[New-bugs-announce] [issue40217] The garbage collector doesn't take in account that objects of heap allocated types hold a strong reference to their type

[STINNER Victor]

New submission from STINNER Victor <vstinner at python.org>:

The bpo-35810 modified the object allocate to hold a *strong* reference to the type in PyObject.ob_type, whereas PyObject.ob_type is a *borrowed* references if the type is statically allocated.

commit 364f0b0f19cc3f0d5e63f571ec9163cf41c62958
Author: Eddie Elizondo <eduardo.elizondorueda at gmail.com>
Date:   Wed Mar 27 07:52:18 2019 -0400

    bpo-35810: Incref heap-allocated types in PyObject_Init (GH-11661)
    
    * Incref heap-allocated types in PyObject_Init
    * Add documentation and porting notes to What's New


The problem is now in some corner cases, the GC fails to visit all referrer of a type and so considers that the type is still alive.

bpo-40149 is a concrete example of such bug.

I propose to modify the GC to take bpo-35810 in account.

... or maybe I just misunderstood bpo-40149 bug :-)

----------
components: Interpreter Core
messages: 365911
nosy: pablogsal, vstinner
priority: normal
severity: normal
status: open
title: The garbage collector doesn't take in account that objects of heap allocated types hold a strong reference to their type
versions: Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue40217>
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