Fix dependencies of process_info(..., message*)

CHANGELOG.md

@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ### Changed
 - handling of demonitors (#281)
+- handling of process_info(..., messages) (#283)
 
 ### Fixed
 - fixed stacktrace information (#276)

src/concuerror.erl

@@ -176,8 +176,9 @@ start(Options, LogMsgs) ->
 
 maybe_cover_compile() ->
   Cover = os:getenv("CONCUERROR_COVER"),
-  case Cover =/= false of
+  case get(concuerror_cover) =:= undefined andalso Cover =/= false of
     true ->
+      put(concuerror_cover, Cover),
       case cover:is_compiled(?MODULE) of
         false ->
           {ok, Modules} = application:get_key(concuerror, modules),
@@ -191,8 +192,8 @@ maybe_cover_compile() ->
 %%------------------------------------------------------------------------------
 
 maybe_cover_export(Args) ->
-  Cover = os:getenv("CONCUERROR_COVER"),
-  case Cover =/= false of
+  Cover = erase(concuerror_cover),
+  case Cover =/= undefined of
     true ->
       Hash = binary:decode_unsigned(erlang:md5(term_to_binary(Args))),
       Out = filename:join([Cover, io_lib:format("~.16b", [Hash])]),

src/concuerror_callback.erl

@@ -311,15 +311,11 @@ built_in(erlang, Display, 1, [Term], _Location, Info)
     end,
   concuerror_logger:print(Info#concuerror_info.logger, standard_io, Chars),
   {{didit, true}, Info};
-%% Process dictionary has been restored here. No need to report such ops.
+%% Inner process dictionary has been restored here. No need to report such ops.
+%% Also can't fail, as only true builtins reach this code.
 built_in(erlang, Name, _Arity, Args, _Location, Info)
   when Name =:= get; Name =:= get_keys; Name =:= put; Name =:= erase ->
-  try
-    {{didit, erlang:apply(erlang, Name, Args)}, Info}
-  catch
-    error:Reason -> {{error, Reason}, Info}
-  end;
-%% XXX: Temporary
+  {{didit, erlang:apply(erlang, Name, Args)}, Info};
 built_in(erlang, hibernate, 3, Args, _Location, Info) ->
   [Module, Name, HibArgs] = Args,
   self() ! {start, Module, Name, HibArgs},
@@ -682,8 +678,13 @@ run_built_in(erlang, process_info, 2, [Pid, Item], Info) when is_atom(Item) ->
             catch error:badarg -> []
             end;
           messages ->
-            #concuerror_info{message_queue = Queue} = TheirInfo,
-            [M || #message{data = M} <- queue:to_list(Queue)];
+            #concuerror_info{logger = Logger} = TheirInfo,
+            Msg =
+              "Concuerror does not properly support"
+              " erlang:process_info(Other, messages),"
+              " returning an empty list instead.~n",
+            ?unique(Logger, ?lwarning, Msg, []),
+            [];
           message_queue_len ->
             #concuerror_info{message_queue = Queue} = TheirInfo,
             queue:len(Queue);
@@ -1852,8 +1853,8 @@ exiting(Reason, Stacktrace, InfoIn) ->
   FunFold = fun(Fun, Acc) -> Fun(Acc) end,
   FunList =
     [fun ets_ownership_exiting_events/1,
-     link_monitor_handlers(links, fun handle_link/4, Links),
-     link_monitor_handlers(monitors, fun handle_monitor/4, Monitors)],
+     link_monitor_handlers(fun handle_link/4, Links),
+     link_monitor_handlers(fun handle_monitor/4, Monitors)],
   NewInfo = ExitInfo#concuerror_info{exit_reason = Reason},
   FinalInfo = lists:foldl(FunFold, NewInfo, FunList),
   ?debug_flag(?loop, exited),
@@ -1911,17 +1912,14 @@ handle_monitor({Ref, P, As}, S, Reason, InfoIn) ->
     instrumented(call, MFArgs, exit, InfoIn),
   NewInfo.
 
-link_monitor_handlers(Type, Handler, LinksOrMonitors) ->
+link_monitor_handlers(Handler, LinksOrMonitors) ->
   fun(Info) ->
       #concuerror_info{exit_reason = Reason} = Info,
-      HandleActive =
+      Fold =
         fun({LinkOrMonitor, S}, InfoIn) ->
-            case S =:= active orelse Type =:= monitors of
-              true -> Handler(LinkOrMonitor, S, Reason, InfoIn);
-              false -> InfoIn
-            end
+            Handler(LinkOrMonitor, S, Reason, InfoIn)
         end,
-      lists:foldl(HandleActive, Info, LinksOrMonitors)
+      lists:foldl(Fold, Info, LinksOrMonitors)
   end.
 
 %%------------------------------------------------------------------------------

src/concuerror_dependencies.erl

@@ -393,14 +393,17 @@ dependent_process_info(#builtin_event{mfargs = {_,_,[Pid, links]}},
       when UnLink =:= link; UnLink =:= unlink -> true;
     _ -> false
   end;
-dependent_process_info(#builtin_event{mfargs = {_,_,[Pid, Msg]}},
-                       Other)
-  when Msg =:= messages; Msg =:= message_queue_len ->
+dependent_process_info(#builtin_event{mfargs = {_,_,[Pid, message_queue_len]}},
+                       Other) ->
   case Other of
     #message_event{recipient = Recipient} ->
       Recipient =:= Pid;
     #receive_event{recipient = Recipient, message = M} ->
       Recipient =:= Pid andalso M =/= 'after';
+    #builtin_event{actor = Recipient, mfargs = {M, F, [_, Args]}} ->
+      Recipient =:= Pid andalso
+        {M, F} =:= {erlang, demonitor} andalso
+        try lists:member(flush, Args) catch _:_ -> false end;
     _ -> false
   end;
 dependent_process_info(#builtin_event{mfargs = {_, _, [Pid, registered_name]}},
@@ -431,6 +434,7 @@ dependent_process_info(#builtin_event{mfargs = {_,_,[_, Safe]}},
     Safe =:= current_stacktrace;
     Safe =:= dictionary;
     Safe =:= heap_size;
+    Safe =:= messages; %% If fixed, it should be an observer of message races
     Safe =:= reductions;
     Safe =:= stack_size;
     Safe =:= status

src/concuerror_instrumenter.erl

@@ -179,6 +179,8 @@ is_unsafe({erlang, F, A}) ->
       StringF = atom_to_list(F),
       not erl_safe(StringF)
   end;
+is_unsafe({erts_internal, garbage_collect, _}) ->
+  false;
 is_unsafe({Safe, _, _})
   when
     Safe =:= binary
@@ -230,7 +232,6 @@ erl_safe("fun_info"              ++ _) -> true;
 erl_safe("function_exported"         ) -> true;
 erl_safe("garbage_collect"           ) -> true;
 erl_safe("get_module_info"           ) -> true;
-erl_safe("hash"                      ) -> true;
 erl_safe("hibernate"                 ) -> false; %% Must be instrumented.
 erl_safe("insert_element"            ) -> true;
 erl_safe("iolist_size"               ) -> true;