File 0129-Polish-the-code.patch of Package erlang
From 4cfa8f47dccb57091fb4e9af43e40fc14f379ee3 Mon Sep 17 00:00:00 2001
From: Raimo Niskanen <raimo@erlang.org>
Date: Fri, 21 Feb 2025 14:30:47 +0100
Subject: [PATCH 3/6] Polish the code
---
lib/stdlib/src/gen_statem.erl | 196 ++++++++++++++++++----------------
1 file changed, 106 insertions(+), 90 deletions(-)
diff --git a/lib/stdlib/src/gen_statem.erl b/lib/stdlib/src/gen_statem.erl
index a1d802a689..6f3fc3c534 100644
--- a/lib/stdlib/src/gen_statem.erl
+++ b/lib/stdlib/src/gen_statem.erl
@@ -839,7 +839,7 @@ and returns. Here are the sequence of steps for a _state transition_:
from the top of this sequence.
> #### Note {: .info }
-> The behaviour of a zero time-out (a time-out with time `0`)
+> The behaviour of a time-out zero (a time-out with time `0`)
> differs subtly from Erlang's `receive ... after 0 ... end`.
>
> The latter receives one message if there is one,
@@ -2101,12 +2101,24 @@ event_type(Type) ->
postponed = [] :: [{event_type(),event_content()}],
timers = #{t0q => []} ::
#{
- %% Timeout 0 Queue.
- %% Marked in the table with TimerRef = 0.
- %% Stored here because they also are updated
- %% by e.g cancel_timer/3.
+ %% Time-out zero Queue.
+ %%
+ %% The t0q is in limbo between the process message mailbox
+ %% and the internal received but not processed event queue.
+ %%
+ %% A time-out zero timer is stored by TimeoutType here
+ %% just like a started timer, but with TimerRef = 0,
+ %% and also in t0q, in start order which is the same
+ %% as trigger order since a new time-out zero event
+ %% is inserted at the end, as the last to trigger.
+ %%
+ %% cancel_timer/3 cancels a timer even if it is in this queue.
+ %%
't0q' := [timeout_event_type()],
+ %% Timer store, keyed by TimeoutType since we want
+ %% to cancel by key.
+ %%
TimeoutType :: timeout_event_type() =>
{TimerRef :: reference() | 0,
TimeoutMsg :: event_content()}},
@@ -3894,44 +3906,36 @@ loop_state_callback_result(
Q)
end.
-%% Ensure that Actions is a list
-%%
-loop_actions(
- P, Debug, S, Q, NextState_NewData,
- NextEventsR, Hibernate, TimeoutsR, Postpone,
- CallEnter, _StateCall, []) ->
- loop_actions(
- P, Debug, S, Q, NextState_NewData,
- NextEventsR, Hibernate, TimeoutsR, Postpone,
- CallEnter);
-loop_actions(
- P, Debug, S, Q, NextState_NewData,
- NextEventsR, Hibernate, TimeoutsR, Postpone,
- CallEnter, StateCall, Actions) ->
- %%
- loop_actions_list(
- P, Debug, S, Q, NextState_NewData,
- NextEventsR, Hibernate, TimeoutsR, Postpone,
- CallEnter, StateCall, listify(Actions)).
+%% Shorcut for no actions and exit from loop when done with Actions
%%
-%% Shortcut for no actions
loop_actions(
P, Debug, S, Q, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postpone,
CallEnter) ->
%%
- %% Shortcut for no actions
case CallEnter andalso P#params.state_enter of
- true ->
+ true when CallEnter ->
loop_state_enter(
P, Debug, S, Q, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postpone);
- false ->
+ false ->
loop_state_transition(
P, Debug, S, Q, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postpone)
end.
+%% Ensure that Actions is a list
+%%
+loop_actions(
+ P, Debug, S, Q, NextState_NewData,
+ NextEventsR, Hibernate, TimeoutsR, Postpone,
+ CallEnter, StateCall, Actions) ->
+ %%
+ loop_actions_list(
+ P, Debug, S, Q, NextState_NewData,
+ NextEventsR, Hibernate, TimeoutsR, Postpone,
+ CallEnter, StateCall, listify(Actions)).
