Fix format_status bug for unregistered gen_event processes

Port the gen_fsm code for format_status to gen_event in order to
prevent a lists:concat([...,pid()]) crash when calling
sys:get_status/1 on an unregistered gen_event process.

Refactor format_status header code from gen_* behaviours to module gen.

Extend the format_status tests in gen_event_SUITE to cover
format_status bugs with anonymous gen_event processes.

1 files changed, 20 insertions, 2 deletions

diff --git a/lib/stdlib/test/gen_event_SUITE.erl b/lib/stdlib/test/gen_event_SUITE.erl
index 4f7de451e3..4c6466d860 100644
--- a/lib/stdlib/test/gen_event_SUITE.erl
+++ b/lib/stdlib/test/gen_event_SUITE.erl
@@ -24,10 +24,12 @@
 -export([start/1, test_all/1, add_handler/1, add_sup_handler/1,
 	 delete_handler/1, swap_handler/1, swap_sup_handler/1,
 	 notify/1, sync_notify/1, call/1, info/1, hibernate/1,
-	 call_format_status/1, error_format_status/1]).
+	 call_format_status/1, call_format_status_anon/1,
+         error_format_status/1]).
 
 all(suite) -> {req, [stdlib], [start, test_all, hibernate,
-			       call_format_status, error_format_status]}.
+			       call_format_status, call_format_status_anon,
+                               error_format_status]}.
 
 %% --------------------------------------
 %% Start an event manager.
@@ -868,6 +870,22 @@ call_format_status(Config) when is_list(Config) ->
     ?line {"Installed handlers", [{_,dummy1_h,_,FmtState,_}]} = HandlerInfo2,
     ok.
 
+call_format_status_anon(suite) ->
+    [];
+call_format_status_anon(doc) ->
+    ["Test that sys:get_status/1,2 calls format_status/2 for anonymous gen_event processes"];
+call_format_status_anon(Config) when is_list(Config) ->
+    ?line {ok, Pid} = gen_event:start(),
+    %% The 'Name' of the gen_event process will be a pid() here, so
+    %% the next line will crash if format_status can't string-ify pids.
+    ?line Status1 = sys:get_status(Pid),
+    ?line ok = gen_event:stop(Pid),
+    Header = "Status for event handler " ++  pid_to_list(Pid),
+    ?line {status, Pid, _, [_, _, Pid, [], Data1]} = Status1,
+    ?line Header = proplists:get_value(header, Data1),
+    ok.
+
+
 error_format_status(suite) ->
     [];
 error_format_status(doc) ->