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authorZandra Norman <[email protected]>2017-04-24 11:07:36 +0200
committerZandra Norman <[email protected]>2017-04-24 11:07:36 +0200
commit37158d81c8a49d77b8ba32dbc560b3064127e24d (patch)
tree43b00d680f459571b2d3d60b874fbdcfdad62eca /lib/stdlib
parent3ab6bcf6f9a44c998610bdf8863c07fb4f221da9 (diff)
parent9e396c8676e5a7eacbe5e7b2d93ee080298eb8fb (diff)
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Merge branch 'zandra/stdlib/optional-callbacks/OTP-13801'
* zandra/stdlib/optional-callbacks/OTP-13801: wx: make wx_object callbacks optional stdlib: Make gen_fsm callbacks optional stdlib: Make gen_event callbacks optional stdlib: Make gen_server callbacks optional
Diffstat (limited to 'lib/stdlib')
-rw-r--r--lib/stdlib/doc/src/gen_event.xml18
-rw-r--r--lib/stdlib/doc/src/gen_fsm.xml19
-rw-r--r--lib/stdlib/doc/src/gen_server.xml18
-rw-r--r--lib/stdlib/src/gen_event.erl19
-rw-r--r--lib/stdlib/src/gen_fsm.erl47
-rw-r--r--lib/stdlib/src/gen_server.erl42
-rw-r--r--lib/stdlib/test/dummy_h.erl6
-rw-r--r--lib/stdlib/test/erl_internal_SUITE.erl6
-rw-r--r--lib/stdlib/test/erl_lint_SUITE.erl10
-rw-r--r--lib/stdlib/test/gen_event_SUITE.erl132
-rw-r--r--lib/stdlib/test/gen_event_SUITE_data/oc_event.erl40
-rw-r--r--lib/stdlib/test/gen_fsm_SUITE.erl151
-rw-r--r--lib/stdlib/test/gen_fsm_SUITE_data/oc_fsm.erl48
-rw-r--r--lib/stdlib/test/gen_server_SUITE.erl175
-rw-r--r--lib/stdlib/test/gen_server_SUITE_data/oc_server.erl37
15 files changed, 709 insertions, 59 deletions
diff --git a/lib/stdlib/doc/src/gen_event.xml b/lib/stdlib/doc/src/gen_event.xml
index 42e952fd46..56cb7974a2 100644
--- a/lib/stdlib/doc/src/gen_event.xml
+++ b/lib/stdlib/doc/src/gen_event.xml
@@ -579,6 +579,13 @@ gen_event:stop -----> Module:terminate/2
<v>Extra = term()</v>
</type>
<desc>
+ <note>
+ <p>This callback is optional, so callback modules need not export it.
+ If a release upgrade/downgrade with <c>Change={advanced,Extra}</c>
+ specified in the <c>.appup</c> file is made when <c>code_change/3</c>
+ isn't implemented the event handler will crash with an <c>undef</c> error
+ reason.</p>
+ </note>
<p>This function is called for an installed event handler that
is to update its internal state during a release
upgrade/downgrade, that is, when the instruction
@@ -759,6 +766,12 @@ gen_event:stop -----> Module:terminate/2
<v>&nbsp;&nbsp;Id = term()</v>
</type>
<desc>
+ <note>
+ <p>This callback is optional, so callback modules need not
+ export it. The <c>gen_event</c> module provides a default
+ implementation of this function that logs about the unexpected
+ <c>Info</c> message, drops it and returns <c>{noreply, State}</c>.</p>
+ </note>
<p>This function is called for each installed event handler when
an event manager receives any other message than an event or
a synchronous request (or a system message).</p>
@@ -815,6 +828,11 @@ gen_event:stop -----> Module:terminate/2
<v>&nbsp;Args = Reason = Term = term()</v>
</type>
<desc>
+ <note>
+ <p>This callback is optional, so callback modules need not
+ export it. The <c>gen_event</c> module provides a default
+ implementation without cleanup.</p>
+ </note>
<p>Whenever an event handler is deleted from an event manager,
this function is called. It is to be the opposite of
<seealso marker="#Module:init/1"><c>Module:init/1</c></seealso>
diff --git a/lib/stdlib/doc/src/gen_fsm.xml b/lib/stdlib/doc/src/gen_fsm.xml
index 719ab2b558..691a039e34 100644
--- a/lib/stdlib/doc/src/gen_fsm.xml
+++ b/lib/stdlib/doc/src/gen_fsm.xml
@@ -562,6 +562,13 @@ gen_fsm:sync_send_all_state_event -----> Module:handle_sync_event/4
<v>Extra = term()</v>
</type>
<desc>
+ <note>
+ <p>This callback is optional, so callback modules need not export it.
+ If a release upgrade/downgrade with <c>Change={advanced,Extra}</c>
+ specified in the <c>appup</c> file is made when <c>code_change/4</c>
+ isn't implemented the process will crash with an <c>undef</c> exit
+ reason.</p>
+ </note>
<p>This function is called by a <c>gen_fsm</c> process when it is to
update its internal state data during a release upgrade/downgrade,
that is, when instruction <c>{update,Module,Change,...}</c>,
@@ -686,6 +693,13 @@ gen_fsm:sync_send_all_state_event -----> Module:handle_sync_event/4
<v>&nbsp;Reason = normal | term()</v>
</type>
<desc>
+ <note>
+ <p>This callback is optional, so callback modules need not
+ export it. The <c>gen_fsm</c> module provides a default
+ implementation of this function that logs about the unexpected
+ <c>Info</c> message, drops it and returns
+ <c>{next_state, StateName, StateData}</c>.</p>
+ </note>
<p>This function is called by a <c>gen_fsm</c> process when it receives
any other message than a synchronous or asynchronous event (or a
system message).</p>
@@ -899,6 +913,11 @@ gen_fsm:sync_send_all_state_event -----> Module:handle_sync_event/4
<v>StateData = term()</v>
</type>
<desc>
+ <note>
+ <p>This callback is optional, so callback modules need not
+ export it. The <c>gen_fsm</c> module provides a default
+ implementation without cleanup.</p>
+ </note>
<p>This function is called by a <c>gen_fsm</c> process when it is about
to terminate. It is to be the opposite of
<seealso marker="#Module:init/1"><c>Module:init/1</c></seealso>
diff --git a/lib/stdlib/doc/src/gen_server.xml b/lib/stdlib/doc/src/gen_server.xml
index 662076b5f0..4540449792 100644
--- a/lib/stdlib/doc/src/gen_server.xml
+++ b/lib/stdlib/doc/src/gen_server.xml
@@ -504,6 +504,13 @@ gen_server:abcast -----> Module:handle_cast/2
<v>Reason = term()</v>
</type>
<desc>
+ <note>
+ <p>This callback is optional, so callback modules need not export it.
