, prop = exp_norm_check_arith pname _prop lexp in
        set_resource_attribute prop path n_lexp loc Sil.Rlock
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  (** Set the resource attribute of the first real argument of method as ignore, the first argument is assumed to be "this" *)
  let execute___method_set_ignore_attribute
      cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args, ret_ids with
    | [_ ; (lexp, typ)], _ ->
        let pname = Cfg.Procdesc.get_proc_name pdesc in
        let n_lexp, prop = exp_norm_check_arith pname _prop lexp in
        set_resource_attribute prop path n_lexp loc Sil.Rignore
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  (** Set the attibute of the value as memory *)
  let execute___set_mem_attribute cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args, ret_ids with
    | [(lexp, typ)], _ ->
        let pname = Cfg.Procdesc.get_proc_name pdesc in
        let n_lexp, prop = exp_norm_check_arith pname _prop lexp in
        set_resource_attribute prop path n_lexp loc (Sil.Rmemory Sil.Mnew)
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  (** Set the attibute of the value as tainted *)
  let execute___set_taint_attribute cfg pdesc instr tenv _prop path ret_ids args callee_name loc
    : Builtin.ret_typ =
    match args, ret_ids with
    | [(lexp, typ)], _ ->
        let pname = Cfg.Procdesc.get_proc_name pdesc in
        let n_lexp, prop = exp_norm_check_arith pname _prop lexp in
        [(Prop.add_or_replace_exp_attribute prop n_lexp (Sil.Ataint pname), path)]
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  (** Set the attibute of the value as untainted *)
  let execute___set_untaint_attribute cfg pdesc instr tenv _prop path ret_ids args callee_name loc
    : Builtin.ret_typ =
    match args, ret_ids with
    | [(lexp, typ)], _ ->
        let pname = Cfg.Procdesc.get_proc_name pdesc in
        let n_lexp, prop = exp_norm_check_arith pname _prop lexp in
        [(Prop.add_or_replace_exp_attribute prop n_lexp (Sil.Auntaint), path)]
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  (** report an error if [lexp] is tainted; otherwise, add untained([lexp]) as a precondition *)
  let execute___check_untainted cfg pdesc instr tenv prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args, ret_ids with
    | [(lexp, typ)], _ ->
        let caller_pname = Cfg.Procdesc.get_proc_name pdesc in
        let n_lexp, prop = exp_norm_check_arith caller_pname prop lexp in
        [(check_untainted n_lexp caller_pname callee_pname prop, path)]
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  (** take a pointer to a struct, and return the value of a hidden field in the struct *)
  let execute___get_hidden_field cfg pdesc instr tenv _prop path ret_ids args callee_name loc
    : Builtin.ret_typ =
    match args with
    | [(lexp, typ)] ->
        let pname = Cfg.Procdesc.get_proc_name pdesc in
        let n_lexp, prop = exp_norm_check_arith pname _prop lexp in
        let ret_val = ref None in
        let return_val p = match !ret_val with
          | Some e -> return_result e p ret_ids
          | None -> p in
        let foot_var = lazy (Sil.Var (Ident.create_fresh Ident.kfootprint)) in
        let filter_fld_hidden (f, _ ) = Ident.fieldname_is_hidden f in
        let has_fld_hidden fsel = IList.exists filter_fld_hidden fsel in
        let do_hpred in_foot hpred = match hpred with
          | Sil.Hpointsto(e, Sil.Estruct (fsel, inst), texp) when Sil.exp_equal e n_lexp && (not (has_fld_hidden fsel)) ->
              let foot_e = Lazy.force foot_var in
              ret_val := Some foot_e;
              let se = Sil.Eexp(foot_e, Sil.inst_none) in
              let fsel' = (Ident.fieldname_hidden, se) :: fsel in
              Sil.Hpointsto(e, Sil.Estruct (fsel', inst), texp)
          | Sil.Hpointsto(e, Sil.Estruct (fsel, _), texp) when Sil.exp_equal e n_lexp && not in_foot && has_fld_hidden fsel ->
              let set_ret_val () =
                match IList.find filter_fld_hidden fsel with
                | _, Sil.Eexp(e, _) -> ret_val := Some e
                | _ -> () in
              set_ret_val();
              hpred
          | _ -> hpred in
