Message 317158 - Python tracker

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Author	methane
Recipients	methane
Date	2018-05-20.07:42:30
SpamBayes Score	-1.0
Marked as misclassified	Yes
Message-id	<1526802151.18.0.682650639539.issue33583@psf.upfronthosting.co.za>
In-reply-to

Content
https://github.com/python/cpython/blob/master/Modules/gcmodule.c#L1750-L1763 PyObject_GC_Resize() calls PyObject_REALLOC(), which can change object's address. But it doesn't relinking: g->gc.gc_prev->gc.gc_next = g g->gc.gc_next->gc.gc_prev = g So this API can't be used for tracked object. In CPython code, all callers use this API for non tracked objects. But if some extension module author used this API for tracked objects, it will cause hard to debug behavior. Which should we do? 1. Add relinking to PyObject_GC_Resize() 2. Add note in the document If 1, should we backport it to 3.7 and 3.6?

https://github.com/python/cpython/blob/master/Modules/gcmodule.c#L1750-L1763

PyObject_GC_Resize() calls PyObject_REALLOC(), which can change object's address.
But it doesn't relinking:

 g->gc.gc_prev->gc.gc_next = g
 g->gc.gc_next->gc.gc_prev = g

So this API can't be used for tracked object.
In CPython code, all callers use this API for non tracked objects.

But if some extension module author used this API for tracked objects, it will cause hard to debug behavior.

Which should we do?

1. Add relinking to PyObject_GC_Resize()
2. Add note in the document

If 1, should we backport it to 3.7 and 3.6?

History
Date	User	Action	Args
2018-05-20 07:42:31	methane	set	recipients: + methane
2018-05-20 07:42:31	methane	set	messageid: <1526802151.18.0.682650639539.issue33583@psf.upfronthosting.co.za>
2018-05-20 07:42:31	methane	link	issue33583 messages
2018-05-20 07:42:30	methane	create