[Python-bugs-list] [ python-Bugs-780714 ] infinite __str__ recursion in thread causes seg fault

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Bugs item #780714, was opened at 2003-07-31 08:37
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Category: Python Interpreter Core
Group: Python 2.3
Status: Open
Resolution: None
Priority: 5
Submitted By: Stefan Gregory (stefan_gregory)
Assigned to: Nobody/Anonymous (nobody)
Summary: infinite __str__ recursion in thread causes seg fault

Initial Comment:
The following code reliably produces a segmentation
fault under Solaris8 in Python2.3, Python2.2,
Python2.1.3 and Python1.5. It produces a Bus Error when
run on Python2.2 under OSX. Clearly it should produce a
Python RuntimeError.

import thread, time

class Frog:

    def __str__(self):
        return str(self)

f = Frog()
thread.start_new_thread(str,(f,))
time.sleep(1000)

This problem manifests in scenarios such as when you
have 2 publishing objects (such as HTMLgen objects) A
and B and you put A inside B and B inside A and each
objects __str__ method calls its childrens __str__
methods and voila! (I hope this might be the reason my
Zope server has been intermitently crashing for the
past year or so though I have not found any recursive
structures yet.)

With Python2.3 gdb reports:

vgetargskeywords (args=0x1bdaf0, keywords=0x0,
format=0xd2579 "0:str", kwlist=0xf7b4c,
p_va=0xfed0C02c) at Python/getargs.c:1167

Though with Python2.1 it dies at line 330 in getargs.c.



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