        let sigma' = IList.map (do_hpred false) (Prop.get_sigma prop) in
        let sigma_fp' = IList.map (do_hpred true) (Prop.get_sigma_footprint prop) in
        let prop' = Prop.replace_sigma_footprint sigma_fp' (Prop.replace_sigma sigma' prop) in
        let prop'' = return_val (Prop.normalize prop') in
        [(prop'', path)]
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  (** take a pointer to a struct and a value, and set a hidden field in the struct to the given value *)
  let execute___set_hidden_field cfg pdesc instr tenv _prop path ret_ids args callee_name loc
    : Builtin.ret_typ =
    match args with
    | [(lexp1, typ1); (lexp2, typ2)] ->
        let pname = Cfg.Procdesc.get_proc_name pdesc in
        let n_lexp1, _prop1 = exp_norm_check_arith pname _prop lexp1 in
        let n_lexp2, prop = exp_norm_check_arith pname _prop1 lexp2 in
        let foot_var = lazy (Sil.Var (Ident.create_fresh Ident.kfootprint)) in
        let filter_fld_hidden (f, _ ) = Ident.fieldname_is_hidden f in
        let has_fld_hidden fsel = IList.exists filter_fld_hidden fsel in
        let do_hpred in_foot hpred = match hpred with
          | Sil.Hpointsto(e, Sil.Estruct (fsel, inst), texp) when Sil.exp_equal e n_lexp1 && not in_foot ->
              let se = Sil.Eexp(n_lexp2, Sil.inst_none) in
              let fsel' = (Ident.fieldname_hidden, se) :: (IList.filter (fun x -> not (filter_fld_hidden x)) fsel) in
              Sil.Hpointsto(e, Sil.Estruct (fsel', inst), texp)
          | Sil.Hpointsto(e, Sil.Estruct (fsel, inst), texp) when Sil.exp_equal e n_lexp1 && in_foot && not (has_fld_hidden fsel) ->
              let foot_e = Lazy.force foot_var in
              let se = Sil.Eexp(foot_e, Sil.inst_none) in
              let fsel' = (Ident.fieldname_hidden, se) :: fsel in
              Sil.Hpointsto(e, Sil.Estruct (fsel', inst), texp)
          | _ -> hpred in
        let sigma' = IList.map (do_hpred false) (Prop.get_sigma prop) in
        let sigma_fp' = IList.map (do_hpred true) (Prop.get_sigma_footprint prop) in
        let prop' = Prop.replace_sigma_footprint sigma_fp' (Prop.replace_sigma sigma' prop) in
        let prop'' = Prop.normalize prop' in
        [(prop'', path)]
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  (* Update the objective-c hidden counter by applying the operation op and the operand delta.*)
  (* Eg. op=+/- delta is an integer *)
  let execute___objc_counter_update
      suppress_npe_report op delta cfg pdesc instr tenv _prop path ret_ids args callee_name loc
    : Builtin.ret_typ =
    match args with
    | [(lexp, typ)] ->
        let typ' = (match Sil.expand_type tenv typ with
            | Sil.Tstruct _ as s -> s
            | Sil.Tptr(t, _) -> Sil.expand_type tenv t
            | s' ->
                L.d_str ("Trying to update hidden field of not a struc. Type: "^(Sil.typ_to_string s'));
                assert false) in
        (* Assumes that lexp is a temp n$1 that has the value of the object. *)
        (* This is the case as a call f(o) it's translates as n$1=*&o; f(n$1) *)
        (* n$2 = *n$1.hidden *)
        let tmp = Ident.create_fresh Ident.knormal in
        let hidden_field = Sil.Lfield(lexp, Ident.fieldname_hidden, typ') in
        let counter_to_tmp = Sil.Letderef(tmp, hidden_field, typ', loc) in
        (* *n$1.hidden = (n$2 +/- delta) *)
        let update_counter = Sil.Set(hidden_field, typ', Sil.BinOp(op, Sil.Var tmp, Sil.Const (Sil.Cint delta)), loc) in
        let update_counter_instrs = [counter_to_tmp; update_counter; Sil.Remove_temps([tmp], loc)] in
        sym_exec_generated suppress_npe_report cfg tenv pdesc update_counter_instrs [(_prop, path)]
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  (* Given a list of args checks if the first is the flag indicating whether is a call to retain/release for which*)
  (* we have to suppress NPE report or not. If the flag is present it is removed from the list of args. *)
  let get_suppress_npe_flag args =
    match args with
    | (Sil.Const (Sil.Cint i), Sil.Tint Sil.IBool):: args' when Sil.Int.isone i ->
        false, args' (* this is a CFRelease/CFRetain *)
    | _ -> true, args

