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(*
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* Copyright (c) 2016 - present Facebook, Inc.
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* All rights reserved.
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*
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* This source code is licensed under the BSD style license found in the
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* LICENSE file in the root directory of this source tree. An additional grant
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* of patent rights can be found in the PATENTS file in the same directory.
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*)
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module L = Logging
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module F = Format
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open Dataflow
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(** Check the sequence of calls to tracing APIs in a method (intraprocedural). *)
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let verbose = false
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let widening_threshold = 10
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(** Tracing methods of the form (package name, class name, begin name, end name). *)
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let tracing_methods =
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let for_testing =
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[
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"", "TraceCallSequence", "begin", "end";
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"", "TraceCallSequence", "beginWrapper", "endWrapper";
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] in
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for_testing @ FbTraceCalls.tracing_methods
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(** Boolean variables to be tracked. *)
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let boolean_variables =
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[
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"shouldTrace";
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]
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(** Report a warning in the spec file of the procedure. *)
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let report_warning description pn pd loc =
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if verbose then L.stderr "ERROR: %s@." description;
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Checkers.ST.report_error pn pd "CHECKERS_TRACE_CALLS_SEQUENCE" loc description
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(** Tracing APIs. *)
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module APIs = struct
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let method_match pn pkgname cname mname =
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match pn with
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| Procname.Java pn_java ->
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Procname.java_get_method pn_java = mname
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&&
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(match pkgname with
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| "" ->
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Procname.java_get_simple_class_name pn_java = cname
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| _ ->
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Procname.java_get_class_name pn_java = pkgname ^ "." ^ cname)
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| _ ->
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false
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let is_begin pn =
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let filter (pkgname, cname, begin_name, _) = method_match pn pkgname cname begin_name in
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IList.exists filter tracing_methods
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let is_end pn =
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let filter (pkgname, cname, _, end_name) = method_match pn pkgname cname end_name in
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IList.exists filter tracing_methods
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let is_begin_or_end pn =
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is_begin pn || is_end pn
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end
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(** Environment for boolean variables. *)
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module Env = struct
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type t = bool StringMap.t
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let empty = StringMap.empty
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let compare = StringMap.compare bool_compare
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let add = StringMap.add
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let remove = StringMap.remove
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let get map name =
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try Some (StringMap.find name map)
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with Not_found -> None
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let pp fmt map =
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let pp_elem fmt (s, b) = F.fprintf fmt "%s:%b" s b in
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let l = StringMap.bindings map in
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if l <> [] then F.fprintf fmt "%a" (pp_seq pp_elem) l
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end
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(** Element for the set domain: an integer (for pending traces), and an environment. *)
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module Elem = struct
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type t = int * Env.t
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let compare (i1, env1) (i2, env2) =
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let n = int_compare i1 i2 in
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if n <> 0 then n else Env.compare env1 env2
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let pp fmt (i, env) = F.fprintf fmt "(%d %a)" i Env.pp env
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let zero = (0, Env.empty)
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let is_consistent (i, _) = i >= 0
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let get_int (i, _) = i
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let get_env (_, env) = env
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let set_env (i, _) env' = (i, env')
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let incr (i, env) = (i + 1, env)
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let decr (i, env) = (i - 1, env)
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end
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module ElemSet = Set.Make(Elem)
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module State = struct
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(** Each number represents the difference between begin() and end() on some path. *)
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type t = ElemSet.t
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let to_string n =
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let pp_intset fmt s =
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ElemSet.iter (fun d -> F.fprintf fmt "%a " Elem.pp d) s in
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let pp fmt () =
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Format.fprintf fmt "{%a}" pp_intset n in
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pp_to_string pp ()
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(** Initial balanced state with empty environment. *)
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let balanced = ElemSet.singleton Elem.zero
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(** State is balanced. *)
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let is_balanced s =
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ElemSet.for_all (fun elem -> Elem.get_int elem = 0) s
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let equal = ElemSet.equal