+ If a release upgrade/downgrade with <c>Change={advanced,Extra}</c>
+ specified in the <c>appup</c> file is made when <c>code_change/3</c>
+ isn't implemented the process will crash with an <c>undef</c> exit
+ reason.</p>
+ </note>
<p>This function is called by a <c>gen_server</c> process when it is
to update its internal state during a release upgrade/downgrade,
that is, when the instruction <c>{update,Module,Change,...}</c>,
@@ -690,6 +697,12 @@ gen_server:abcast -----> Module:handle_cast/2
<v>&nbsp;Reason = normal | term()</v>
</type>
<desc>
+ <note>
+ <p>This callback is optional, so callback modules need not
+ export it. The <c>gen_server</c> module provides a default
+ implementation of this function that logs about the unexpected
+ <c>Info</c> message, drops it and returns <c>{noreply, State}</c>.</p>
+ </note>
<p>This function is called by a <c>gen_server</c> process when a
time-out occurs or when it receives any other message than a
synchronous or asynchronous request (or a system message).</p>
@@ -750,6 +763,11 @@ gen_server:abcast -----> Module:handle_cast/2
<v>State = term()</v>
</type>
<desc>
+ <note>
+ <p>This callback is optional, so callback modules need not
+ export it. The <c>gen_server</c> module provides a default
+ implementation without cleanup.</p>
+ </note>
<p>This function is called by a <c>gen_server</c> process when it is
about to terminate. It is to be the opposite of
<seealso marker="#Module:init/1"><c>Module:init/1</c></seealso>
diff --git a/lib/stdlib/src/gen_event.erl b/lib/stdlib/src/gen_event.erl
index 0aebf1bdc5..0c50b2aa08 100644
--- a/lib/stdlib/src/gen_event.erl
+++ b/lib/stdlib/src/gen_event.erl
@@ -109,7 +109,8 @@
State :: term(),
Status :: term().
--optional_callbacks([format_status/2]).
+-optional_callbacks(
+ [handle_info/2, terminate/2, code_change/3, format_status/2]).
%%---------------------------------------------------------------------------
@@ -577,6 +578,10 @@ server_update(Handler1, Func, Event, SName) ->
do_terminate(Mod1, Handler1, remove_handler, State,
remove, SName, normal),
no;
+ {'EXIT', {undef, [{Mod1, handle_info, [_,_], _}|_]}} ->
+ error_logger:warning_msg("** Undefined handle_info in ~p~n"
+ "** Unhandled message: ~p~n", [Mod1, Event]),
+ {ok, Handler1};
Other ->
do_terminate(Mod1, Handler1, {error, Other}, State,
Event, SName, crash),
@@ -698,9 +703,15 @@ server_call_update(Handler1, Query, SName) ->
end.
do_terminate(Mod, Handler, Args, State, LastIn, SName, Reason) ->
- Res = (catch Mod:terminate(Args, State)),
- report_terminate(Handler, Reason, Args, State, LastIn, SName, Res),
- Res.
+ case erlang:function_exported(Mod, terminate, 2) of
+ true ->
+ Res = (catch Mod:terminate(Args, State)),
+ report_terminate(Handler, Reason, Args, State, LastIn, SName, Res),
+ Res;
+ false ->
+ report_terminate(Handler, Reason, Args, State, LastIn, SName, ok),
+ ok
+ end.
report_terminate(Handler, crash, {error, Why}, State, LastIn, SName, _) ->
report_terminate(Handler, Why, State, LastIn, SName);
diff --git a/lib/stdlib/src/gen_fsm.erl b/lib/stdlib/src/gen_fsm.erl
index e925a75fe8..39a8fd42fe 100644
--- a/lib/stdlib/src/gen_fsm.erl
+++ b/lib/stdlib/src/gen_fsm.erl
@@ -169,7 +169,8 @@
State :: term(),
Status :: term().
--optional_callbacks([format_status/2]).
+-optional_callbacks(
+ [handle_info/3, terminate/3, code_change/4, format_status/2]).
%%% ---------------------------------------------------
%%% Starts a generic state machine.
@@ -466,6 +467,10 @@ handle_msg(Msg, Parent, Name, StateName, StateData, Mod, _Time) -> %No debug her
StateName, NStateData, [])),
reply(From, Reply),
exit(R);
+ {'EXIT', {undef, [{Mod, handle_info, [_,_,_], _}|_]}} ->
+ error_logger:warning_msg("** Undefined handle_info in ~p~n"
+ "** Unhandled message: ~p~n", [Mod, Msg]),
+ loop(Parent, Name, StateName, StateData, Mod, infinity, []);
{'EXIT', What} ->
terminate(What, Name, Msg, Mod, StateName, StateData, []);
Reply ->
@@ -540,24 +545,30 @@ reply(Name, {To, Tag}, Reply, Debug, StateName) ->
-spec terminate(term(), _, _, atom(), _, _, _) -> no_return().