  let execute___objc_retain_impl cfg pdesc instr tenv _prop path ret_ids args callee_name loc
    : Builtin.ret_typ =
    let suppress_npe_report, args' = get_suppress_npe_flag args in
    match args' with
    | [(lexp, typ)] ->
        let prop = return_result lexp _prop ret_ids in
        execute___objc_counter_update suppress_npe_report (Sil.PlusA) (Sil.Int.one)
          cfg pdesc instr tenv prop path ret_ids args' callee_name loc
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  let execute___objc_retain cfg pdesc instr tenv _prop path ret_ids args callee_name loc
    : Builtin.ret_typ =
    if !Config.objc_memory_model_on then
      execute___objc_retain_impl cfg pdesc instr tenv _prop path ret_ids args callee_name loc
    else execute___no_op _prop path

  let execute___objc_retain_cf cfg pdesc instr tenv _prop path ret_ids args callee_name loc
    : Builtin.ret_typ =
    execute___objc_retain_impl cfg pdesc instr tenv _prop path ret_ids args callee_name loc

  let execute___objc_release_impl cfg pdesc instr tenv _prop path ret_ids args callee_name loc
    : Builtin.ret_typ =
    let suppress_npe_flag, args' = get_suppress_npe_flag args in
    execute___objc_counter_update suppress_npe_flag (Sil.MinusA) (Sil.Int.one)
      cfg pdesc instr tenv _prop path ret_ids args' callee_name loc

  let execute___objc_release cfg pdesc instr tenv _prop path ret_ids args callee_name loc
    : Builtin.ret_typ =
    if !Config.objc_memory_model_on then
      execute___objc_release_impl cfg pdesc instr tenv _prop path ret_ids args callee_name loc
    else execute___no_op _prop path

  let execute___objc_release_cf cfg pdesc instr tenv _prop path ret_ids args callee_name loc
    : Builtin.ret_typ =
    execute___objc_release_impl cfg pdesc instr tenv _prop path ret_ids args callee_name loc

  (** Set the attibute of the value as objc autoreleased *)
  let execute___set_autorelease_attribute
      cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args, ret_ids with
    | [(lexp, typ)], _ ->
        let pname = Cfg.Procdesc.get_proc_name pdesc in
        let prop = return_result lexp _prop ret_ids in
        if !Config.objc_memory_model_on then
          let n_lexp, prop = exp_norm_check_arith pname prop lexp in
          let prop' = Prop.add_or_replace_exp_attribute prop n_lexp Sil.Aautorelease in
          [(prop', path)]
        else execute___no_op prop path
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  (** Release all the objects in the pool *)
  let execute___release_autorelease_pool
      cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    if !Config.objc_memory_model_on then
      let autoreleased_objects = Prop.get_atoms_with_attribute Sil.Aautorelease _prop in
      let prop = Prop.remove_attribute Sil.Aautorelease _prop in
      let call_release res exp =
        match res with
        | (prop, path):: _ ->
            (try
               let hpred = IList.find (function
                   | Sil.Hpointsto(e1, _, _) -> Sil.exp_equal e1 exp
                   | _ -> false) (Prop.get_sigma _prop) in
               match hpred with
               | Sil.Hpointsto(_, _, Sil.Sizeof (typ, st)) ->
                   let res1 =
                     execute___objc_release cfg pdesc instr tenv prop path ret_ids
                       [(exp, typ)] callee_pname loc in
                   res1
               | _ -> res
             with Not_found -> res)
        | [] -> res in
      IList.fold_left call_release [(prop, path)] autoreleased_objects
    else execute___no_op _prop path

  let execute___objc_cast cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args with
    | [(_val1, typ1); (_texp2, typ2)] when IList.length ret_ids <= 1 ->
        let pname = Cfg.Procdesc.get_proc_name pdesc in
        let val1, __prop = exp_norm_check_arith pname _prop _val1 in
        let texp2, prop = exp_norm_check_arith pname __prop _texp2 in
        (try
           let hpred = IList.find (function
               | Sil.Hpointsto(e1, _, _) -> Sil.exp_equal e1 val1
               | _ -> false) (Prop.get_sigma prop) in
           match hpred, texp2 with
           | Sil.Hpointsto(val1, _, texp1), Sil.Sizeof (typ, st) ->
               let prop' = replace_ptsto_texp prop val1 texp2 in
               [(return_result val1 prop' ret_ids, path)]
           | _ -> [(return_result val1 prop ret_ids, path)]
         with Not_found -> [(return_result val1 prop ret_ids, path)])
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  let execute_abort cfg pdesc instr tenv prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    raise (Exceptions.Precondition_not_found (Localise.verbatim_desc (Procname.to_string callee_pname), try assert false with Assert_failure x -> x))

