Revert "[clang] Removing the case of flagging npes in initialisers. This causes many FPs."

Summary:
This reverts commit 306f5b71c24042c89f71848898402cbc9269c543.
Turns out that developers think that this bugs should be fixed. So leaving it in for now until I gather more information.

infer/src/backend/prover.ml

@@ -821,8 +821,9 @@ let check_inconsistency_base prop =
           Sil.pvar_is_seed pv
       | _ -> false in
     list_exists do_hpred sigma in
-  let inconsistent_self () = (* "self" cannot be null in ObjC *)
+  let inconsistent_self () = (* "self" cannot be null in ObjC, outside of initializers *)
     let procdesc = Cfg.Node.get_proc_desc (State.get_node ()) in
+    let procname = Cfg.Procdesc.get_proc_name procdesc in
     let procedure_attr = Cfg.Procdesc.get_attributes procdesc in
     let do_hpred = function
       | Sil.Hpointsto (Sil.Lvar pv, Sil.Eexp (e, _), _) ->
@@ -830,7 +831,8 @@ let check_inconsistency_base prop =
           Sil.exp_equal e Sil.exp_zero &&
           Sil.pvar_is_seed pv &&
           Sil.pvar_get_name pv = Mangled.from_string "self" &&
-          procedure_attr.Sil.is_objc_instance_method
+          procedure_attr.Sil.is_objc_instance_method &&
+          not (Procname.is_constructor procname)
       | _ -> false in
     list_exists do_hpred sigma in
   let inconsistent_atom = function

infer/src/backend/symExec.ml

@@ -784,6 +784,13 @@ let handle_special_cases_call tenv cfg pname actual_params =
   else pname, actual_params
 
 let handle_objc_method_call actual_pars actual_params pre tenv cfg ret_ids pdesc callee_pname loc path =
+  let receiver_self receiver prop =
+    list_exists (fun hpred ->
+            match hpred with
+            | Sil.Hpointsto (Sil.Lvar pv, Sil.Eexp (e, _), _) ->
+                Sil.exp_equal e receiver && Sil.pvar_is_seed pv &&
+                Sil.pvar_get_name pv = Mangled.from_string "self"
+            | _ -> false) (Prop.get_sigma prop) in
   let path_description = "Message "^(Procname.to_simplified_string callee_pname)^" with receiver nil returns nil." in
   let receiver = (match actual_pars with
       | (e, _):: _ -> e
@@ -793,6 +800,10 @@ let handle_objc_method_call actual_pars actual_params pre tenv cfg ret_ids pdesc
     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 prop_null =
+    match ret_ids with
+    | [ret_id] -> Prop.conjoin_eq (Sil.Var ret_id) Sil.exp_zero pre
+    | _ -> pre in
   let add_objc_null_attribute_or_nullify_result prop =
     match ret_ids with
     | [ret_id] ->
@@ -815,16 +826,22 @@ let handle_objc_method_call actual_pars actual_params pre tenv cfg ret_ids pdesc
       | _ -> false 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 is_receiver_self = receiver_self receiver pre in
+        let pre_with_attr_or_null =
+          if is_receiver_self then prop_null
+          else 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 = list_hd (Propset.to_proplist propset) in
-          let path = Paths.Path.add_description path path_description in
+          let path =
+            if is_receiver_self then path
+            else 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
@@ -832,6 +849,7 @@ let normalize_params pdesc prop actual_params =
   let prop, args = list_fold_left norm_arg (prop, []) actual_params in
   (prop, list_rev args)
 
+
 (** 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 =
@@ -1146,7 +1164,7 @@ and call_unknown_or_scan is_scan cfg pdesc tenv pre path
     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 ->
+             when res_action.Sil.ra_res = Sil.Rfile ->
             Prop.remove_attribute res q
         | _ -> q in
       list_fold_left do_attribute p (Prop.get_exp_attributes p e) in

infer/tests/endtoend/objc/NPESelfTest.java

@@ -60,8 +60,8 @@ public class NPESelfTest {
       throws InterruptedException, IOException, InferException {
     InferResults inferResults = InferRunner.runInferObjC(inferCmdNPD);
     assertThat(
-        "NPE should not be found", inferResults,
-        doesNotContain(
+        "NPE should be found", inferResults,
+        contains(
             NULL_DEREFERENCE,
             NPE_FILE,
             "init"));