+
%% Process the returned actions
%%
loop_actions_list(
@@ -3939,16 +3943,10 @@ loop_actions_list(
NextEventsR, Hibernate, TimeoutsR, Postpone,
CallEnter, _StateCall, []) ->
%%
- case P#params.state_enter of
- true when CallEnter ->
- loop_state_enter(
- P, Debug, S, Q, NextState_NewData,
- NextEventsR, Hibernate, TimeoutsR, Postpone);
- _ ->
- loop_state_transition(
- P, Debug, S, Q, NextState_NewData,
- NextEventsR, Hibernate, TimeoutsR, Postpone)
- end;
+ loop_actions(
+ P, Debug, S, Q, NextState_NewData,
+ NextEventsR, Hibernate, TimeoutsR, Postpone,
+ CallEnter);
loop_actions_list(
P, Debug, S, Q, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postpone,
@@ -4473,7 +4471,7 @@ loop_next_events(
Timers) ->
%%
%% Optimization when there are no timeouts
- %% hence no zero timeout events to append to Events
+ %% hence no time-out zero events to append to Events
%% - avoid loop_timeouts
loop_done(
P, Debug,
@@ -4490,25 +4488,25 @@ loop_next_events(
Timers) ->
%%
Seen = #{},
- TimeoutEvents = [],
+ T0Events = [],
loop_timeouts(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers, Seen, TimeoutEvents).
+ Timers, Seen, T0Events).
-%% Continue state transition with processing of timeouts
+%% Continue state transition with processing of time-outs
%% and finally inserted events
%%
loop_timeouts(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, [], Postponed,
- Timers, _Seen, TimeoutEvents) ->
+ Timers, _Seen, T0Events) ->
%%
- %% End of timeouts
+ %% End of time-outs
%%
- case TimeoutEvents of
+ case T0Events of
[] ->
S_1 =
S#state{
@@ -4523,7 +4521,7 @@ loop_timeouts(
S#state{
state_data = NextState_NewData,
postponed = Postponed,
- timers = Timers#{t0q := T0Q ++ TimeoutEvents},
+ timers = Timers#{t0q := T0Q ++ T0Events},
hibernate = Hibernate},
loop_done(P, Debug, S_1, Events, NextEventsR)
end;
@@ -4531,7 +4529,7 @@ loop_timeouts(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, [Timeout|TimeoutsR], Postponed,
- Timers, Seen, TimeoutEvents) ->
+ Timers, Seen, T0Events) ->
%%
TimeoutType = element(1, Timeout),
case Seen of
@@ -4541,35 +4539,35 @@ loop_timeouts(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers, Seen, TimeoutEvents);
+ Timers, Seen, T0Events);
#{} ->
case Timeout of
{_,Time,TimeoutMsg} ->
%% Relative timeout or update
- loop_timeouts_start(
+ loop_timeouts(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers, Seen, TimeoutEvents,
+ Timers, Seen, T0Events,
TimeoutType, Time, TimeoutMsg, []);
{_,Time,TimeoutMsg,TimeoutOpts} ->
%% Absolute timeout
- loop_timeouts_start(
+ loop_timeouts(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers, Seen, TimeoutEvents,
+ Timers, Seen, T0Events,
TimeoutType, Time, TimeoutMsg, listify(TimeoutOpts))
end
end.
-%% Loop helper to start or restart a timeout
+%% Loop helper to handle one time-out
%%
-loop_timeouts_start(
+loop_timeouts(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers, Seen, TimeoutEvents,
+ Timers, Seen, T0Events,
TimeoutType, Time, TimeoutMsg, TimeoutOpts) ->
%%
case Time of
@@ -4579,24 +4577,24 @@ loop_timeouts_start(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers, Seen, TimeoutEvents,
+ Timers, Seen, T0Events,
TimeoutType);
update ->
loop_timeouts_update(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers, Seen, TimeoutEvents,
+ Timers, Seen, T0Events,
TimeoutType, TimeoutMsg);
0 ->
- %% (Re)start zero timeout
+ %% (Re)start time-out zero
TimerRef = 0,
- TimeoutEvents_1 = [TimeoutType | TimeoutEvents],
+ T0Events_1 = [TimeoutType | T0Events],
loop_timeouts_register(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers, Seen, TimeoutEvents_1,
+ Timers, Seen, T0Events_1,
TimeoutType, Time, TimeoutMsg, TimeoutOpts, TimerRef);
_ ->
%% (Re)start the timer
@@ -4606,7 +4604,7 @@ loop_timeouts_start(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers, Seen, TimeoutEvents,
+ Timers, Seen, T0Events,
TimeoutType, Time, TimeoutMsg, TimeoutOpts, TimerRef)
end.