  let execute_exit cfg pdesc instr tenv prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    execute_diverge prop path

  let _execute_free tenv mk loc acc iter =
    match Prop.prop_iter_current iter with
    | (Sil.Hpointsto(lexp, se, _), []) ->
        let prop = Prop.prop_iter_remove_curr_then_to_prop iter in
        let pname = Sil.mem_dealloc_pname mk in
        let ra = { Sil.ra_kind = Sil.Rrelease; Sil.ra_res = Sil.Rmemory mk; Sil.ra_pname = pname; Sil.ra_loc = loc; Sil.ra_vpath = None } in
        (* mark value as freed *)
        let p_res =
          Prop.add_or_replace_exp_attribute_check_changed
            Tabulation.check_attr_dealloc_mismatch
            prop
            lexp
            (Sil.Aresource ra) in
        p_res :: acc
    | (Sil.Hpointsto _, o :: os) -> assert false (* alignment error *)
    | _ -> assert false (* should not happen *)

  let _execute_free_nonzero mk pdesc tenv instr prop path lexp typ loc =
    try
      begin
        match Prover.is_root prop lexp lexp with
        | None ->
            L.d_strln ".... Alignment Error: Freed a non root ....";
            assert false
        | Some _ ->
            let prop_list =
              IList.fold_left (_execute_free tenv mk loc) []
                (Rearrange.rearrange pdesc tenv lexp typ prop loc) in
            IList.rev prop_list
      end
    with Rearrange.ARRAY_ACCESS ->
      if (!Config.array_level = 0) then assert false
      else begin
        L.d_strln ".... Array containing allocated heap cells ....";
        L.d_str "  Instr: "; Sil.d_instr instr; L.d_ln ();
        L.d_str "  PROP: "; Prop.d_prop prop; L.d_ln ();
        raise (Exceptions.Array_of_pointsto (try assert false with Assert_failure x -> x))
      end

  let execute_free mk cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args with
    | [(lexp, typ)] ->
        begin
          let pname = Cfg.Procdesc.get_proc_name pdesc in
          let n_lexp, prop = exp_norm_check_arith pname _prop lexp in
          let prop_nonzero = (* case n_lexp!=0 *)
            Propset.to_proplist (prune_polarity tenv true n_lexp prop) in
          let prop_zero = (* case n_lexp==0 *)
            Propset.to_proplist (prune_polarity tenv false n_lexp prop) in
          let plist =
            prop_zero @ (* model: if 0 then skip else _execute_free_nonzero *)
            IList.flatten (IList.map (fun p ->
                _execute_free_nonzero mk pdesc tenv instr p path
                  (Prop.exp_normalize_prop p lexp) typ loc) prop_nonzero) in
          IList.map (fun p -> (p, path)) plist
        end
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  let execute_alloc mk can_return_null cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    let pname = Cfg.Procdesc.get_proc_name pdesc in
    let rec evaluate_char_sizeof e = match e with
      | Sil.Var _ -> e
      | Sil.UnOp (uop, e', typ) ->
          Sil.UnOp (uop, evaluate_char_sizeof e', typ)
      | Sil.BinOp (bop, e1', e2') ->
          Sil.BinOp (bop, evaluate_char_sizeof e1', evaluate_char_sizeof e2')
      | Sil.Const _ | Sil.Cast _ | Sil.Lvar _ | Sil.Lfield _ | Sil.Lindex _ -> e
      | Sil.Sizeof (Sil.Tarray(Sil.Tint ik, size), _) when Sil.ikind_is_char ik ->
          evaluate_char_sizeof size
      | Sil.Sizeof _ -> e in
    let handle_sizeof_exp size_exp =
      Sil.Sizeof (Sil.Tarray (Sil.Tint Sil.IChar, size_exp), Sil.Subtype.exact) in
    let size_exp = match args with
      | [(size_exp, _)] -> (* for malloc and __new *)
          size_exp
      | [(num_obj, _); (base_exp, _)] -> (* for __new_array *)
          Sil.BinOp (Sil.Mult, num_obj, base_exp)
      | _ ->
          raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x)) in
    let ret_id = match ret_ids with
      | [ret_id] -> ret_id
      | _ -> Ident.create_fresh Ident.kprimed in
    let size_exp', prop =
      let n_size_exp, prop = exp_norm_check_arith pname _prop size_exp in
      let n_size_exp' = evaluate_char_sizeof n_size_exp in
      Prop.exp_normalize_prop prop n_size_exp', prop in
    let cnt_te = handle_sizeof_exp size_exp' in
    let id_new = Ident.create_fresh Ident.kprimed in
    let exp_new = Sil.Var id_new in
    let ptsto_new =
      Prop.mk_ptsto_exp (Some tenv) Prop.Fld_init (exp_new, cnt_te, None) Sil.Ialloc in
    let prop_plus_ptsto =
      let pname = Sil.mem_alloc_pname mk in
      let prop' = Prop.normalize (Prop.prop_sigma_star prop [ptsto_new]) in
      let ra = { Sil.ra_kind = Sil.Racquire; Sil.ra_res = Sil.Rmemory mk; Sil.ra_pname = pname; Sil.ra_loc = loc; Sil.ra_vpath = None } in
      (* mark value as allocated *)
      Prop.add_or_replace_exp_attribute prop' exp_new (Sil.Aresource ra) in
    let prop_alloc = Prop.conjoin_eq (Sil.Var ret_id) exp_new prop_plus_ptsto in
    if can_return_null then
      let prop_null = Prop.conjoin_eq (Sil.Var ret_id) Sil.exp_zero prop in
      [(prop_alloc, path); (prop_null, path)]
    else [(prop_alloc, path)]