terminate(Reason, Name, Msg, Mod, StateName, StateData, Debug) ->
- case catch Mod:terminate(Reason, StateName, StateData) of
- {'EXIT', R} ->
- FmtStateData = format_status(terminate, Mod, get(), StateData),
- error_info(R, Name, Msg, StateName, FmtStateData, Debug),
- exit(R);
- _ ->
- case Reason of
- normal ->
- exit(normal);
- shutdown ->
- exit(shutdown);
- {shutdown,_}=Shutdown ->
- exit(Shutdown);
+ case erlang:function_exported(Mod, terminate, 3) of
+ true ->
+ case catch Mod:terminate(Reason, StateName, StateData) of
+ {'EXIT', R} ->
+ FmtStateData = format_status(terminate, Mod, get(), StateData),
+ error_info(R, Name, Msg, StateName, FmtStateData, Debug),
+ exit(R);
_ ->
- FmtStateData = format_status(terminate, Mod, get(), StateData),
- error_info(Reason,Name,Msg,StateName,FmtStateData,Debug),
- exit(Reason)
- end
+ ok
+ end;
+ false ->
+ ok
+ end,
+ case Reason of
+ normal ->
+ exit(normal);
+ shutdown ->
+ exit(shutdown);
+ {shutdown,_}=Shutdown ->
+ exit(Shutdown);
+ _ ->
+ FmtStateData1 = format_status(terminate, Mod, get(), StateData),
+ error_info(Reason,Name,Msg,StateName,FmtStateData1,Debug),
+ exit(Reason)
end.
error_info(Reason, Name, Msg, StateName, StateData, Debug) ->
diff --git a/lib/stdlib/src/gen_server.erl b/lib/stdlib/src/gen_server.erl
index 284810c971..8504af86f8 100644
--- a/lib/stdlib/src/gen_server.erl
+++ b/lib/stdlib/src/gen_server.erl
@@ -146,8 +146,8 @@
State :: term(),
Status :: term().
--optional_callbacks([format_status/2]).
-
+-optional_callbacks(
+ [handle_info/2, terminate/2, code_change/3, format_status/2]).
%%% -----------------------------------------------------------------
%%% Starts a generic server.
@@ -602,6 +602,17 @@ try_dispatch(Mod, Func, Msg, State) ->
catch
throw:R ->
{ok, R};
+ error:undef = R when Func == handle_info ->
+ case erlang:function_exported(Mod, handle_info, 2) of
+ false ->
+ error_logger:warning_msg("** Undefined handle_info in ~p~n"
+ "** Unhandled message: ~p~n",
+ [Mod, Msg]),
+ {ok, {noreply, State}};
+ true ->
+ Stacktrace = erlang:get_stacktrace(),
+ {'EXIT', {R, Stacktrace}, {R, Stacktrace}}
+ end;
error:R ->
Stacktrace = erlang:get_stacktrace(),
{'EXIT', {R, Stacktrace}, {R, Stacktrace}};
@@ -625,17 +636,22 @@ try_handle_call(Mod, Msg, From, State) ->
end.
try_terminate(Mod, Reason, State) ->
- try
- {ok, Mod:terminate(Reason, State)}
- catch
- throw:R ->
- {ok, R};
- error:R ->
- Stacktrace = erlang:get_stacktrace(),
- {'EXIT', {R, Stacktrace}, {R, Stacktrace}};
- exit:R ->
- Stacktrace = erlang:get_stacktrace(),
- {'EXIT', R, {R, Stacktrace}}
+ case erlang:function_exported(Mod, terminate, 2) of
+ true ->
+ try
+ {ok, Mod:terminate(Reason, State)}
+ catch
+ throw:R ->
+ {ok, R};
+ error:R ->
+ Stacktrace = erlang:get_stacktrace(),
+ {'EXIT', {R, Stacktrace}, {R, Stacktrace}};
+ exit:R ->
+ Stacktrace = erlang:get_stacktrace(),
+ {'EXIT', R, {R, Stacktrace}}
+ end;
+ false ->
+ {ok, ok}
end.
diff --git a/lib/stdlib/test/dummy_h.erl b/lib/stdlib/test/dummy_h.erl
index bc89cb4fde..70c0eafbdf 100644
--- a/lib/stdlib/test/dummy_h.erl
+++ b/lib/stdlib/test/dummy_h.erl
@@ -26,6 +26,8 @@
init(make_error) ->
{error, my_error};
+init({state, State}) ->
+ {ok, State};
init([Parent]) ->
{ok, Parent}; %% We will send special responses for every handled event.
init([Parent,hibernate]) ->
@@ -83,7 +85,9 @@ terminate(swap, State) ->
{ok, State};
terminate({error, {return, faulty}}, Parent) ->
Parent ! {dummy_h, returned_error};
+terminate(_Reason, {undef_in_terminate, {Mod, Fun}}) ->
+ Mod:Fun(),
+ ok;
terminate(_Reason, _State) ->
ok.
-
diff --git a/lib/stdlib/test/erl_internal_SUITE.erl b/lib/stdlib/test/erl_internal_SUITE.erl
index bfa48de6b7..099f21f905 100644
--- a/lib/stdlib/test/erl_internal_SUITE.erl
+++ b/lib/stdlib/test/erl_internal_SUITE.erl
@@ -97,11 +97,11 @@ callbacks(supervisor) ->
optional_callbacks(application) ->
[];
optional_callbacks(gen_server) ->
- [{format_status,2}];
+ [{handle_info, 2}, {terminate, 2}, {code_change, 3}, {format_status, 2}];
optional_callbacks(gen_fsm) ->
- [{format_status,2}];
+ [{handle_info, 3}, {terminate, 3}, {code_change, 4}, {format_status, 2}];
optional_callbacks(gen_event) ->
- [{format_status,2}];
+ [{handle_info, 2}, {terminate, 2}, {code_change, 3}, {format_status, 2}];
optional_callbacks(supervisor_bridge) ->
[];
optional_callbacks(supervisor) ->
diff --git a/lib/stdlib/test/erl_lint_SUITE.erl b/lib/stdlib/test/erl_lint_SUITE.erl
index c469624fb4..03cad2c093 100644
--- a/lib/stdlib/test/erl_lint_SUITE.erl
+++ b/lib/stdlib/test/erl_lint_SUITE.erl
@@ -3058,10 +3058,7 @@ behaviour_multiple(Config) when is_list(Config) ->
handle_info(_, _) -> ok.
">>,
[],
- {warnings,[{1,erl_lint,
- {undefined_behaviour_func,{code_change,3},gen_server}},
- {1,erl_lint,{undefined_behaviour_func,{init,1},gen_server}},
- {1,erl_lint,{undefined_behaviour_func,{terminate,2},gen_server}},
+ {warnings,[{1,erl_lint,{undefined_behaviour_func,{init,1},gen_server}},
{2,erl_lint,{undefined_behaviour_func,{init,1},supervisor}},
{2,
erl_lint,
@@ -3075,10 +3072,7 @@ behaviour_multiple(Config) when is_list(Config) ->
handle_info(_, _) -> ok.
