Jonas Hahnfeld <hah...@hahnjo.de> writes:
> Am Dienstag, dem 06.07.2021 um 17:03 +0200 schrieb David Kastrup:
>> Jean Abou Samra <j...@abou-samra.fr> writes:
>>
>> > For example, if I were the author of the below code, how
>> > would I understand that the mmrest_event_ should be
>> > unprotected?
>> >
>> > void
>> > Part_combine_iterator::kill_mmrest (Context *c)
>> > {
>> > if (!mmrest_event_)
>> > {
>> > mmrest_event_ = new Stream_event
>> > (Lily::ly_make_event_class (ly_symbol2scm ("multi-measure-rest-event")));
>> > set_property (mmrest_event_, "duration", SCM_EOL);
>> > mmrest_event_->unprotect ();
>> > }
>> >
>> > c->event_source ()->broadcast (mmrest_event_);
>> > }
>>
>> Uh, after the call to mmrest_event_->unprotect () there is nothing that
>> would protect the newly created mmrest_event_ .
>
> Sure there is, the snippet is just too small to show the marking:
>
> void
> Part_combine_iterator::derived_mark () const
> {
> Simultaneous_music_iterator::derived_mark ();
>
> if (mmrest_event_)
> scm_gc_mark (mmrest_event_->self_scm ());
> }
>
> The code makes perfect sense: If mmrest_event_ isn't set yet, the block
> will allocate and unprotect a new object so that before the broadcast,
> there is an event under the control of the iterator object for all
> possible flows through the function.
Ah, I overlooked that mmrest_event_ is not a local variable. Sorry for
the confusion.
--
David Kastrup