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let has_zero s = ElemSet.exists (fun elem -> Elem.get_int elem = 0) s
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(** Map a function to the elements of the set, and filter out inconsistencies. *)
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let map2 (f : Elem.t -> Elem.t list) (s : t) : t =
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let l = ElemSet.elements s in
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let l' = IList.filter Elem.is_consistent (IList.flatten (IList.map f l)) in
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IList.fold_right ElemSet.add l' ElemSet.empty
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let map (f : Elem.t -> Elem.t) s =
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map2 (fun elem -> [f elem]) s
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(** Increment the number of begin/start. *)
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let incr s =
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map Elem.incr s
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(** Decrement the number of begin/start. *)
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let decr s =
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map Elem.decr s
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(** Max value of the set. *)
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let max s =
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ElemSet.max_elt s
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(** Prune the value of name w.r.t. boolean b. *)
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let prune s name b =
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let f elem =
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let env = Elem.get_env elem in
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match Env.get env name with
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| None ->
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let env' = Env.add name b env in
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let elem' = Elem.set_env elem env' in
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[elem']
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| Some b' ->
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if bool_equal b b' then [elem]
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else [] in
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map2 f s
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(** Set name to the given bool, or nondeterministic if None. *)
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let set_bool s name b_opt =
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let f elem =
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let env = Elem.get_env elem in
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let env' = match b_opt with
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| None -> Env.remove name env
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| Some b -> Env.add name b env in
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Elem.set_env elem env' in
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map f s
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(** Stop growing sets if they go beyond a threshold. *)
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let widening s_before s_after =
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if ElemSet.cardinal s_after <= widening_threshold
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then s_after
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else s_before
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(** Join two states and perform widening if necessary. *)
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let join s1 s2 =
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let s' = ElemSet.union s1 s2 in
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let s'' = widening s1 s' in
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if verbose then L.stderr " join %s %s --> %s@." (to_string s1) (to_string s2) (to_string s'');
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s''
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end
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(** Abstract domain for automata whose state transitions are triggered by calls. *)
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module Automaton = struct
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(** Transfer function for a procedure call. *)
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let do_call caller_pn caller_pd callee_pn (s : State.t) loc : State.t =
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let method_name () = match callee_pn with
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| Procname.Java pname_java ->
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Procname.java_get_method pname_java
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| _ ->
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Procname.to_simplified_string callee_pn in
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if APIs.is_begin callee_pn then
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begin
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if verbose then L.stderr " calling %s@." (method_name ());
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State.incr s
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end
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else if APIs.is_end callee_pn then
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begin
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if verbose then L.stderr " calling %s@." (method_name ());
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if State.has_zero s then report_warning "too many end/stop" caller_pn caller_pd loc;
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State.decr s
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end
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else s
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(** Transfer function for an instruction. *)
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let do_instr pn pd (instr : Sil.instr) (state : State.t) : State.t =
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match instr with
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| Sil.Call (_, Sil.Const (Sil.Cfun callee_pn), _, loc, _) ->
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do_call pn pd callee_pn state loc
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| _ -> state
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(** Check if the final state contains any numbers other than zero (balanced). *)
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let check_final_state pn pd exit_node (s : State.t) : unit =
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if verbose then L.stderr "@.Final: %s@." (State.to_string s);
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if not (State.is_balanced s) then
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begin
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let description = Printf.sprintf "%d missing end/stop" (Elem.get_int (State.max s)) in
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let loc = Cfg.Node.get_loc exit_node in
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report_warning description pn pd loc
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end
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end
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(** Abstract domain to track the value of specific boolean variables. *)
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module BooleanVars = struct
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(** Check if the expression exp is one of the listed boolean variables. *)
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let exp_boolean_var exp = match exp with
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| Sil.Lvar pvar when Sil.pvar_is_local pvar ->
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let name = Mangled.to_string (Sil.pvar_get_name pvar) in
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if IList.mem string_equal name boolean_variables
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then Some name
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else None
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| _ -> None