@@ -4617,7 +4615,7 @@ loop_timeouts_register(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers, Seen, TimeoutEvents,
+ Timers, Seen, T0Events,
TimeoutType, Time, TimeoutMsg, TimeoutOpts, TimerRef) ->
%%
case Debug of
@@ -4625,7 +4623,7 @@ loop_timeouts_register(
loop_timeouts_register(
P, Debug, S, Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers, Seen, TimeoutEvents,
+ Timers, Seen, T0Events,
TimeoutType, TimerRef, TimeoutMsg);
_ ->
{State,_Data} = NextState_NewData,
@@ -4638,21 +4636,21 @@ loop_timeouts_register(
loop_timeouts_register(
P, Debug_1, S, Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers, Seen, TimeoutEvents,
+ Timers, Seen, T0Events,
TimeoutType, TimerRef, TimeoutMsg)
end.
%%
loop_timeouts_register(
P, Debug, S, Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers, Seen, TimeoutEvents,
+ Timers, Seen, T0Events,
TimeoutType, TimerRef, TimeoutMsg) ->
%%
case Timers of
#{TimeoutType := {0,_OldTimeoutMsg},
t0q := T0Q} ->
- %% Cancel the running timer,
- %% and update timer type and ref
+ %% There is no running timer, but cancel the
+ %% time-out zero event and register the new timer
Timers_1 =
Timers
#{TimeoutType := {0,TimeoutMsg},
@@ -4661,25 +4659,24 @@ loop_timeouts_register(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers_1, Seen#{TimeoutType => true}, TimeoutEvents);
+ Timers_1, Seen#{TimeoutType => true}, T0Events);
#{TimeoutType := {OldTimerRef,_OldTimeoutMsg}} ->
- %% Cancel the running timer,
- %% and update timer type and ref
+ %% Cancel the running timer, and register the new
cancel_timer(OldTimerRef),
Timers_1 = Timers#{TimeoutType := {TimerRef,TimeoutMsg}},
loop_timeouts(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers_1, Seen#{TimeoutType => true}, TimeoutEvents);
+ Timers_1, Seen#{TimeoutType => true}, T0Events);
#{} ->
- %% Insert the new timer type and ref
+ %% Register the new timer
Timers_1 = Timers#{TimeoutType => {TimerRef,TimeoutMsg}},
loop_timeouts(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers_1, Seen#{TimeoutType => true}, TimeoutEvents)
+ Timers_1, Seen#{TimeoutType => true}, T0Events)
end.
%% Loop helper to cancel a timeout
@@ -4688,14 +4685,14 @@ loop_timeouts_cancel(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers, Seen, TimeoutEvents, TimeoutType) ->
+ Timers, Seen, T0Events, TimeoutType) ->
%% This function body should have been:
%% Timers_1 = cancel_timer(TimeoutType, Timers),
%% loop_timeouts(
%% P, Debug, S,
%% Events, NextState_NewData,
%% NextEventsR, Hibernate, TimeoutsR, Postponed,
- %% Timers_1, Seen#{TimeoutType => true}, TimeoutEvents).
+ %% Timers_1, Seen#{TimeoutType => true}, T0Events).
