[inferbo] Do not store dummy idents into stack

Summary:
:
Do not store dummy `_` into the stack.
This makes debugging a lot easier

Reviewed By: skcho

Differential Revision: D5275941

fbshipit-source-id: ce329a5

infer/src/bufferoverrun/bufferOverrunChecker.ml

@@ -313,6 +313,9 @@ struct
         | Load (id, exp, _, loc) ->
             let locs = Sem.eval exp mem loc |> Dom.Val.get_all_locs in
             let v = Dom.Mem.find_heap_set locs mem in
+            if Ident.is_none id then
+              mem
+            else
               Dom.Mem.add_stack (Loc.of_var (Var.of_id id)) v mem
               |> Dom.Mem.load_alias id exp
         | Store (exp1, _, exp2, loc) ->