">>,
[],
- {warnings,[{1,erl_lint,
- {undefined_behaviour_func,{code_change,3},gen_server}},
- {1,erl_lint,{undefined_behaviour_func,{init,1},gen_server}},
- {1,erl_lint,{undefined_behaviour_func,{terminate,2},gen_server}},
+ {warnings,[{1,erl_lint,{undefined_behaviour_func,{init,1},gen_server}},
{2,erl_lint,{undefined_behaviour_func,{init,1},supervisor}},
{2,
erl_lint,
diff --git a/lib/stdlib/test/gen_event_SUITE.erl b/lib/stdlib/test/gen_event_SUITE.erl
index 9a7400c84e..3f949ca109 100644
--- a/lib/stdlib/test/gen_event_SUITE.erl
+++ b/lib/stdlib/test/gen_event_SUITE.erl
@@ -22,13 +22,17 @@
-include_lib("common_test/include/ct.hrl").
-export([all/0, suite/0,groups/0,init_per_suite/1, end_per_suite/1,
- init_per_group/2,end_per_group/2]).
+ init_per_group/2,end_per_group/2, init_per_testcase/2,
+ end_per_testcase/2]).
-export([start/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, call_format_status_anon/1,
error_format_status/1, get_state/1, replace_state/1,
- start_opt/1]).
+ start_opt/1,
+ undef_init/1, undef_handle_call/1, undef_handle_event/1,
+ undef_handle_info/1, undef_code_change/1, undef_terminate/1,
+ undef_in_terminate/1]).
suite() -> [{ct_hooks,[ts_install_cth]}].
@@ -36,13 +40,16 @@ all() ->
[start, {group, test_all}, hibernate,
call_format_status, call_format_status_anon, error_format_status,
get_state, replace_state,
- start_opt].
+ start_opt, {group, undef_callbacks}, undef_in_terminate].
groups() ->
[{test_all, [],
[add_handler, add_sup_handler, delete_handler,
swap_handler, swap_sup_handler, notify, sync_notify,
- call, info]}].
+ call, info]},
+ {undef_callbacks, [],
+ [undef_init, undef_handle_call, undef_handle_event, undef_handle_info,
+ undef_code_change, undef_terminate]}].
init_per_suite(Config) ->
Config.
@@ -50,12 +57,40 @@ init_per_suite(Config) ->
end_per_suite(_Config) ->
ok.
+init_per_group(undef_callbacks, Config) ->
+ DataDir = ?config(data_dir, Config),
+ Event1 = filename:join(DataDir, "oc_event.erl"),
+ {ok, oc_event} = compile:file(Event1),
+ Config;
init_per_group(_GroupName, Config) ->
Config.
end_per_group(_GroupName, Config) ->
Config.
+init_per_testcase(Case, Config) when Case == undef_handle_call;
+ Case == undef_handle_info;
+ Case == undef_handle_event;
+ Case == undef_code_change;
+ Case == undef_terminate ->
+ {ok, Pid} = oc_event:start(),
+ [{event_pid, Pid}|Config];
+init_per_testcase(undef_init, Config) ->
+ {ok, Pid} = gen_event:start({local, oc_init_event}),
+ [{event_pid, Pid}|Config];
+init_per_testcase(_Case, Config) ->
+ Config.
+
+end_per_testcase(Case, Config) when Case == undef_init;
+ Case == undef_handle_call;
+ Case == undef_handle_info;
+ Case == undef_handle_event;
+ Case == undef_code_change;
+ Case == undef_terminate ->
+ Pid = ?config(event_pid, Config),
+ gen_event:stop(Pid);
+end_per_testcase(_Case, _Config) ->
+ ok.
%% --------------------------------------
%% Start an event manager.
@@ -1055,3 +1090,92 @@ replace_state(Config) when is_list(Config) ->
ok = sys:resume(Pid),
[{dummy1_h,false,NState3}] = sys:get_state(Pid),
ok.
+
+%% No default provided for init, so it should fail
+undef_init(Config) ->
+ Pid = ?config(event_pid, Config),
+ {'EXIT', {undef, [{oc_init_event, init, [_], _}|_]}}
+ = gen_event:add_handler(Pid, oc_init_event, []),
+ ok.
+
+%% No default provided for init, so it should fail
+undef_handle_call(Config) when is_list(Config) ->
+ Pid = ?config(event_pid, Config),
+ {error, {'EXIT', {undef, [{oc_event, handle_call, _, _}|_]}}}
+ = gen_event:call(Pid, oc_event, call_msg),
+ [] = gen_event:which_handlers(Pid),
+ ok.
+
+%% No default provided for init, so it should fail
+undef_handle_event(Config) ->
+ Pid = ?config(event_pid, Config),
+ ok = gen_event:sync_notify(Pid, event_msg),
+ [] = gen_event:which_handlers(Pid),
+
+ gen_event:add_handler(oc_event, oc_event, []),
+ [oc_event] = gen_event:which_handlers(Pid),
+
+ ok = gen_event:notify(Pid, event_msg),
+ [] = gen_event:which_handlers(Pid),
+ ok.
+
+%% Defaulting to doing nothing with a log warning.
+undef_handle_info(Config) when is_list(Config) ->
+ error_logger_forwarder:register(),
+ Pid = ?config(event_pid, Config),
+ Pid ! hej,
+ wait_until_processed(Pid, hej, 10),
+ [oc_event] = gen_event:which_handlers(Pid),
+ receive
+ {warning_msg, _GroupLeader,
+ {Pid, "** Undefined handle_info in " ++ _, [oc_event, hej]}} ->
+ ok;
+ Other ->
+ io:format("Unexpected: ~p", [Other]),
+ ct:fail(failed)
+ end.
+
+wait_until_processed(_Pid, _Message, 0) ->
+ ct:fail(not_processed);
+wait_until_processed(Pid, Message, N) ->
+ {messages, Messages} = erlang:process_info(Pid, messages),
+ case lists:member(Message, Messages) of
+ true ->
+ timer:sleep(100),
+ wait_until_processed(Pid, Message, N-1);
+ false ->
+ ok
+ end.
