[dead store objc] Do not report dead store in a captured variable of an objc block

Reviewed By: sblackshear

Differential Revision: D6136733

fbshipit-source-id: 568c36d

infer/src/IR/Typ.ml

@@ -722,6 +722,12 @@ module Procname = struct
         "Linters_dummy_method"
 
 
+  (** Return whether the procname is a block procname. *)
+  let is_objc_block = function Block _ -> true | _ -> false
+
+  (** Return whether the procname is a cpp lambda. *)
+  let is_cpp_lambda procname = String.is_substring ~substring:"operator()" (get_method procname)
+
   (** Return the language of the procedure. *)
   let get_language = function
     | ObjC_Cpp _ ->

infer/src/IR/Typ.mli

@@ -332,6 +332,12 @@ module Procname : sig
   val get_method : t -> string
   (** Return the method/function of a procname. *)
 
+  val is_objc_block : t -> bool
+  (** Return whether the procname is a block procname. *)
+
+  val is_cpp_lambda : t -> bool
+  (** Return whether the procname is a cpp lambda. *)
+
   val hash_pname : t -> int
   (** Hash function for procname. *)
 

infer/src/checkers/liveness.ml

@@ -61,6 +61,25 @@ end
 module CFG = ProcCfg.OneInstrPerNode (ProcCfg.Backward (ProcCfg.Exceptional))
 module Analyzer = AbstractInterpreter.Make (CFG) (TransferFunctions)
 
+let is_captured_var procdesc pvar =
+  let procname = Procdesc.get_proc_name procdesc in
+  let pvar_name = Pvar.get_name pvar in
+  let pvar_matches (name, _) = Mangled.equal name pvar_name in
+  let is_captured_var_cpp_lambda =
+    (* var is captured if the procedure is a lambda and the var is not in the locals or formals *)
+    Typ.Procname.is_cpp_lambda procname
+    && not
+         ( List.exists ~f:pvar_matches (Procdesc.get_locals procdesc)
+         || List.exists ~f:pvar_matches (Procdesc.get_formals procdesc) )
+  in
+  let is_captured_var_objc_block =
+    (* var is captured if the procedure is a objc block and the var is in the captured *)
+    Typ.Procname.is_objc_block procname
+    && List.exists ~f:pvar_matches (Procdesc.get_captured procdesc)
+  in
+  is_captured_var_cpp_lambda || is_captured_var_objc_block
+
+
 let is_whitelisted_var var =
   let whitelisted_vars = ["__assert_file__"; "__assert_fn__"] in
   List.exists
@@ -73,24 +92,11 @@ let checker {Callbacks.tenv; summary; proc_desc} : Specs.summary =
   let invariant_map =
     Analyzer.exec_cfg cfg (ProcData.make_default proc_desc tenv) ~initial:Domain.empty ~debug:true
   in
-  let procname = Procdesc.get_proc_name proc_desc in
-  let is_cpp_lambda =
-    String.is_substring ~substring:"operator()" (Typ.Procname.get_method procname)
-  in
-  let is_captured_var pvar =
-    let pvar_name = Pvar.get_name pvar in
-    let pvar_matches (name, _) = Mangled.equal name pvar_name in
-    (* var is captured if the procedure is a lambda and the var is not in the locals or formals *)
-    is_cpp_lambda
-    && not
-         ( List.exists ~f:pvar_matches (Procdesc.get_locals proc_desc)
-         || List.exists ~f:pvar_matches (Procdesc.get_formals proc_desc) )
-  in
   let report_dead_store live_vars = function
     | Sil.Store (Lvar pvar, _, _, loc)
       when not
              ( Pvar.is_frontend_tmp pvar || Pvar.is_return pvar || Pvar.is_global pvar
-             || Domain.mem (Var.of_pvar pvar) live_vars || is_captured_var pvar
+             || Domain.mem (Var.of_pvar pvar) live_vars || is_captured_var proc_desc pvar
              || is_whitelisted_var pvar ) ->
         let issue_id = IssueType.dead_store.unique_id in
         let message = F.asprintf "The value written to %a is never used" (Pvar.pp Pp.text) pvar in
@@ -114,3 +120,4 @@ let checker {Callbacks.tenv; summary; proc_desc} : Specs.summary =
   in
   List.iter (CFG.nodes cfg) ~f:report_on_node ;
   summary
+

infer/tests/codetoanalyze/objc/liveness/CapturedVariableExample.m

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2017 - 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.
+ */
+#import <Foundation/Foundation.h>
+
+@interface A : NSObject
+@end
+
+typedef void (^MyBlock)();
+
+@interface C : NSObject
+
++ (void)use_block:(MyBlock)block;
+
+@end
+
+@implementation A
+
++ (A*)g {
+  __block A* a;
+  [C use_block:^() {
+    a = [A new];
+  }];
+  return a;
+};
+
+@end

infer/tests/codetoanalyze/objc/liveness/NSParameterAssertExample.m

@@ -20,11 +20,10 @@
     __assert_fn__ = __assert_fn__ ? __assert_fn__ : @"<Unknown Function>";
     NSString* __assert_file__ = [NSString stringWithUTF8String:"A.m"];
     __assert_file__ = __assert_file__ ? __assert_file__ : @"<Unknown File>";
-    [[NSAssertionHandler currentHandler]
-        handleFailureInFunction:__assert_fn__
-                           file:__assert_file__
-                     lineNumber:23
-                    description:(@"Hello")];
+    [[NSAssertionHandler currentHandler] handleFailureInFunction:__assert_fn__
+                                                            file:__assert_file__
+                                                      lineNumber:23
+                                                     description:(@"Hello")];
   }
 }