Add formatting for emfile and for various system limits

src/error_logger_lager_h.erl

@@ -156,7 +156,23 @@ format_reason({badarith, [MFA|_]}) ->
     ["bad arithmetic expression in ", format_mfa(MFA)];
 format_reason({{badmatch, Val}, [MFA|_]}) ->
     [io_lib:format("no match of right hand value ~w in ", [Val]), format_mfa(MFA)];
-%format_reason({system_limit,
+format_reason({emfile, _Trace}) ->
+    "maximum number of file descriptors exhausted, check ulimit -n";
+format_reason({system_limit, [{M, F, _}|_] = Trace}) ->
+    Limit = case {M, F} of
+        {erlang, open_port} ->
+            "maximum number of ports exceeded";
+        {erlang, spawn} ->
+            "maximum number of processes exceeded";
+        {erlang, spawn_opt} ->
+            "maximum number of processes exceeded";
+        {erlang, list_to_atom} ->
+            "tried to create an atom larger than 255, or maximum atom count exceeded";
+        _ ->
+            {Str, _} = trunc_io:print(Trace, 500),
+            Str
+    end,
+    ["system limit: ", Limit];
 format_reason({badarg, [MFA,MFA2|_]}) ->
     case MFA of
         {_M, _F, A} when is_list(A) ->

test/crash.erl

@@ -55,6 +55,13 @@ handle_call(badarg2, _, State) ->
 handle_call(system_limit, _, State) ->
 	Res = list_to_atom(lists:flatten(lists:duplicate(256, "a"))),
 	{reply, Res, State};
+handle_call(process_limit, _, State) ->
+    %% run with +P 300 to make this crash
+    [erlang:spawn(fun() -> timer:sleep(5000) end) || _ <- lists:seq(0, 500)],
+    {reply, ok, State};
+handle_call(port_limit, _, State) ->
+    [erlang:open_port({spawn, "ls"}, []) || _ <- lists:seq(0, 1024)],
+    {reply, ok, State};
 handle_call(noproc, _, State) ->
 	Res = gen_event:call(foo, bar, baz),
 	{reply, Res, State};