  let execute_pthread_create cfg pdesc instr tenv prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args with
    | [thread; attr; start_routine; arg] ->
        let routine_name = Prop.exp_normalize_prop prop (fst start_routine) in
        let routine_arg = Prop.exp_normalize_prop prop (fst arg) in
        (match routine_name, (snd start_routine) with
         | Sil.Lvar pvar, _ ->
             let fun_name = Sil.pvar_get_name pvar in
             let fun_string = Mangled.to_string fun_name in
             L.d_strln ("pthread_create: calling function " ^ fun_string);
             begin
               match Specs.get_summary (Procname.from_string_c_fun fun_string) with
               | None -> assert false
               | Some callee_summary ->
                   sym_exec_call
                     cfg pdesc tenv prop path ret_ids [(routine_arg, snd arg)] callee_summary loc
             end
         | _ ->
             L.d_str "pthread_create: unknown function "; Sil.d_exp routine_name; L.d_strln ", skipping call.";
             [(prop, path)])
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  let execute_skip cfg pdesc instr tenv prop path ret_ids args callee_pname loc : Builtin.ret_typ =
    [(prop, path)]

  let execute_scan_function
      skip_n_arguments cfg pdesc instr tenv prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args with
    | _ when IList.length args >= skip_n_arguments ->
        let varargs = ref args in
        for i = 1 to skip_n_arguments do varargs := IList.tl !varargs done;
        call_unknown_or_scan true cfg pdesc tenv prop path ret_ids None !varargs callee_pname loc
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  let execute__unwrap_exception cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args with
    | [(ret_exn, _)] ->
        begin
          let pname = Cfg.Procdesc.get_proc_name pdesc in
          let n_ret_exn, prop = exp_norm_check_arith pname _prop ret_exn in
          match n_ret_exn with
          | Sil.Const (Sil.Cexn exp) ->
              let prop_with_exn = return_result exp prop ret_ids in
              [(prop_with_exn, path)]
          | _ -> assert false
        end
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  let execute_return_first_argument cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args with
    | (_arg1, _):: _ ->
        let pname = Cfg.Procdesc.get_proc_name pdesc in
        let arg1, prop = exp_norm_check_arith pname _prop _arg1 in
        let prop' = return_result arg1 prop ret_ids in
        [(prop', path)]
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  let execute___split_get_nth cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args with
    | [(lexp1, _); (lexp2, _); (lexp3, _)] ->
        let pname = Cfg.Procdesc.get_proc_name pdesc in
        let n_lexp1, prop = exp_norm_check_arith pname _prop lexp1 in
        let n_lexp2, prop = exp_norm_check_arith pname _prop lexp2 in
        let n_lexp3, prop = exp_norm_check_arith pname _prop lexp3 in
        (match n_lexp1, n_lexp2, n_lexp3 with
         | Sil.Const (Sil.Cstr str1), Sil.Const (Sil.Cstr str2), Sil.Const (Sil.Cint n_sil) ->
             (let n = Sil.Int.to_int n_sil in
              try
                let parts = Str.split (Str.regexp_string str2) str1 in
                let n_part = IList.nth parts n in
                let res = Sil.Const (Sil.Cstr n_part) in
                [(return_result res prop ret_ids, path)]
              with Not_found -> assert false)
         | _ -> [(prop, path)])
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  let execute___create_tuple cfg pdesc instr tenv prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    let el = IList.map fst args in
    let res = Sil.Const (Sil.Ctuple el) in
    [(return_result res prop ret_ids, path)]