+
+%% No default provided for init, so it should fail
+undef_code_change(Config) when is_list(Config) ->
+ Pid = ?config(event_pid, Config),
+ {error, {'EXIT', {undef, [{oc_event, code_change, [_, _, _], _}|_]}}} =
+ fake_upgrade(Pid, oc_event),
+ [oc_event] = gen_event:which_handlers(Pid),
+ ok.
+
+%% Defaulting to doing nothing. Test that it works when not defined.
+undef_terminate(Config) when is_list(Config) ->
+ Pid = ?config(event_pid, Config),
+ ok = gen_event:delete_handler(Pid, oc_event, []),
+ [] = gen_event:which_handlers(Pid),
+ ok.
+
+%% Test that the default implementation doesn't catch the wrong undef error
+undef_in_terminate(_Config) ->
+ {ok, Pid} = gen_event:start({local, dummy}),
+ State = {undef_in_terminate, {dummy_h, terminate}},
+ ok = gen_event:add_handler(Pid, dummy_h, {state, State}),
+ [dummy_h] = gen_event:which_handlers(Pid),
+ {'EXIT', {undef, [{dummy_h, terminate, [], []}|_]}}
+ = gen_event:delete_handler(Pid, dummy_h, []),
+ [] = gen_event:which_handlers(Pid),
+ ok.
+
+fake_upgrade(Pid, Mod) ->
+ sys:suspend(Pid),
+ sys:replace_state(Pid, fun(S) -> {new, S} end),
+ Ret = sys:change_code(Pid, Mod, old_vsn, []),
+ ok = sys:resume(Pid),
+ Ret.
diff --git a/lib/stdlib/test/gen_event_SUITE_data/oc_event.erl b/lib/stdlib/test/gen_event_SUITE_data/oc_event.erl
new file mode 100644
index 0000000000..eb664ef550
--- /dev/null
+++ b/lib/stdlib/test/gen_event_SUITE_data/oc_event.erl
@@ -0,0 +1,40 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2017. All Rights Reserved.
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%% http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%% %CopyrightEnd%
+%%
+-module(oc_event).
+
+-behaviour(gen_event).
+
+%% API
+-export([start/0]).
+
+%% gen_event callbacks
+-export([init/1]).
+
+-define(SERVER, ?MODULE).
+
+-record(state, {}).
+
+start() ->
+ {ok, Pid} = gen_event:start({local, ?SERVER}),
+ gen_event:add_handler(?SERVER, ?MODULE, []),
+ {ok, Pid}.
+
+init([]) ->
+ {ok, #state{}}.
diff --git a/lib/stdlib/test/gen_fsm_SUITE.erl b/lib/stdlib/test/gen_fsm_SUITE.erl
index d6bb002b5f..361680a9b2 100644
--- a/lib/stdlib/test/gen_fsm_SUITE.erl
+++ b/lib/stdlib/test/gen_fsm_SUITE.erl
@@ -39,6 +39,11 @@
call_format_status/1, error_format_status/1, terminate_crash_format/1,
get_state/1, replace_state/1]).
+-export([undef_handle_event/1, undef_handle_sync_event/1, undef_handle_info/1,
+ undef_init/1, undef_code_change/1, undef_terminate1/1, undef_terminate2/1]).
+
+-export([undef_in_handle_info/1, undef_in_terminate/1]).
+
-export([hibernate/1,hiber_idle/3,hiber_wakeup/3,hiber_idle/2,hiber_wakeup/2]).
-export([enter_loop/1]).
@@ -48,7 +53,7 @@
%% The gen_fsm behaviour
-export([init/1, handle_event/3, handle_sync_event/4, terminate/3,
- handle_info/3, format_status/2]).
+ handle_info/3, format_status/2, code_change/4]).
-export([idle/2, idle/3,
timeout/2,
wfor_conf/2, wfor_conf/3,
@@ -63,7 +68,8 @@ suite() -> [{ct_hooks,[ts_install_cth]}].
all() ->
[{group, start}, {group, abnormal}, shutdown,
- {group, sys}, hibernate, enter_loop].
+ {group, sys}, hibernate, enter_loop, {group, undef_callbacks},
+ undef_in_handle_info, undef_in_terminate].
groups() ->
[{start, [],
@@ -74,7 +80,10 @@ groups() ->
{abnormal, [], [abnormal1, abnormal2]},
{sys, [],
[sys1, call_format_status, error_format_status, terminate_crash_format,
- get_state, replace_state]}].
+ get_state, replace_state]},
+ {undef_callbacks, [],
+ [undef_handle_event, undef_handle_sync_event, undef_handle_info,
+ undef_init, undef_code_change, undef_terminate1, undef_terminate2]}].
init_per_suite(Config) ->
Config.
@@ -82,6 +91,11 @@ init_per_suite(Config) ->
end_per_suite(_Config) ->
ok.
+init_per_group(undef_callbacks, Config) ->
+ DataDir = ?config(data_dir, Config),
+ Server = filename:join(DataDir, "oc_fsm.erl"),
+ {ok, oc_fsm} = compile:file(Server),
+ Config;
init_per_group(_GroupName, Config) ->
Config.
@@ -868,6 +882,99 @@ enter_loop(Reg1, Reg2) ->
gen_fsm:enter_loop(?MODULE, [], state0, [])
end.
+%% Start should return an undef error if init isn't implemented
+undef_init(Config) when is_list(Config) ->
+ {error, {undef, [{oc_init_fsm, init, [[]], []}|_]}}
+ = gen_fsm:start(oc_init_fsm, [], []),
+ ok.
+
+%% Test that the server crashes correctly if the handle_event callback is
+%% not exported in the callback module
+undef_handle_event(Config) when is_list(Config) ->
+ {ok, FSM} = gen_fsm:start(oc_fsm, [], []),
+ MRef = monitor(process, FSM),
+ gen_fsm:send_all_state_event(FSM, state_name),
+ ok = verify_undef_down(MRef, FSM, oc_fsm, handle_event).
+
+%% Test that the server crashes correctly if the handle_sync_event callback is
+%% not exported in the callback module
+undef_handle_sync_event(Config) when is_list(Config) ->
+ {ok, FSM} = gen_fsm:start(oc_fsm, [], []),
+ try
+ gen_fsm:sync_send_all_state_event(FSM, state_name),
+ ct:fail(should_crash)
+ catch exit:{{undef, [{oc_fsm, handle_sync_event, _, _}|_]},_} ->
+ ok
+ end.
