Message 401642 - Python tracker

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In-reply-to
Author	mattip
Recipients	Alexander.Belopolsky, Arfrever, Robin.Schreiber, amaury.forgeotdarc, belopolsky, jcea, jhaberman, lekma, loewis, mattip, petr.viktorin, pitrou
Date	2021年09月11日.16:55:03
SpamBayes Score	-1.0
Marked as misclassified	Yes
Message-id	<1631379303.59.0.239783914379.issue15870@roundup.psfhosted.org>

Content
>> I wouldn't recommend [setting ob_type] after PyType_Ready is called. > Why not? What bad things will happen? It seems to be working so far. It breaks the unwritten contract that "once PyType_Ready is called, the C struct will not be modified". This is implemented in PyPy, since calling PyType_Ready creates the PyPy object in the interpreter based on the C structure. Any further changes will not be reflected in the PyPy interpreter object, so now the python-level and c-level objects do not agree what type(obj) is. We have discussed this in the PyPy team, and would like to propose relaxing the contract to state that "if the c-level contents of an object are modified, PyType_Modified must be called to re-synce the python level and c-level objects"

Content

>> I wouldn't recommend [setting ob_type] after PyType_Ready is called.
> Why not? What bad things will happen? It seems to be working so far.
It breaks the unwritten contract that "once PyType_Ready is called, the C struct will not be modified". This is implemented in PyPy, since calling PyType_Ready creates the PyPy object in the interpreter based on the C structure. Any further changes will not be reflected in the PyPy interpreter object, so now the python-level and c-level objects do not agree what type(obj) is.
We have discussed this in the PyPy team, and would like to propose relaxing the contract to state that "if the c-level contents of an object are modified, PyType_Modified must be called to re-synce the python level and c-level objects"

History
Date	User	Action	Args
2021年09月11日 16:55:03	mattip	set	recipients: + mattip, loewis, jcea, amaury.forgeotdarc, belopolsky, pitrou, Arfrever, petr.viktorin, lekma, Alexander.Belopolsky, Robin.Schreiber, jhaberman
2021年09月11日 16:55:03	mattip	set	messageid: <1631379303.59.0.239783914379.issue15870@roundup.psfhosted.org>
2021年09月11日 16:55:03	mattip	link	issue15870 messages
2021年09月11日 16:55:03	mattip	create

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