[Python-bugs-list] [ python-Bugs-489672 ] memory leak in test_sre

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Bugs item #489672, was opened at 2001-12-05 18:45
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Category: Regular Expressions
Group: Python 2.2
Status: Open
Resolution: None
Priority: 7
Submitted By: Neal Norwitz (nnorwitz)
>Assigned to: Guido van Rossum (gvanrossum)
Summary: memory leak in test_sre

Initial Comment:
leak when running test_sre

see attached file for details

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>Comment By: Guido van Rossum (gvanrossum)
Date: 2001-12-06 20:09

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I think I've found this. There's a missing Py_DECREF(filter)
in pattern_subx() in _sre.c. I'll check it in once I've got
more confidence in the fix.

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Comment By: Guido van Rossum (gvanrossum)
Date: 2001-12-06 19:44

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>From email. That was it.  With two backslashes it leaks like
a sieve.

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Comment By: Tim Peters (tim_one)
Date: 2001-12-06 19:04

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Guido, did you take the snippet from email or from the web 
page?  It doesn't "look right" in email (for a change!).  
The 2nd argument to re.sub must have two backslashes; one 
of them vanishes in the email version ... I'll try 
attaching it as a file.

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Comment By: Guido van Rossum (gvanrossum)
Date: 2001-12-06 18:56

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Hm. For me (on Linux) that snippet doesn't leak at all. Are
you sure this is it?

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Comment By: Tim Peters (tim_one)
Date: 2001-12-06 18:35

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This derived snippet leaks at a prodigious rate:

import re
while 1: re.sub('(a)', '\1', 'a')

Variations don't leak if the capturing group is removed 
from the regexp, or if the replacement text doesn't 
reference the group.

I'm reassigning to /F based on that evidence (it appears to 
have to do with re.sub internals, not with a general Python 
screwup).

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Comment By: Tim Peters (tim_one)
Date: 2001-12-06 15:18

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Hard?  Unpleasant?  Mine <wink>!  Reassigned to me, cuz in 
a moment of weakness I said I would.

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Comment By: Guido van Rossum (gvanrossum)
Date: 2001-12-06 14:08

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It's hard to make progress on this. In a loop it doesn't
leak or leaks too slowly to be useful. The code is not in a
function so it's hard to whittle down effectively.

The first leak reported by Purify is a string literal (or
actially, 4 string literals); this isn't much of a hint
since the code is chock full of those.

The second leak reported is also a string, but one created
through concatenation. There aren't too many of those in
test_sre.py, but still, who knows which one it is...

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