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Title: exceeding obscure weakproxy bug
Type: behavior Stage: needs patch
Components: Interpreter Core Versions: Python 3.1, Python 3.2, Python 3.3
Status: open Resolution:
Dependencies: Superseder:
Assigned To: Nosy List: ajaksu2, amaury.forgeotdarc, bruno.dupuis, mrabarnett, mwh, orsenthil, pitrou
Priority: low Keywords: patch

Created on 2004-11-29 16:10 by mwh, last changed 2022-04-11 14:56 by admin.

File name Uploaded Description Edit
issue1075356.patch mrabarnett, 2012-12-19 22:53
Messages (6)
msg60608 - (view) Author: Michael Hudson (mwh) (Python committer) Date: 2004-11-29 16:10
Broadly speaking, this line (488 in today's CVS) in
Python/weakref.c isn't right:

WRAP_UNARY(proxy_int, PyNumber_Int)

because PyNumber_Int will convert from a string
argument.  You can "exploit" this like so:

class U(unicode): pass

u = U("1")
except TypeError:
    print "raised, good"
    print "didn't raise, bad"
import _weakref

except TypeError:
    print "raised, good"
    print "didn't raise, bad"


raised, good
didn't raise, bad

for me).  I think the fix is PyNumber_Int ->
PyInt_AsLong, but haven't checked that.
msg82168 - (view) Author: Daniel Diniz (ajaksu2) * (Python triager) Date: 2009-02-15 20:41
Confirmed with rev69546.
msg125274 - (view) Author: Antoine Pitrou (pitrou) * (Python committer) Date: 2011-01-04 01:30
Works fine under 3.x.
msg125337 - (view) Author: Amaury Forgeot d'Arc (amaury.forgeotdarc) * (Python committer) Date: 2011-01-04 16:24
It's not fixed. range() now uses the tp_index slot, in weakrefs this becomes:
    WRAP_UNARY(proxy_index, PyNumber_Index)
and indeed PyNumber_Index does not accept strings.

But try with time.sleep() instead; here the line
    WRAP_UNARY(proxy_float, PyNumber_Float)
is involved:

import _weakref, time

class U(str): pass
u = U("1")

except TypeError:
    print("raised, good")
    print("didn't raise, bad")

except TypeError:
    print("raised, good")
    print("didn't raise, bad")
msg126916 - (view) Author: Senthil Kumaran (orsenthil) * (Python committer) Date: 2011-01-24 05:07
I find this problem with 3.x and not with 2.x codeline
msg177789 - (view) Author: Matthew Barnett (mrabarnett) * (Python triager) Date: 2012-12-19 22:53
The patch "issue1075356.patch" is my attempt to fix this bug.

'PyArg_ParseTuple', etc, eventually call 'convertsimple'. What this patch does is to insert some code at the start of 'convertsimple' that checks whether the argument is a weakref proxy and, if it is, fetch the object to which the proxy refers. From then on it's working with the true argument, so it'll work just like would have done if it been given the proxied object itself originally.
Date User Action Args
2022-04-11 14:56:08adminsetgithub: 41243
2012-12-19 22:53:19mrabarnettsetfiles: + issue1075356.patch
versions: + Python 3.3
nosy: + mrabarnett

messages: + msg177789

keywords: + patch
2012-12-01 00:14:51bruno.dupuissetnosy: + bruno.dupuis
2011-01-24 05:07:00orsenthilsetnosy: + orsenthil

messages: + msg126916
versions: + Python 3.1, Python 3.2, - Python 2.7
2011-01-04 16:24:07amaury.forgeotdarcsetnosy: + amaury.forgeotdarc
messages: + msg125337
2011-01-04 01:30:59pitrousetversions: - Python 3.1, Python 3.2
nosy: + pitrou

messages: + msg125274

stage: test needed -> needs patch
2010-08-19 18:38:12BreamoreBoysetversions: + Python 3.1, Python 2.7, Python 3.2, - Python 2.6
2009-02-15 20:41:45ajaksu2settype: behavior
stage: test needed
messages: + msg82168
nosy: + ajaksu2
versions: + Python 2.6, - Python 2.4
2004-11-29 16:10:35mwhcreate