New submission from Armin Rigo <ar...@users.sourceforge.net>:
PyWeakref_GetObject(wref) returns a borrowed reference, but that's rather
dangerous. The fact that wref stays alive does not prevent the returned object
from being collected (by definition -- wref is a weak reference). That means
that either we must explicitly and immediately do a Py_INCREF() (and later
Py_DECREF()) on the result of the function, or we must use it for a very short
time.
As an example of why this interface encourages buggy behavior, the sole user of
PyWeakref_GetObject() in Module/* is Module/_sqlite/connection.c, which does
statement = PyWeakref_GetObject(weakref);
and then call some functions passing 'statement' as argument. The called
functions can do anything (because they release the GIL). So in particular
they can cause 'statement' to be freed while still in use, either directly or
indirectly via the cycle-GC.
This should be fixed; I suggest deprecating PyWeakref_GetObject() and adding
another C API function that does not return a borrowed reference.
----------
components: Interpreter Core
messages: 104634
nosy: arigo
priority: normal
severity: normal
status: open
title: PyWeakref_GetObject
type: crash
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue8578>
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