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(** Transfer function for an instruction. *)
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let do_instr _ _ idenv (instr : Sil.instr) (state : State.t) : State.t =
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(** Normalize a boolean condition. *)
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let normalize_condition cond_e =
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match cond_e with
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| Sil.UnOp (Sil.LNot, Sil.BinOp (Sil.Eq, e1, e2), _) ->
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Sil.BinOp (Sil.Ne, e1, e2)
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| Sil.UnOp (Sil.LNot, Sil.BinOp (Sil.Ne, e1, e2), _) ->
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Sil.BinOp (Sil.Eq, e1, e2)
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| _ -> cond_e in
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(** Normalize an instruction. *)
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let normalize_instr = function
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| Sil.Prune (cond_e, loc, tb, ik) ->
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let cond_e' = normalize_condition cond_e in
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Sil.Prune (cond_e', loc, tb, ik)
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| instr -> instr in
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match normalize_instr instr with
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| Sil.Prune (Sil.BinOp (Sil.Eq, _cond_e, Sil.Const (Sil.Cint i)), _, _, _)
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when Sil.Int.iszero i ->
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let cond_e = Idenv.expand_expr idenv _cond_e in
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let state' = match exp_boolean_var cond_e with
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| Some name ->
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if verbose then L.stderr " prune false on %s@." name;
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State.prune state name false
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| None -> state in
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state'
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| Sil.Prune (Sil.BinOp (Sil.Ne, _cond_e, Sil.Const (Sil.Cint i)), _, _, _)
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when Sil.Int.iszero i ->
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let cond_e = Idenv.expand_expr idenv _cond_e in
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let state' = match exp_boolean_var cond_e with
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| Some name ->
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if verbose then L.stderr " prune true on %s@." name;
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State.prune state name true
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| None -> state in
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state'
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| Sil.Set (_e1, _, e2, _) ->
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let e1 = Idenv.expand_expr idenv _e1 in
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let state' = match exp_boolean_var e1 with
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| Some name ->
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let b_opt = match e2 with
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| Sil.Const (Sil.Cint i) -> Some (not (Sil.Int.iszero i))
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| _ -> None in
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if verbose then
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begin
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let b_str = match b_opt with
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| None -> "nondet"
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| Some b -> string_of_bool b in
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L.stderr " setting %s to %s@." name b_str
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end;
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State.set_bool state name b_opt
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| None -> state in
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state'
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| _ -> state
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let check_final_state _ _ _ _ =
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()
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end
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(** State transformation for a cfg node. *)
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let do_node pn pd idenv _ node (s : State.t) : (State.t list) * (State.t list) =
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if verbose then L.stderr "N:%d S:%s@." (Cfg.Node.get_id node) (State.to_string s);
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let curr_state = ref s in
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let do_instr instr : unit =
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let state1 = Automaton.do_instr pn pd instr !curr_state in
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let state2 = BooleanVars.do_instr pn pd idenv instr state1 in
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curr_state := state2 in
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IList.iter do_instr (Cfg.Node.get_instrs node);
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[!curr_state], [!curr_state]
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(** Check the final state at the end of the analysis. *)
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let check_final_state proc_name proc_desc exit_node final_s =
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Automaton.check_final_state proc_name proc_desc exit_node final_s;
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BooleanVars.check_final_state proc_name proc_desc exit_node final_s
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(** Check that the trace calls are balanced.
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This is done by using the most general control flow including exceptions.
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The begin() and end() function are assumed not to throw exceptions. *)
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let callback_check_trace_call_sequence { Callbacks.proc_desc; proc_name; idenv; tenv } : unit =
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let module DFTrace = MakeDF(struct
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type t = State.t
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let equal = State.equal
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let join = State.join
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let do_node = do_node proc_name proc_desc idenv
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let proc_throws pn =
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if APIs.is_begin_or_end pn
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then DoesNotThrow (* assume the tracing function do not throw *)
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else DontKnow
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end) in
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let do_check () =
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begin
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if verbose then L.stderr "@.--@.PROC: %a@." Procname.pp proc_name;
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let transitions = DFTrace.run tenv proc_desc State.balanced in
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let exit_node = Cfg.Procdesc.get_exit_node proc_desc in
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match transitions exit_node with
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| DFTrace.Transition (final_s, _, _) ->
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check_final_state proc_name proc_desc exit_node final_s
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| DFTrace.Dead_state -> ()
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end in
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if not (APIs.is_begin_or_end proc_name) then do_check ()
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