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using address-taken analysis for nullify placement rather than alias analysis

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Reviewed By: jeremydubreil

Differential Revision: D3030423

fb-gh-sync-id: 447b040
shipit-source-id: 447b040
master
Sam Blackshear 9 years ago committed by Facebook Github Bot 3
parent 97cb854e5c
commit 2991bd3fc3
4 changed files with 45 additions and 20 deletions
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24
infer/src/backend/preanal.ml
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@ -111,18 +111,21 @@ let rec def_instr cfg (instr: Sil.instr) acc =
and def_instrl cfg instrs acc =
IList.fold_left (fun acc' i -> def_instr cfg i acc') acc instrs
(* computes the addresses that are assigned to something or passed as parameters to*)
(* a functions. These will be considered becoming possibly aliased *)
(* computes the addresses that are assigned to something or passed as parameters to a function.
these will be considered aliased. *)
let aliasing_instr cfg pdesc (instr: Sil.instr) acc =
match instr with
| Sil.Set (_, _, e, _) -> use_exp cfg pdesc e acc
| Sil.Set (_, Sil.Tptr (_, _), exp, _) ->
use_exp cfg pdesc exp acc
| Sil.Call (_, _, argl, _, _) ->
let argl'= fst (IList.split argl) in
IList.fold_left (fun acc' e' -> use_exp cfg pdesc e' acc') acc argl'
| Sil.Letderef _ | Sil.Prune _ -> acc
| Sil.Nullify _ -> acc
| Sil.Abstract _ | Sil.Remove_temps _ | Sil.Stackop _ | Sil.Declare_locals _ -> acc
| Sil.Goto_node _ -> acc
IList.fold_left
(fun acc (arg, typ) -> match typ with
| Sil.Tptr _ -> use_exp cfg pdesc arg acc
| _ -> acc)
acc
argl
| Sil.Set _ | Sil.Letderef _ | Sil.Prune _ | Sil.Nullify _ | Sil.Abstract _ | Sil.Remove_temps _
| Sil.Stackop _ | Sil.Declare_locals _ | Sil.Goto_node _ -> acc
(* computes possible alisased var *)
let def_aliased_var cfg pdesc instrs acc =
@ -226,7 +229,8 @@ let analyze_proc cfg pdesc cand =
try
while true do
let node = Worklist.pick () in
aliased_var := Vset.union (compute_aliased cfg node !aliased_var) !aliased_var;
if not (!Config.curr_language = Config.Java) then
aliased_var := Vset.union (compute_aliased cfg node !aliased_var) !aliased_var;
let curr_live = Table.get_live node in
let preds = AllPreds.get_preds node in
let live_at_predecessors =

12
infer/tests/codetoanalyze/c/errors/local_vars/local_vars.c
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@ -49,3 +49,15 @@ int t() {
}
return 0;
}
int address_taken() {
int** x;
int* y;
int i = 7;
y = &i;
x = &y;
// if we don't reason about taken addresses while adding nullify instructions,
// we'll add
// `nullify(y)` here and report a false NPE on the next line
return **x;
}

