Bugs item #992017, was opened at 2004-07-16 01:56
Message generated for change (Comment added) made by birkenfeld
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Category: Python Interpreter Core
>Group: Python 2.4
Status: Open
Resolution: None
Priority: 6
Submitted By: Ted Bach (bachtor)
Assigned to: Nobody/Anonymous (nobody)
Summary: code that generates a segfault on Python 2.1-2.3
Initial Comment:
On a Redhat Linux 9 based system, the following causes
a segfault:
""" In python, you can call any expression.
"""
class foo:
def __init__(s,times=1):
s.times = times
def __call__(s): print s.times
def __mul__(s,o): return foo(o)
def __coerce__(s,o):
if isinstance(o,int):
return o,s
(foo(3)*10)() # no segfault
(10*foo(3))() # segfaults
# prints 10
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>Comment By: Reinhold Birkenfeld (birkenfeld)
Date: 2005-06-08 19:26
Message:
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Still persists with Python 2.4.
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Comment By: Armin Rigo (arigo)
Date: 2004-08-07 23:44
Message:
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Here is a shorter example:
class foo:
def __coerce__(self, other):
return other, self
foo()+1 # segfault: infinite recursion in C
classobject.c seems hopelessly prone to infinite recursion in C: whenever an
operation needs coercion, __coerce__ is called and the operator PyNumber_Xxx()
is called again on the result. The most obvious cases of recursion are taken
care of, but there are and will always be more convoluted ways to create this
recursion.
There might be a way to solve the problem cleanly but currently I only see the
solution of adding a C recursion check (Py_EnterRecursiveCall /
Py_LeaveRecursiveCall).
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Comment By: Dima Dorfman (ddorfman)
Date: 2004-07-22 16:18
Message:
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This is not the same problem as bug #980352; this one is an infinite recusion
in the instance code (deriving foo from object makes the example work).
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Comment By: Michael Hudson (mwh)
Date: 2004-07-16 15:45
Message:
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Isn't this likely to be a dup of bug
[ 980352 ] coercion results used dangerously
? I haven't thought about either very hard, but both involve
__coerce__ and core dumps...
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