Bugs item #1120452, was opened at 2005-02-11 00:04
Message generated for change (Comment added) made by nascheme
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Category: Regular Expressions
Group: Python 2.4
>Status: Closed
>Resolution: Duplicate
Priority: 7
Submitted By: Viktor Ferenczi (complex)
>Assigned to: Neil Schemenauer (nascheme)
Summary: Python 2.4.0 crashes with a segfault, EXAMPLE ATTACHED
Initial Comment:
Running the attached example crashes python 2.4.0 on linux (segfault) and
Windows. Python is compiled on Debian Linux 3.0r3 (Woody). On Windows XP, I
used the MSI installer downloaded from python.org
This may be a problem with the regular expression module, but I'm not sure.
Please assign a new category if it appears as a regexp bug.
This bug causes permanent crashes in my new WEB applications. Old apps not
using regexp and PyMeld seem to run correctly.
Thanks for 2.4.1.
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>Comment By: Neil Schemenauer (nascheme)
Date: 2005-03-01 23:16
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Closed as a duplicate of #1072259. The fix has already been
backported to release24-maint.
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Comment By: Amaury Forgeot d'Arc (amauryf)
Date: 2005-03-01 11:59
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I can reliably reproduce the problem on w2k using 2.4.0,
debug build under Purify.
Here is the testcase (using the files in the attached example):
>>> import re,PyMeld
>>> s=file("player.html").read()
>>> print re.search(PyMeld.openIDTagRE,s)
Applying the patch for bug #1072259 (_sre.c 2.110) causes
the bug to disappear, and Purify does not complain.
I suggest to consider this as a duplicate for bug #1072259
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Comment By: Kurt B. Kaiser (kbk)
Date: 2005-02-24 03:24
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The IDLE subprocess does different things with memory
because it's threaded, with one thread minding the sockets
and the other executing user code. So I'd stay away from
IDLE when working on this. (Also, the debug traces are
excessively complex.)
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Comment By: Neil Schemenauer (nascheme)
Date: 2005-02-24 00:32
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I can reproduce the crash on my machine if I revert the
patch for bug #1072259 (_sre.c 2.110). Here's what gdb says:
0x0810342a in sre_match (state=0xbfffca80, pattern=0x81bfbf2)
at ../Modules/_sre.c:854
854 state->mark[j++] = NULL;
(gdb) p j
$7 = -1209149847
(gdb) p &(state->mark)
$8 = (void *(*)[200]) 0xbfffcaa8
(gdb) p &j
$9 = (int *) 0xbfffc9c0
Either the bug has been fixed or _sre has been changed
enough that the test no longer triggers a crash.
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Comment By: Jim Jewett (jimjjewett)
Date: 2005-02-22 23:58
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It probably is a memory scribble bug, though it might not be in
re. For instance, the __getattr__ and __setattr__ try to do
some shortcuts saving position, and they may cause the out-
of-bounds.
The crashes are very dependent on order.
I wasn't kidding when I said it ran fine and printed None if run
as a whole, but crashed when the same lines were input one
by one. (Which gave idle a chance to do different things with
memory in between, and didn't define a function object.)
Also note that the second attribute access (even to a
previously OK attribute) could cause a crash, unless it had
had a chance to clear things up first -- but then it raised a
MemoryError, when I almost certainly wasn't yet out of RAM.
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Comment By: Viktor Ferenczi (complex)
Date: 2005-02-22 15:19
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Some additional information and summary:
My machine is a 3.0Hz Intel P4 with 1Gbyte memory, without
overclocking. I use 2 antivirus (1 active) and 3 antispyware
apps + firewall. The memory has been tested for 6 hours with
Knoppix's memtest without any error, so my machine can be
considered to be stable.
The attached script can crash python 2.4.0 at least for me
and jumjjewett. Do not run the script from IDLE, since it
can hide the segfault. I usually run my scripts from SciTE
(see: www.scintilla.org ).
The bug can be reproduced on stock Python 2.4.0 (MSI
installer). PyMeld is pure python (uses only the standard
library), no C extension modules used. I did not test this
bug with the latest CVS versions of Python 2.4. Is produces
segfault under Linux.
I'll try to narrow down this bug for specific regex patterns.
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Comment By: Michael Hudson (mwh)
Date: 2005-02-22 14:51
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Well, I still can't make it crash. Can one of you provide a crashing driver
script? Better still would be finding which regexp and which input is the
problem.
(Unless it's a memory-scribble random crasher type bug...)
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Comment By: Viktor Ferenczi (complex)
Date: 2005-02-22 13:07
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This bug is a segfault, a real crash using only the stock 2.4.0. It has been
reproduced correctly by jimjjewett. It seems to be a regexp related bug. I've
changed the category to pass this bug to a regexp expert. Thanks for any help.
- Complex
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Comment By: Kurt B. Kaiser (kbk)
Date: 2005-02-20 01:56
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The restart in IDLE will occur if the subprocess is terminated or
segfaults.
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Comment By: Jim Jewett (jimjjewett)
Date: 2005-02-11 19:55
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__gettattr__ alone can provoke the crash, if used several
times, and on sub-melds.
I can print both StreamURL1 and StreamURL2.
If I ask it for p.StreamURL2.src and p.StreamURL1.value,
it prints whichever one I ask for first, and then crashes on
the second. I did get it to print both (not assign, just
__getattr__) by first getting several other attributes from
p.StreamURL1, including some that didn't exist, so that
there was a raise AttributeError in between. Doing this a
half dozen times, I provoked a MemoryError.
"""
>>> p.StreamURL1.value
'mss://stream.url'
>>> p.StreamURL2.src
Traceback (most recent call last):
File "<pyshell#68>", line 1, in -toplevel-
p.StreamURL2.src
File "C:\Python24\Lib\site-packages\segfault240\PyMeld.
py", line 475, in __getattr__
start = self._findElementFromID(name)
File "C:\Python24\Lib\site-packages\segfault240\PyMeld.
py", line 425, in _findElementFromID
match = _findIDMatch(nodeID, subset)
File "C:\Python24\Lib\site-packages\segfault240\PyMeld.
py", line 282, in _findIDMatch
match = re.search(thisRE, text)
File "C:\Python24\lib\sre.py", line 134, in search
return _compile(pattern, flags).search(string)
MemoryError
>>>
"""
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Comment By: Jim Jewett (jimjjewett)
Date: 2005-02-11 19:36
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Partially reproduced on Windows XP. (Using the stock 2.4.
0 msi)
Just loading it in IDLE and hitting F5 (run), it prints None,
as though it had succeeded perfectly.
Typing in the commands from index.py by hand, I can get
it to give me the "encountered an error; Tell Microsoft?"
box, but IDLE only restarts instead of actually crashing.
There seems to a problem between the __getattr__ and
the __setattr__ in PyMeld.
"""
>>> p=Meld(open('player.html','rb').read())
>>> p.StreamURL1.value
'mss://stream.url'
>>> p.StreamURL2
<PyMeld.Meld instance at 0x00B455F8>
>>> p.StreamURL2.src
'mms://stream.url'
>>> v=Video()
>>> v.stream
's'
>>> p.StreamURL1.value=v.stream
>>> p.StreamURL1.value
>>> ================================
RESTART
================================
>>>
"""
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Comment By: Michael Hudson (mwh)
Date: 2005-02-11 14:57
Message:
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What do you do to make it crash? "python index.py"?
It doesn't fail for me with CVS HEAD.
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