[Python-bugs-list] [ python-Bugs-441664 ] Python crash on del of a slice of a mmap

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Bugs item #441664, was opened at 2001-07-16 04:39
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>Category: Extension Modules
Group: None
>Status: Closed
>Resolution: Fixed
Priority: 5
Submitted By: Alex Martelli (aleax)
>Assigned to: Thomas Wouters (twouters)
Summary: Python crash on del of a slice of a mmap

Initial Comment:
Python 2.1.1c1 (#19, Jul 13 2001, 00:25:06) [MSC 32 
bit (Intel)] on win32
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information.
>>> flob=open('foo.txt','r+')
>>> import mmap
>>> mm=mmap.mmap(flob.fileno(),0)
>>> mm[:]
'uno\r\ndue\r\ntre\r\ne quattro\r\n'
>>> del mm[:10]

This crashes the Python interpreter.  Reproduced on 
both Windows/98 and NT4 SP6a.

I think it's a very simple bug at line 666 (sic!) of 
mmapmodule.c: it calls PyString_Check(v), without 
previously checking v!=0, and that macro defererences 
v (line 52 of stringobject.h); but slice deletion 
calls slice-assignment exactly with v set to 0.  So I 
believe it should be fixed by just checking v!=0 and 
giving a msg about mmap not supporting slice deletion, 
just before line 666 in mmapmodule.c.  Hopefully can 
still be done for 2.1.1 final...?


Alex


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>Comment By: Thomas Wouters (twouters)
Date: 2001-07-16 08:49

Message:
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Actually, the crash happens both on a del of the slice and
of an item, and on UNIX as well as Windows -- and any other
platform that could compile it. It's been around at least
since 2.0, and probably forever.

Your diagnosis is spot-on, by the way, that made it easy to
fix :) Fixed in revision 2.32 (head) and 2.27.4.2 (2.1.1
tree) so it'll be fixed in Python 2.2a1 and Python 2.1.1-final.


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