+
+%% The fsm should log but not crash if the handle_info callback is
+%% calling an undefined function
+undef_handle_info(Config) when is_list(Config) ->
+ error_logger_forwarder:register(),
+ {ok, FSM} = gen_fsm:start(oc_fsm, [], []),
+ MRef = monitor(process, FSM),
+ FSM ! hej,
+ receive
+ {'DOWN', MRef, process, FSM, _} ->
+ ct:fail(should_not_crash)
+ after 500 ->
+ ok
+ end,
+ receive
+ {warning_msg, _GroupLeader,
+ {FSM, "** Undefined handle_info in " ++ _, [oc_fsm, hej]}} ->
+ ok;
+ Other ->
+ io:format("Unexpected: ~p", [Other]),
+ ct:fail(failed)
+ end.
+
+%% The upgrade should fail if code_change is expected in the callback module
+%% but not exported, but the fsm should continue with the old code
+undef_code_change(Config) when is_list(Config) ->
+ {ok, FSM} = gen_fsm:start(oc_fsm, [], []),
+ {error, {'EXIT', {undef, [{oc_fsm, code_change, [_, _, _, _], _}|_]}}}
+ = fake_upgrade(FSM, oc_fsm),
+ ok.
+
+%% Test the default implementation of terminate with normal reason if the
+%% callback module does not export it
+undef_terminate1(Config) when is_list(Config) ->
+ {ok, FSM} = gen_fsm:start(oc_fsm, [], []),
+ MRef = monitor(process, FSM),
+ ok = gen_fsm:stop(FSM),
+ ok = verify_down_reason(MRef, FSM, normal).
+
+%% Test the default implementation of terminate with error reason if the
+%% callback module does not export it
+undef_terminate2(Config) when is_list(Config) ->
+ {ok, FSM} = gen_fsm:start(oc_fsm, [], []),
+ MRef = monitor(process, FSM),
+ ok = gen_fsm:stop(FSM, {error, test}, infinity),
+ ok = verify_down_reason(MRef, FSM, {error, test}).
+
+%% Test that the server crashes correctly if the handle_info callback is
+%% calling an undefined function
+undef_in_handle_info(Config) when is_list(Config) ->
+ {ok, FSM} = gen_fsm:start(?MODULE, [], []),
+ MRef = monitor(process, FSM),
+ FSM ! {call_undef_fun, {?MODULE, handle_info}},
+ verify_undef_down(MRef, FSM, ?MODULE, handle_info),
+ ok.
+
+%% Test that the server crashes correctly if the terminate callback is
+%% calling an undefined function
+undef_in_terminate(Config) when is_list(Config) ->
+ State = {undef_in_terminate, {?MODULE, terminate}},
+ {ok, FSM} = gen_fsm:start(?MODULE, {state_data, State}, []),
+ try
+ gen_fsm:stop(FSM),
+ ct:fail(failed)
+ catch
+ exit:{undef, [{?MODULE, terminate, _, _}|_]} ->
+ ok
+ end.
+
%%
%% Functionality check
%%
@@ -962,7 +1069,31 @@ do_sync_disconnect(FSM) ->
yes = gen_fsm:sync_send_event(FSM, disconnect),
check_state(FSM, idle).
+verify_down_reason(MRef, Pid, Reason) ->
+ receive
+ {'DOWN', MRef, process, Pid, Reason} ->
+ ok;
+ {'DOWN', MRef, process, Pid, Other}->
+ ct:fail({wrong_down_reason, Other})
+ after 5000 ->
+ ct:fail(should_shutdown)
+ end.
+verify_undef_down(MRef, Pid, Mod, Fun) ->
+ ok = receive
+ {'DOWN', MRef, process, Pid,
+ {undef, [{Mod, Fun, _, _}|_]}} ->
+ ok
+ after 5000 ->
+ ct:fail(should_crash)
+ end.
+
+fake_upgrade(Pid, Mod) ->
+ sys:suspend(Pid),
+ sys:replace_state(Pid, fun(State) -> {new, State} end),
+ Ret = sys:change_code(Pid, Mod, old_vsn, []),
+ ok = sys:resume(Pid),
+ Ret.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%
@@ -992,6 +1123,9 @@ init(_) ->
terminate(_, _State, crash_terminate) ->
exit({crash, terminate});
+terminate(_, _, {undef_in_terminate, {Mod, Fun}}) ->
+ Mod:Fun(),
+ ok;
terminate({From, stopped}, State, _Data) ->
From ! {self(), {stopped, State}},
ok;
@@ -1089,7 +1223,9 @@ handle_info(hibernate_now, _SName, _State) ->
{next_state, hiber_idle, [], hibernate};
handle_info(hibernate_later, _SName, _State) ->
{next_state, hiber_idle, hibernate_me, 1000};
-
+handle_info({call_undef_fun, {Mod, Fun}}, State, Data) ->
+ Mod:Fun(),
+ {next_state, State, Data};
handle_info(Info, _State, Data) ->
{stop, {unexpected,Info}, Data}.
@@ -1134,6 +1270,13 @@ format_status(terminate, [_Pdict, StateData]) ->
format_status(normal, [_Pdict, _StateData]) ->
[format_status_called].
+code_change(_OldVsn, State,
+ {idle, {undef_in_code_change, {Mod, Fun}}} = Data, _Extra) ->
+ Mod:Fun(),
+ {ok, State, Data};
+code_change(_OldVsn, State, Data, _Extra) ->
+ {ok, State, Data}.
+
get_messages() ->
receive
Msg -> [Msg|get_messages()]
diff --git a/lib/stdlib/test/gen_fsm_SUITE_data/oc_fsm.erl b/lib/stdlib/test/gen_fsm_SUITE_data/oc_fsm.erl
new file mode 100644
index 0000000000..27fb1bc3b6
--- /dev/null
+++ b/lib/stdlib/test/gen_fsm_SUITE_data/oc_fsm.erl
@@ -0,0 +1,48 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2017. All Rights Reserved.
