Reviewed By: jeremydubreil Differential Revision: D6458969 fbshipit-source-id: 2c214b3master
Dulma Churchill
7 years ago
committed by
Facebook Github Bot
parent
d25754597d
commit
1d0b6050a6
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(*
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* Copyright (c) 2017 - 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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let get_cycle root prop =
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let sigma = prop.Prop.sigma in
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let get_points_to e =
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match e with
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| Sil.Eexp (e', _) ->
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List.find
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~f:(fun hpred ->
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match hpred with Sil.Hpointsto (e'', _, _) -> Exp.equal e'' e' | _ -> false)
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sigma
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| _ ->
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None
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in
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let print_cycle cyc =
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L.d_str "Cycle= " ;
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List.iter
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~f:(fun ((e, t), f, e') ->
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match (e, e') with
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| Sil.Eexp (e, _), Sil.Eexp (e', _) ->
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L.d_str
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( "(" ^ Exp.to_string e ^ ": " ^ Typ.to_string t ^ ", " ^ Typ.Fieldname.to_string f
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^ ", " ^ Exp.to_string e' ^ ")" )
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| _ ->
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())
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cyc ;
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L.d_strln ""
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in
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(* Perform a dfs of a graph stopping when e_root is reached.
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Returns a pair (path, bool) where path is a list of edges ((e1,type_e1),f,e2)
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describing the path to e_root and bool is true if e_root is reached. *)
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let rec dfs e_root et_src path el visited =
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match el with
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| [] ->
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(path, false)
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| (f, e) :: el' ->
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if Sil.equal_strexp e e_root then ((et_src, f, e) :: path, true)
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else if List.mem ~equal:Sil.equal_strexp visited e then (path, false)
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else
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let visited' = fst et_src :: visited in
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let res =
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match get_points_to e with
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| None ->
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(path, false)
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| Some Sil.Hpointsto (_, Sil.Estruct (fl, _), Exp.Sizeof {typ= te}) ->
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dfs e_root (e, te) ((et_src, f, e) :: path) fl visited'
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| _ ->
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(path, false)
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(* check for lists *)
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in
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if snd res then res else dfs e_root et_src path el' visited'
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in
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L.d_strln "Looking for cycle with root expression: " ;
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Sil.d_hpred root ;
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L.d_strln "" ;
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match root with
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| Sil.Hpointsto (e_root, Sil.Estruct (fl, _), Exp.Sizeof {typ= te}) ->
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let se_root = Sil.Eexp (e_root, Sil.Inone) in
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(* start dfs with empty path and expr pointing to root *)
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let pot_cycle, res = dfs se_root (se_root, te) [] fl [] in
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if res then ( print_cycle pot_cycle ; pot_cycle )
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else (
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L.d_strln "NO cycle found from root" ;
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[] )
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| _ ->
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L.d_strln "Root exp is not an allocated object. No cycle found" ;
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[]
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let get_retain_cycle_dotty prop_ cycle =
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match prop_ with
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| None ->
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None
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| Some Some prop_ ->
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Dotty.dotty_prop_to_str prop_ cycle
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| _ ->
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None
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let get_var_retain_cycle prop_ =
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let sigma = prop_.Prop.sigma in
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let is_pvar v h =
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match h with
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| Sil.Hpointsto (Exp.Lvar _, v', _) when Sil.equal_strexp v v' ->
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true
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| _ ->
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false
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in
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let is_hpred_block v h =
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match (h, v) with
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| Sil.Hpointsto (e, _, Exp.Sizeof {typ}), Sil.Eexp (e', _)
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when Exp.equal e e' && Typ.is_block_type typ ->
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true
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| _, _ ->
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false
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in
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let find v = List.find ~f:(is_pvar v) sigma |> Option.map ~f:Sil.hpred_get_lhs in
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let find_block v =
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if List.exists ~f:(is_hpred_block v) sigma then Some (Exp.Lvar Sil.block_pvar) else None
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in
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let sexp e = Sil.Eexp (e, Sil.Inone) in
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let find_or_block ((e, t), f, e') =
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match find e with
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| Some pvar ->
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[((sexp pvar, t), f, e')]
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| _ ->
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match find_block e with
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| Some blk ->
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[((sexp blk, t), f, e')]
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| _ ->
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let sizeof = {Exp.typ= t; nbytes= None; dynamic_length= None; subtype= Subtype.exact} in
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[((sexp (Exp.Sizeof sizeof), t), f, e')]
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in
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(* returns the pvars of the first cycle we find in sigma.
