[WIP] bpo-39873: _PyObject_CAST() check if the object is valid #18803
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vstinner
requested review from
brettcannon,
encukou,
ericsnowcurrently,
ncoghlan and
warsaw
as code owners
In debug mode, _PyObject_CAST() now checks if the argument is valid Python object. The new _PyObject_Cast() function is a tradeoff between correctness and performance: it implements way less checks than _PyObject_CheckConsistency(). It only checks 3 things: * check the pointer itself with _PyMem_IsPtrFreed() * check that ob_refcnt >= 0 * check ob_type with _PyMem_IsPtrFreed() Tolerate ob_refcnt==0 to allow to use _PyObject_CAST() in deallocator functions like unicode_dealloc().
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PR rebased on master, since I merged two other changes related to https://bugs.python.org/issue39873 |
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This change was mostly an experimentation. But I'm not sure that it does solve any issue. The change is more intrusive than what I expected. I prefer to abandon it. |
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In debug mode, _PyObject_CAST() now checks if the argument is valid
Python object. The new _PyObject_Cast() function is a tradeoff
between correctness and performance: it implements way less checks
than _PyObject_CheckConsistency(). It only checks 3 things:
Tolerate ob_refcnt==0 to allow to use _PyObject_CAST() in deallocator
functions like unicode_dealloc().
https://bugs.python.org/issue39873