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

首先运行 https://3v4l.org/USrWu 中的复现，并将其与 https://3v4l.org/mgoqd 中更新后的示例进行比较，重点关注 GC、析构函数、引用计数和 WeakReference::get()。当在一次 GC 运行期间断开的循环能够立即释放对象，使两个 WeakReference 检查都与预期输出一致且无需第二次运行 GC 时，即可视为完成。