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%% http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%% %CopyrightEnd%
+%%
+-module(oc_fsm).
+
+-behaviour(gen_fsm).
+
+%% API
+-export([start/0]).
+
+%% gen_fsm callbacks
+-export([init/1,
+ state_name/2,
+ state_name/3]).
+
+-define(SERVER, ?MODULE).
+
+-record(state, {}).
+
+start() ->
+ gen_fsm:start({local, ?SERVER}, ?MODULE, [], []).
+
+init([]) ->
+ {ok, state_name, #state{}}.
+
+state_name(_Event, State) ->
+ {next_state, state_name, State}.
+
+state_name(_Event, _From, State) ->
+ Reply = ok,
+ {reply, Reply, state_name, State}.
+
diff --git a/lib/stdlib/test/gen_server_SUITE.erl b/lib/stdlib/test/gen_server_SUITE.erl
index 6888cb8c58..3fb9b3627b 100644
--- a/lib/stdlib/test/gen_server_SUITE.erl
+++ b/lib/stdlib/test/gen_server_SUITE.erl
@@ -34,7 +34,10 @@
spec_init_global_registered_parent/1,
otp_5854/1, hibernate/1, otp_7669/1, call_format_status/1,
error_format_status/1, terminate_crash_format/1,
- get_state/1, replace_state/1, call_with_huge_message_queue/1
+ get_state/1, replace_state/1, call_with_huge_message_queue/1,
+ undef_handle_call/1, undef_handle_cast/1, undef_handle_info/1,
+ undef_init/1, undef_code_change/1, undef_terminate1/1,
+ undef_terminate2/1, undef_in_terminate/1, undef_in_handle_info/1
]).
-export([stop1/1, stop2/1, stop3/1, stop4/1, stop5/1, stop6/1, stop7/1,
@@ -50,7 +53,7 @@
%% The gen_server behaviour
-export([init/1, handle_call/3, handle_cast/2,
- handle_info/2, terminate/2, format_status/2]).
+ handle_info/2, code_change/3, terminate/2, format_status/2]).
suite() ->
[{ct_hooks,[ts_install_cth]},
@@ -66,11 +69,16 @@ all() ->
otp_7669,
call_format_status, error_format_status, terminate_crash_format,
get_state, replace_state,
- call_with_huge_message_queue].
+ call_with_huge_message_queue, {group, undef_callbacks},
+ undef_in_terminate, undef_in_handle_info].
groups() ->
[{stop, [],
- [stop1, stop2, stop3, stop4, stop5, stop6, stop7, stop8, stop9, stop10]}].
+ [stop1, stop2, stop3, stop4, stop5, stop6, stop7, stop8, stop9, stop10]},
+ {undef_callbacks, [],
+ [undef_handle_call, undef_handle_cast, undef_handle_info,
+ undef_init, undef_code_change, undef_terminate1, undef_terminate2]}].
+
init_per_suite(Config) ->
Config.
@@ -78,6 +86,11 @@ init_per_suite(Config) ->
end_per_suite(_Config) ->
ok.
+init_per_group(undef_callbacks, Config) ->
+ DataDir = ?config(data_dir, Config),
+ Server = filename:join(DataDir, "oc_server.erl"),
+ {ok, oc_server} = compile:file(Server),
+ Config;
init_per_group(_GroupName, Config) ->
Config.
@@ -93,6 +106,7 @@ init_per_testcase(Case, Config) when Case == call_remote1;
Case == call_remote_n3 ->
{ok,N} = start_node(hubba),
[{node,N} | Config];
+
init_per_testcase(_Case, Config) ->
Config.
@@ -1260,6 +1274,141 @@ echo_loop() ->
echo_loop()
end.
+%% Test the default implementation of terminate if the callback module
+%% does not export it
+undef_terminate1(Config) when is_list(Config) ->
+ {ok, Server} = gen_server:start(oc_server, [], []),
+ MRef = monitor(process, Server),
+ ok = gen_server:stop(Server),
+ ok = verify_down_reason(MRef, Server, normal).
+
+%% Test the default implementation of terminate if the callback module
+%% does not export it
+undef_terminate2(Config) when is_list(Config) ->
+ {ok, Server} = gen_server:start(oc_server, [], []),
+ MRef = monitor(process, Server),
+ ok = gen_server:stop(Server, {error, test}, infinity),
+ ok = verify_down_reason(MRef, Server, {error, test}).
+
+%% Start should return an undef error if init isn't implemented
+undef_init(_Config) ->
+ {error, {undef, [{oc_init_server, init, [_], _}|_]}} =
+ gen_server:start(oc_init_server, [], []),
+ process_flag(trap_exit, true),
+ {error, {undef, [{oc_init_server, init, [_], _}|_]}} =
+ (catch gen_server:start_link(oc_init_server, [], [])),
+ receive
+ {'EXIT', Server,
+ {undef, [{oc_init_server, init, [_], _}|_]}} when is_pid(Server) ->
+ ok
+ after 1000 ->
+ ct:fail(expected_exit_msg)
+ end.
+
+%% The upgrade should fail if code_change is expected in the callback module
+%% but not exported, but the server should continue with the old code
+undef_code_change(Config) when is_list(Config) ->
+ {ok, Server} = gen_server:start(oc_server, [], []),
+ {error, {'EXIT', {undef, [{oc_server, code_change, [_, _, _], _}|_]}}}
+ = fake_upgrade(Server, ?MODULE),
+ true = is_process_alive(Server).
+
+%% The server should crash if the handle_call callback is
+%% not exported in the callback module
+undef_handle_call(_Config) ->
+ {ok, Server} = gen_server:start(oc_server, [], []),
+ try
+ gen_server:call(Server, call_msg),
+ ct:fail(should_crash)
+ catch exit:{{undef, [{oc_server, handle_call, _, _}|_]},
+ {gen_server, call, _}} ->
+ ok
+ end.
+
+%% The server should crash if the handle_cast callback is
+%% not exported in the callback module
+undef_handle_cast(_Config) ->
+ {ok, Server} = gen_server:start(oc_server, [], []),
+ MRef = monitor(process, Server),
+ gen_server:cast(Server, cast_msg),
+ verify_undef_down(MRef, Server, oc_server, handle_cast),
+ ok.
