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Date: Tue, 27 Mar 2012 22:38:11 -0400
From: Dave Angel <d@davea.name>
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To: Michael Poeltl <michael.poeltl@univie.ac.at>
Subject: Re: python segfault
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On 03/27/2012 06:27 PM, Michael Poeltl wrote:
> hi,
>
> can anybody tell why this 'little stupid *thing* of code' let's python-3.2.2, 2.6.X or python 2.7.2 segfault?
>
>>> def get_steps2(pos=0, steps=0):
> ...     if steps == 0:
> ...         pos = random.randint(-1,1)
> ...     if pos == 0:
> ...         return steps
> ...     steps += 2
> ...     pos += random.randint(-1,1)
> ...     return get_steps2(pos,steps)
> ...
> <SNIP>
> 0
> 2
> 8
> 0
> Segmentation fault
> ?>
>
> funny, isn't it?
> I was able to reproduce this segfault on various machines (32bit 64bit), ubuntu, slackware, debian
> python.X segfaults on all of them
>
> thx
> Michael

Others have explained why you can't just raise the recursion limit to 
arbitrarily large values, and why there's no particular bound on the 
possible recursion size.  But the real question is why you don't do the 
completely trivial conversion to a non-recursive equivalent.

All you need do is add a while True:  to the beginning of the function, 
and remove the return statement.



-- 

DaveA