20
infer/tests/codetoanalyze/cpp/frontend/types/typeid_expr.cpp.dot
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@ -134,7 +134,7 @@ digraph iCFG {
32 -> 31 ;
31 [label="31: DeclStmt \n n$5=_fun___cxx_typeid(sizeof(class std::type_info ):void ,n$5.__type_name:void ,&t:int ) [line 31]\n n$6=*n$5:class std::type_info [line 31]\n n$7=_fun_std::type_info_name(n$5:class std::type_info &) [line 31]\n *&t_type_info:char *=n$7 [line 31]\n REMOVE_TEMPS(n$5,n$6,n$7); [line 31]\n " shape="box"]
31 [label="31: DeclStmt \n n$5=_fun___cxx_typeid(sizeof(class std::type_info ):void ,n$5.__type_name:void ,&t:int ) [line 31]\n n$6=*n$5:class std::type_info [line 31]\n n$7=_fun_std::type_info_name(n$5:class std::type_info &) [line 31]\n *&t_type_info:char *=n$7 [line 31]\n REMOVE_TEMPS(n$5,n$6,n$7); [line 31]\n NULLIFY(&t,false); [line 31]\n " shape="box"]
31 -> 30 ;
@ -142,11 +142,11 @@ digraph iCFG {
30 -> 25 ;
29 [label="29: Return Stmt \n *&return:int =(1 / 0) [line 36]\n NULLIFY(&person,false); [line 36]\n NULLIFY(&t,false); [line 36]\n APPLY_ABSTRACTION; [line 36]\n " shape="box"]
29 [label="29: Return Stmt \n *&return:int =(1 / 0) [line 36]\n NULLIFY(&person,false); [line 36]\n APPLY_ABSTRACTION; [line 36]\n " shape="box"]
29 -> 23 ;
28 [label="28: Return Stmt \n *&return:int =0 [line 34]\n NULLIFY(&person,false); [line 34]\n NULLIFY(&t,false); [line 34]\n APPLY_ABSTRACTION; [line 34]\n " shape="box"]
28 [label="28: Return Stmt \n *&return:int =0 [line 34]\n NULLIFY(&person,false); [line 34]\n APPLY_ABSTRACTION; [line 34]\n " shape="box"]
28 -> 23 ;
@ -163,14 +163,14 @@ digraph iCFG {
25 -> 26 ;
25 -> 27 ;
24 [label="24: + \n NULLIFY(&person_type_info,false); [line 33]\n NULLIFY(&t_type_info,false); [line 33]\n NULLIFY(&person,false); [line 33]\n NULLIFY(&t,false); [line 33]\n " ]
24 [label="24: + \n NULLIFY(&person_type_info,false); [line 33]\n NULLIFY(&t,false); [line 33]\n NULLIFY(&t_type_info,false); [line 33]\n NULLIFY(&person,false); [line 33]\n " ]
24 -> 23 ;
23 [label="23: Exit person_typeid_name \n " color=yellow style=filled]
22 [label="22: Start person_typeid_name\nFormals: \nLocals: person_type_info:char * t_type_info:char * t:int person:class Person \n DECLARE_LOCALS(&return,&person_type_info,&t_type_info,&t,&person); [line 28]\n NULLIFY(&person_type_info,false); [line 28]\n NULLIFY(&t_type_info,false); [line 28]\n " color=yellow style=filled]
22 [label="22: Start person_typeid_name\nFormals: \nLocals: person_type_info:char * t_type_info:char * t:int person:class Person \n DECLARE_LOCALS(&return,&person_type_info,&t_type_info,&t,&person); [line 28]\n NULLIFY(&person_type_info,false); [line 28]\n NULLIFY(&t,false); [line 28]\n NULLIFY(&t_type_info,false); [line 28]\n " color=yellow style=filled]
22 -> 33 ;
@ -182,11 +182,11 @@ digraph iCFG {
20 -> 15 ;
19 [label="19: Return Stmt \n *&return:int =(1 / 0) [line 25]\n NULLIFY(&person,false); [line 25]\n NULLIFY(&t,false); [line 25]\n APPLY_ABSTRACTION; [line 25]\n " shape="box"]
19 [label="19: Return Stmt \n *&return:int =(1 / 0) [line 25]\n NULLIFY(&person,false); [line 25]\n APPLY_ABSTRACTION; [line 25]\n " shape="box"]
19 -> 13 ;
18 [label="18: Return Stmt \n *&return:int =1 [line 23]\n NULLIFY(&person,false); [line 23]\n NULLIFY(&t,false); [line 23]\n APPLY_ABSTRACTION; [line 23]\n " shape="box"]
18 [label="18: Return Stmt \n *&return:int =1 [line 23]\n NULLIFY(&person,false); [line 23]\n APPLY_ABSTRACTION; [line 23]\n " shape="box"]
18 -> 13 ;
@ -198,19 +198,19 @@ digraph iCFG {
16 -> 18 ;
15 [label="15: Call _fun_std::type_info_operator== \n n$0=_fun___cxx_typeid(sizeof(class std::type_info ):void ,n$0.__type_name:void ,&t:int ) [line 22]\n n$1=_fun___cxx_typeid(sizeof(class std::type_info ):void ,n$1.__type_name:void ,&person:class Person ) [line 22]\n n$2=_fun_std::type_info_operator==(n$0:class std::type_info &,n$1:class std::type_info &) [line 22]\n " shape="box"]
15 [label="15: Call _fun_std::type_info_operator== \n n$0=_fun___cxx_typeid(sizeof(class std::type_info ):void ,n$0.__type_name:void ,&t:int ) [line 22]\n n$1=_fun___cxx_typeid(sizeof(class std::type_info ):void ,n$1.__type_name:void ,&person:class Person ) [line 22]\n n$2=_fun_std::type_info_operator==(n$0:class std::type_info &,n$1:class std::type_info &) [line 22]\n NULLIFY(&t,false); [line 22]\n " shape="box"]
15 -> 16 ;
15 -> 17 ;
14 [label="14: + \n NULLIFY(&person,false); [line 22]\n NULLIFY(&t,false); [line 22]\n " ]
14 [label="14: + \n NULLIFY(&t,false); [line 22]\n NULLIFY(&person,false); [line 22]\n " ]
14 -> 13 ;
13 [label="13: Exit person_typeid \n " color=yellow style=filled]
12 [label="12: Start person_typeid\nFormals: \nLocals: t:int person:class Person \n DECLARE_LOCALS(&return,&t,&person); [line 19]\n " color=yellow style=filled]
12 [label="12: Start person_typeid\nFormals: \nLocals: t:int person:class Person \n DECLARE_LOCALS(&return,&t,&person); [line 19]\n NULLIFY(&t,false); [line 19]\n " color=yellow style=filled]
12 -> 21 ;

9
infer/tests/codetoanalyze/objc/errors/npe/block.m
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@ -80,4 +80,13 @@
_block_field(); // Ivar not nullable
}
- (int)check_nullify {
int i = 7;
int* x = &i;
int (^my_block)(void) = ^() {
return *x; // we'll get a false NPE here if we nullify x too early.
};
return my_block();
}
@end

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