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This is an heuristic that works if there is one cycle.
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In case there are more than one cycle we may return not necessarily
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the one we are looking for. *)
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let rec do_sigma sigma_todo =
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match sigma_todo with
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| [] ->
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[]
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| hp :: sigma' ->
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let cycle = get_cycle hp prop_ in
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L.d_strln "Filtering pvar in cycle " ;
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let cycle' = List.concat_map ~f:find_or_block cycle in
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if List.is_empty cycle' then do_sigma sigma' else cycle'
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in
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do_sigma sigma
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(** Checks if cycle has fields (derived from a property or directly defined as ivar) with attributes
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weak/unsafe_unretained/assing *)
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let cycle_has_weak_or_unretained_or_assign_field tenv cycle =
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(* returns items annotation for field fn in struct t *)
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let get_item_annotation (t: Typ.t) fn =
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match t.desc with
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| Tstruct name
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-> (
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let equal_fn (fn', _, _) = Typ.Fieldname.equal fn fn' in
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match Tenv.lookup tenv name with
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| Some {fields; statics} ->
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List.find ~f:equal_fn (fields @ statics) |> Option.value_map ~f:trd3 ~default:[]
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| None ->
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[] )
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| _ ->
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[]
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in
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let rec has_weak_or_unretained_or_assign params =
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match params with
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| [] ->
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false
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| att :: _
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when String.equal Config.unsafe_unret att || String.equal Config.weak att
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|| String.equal Config.assign att ->
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true
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| _ :: params' ->
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has_weak_or_unretained_or_assign params'
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in
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let do_annotation ((a: Annot.t), _) =
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( String.equal a.class_name Config.property_attributes
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|| String.equal a.class_name Config.ivar_attributes )
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&& has_weak_or_unretained_or_assign a.parameters
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in
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let rec do_cycle c =
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match c with
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| [] ->
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false
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| ((_, t), fn, _) :: c' ->
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let ia = get_item_annotation t fn in
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if List.exists ~f:do_annotation ia then true else do_cycle c'
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in
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do_cycle cycle
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let exn_retain_cycle original_prop hpred cycle =
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let cycle_dotty = get_retain_cycle_dotty original_prop cycle in
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let desc = Errdesc.explain_retain_cycle cycle (State.get_loc ()) cycle_dotty in
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Exceptions.Retain_cycle (hpred, desc, __POS__)
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let report_cycle tenv hpred original_prop =
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(* When there is a cycle in objc we ignore it
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only if it's empty or it has weak or unsafe_unretained fields.
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Otherwise we report a retain cycle. *)
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let remove_opt prop_ = match prop_ with Some Some p -> p | _ -> Prop.prop_emp in
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let cycle = get_var_retain_cycle (remove_opt original_prop) in
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let ignore_cycle =
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Int.equal (List.length cycle) 0 || cycle_has_weak_or_unretained_or_assign_field tenv cycle
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in
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(ignore_cycle, exn_retain_cycle original_prop hpred cycle)
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@ -0,0 +1,10 @@
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(*
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* Copyright (c) 2017 - 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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val report_cycle : Tenv.t -> Sil.hpred -> Prop.normal Prop.t option option -> bool * exn
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@ -0,0 +1,50 @@
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/*
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* Copyright (c) 2017 - 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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#import <Foundation/NSObject.h>
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@class AFeed;
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@interface Adapter : NSObject
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@property(nonatomic, strong) AFeed* feed;
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@end
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@implementation Adapter
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@end
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@interface AFeed : NSObject
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@property(nonatomic, weak) Adapter* adapter;
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@end
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@implementation AFeed
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@end
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@interface RetainCycleExampleWeak : NSObject
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@property(nonatomic, strong) AFeed* feed;
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@end
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@implementation RetainCycleExampleWeak
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- (void)test {
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_feed.adapter.feed = _feed;
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}
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- (void)main1 {
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RetainCycleExampleWeak* b = [RetainCycleExampleWeak new];
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[b test];
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}
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@end
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