+
+%% The server should log but not crash if the handle_info callback is
+%% calling an undefined function
+undef_handle_info(Config) when is_list(Config) ->
+ error_logger_forwarder:register(),
+ {ok, Server} = gen_server:start(oc_server, [], []),
+ Server ! hej,
+ wait_until_processed(Server, hej, 10),
+ true = is_process_alive(Server),
+ receive
+ {warning_msg, _GroupLeader,
+ {Server, "** Undefined handle_info in " ++ _, [oc_server, hej]}} ->
+ ok;
+ Other ->
+ io:format("Unexpected: ~p", [Other]),
+ ct:fail(failed)
+ end.
+
+%% Test that the default implementation of terminate isn't catching the
+%% wrong undef error
+undef_in_terminate(Config) when is_list(Config) ->
+ State = {undef_in_terminate, {oc_server, terminate}},
+ {ok, Server} = gen_server:start(?MODULE, {state, State}, []),
+ try
+ gen_server:stop(Server),
+ ct:fail(failed)
+ catch
+ exit:{undef, [{oc_server, terminate, [], _}|_]} ->
+ ok
+ end.
+
+%% Test that the default implementation of handle_info isn't catching the
+%% wrong undef error
+undef_in_handle_info(Config) when is_list(Config) ->
+ {ok, Server} = gen_server:start(?MODULE, [], []),
+ MRef = monitor(process, Server),
+ Server ! {call_undef_fun, ?MODULE, handle_info},
+ verify_undef_down(MRef, Server, ?MODULE, handle_info),
+ ok.
+
+verify_down_reason(MRef, Server, Reason) ->
+ receive
+ {'DOWN', MRef, process, Server, Reason} ->
+ ok
+ after 5000 ->
+ ct:fail(failed)
+ end.
+
+verify_undef_down(MRef, Pid, Mod, Fun) ->
+ ok = receive
+ {'DOWN', MRef, process, Pid,
+ {undef, [{Mod, Fun, _, _}|_]}} ->
+ ok
+ after 5000 ->
+ ct:fail(should_crash)
+ end.
+
+fake_upgrade(Pid, Mod) ->
+ sys:suspend(Pid),
+ sys:replace_state(Pid, fun(State) -> {new, State} end),
+ Ret = sys:change_code(Pid, Mod, old_vsn, []),
+ ok = sys:resume(Pid),
+ Ret.
+
+wait_until_processed(_Pid, _Message, 0) ->
+ ct:fail(not_processed);
+wait_until_processed(Pid, Message, N) ->
+ {messages, Messages} = erlang:process_info(Pid, messages),
+ case lists:member(Message, Messages) of
+ true ->
+ timer:sleep(100),
+ wait_until_processed(Pid, Message, N-1);
+ false ->
+ ok
+ end.
+
%%--------------------------------------------------------------
%% Help functions to spec_init_*
start_link(Init, Options) ->
@@ -1383,6 +1532,9 @@ handle_call(stop_shutdown, _From, State) ->
{stop,shutdown,State};
handle_call(shutdown_reason, _From, _State) ->
exit({shutdown,reason});
+handle_call({call_undef_fun, Mod, Fun}, _From, State) ->
+ Mod:Fun(),
+ {reply, ok, State};
handle_call(stop_shutdown_reason, _From, State) ->
{stop,{shutdown,stop_reason},State}.
@@ -1396,6 +1548,9 @@ handle_cast(hibernate_now, _State) ->
handle_cast(hibernate_later, _State) ->
timer:send_after(1000,self(),hibernate_now),
{noreply, []};
+handle_cast({call_undef_fun, Mod, Fun}, State) ->
+ Mod:Fun(),
+ {noreply, State};
handle_cast({From, stop}, State) ->
io:format("BAZ"),
{stop, {From,stopped}, State}.
@@ -1420,6 +1575,9 @@ handle_info(timeout, {delayed_cast, From}) ->
handle_info(timeout, {delayed_info, From}) ->
From ! {self(), delayed_info},
{noreply, []};
+handle_info({call_undef_fun, Mod, Fun}, State) ->
+ Mod:Fun(),
+ {noreply, State};
handle_info({From, handle_info}, _State) ->
From ! {self(), handled_info},
{noreply, []};
@@ -1433,6 +1591,12 @@ handle_info({From, stop}, State) ->
handle_info(_Info, State) ->
{noreply, State}.
+code_change(_OldVsn,
+ {new, {undef_in_code_change, {Mod, Fun}}} = State,
+ _Extra) ->
+ Mod:Fun(),
+ {ok, State}.
+
terminate({From, stopped}, _State) ->
io:format("FOOBAR"),
From ! {self(), stopped},
@@ -1442,6 +1606,9 @@ terminate({From, stopped_info}, _State) ->
ok;
terminate(_, crash_terminate) ->
exit({crash, terminate});
+terminate(_, {undef_in_terminate, {Mod, Fun}}) ->
+ Mod:Fun(),
+ ok;
terminate(_Reason, _State) ->
ok.
diff --git a/lib/stdlib/test/gen_server_SUITE_data/oc_server.erl b/lib/stdlib/test/gen_server_SUITE_data/oc_server.erl
new file mode 100644
index 0000000000..4ba37987f3
--- /dev/null
+++ b/lib/stdlib/test/gen_server_SUITE_data/oc_server.erl
@@ -0,0 +1,37 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2017. All Rights Reserved.
+%%
+%% Licensed under the Apache License, Version 2.0 (the "License");
+%% you may not use this file except in compliance with the License.
+%% You may obtain a copy of the License at
+%%
+%% http://www.apache.org/licenses/LICENSE-2.0
+%%
+%% Unless required by applicable law or agreed to in writing, software
+%% distributed under the License is distributed on an "AS IS" BASIS,
+%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+%% See the License for the specific language governing permissions and
+%% limitations under the License.
+%%
+%% %CopyrightEnd%
+%%
+-module(oc_server).
+
+-behaviour(gen_server).
+
+%% API
+-export([start/0]).
+
+%% gen_server callbacks
+-export([init/1]).
+
+-record(state, {}).
+
+start() ->
+ gen_server:start({local, ?MODULE}, ?MODULE, [], []).
+
+init([]) ->
+ {ok, #state{}}.
+