  let execute___tuple_get_nth cfg pdesc instr tenv _prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    match args with
    | [(lexp1, _); (lexp2, _)] ->
        let pname = Cfg.Procdesc.get_proc_name pdesc in
        let n_lexp1, _prop' = exp_norm_check_arith pname _prop lexp1 in
        let n_lexp2, prop = exp_norm_check_arith pname _prop' lexp2 in
        (match n_lexp1, n_lexp2 with
         | Sil.Const (Sil.Ctuple el), Sil.Const (Sil.Cint i) ->
             let n = Sil.Int.to_int i in
             let en = IList.nth el n in
             [(return_result en prop ret_ids, path)]
         | _ -> [(prop, path)])
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  (* forces the expression passed as parameter to be assumed true at the point where this
     builtin is called, blocks if this causes an inconsistency *)
  let execute___infer_assume
      cfg pdesc instr tenv prop path ret_ids args callee_pname loc: Builtin.ret_typ =
    match args with
    | [(lexp, typ)] ->
        let prop_assume = Prop.conjoin_eq lexp (Sil.exp_bool true) prop in
        if Prover.check_inconsistency prop_assume then  execute_diverge prop_assume path
        else [(prop_assume, path)]
    | _ -> raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x))

  (* creates a named error state *)
  let execute___infer_fail cfg pdesc instr tenv prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    let error_str =
      match args with
      | [(lexp_msg, _)] ->
          begin
            match Prop.exp_normalize_prop prop lexp_msg with
            | Sil.Const (Sil.Cstr str) -> str
            | _ -> assert false
          end
      | _ ->
          raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x)) in
    let set_instr =
      Sil.Set (Sil.Lvar Sil.custom_error, Sil.Tvoid, Sil.Const (Sil.Cstr error_str), loc) in
    sym_exec_generated true cfg tenv pdesc [set_instr] [(prop, path)]

  (* translate builtin assertion failure *)
  let execute___assert_fail cfg pdesc instr tenv prop path ret_ids args callee_pname loc
    : Builtin.ret_typ =
    let error_str =
      match args with
      | l when IList.length l = 4 ->
          Config.default_failure_name
      | _ ->
          raise (Exceptions.Wrong_argument_number (try assert false with Assert_failure x -> x)) in
    let set_instr =
      Sil.Set (Sil.Lvar Sil.custom_error, Sil.Tvoid, Sil.Const (Sil.Cstr error_str), loc) in
    sym_exec_generated true cfg tenv pdesc [set_instr] [(prop, path)]

  let _ = Builtin.register "__method_set_ignore_attribute" execute___method_set_ignore_attribute
  let _ = Builtin.register "__builtin_va_arg" execute___builtin_va_arg (* model va_arg *)
  let _ = Builtin.register "__builtin_va_copy" execute_skip (** NOTE: __builtin_va_copy should have been handled in the translation already (see frontend.ml) *)
  let _ = Builtin.register "__builtin_va_end" execute_skip (* model va_end as skip *)
  let _ = Builtin.register "__builtin_va_start" execute_skip (** NOTE: __builtin_va_start should have been handled in the translation already (see frontend.ml) *)
  let __create_tuple = Builtin.register "__create_tuple" execute___create_tuple (* create a tuple value from the arguments *)
  let __delete = Builtin.register "__delete" (execute_free Sil.Mnew) (* like free *)
  let __delete_array = Builtin.register "__delete_array" (execute_free Sil.Mnew_array) (* like free *)
  let __exit = Builtin.register "_exit" execute_exit (* _exit from C library *)
  let __get_array_size = Builtin.register "__get_array_size" execute___get_array_size (* return the size of the array passed as a parameter *)
  let _ = Builtin.register "__get_hidden_field" execute___get_hidden_field   (* return the value of a hidden field in the struct *)
  let __get_type_of = Builtin.register "__get_type_of" execute___get_type_of (* return the get the type of the allocated object passed as a parameter *)
  let __instanceof = Builtin.register "__instanceof" execute___instanceof (** [__instanceof(val,typ)] implements java's [val instanceof typ] *)
  let __cast = Builtin.register "__cast" execute___cast (** [__cast(val,typ)] implements java's [typ(val)] *)
  let __new = Builtin.register "__new" (execute_alloc Sil.Mnew false) (* like malloc, but always succeeds *)
  let __new_array = Builtin.register "__new_array" (execute_alloc Sil.Mnew_array false) (* like malloc, but always succeeds *)
  let __objc_alloc = Builtin.register "__objc_alloc" (execute_alloc Sil.Mobjc true) (* Objective C alloc *)
  let __objc_alloc_no_fail = Builtin.register "__objc_alloc_no_fail" (execute_alloc Sil.Mobjc false) (* like __objc_alloc, but does not return nil *)
  let __placement_delete = Builtin.register "__placement_delete" execute_skip (* placement delete is skip *)
  let __placement_new = Builtin.register "__placement_new" execute_return_first_argument (* placement new returns the first argument *)
  let _ = Builtin.register "__print_value" execute___print_value (* print a value as seen by the engine *)
  let __set_array_size = Builtin.register "__set_array_size" execute___set_array_size (* set the size of the array passed as a parameter *)
  let __set_file_attribute = Builtin.register "__set_file_attribute" execute___set_file_attribute (* set the attribute of the parameter as file *)
  let __set_lock_attribute = Builtin.register "__set_lock_attribute" execute___set_lock_attribute (* set the attribute of the parameter as file *)
  let __set_mem_attribute = Builtin.register "__set_mem_attribute" execute___set_mem_attribute (* set the attribute of the parameter as memory *)
  let __set_autorelease_attribute = Builtin.register "__set_autorelease_attribute" execute___set_autorelease_attribute (* set the attribute of the parameter as autorelease *)
  let __objc_release_autorelease_pool = Builtin.register "__objc_release_autorelease_pool" execute___release_autorelease_pool (* set the attribute of the parameter as autorelease *)
  let __split_get_nth = Builtin.register "__split_get_nth" execute___split_get_nth (* splits a string given a separator and returns the nth string *)

