[Patches] [ python-Patches-1517042 ] Fix for Lib/test/crashers/gc_inspection.py
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Tue Jul 25 20:08:06 CEST 2006
Patches item #1517042, was opened at 2006-07-04 16:39
Message generated for change (Comment added) made by arigo
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Category: Core (C code)
Group: Python 2.5
Status: Open
Resolution: None
Priority: 2
Submitted By: Collin Winter (collinwinter)
Assigned to: Nobody/Anonymous (nobody)
Summary: Fix for Lib/test/crashers/gc_inspection.py
Initial Comment:
The attached patch fixes the bug pointed out in
crashers/gc_inspection.py, namely that
gc.get_referrers() can be used to see objects (in this
case tuples) before their built, leading to segfaults.
The patch works by modifying
Objects/abstract.c:PySequence_AsTuple, wrapping the
call to PyIter_Next() with _PyObject_GC_TRACK/UNTRACK
calls. This has the effect of hiding the being-created
tuple from gc.get_referrers() while fetching the next
item from the iterator.
Also attached is a patch to crashers/gc_inspection.py
itself, which allows the test to actually pass (the
previous version would raise IndexErrors in the event
the test passed).
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>Comment By: Armin Rigo (arigo)
Date: 2006-07-25 18:08
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This patch is pointless. I recommend rejecting it.
The crashers/gc_inspection.py was just one example among
many of crashing Python with gc.get_referrers(). I don't
see why we should care to fix just this specific way.
What would be needed is a complete review, possibly with
an API change to decouple object creation and GC
registration, and appropriate documentation for extension
module writers. I don't think it's likely to happen though.
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Comment By: Neal Norwitz (nnorwitz)
Date: 2006-07-06 06:28
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Note that the declaration of item needs to be moved to the
top of the scope so it can compile with C89.
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Comment By: Raymond Hettinger (rhettinger)
Date: 2006-07-05 22:31
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Crashers based on gc.get_referrers() should not be
considered real bugs. It is certainly not worth
complexifying the code or slowing it down just to preclude
these little perverse safe-cracking exercises. Also, it
is not worth the risk of introducing a real bug when the
code was working fine.
That being said, if the code is genuinely defective and
has potential to cause real-world problems, then it should
be fixed. I would think that if there were a long-
standing problem with tuples, it would have manifested
itself long ago.
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Comment By: Collin Winter (collinwinter)
Date: 2006-07-05 17:36
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The improve_gc_inspection.patch file has been superseded by
a patch attached to bug #1517663. The bug details another
interpreter crash in the same vein as the one fix in tuple()
by this patch.
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