Ref counting based object release is not applied if cycle is broken in destructor during GC run

Description

repro: https://3v4l.org/USrWu

see UPDATE below

It seems the GC can be improved. Currently, when a cycle is broken during GC run, a 2nd run of GC is needed to really release the object.

https://github.com/php/php-src/commit/b58d74547f "solves this issue" since PHP 8.2+, but is that the most efficient solution for everything? If a cycle (all cycles/references to an object) is explicitly broken during GC, is there anything againts releasing that object by standard refcounting?

Resulted in this output:

d
gc
bool(true) <- notice object is kept alive after the destructor has broken the cycle (and refcount dropped to 0)
gc rerun
bool(false)
bool(false)
done

But I expected this output instead:

d
gc
bool(false)
gc rerun
bool(false)
bool(false)
done

UPDATE:

Based on https://3v4l.org/mgoqd I would call this a bug as 2nd WeakReference::get() call is expected to always give the same result if no GC is run in between the calls.

PHP Version

any (tested PHP 7.4, 8.3)

Operating System

any

Beginne mit der Ausführung der Reproduktion unter https://3v4l.org/USrWu und vergleiche sie mit dem aktualisierten Beispiel unter https://3v4l.org/mgoqd. Konzentriere dich dabei auf GC, Destruktoren, Referenzzähler und WeakReference::get(). Die Aufgabe ist abgeschlossen, wenn ein während eines GC-Laufs durchbrochener Zyklus das Objekt sofort freigibt, sodass beide WeakReference-Prüfungen ohne einen zweiten GC-Lauf mit der erwarteten Ausgabe übereinstimmen.