  (* builtin function to externally create new errors *)
  let __infer_fail = Builtin.register "__infer_fail" execute___infer_fail
  let __assert_fail = Builtin.register "__assert_fail" execute___assert_fail

  let _ = Builtin.register "__set_hidden_field" execute___set_hidden_field  (* set a hidden field in the struct to the given value *)
  let _ = Builtin.register "__set_taint_attribute" execute___set_taint_attribute (* set the attribute of the parameter as tainted *)
  let _ = Builtin.register "__set_untaint_attribute" execute___set_untaint_attribute (* set the attribute of the parameter as tainted *)
  let _ = Builtin.register "__check_untainted" execute___check_untainted (* report a taint error if the parameter is tainted, and assume it is untainted afterward *)
  let __objc_retain = Builtin.register "__objc_retain" execute___objc_retain (* objective-c "retain" *)
  let __objc_release = Builtin.register "__objc_release" execute___objc_release (* objective-c "release" *)
  let __objc_retain_cf = Builtin.register "__objc_retain_cf" execute___objc_retain_cf (* objective-c "retain" *)
  let __objc_release_cf = Builtin.register "__objc_release_cf" execute___objc_release_cf (* objective-c "release" *)
  let __objc_cast = Builtin.register "__objc_cast" execute___objc_cast (* objective-c "cast" *)
  let _ = Builtin.register "__throw" execute_skip (** NOTE: __throw should have been handled in the translation already (see frontend.ml) *)
  let __tuple_get_nth = Builtin.register "__tuple_get_nth" execute___tuple_get_nth (* return the nth element of a tuple *)
  let __unwrap_exception = Builtin.register "__unwrap_exception" execute__unwrap_exception (* the correct function to unwrapp execption remains to be written *)
  let __infer_assume = Builtin.register "__infer_assume" execute___infer_assume
  let _ = Builtin.register "abort" execute_abort (* abort from C library *)
  let _ = Builtin.register "exit" execute_exit (* exit from C library *)
  let _ = Builtin.register "free" (execute_free Sil.Mmalloc) (* free from C library, requires allocated memory *)
  let _ = Builtin.register "fscanf" (execute_scan_function 2) (* fscanf from C library *)
  let _ = Builtin.register "fwscanf" (execute_scan_function 2) (* vsscanf from C library *)
  let _ = Builtin.register "malloc" (execute_alloc Sil.Mmalloc true) (* malloc from C library *)
  let malloc_no_fail = Builtin.register "malloc_no_fail" (execute_alloc Sil.Mmalloc false) (* malloc from ObjC library *)
  let _ = Builtin.register "pthread_create" execute_pthread_create (* register execution handler for pthread_create *)
  let _ = Builtin.register "scanf" (execute_scan_function 1) (* scanf from C library *)
  let _ = Builtin.register "sscanf" (execute_scan_function 2) (* sscanf from C library *)
  let _ = Builtin.register "swscanf" (execute_scan_function 2) (* vsscanf from C library *)
  let _ = Builtin.register "vfscanf" (execute_scan_function 2) (* vfwscanf from C library *)
  let _ = Builtin.register "vfwscanf" (execute_scan_function 2) (* vsscanf from C library *)
  let _ = Builtin.register "vscanf" (execute_scan_function 1) (* vscanf from C library *)
  let _ = Builtin.register "vsscanf" (execute_scan_function 2) (* vsscanf from C library *)
  let _ = Builtin.register "vswscanf" (execute_scan_function 2) (* vsscanf from C library *)
  let _ = Builtin.register "vwscanf" (execute_scan_function 1) (* vsscanf from C library *)
  let _ = Builtin.register "wscanf" (execute_scan_function 1) (* vsscanf from C library *)