%%
%% Explicitly separate cases to get separate code paths for when
%% the map key exists vs. not, since otherwise the external call
@@ -4710,23 +4707,34 @@ loop_timeouts_cancel(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers_1, Seen#{TimeoutType => true}, TimeoutEvents);
+ Timers_1, Seen#{TimeoutType => true}, T0Events);
#{} ->
loop_timeouts(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers, Seen#{TimeoutType => true}, TimeoutEvents)
+ Timers, Seen#{TimeoutType => true}, T0Events)
end.
-%% Loop helper to update the timeout message,
-%% or start a zero timeout if no timer is running
+%% Loop helper to update the time-out message for a running timer.
+%%
+%% If there is no such running timer it is probably a user mistake.
+%% But we cannot return an error, so we make the best of the situation,
+%% as in pretend that we immediately start at timer and update the message.
+%%
+%% We have no time-out value for the timer so we must select between
+%% 0 or 'infinity' since any other would be plain stupid.
+%% We select a 0 time-out since 'infinity' would render a timer
+%% that would never expire so the user mistake would be silently ignored.
+%%
+%% With time 0 an event has to be immediately created so the user will
+%% at least get a surprising message, which should be the best we can do...
%%
loop_timeouts_update(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
- Timers, Seen, TimeoutEvents,
+ Timers, Seen, T0Events,
TimeoutType, TimeoutMsg) ->
%%
case Timers of
@@ -4737,16 +4745,16 @@ loop_timeouts_update(
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
Timers_1, Seen#{TimeoutType => true},
- TimeoutEvents);
+ T0Events);
#{} ->
Timers_1 = Timers#{TimeoutType => {0, TimeoutMsg}},
- TimeoutEvents_1 = [TimeoutType|TimeoutEvents],
+ T0Events_1 = [TimeoutType|T0Events],
loop_timeouts(
P, Debug, S,
Events, NextState_NewData,
NextEventsR, Hibernate, TimeoutsR, Postponed,
Timers_1, Seen#{TimeoutType => true},
- TimeoutEvents_1)
+ T0Events_1)
end.
%% Place inserted events first in the event queue
@@ -4764,7 +4772,7 @@ loop_done(P, Debug, S, Events, NextEventsR) ->
end.
%%
%% State transition is done, keep looping if there are
-%% enqueued events, or if there are zero timeouts,
+%% enqueued events, or if there are time-out zero events,
%% otherwise get a new event
%%
loop_done(P, Debug, S, Q) ->
@@ -4776,19 +4784,25 @@ loop_done(P, Debug, S, Q) ->
case Q of
[] ->
case S#state.timers of
- #{t0q := [TimeoutType|_]} = Timers ->
- #{TimeoutType := {0 = TimerRef, TimeoutMsg}} = Timers,
- Timers_1 = cancel_timer(TimeoutType, TimerRef, Timers),
+ #{t0q := [TimeoutType|TimeoutTypes]} = Timers ->
+ %%
+ %% Take the first event from the time-out zero queue
+ %%
+ #{TimeoutType := {0, TimeoutMsg}} = Timers,
+ Timers_1 =
+ maps:remove(
+ TimeoutType, Timers#{t0q := TimeoutTypes}),
S_1 = S#state{timers = Timers_1},
Event = {TimeoutType,TimeoutMsg},
loop_msg_event(
P, Debug, S_1, Event, S#state.hibernate);
#{} ->
- %% Get a new event
- loop(P, Debug, S)
+ loop(P, Debug, S) % Get a new event
end;
[_|_] ->
+ %%
%% Loop until out of enqueued events
+ %%
loop_event(P, Debug, S, Q, S#state.hibernate)
end.
@@ -5354,7 +5368,7 @@ listify(Item) ->
cancel_timer(TimerRef),
case erlang:cancel_timer(TimerRef) of
false ->
- %% No timer found and we have not seen the timeout message
+ %% No timer found and we have not seen the time-out message
receive
{timeout,(TimerRef),_} ->
ok
@@ -5366,6 +5380,8 @@ listify(Item) ->
%%
%% Cancel erlang: timer and consume timeout message
%%
+%% Requires that the time-out message has not been received
+%%
-compile({inline, [cancel_timer/1]}).
cancel_timer(TimerRef) ->
?cancel_timer(TimerRef).
--
2.43.0
