Handle uncaught throws in a gen_* process better

src/error_logger_lager_h.erl

@@ -274,6 +274,9 @@ format_mfa({M, F, A, Props}) when is_list(Props) ->
         Line ->
             [format_mfa({M, F, A}), io_lib:format(" line ~w", [Line])]
     end;
+format_mfa([{M, F, A, Props}, _]) when is_list(Props) ->
+   %% this kind of weird stacktrace can be generated by a uncaught throw in a gen_server
+   format_mfa({M, F, A, Props});
 format_mfa(Other) ->
     io_lib:format("~w", [Other]).
 

test/crash.erl

@@ -85,6 +85,8 @@ handle_call(badarity, _, State) ->
 	F = fun(A, B, C) -> A + B + C end,
 	Res = F(State),
 	{reply, Res, State};
+handle_call(throw, _, State) ->
+	throw(a_ball);
 handle_call(_Call, _From, State) ->
 	{reply, ok, State}.
 

test/lager_test_backend.erl

@@ -305,6 +305,15 @@ error_logger_redirect_crash_test_() ->
                         ?assertEqual(Expected, lists:flatten(Msg))
                 end
             },
+           {"bad return value uncaught throw",
+                fun() ->
+                        Pid = whereis(crash),
+                        crash(throw),
+                        {_, _, Msg} = pop(),
+                        Expected = lists:flatten(io_lib:format("[error] ~w gen_server crash terminated with reason: bad return value: a_ball", [Pid])),
+                        ?assertEqual(Expected, lists:flatten(Msg))
+                end
+            },
             {"case clause",
                 fun() ->
                         Pid = whereis(crash),