  let execute_objc_alloc_no_fail cfg pdesc tenv symb_state ret_ids typ loc =
    let alloc_fun = Sil.Const (Sil.Cfun __objc_alloc_no_fail) in
    let ptr_typ = Sil.Tptr (typ, Sil.Pk_pointer) in
    let sizeof_typ = Sil.Sizeof (typ, Sil.Subtype.exact) in
    let alloc_instr = Sil.Call (ret_ids, alloc_fun, [sizeof_typ, ptr_typ], loc, Sil.cf_default) in
    sym_exec_generated false cfg tenv pdesc [alloc_instr] symb_state

  let execute_objc_NSArray_alloc_no_fail cfg pdesc tenv symb_state ret_ids loc =
    let nsarray_typ = Sil.Tvar (Typename.TN_csu (Csu.Class, Mangled.from_string "NSArray")) in
    let nsarray_typ = Sil.expand_type tenv nsarray_typ in
    execute_objc_alloc_no_fail cfg pdesc tenv symb_state ret_ids nsarray_typ loc

  let execute_NSArray_arrayWithObjects_count cfg pdesc instr tenv prop path ret_ids args callee_pname loc =
    let n_formals = 1 in
    let res' = sym_exe_check_variadic_sentinel ~fails_on_nil: true cfg pdesc tenv prop path n_formals args (0,1) callee_pname loc in
    execute_objc_NSArray_alloc_no_fail cfg pdesc tenv res' ret_ids loc

  let execute_NSArray_arrayWithObjects cfg pdesc instr tenv prop path ret_ids args callee_pname loc =
    let n_formals = 1 in
    let res' = sym_exe_check_variadic_sentinel cfg pdesc tenv prop path n_formals args (0,1) callee_pname loc in
    execute_objc_NSArray_alloc_no_fail cfg pdesc tenv res' ret_ids loc

  let _ =
    let method_kind = Procname.mangled_of_objc_method_kind Procname.Class_objc_method in
    Builtin.register_procname
      (Procname.mangled_c_method "NSArray" "arrayWithObjects:count:" method_kind)
      execute_NSArray_arrayWithObjects_count
  let _ =
    let method_kind = Procname.mangled_of_objc_method_kind Procname.Class_objc_method in
    Builtin.register_procname
      (Procname.mangled_c_method "NSArray" "arrayWithObjects:" method_kind)
      execute_NSArray_arrayWithObjects

  let execute_objc_NSDictionary_alloc_no_fail cfg pdesc tenv symb_state ret_ids loc =
    let nsdictionary_typ =
      Sil.Tvar (Typename.TN_csu (Csu.Class, Mangled.from_string "NSDictionary")) in
    let nsdictionary_typ =
      Sil.expand_type tenv nsdictionary_typ in
    execute_objc_alloc_no_fail cfg pdesc tenv symb_state ret_ids nsdictionary_typ loc

  let execute___objc_dictionary_literal cfg pdesc instr tenv prop path ret_ids args callee_pname loc =
    let n_formals = 1 in
    let res' =
      sym_exe_check_variadic_sentinel ~fails_on_nil: true cfg pdesc tenv prop path
        n_formals args (0,1) callee_pname loc in
    execute_objc_NSDictionary_alloc_no_fail cfg pdesc tenv res' ret_ids loc

  let __objc_dictionary_literal =
    let method_kind = Procname.mangled_of_objc_method_kind Procname.Class_objc_method in
    let pname = Procname.mangled_c_method "NSDictionary" "__objc_dictionary_literal:" method_kind in
    Builtin.register_procname pname execute___objc_dictionary_literal;
    pname

end
(* ============== END of ModelBuiltins ============== *)