Merge branch 'sv/format_status_error_info' into dev

* sv/format_status_error_info:
  Add support for the format_status callback to gen_event
  Extend format_status for gen_server/gen_fsm termination error logging

OTP-8630 sv/format_status_error_info

When a gen_server, gen_fsm process, or gen_event terminates abnormally,
sometimes the text representation of the process state can occupy many
lines of the error log, depending on the definition of the state term. A
mechanism to trim out parts of the state from the log has been added (using
a format_status/2 callback). See the documentation.

1 files changed, 18 insertions, 5 deletions

diff --git a/lib/stdlib/src/gen_server.erl b/lib/stdlib/src/gen_server.erl
index 1c9e5270b6..dc8e7ecd16 100644
--- a/lib/stdlib/src/gen_server.erl
+++ b/lib/stdlib/src/gen_server.erl
@@ -705,7 +705,18 @@ terminate(Reason, Name, Msg, Mod, State, Debug) ->
 		{shutdown,_}=Shutdown ->
 		    exit(Shutdown);
 		_ ->
-		    error_info(Reason, Name, Msg, State, Debug),
+		    FmtState =
+			case erlang:function_exported(Mod, format_status, 2) of
+			    true ->
+				Args = [get(), State],
+				case catch Mod:format_status(terminate, Args) of
+				    {'EXIT', _} -> State;
+				    Else -> Else
+				end;
+			    _ ->
+				State
+			end,
+		    error_info(Reason, Name, Msg, FmtState, Debug),
 		    exit(Reason)
 	    end
     end.
@@ -836,15 +847,17 @@ format_status(Opt, StatusData) ->
 	      end,
     Header = lists:concat(["Status for generic server ", NameTag]),
     Log = sys:get_debug(log, Debug, []),
-    Specfic = 
+    DefaultStatus = [{data, [{"State", State}]}],
+    Specfic =
 	case erlang:function_exported(Mod, format_status, 2) of
 	    true ->
 		case catch Mod:format_status(Opt, [PDict, State]) of
-		    {'EXIT', _} -> [{data, [{"State", State}]}];
-		    Else -> Else
+		    {'EXIT', _} -> DefaultStatus;
+                    StatusList when is_list(StatusList) -> StatusList;
+		    Else -> [Else]
 		end;
 	    _ ->
-		[{data, [{"State", State}]}]
+		DefaultStatus
 	end,
     [{header, Header},
      {data, [{"Status", SysState},