[Jython-bugs] [ jython-Bugs-222789 ] __builtin__.id() does not return unique values for different

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Bugs item #222789, was opened at 2000-11-18 18:46
Message generated for change (Comment added) made by gbgbgb50
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Category: Core
Group: Deferred
Status: Closed
Resolution: Fixed
Priority: 1
Private: No
Submitted By: Finn Bock (bckfnn)
Assigned to: Samuele Pedroni (pedronis)
Summary: __builtin__.id() does not return unique values for different

Initial Comment:
According to the Python library documentation, the "id" builtin
function will return unique integers for different objects. The
documentation for java's hashCode makes no such garantee. The new
hotspot VM change the behavior of the JDK and the hashCode (and
identifyHashCode) function can return the same integer for different
objects.

pickle.py assumes that id() returns unique values.


======= From Python docs "__builtin__.id()"=========
Return the `identity' of an object. This is an integer which is
guaranteed to be unique and constant for this object during its
lifetime.

======= From Java docs "Object.hashCode()" =========
As much as is reasonably practical, the hashCode method defined by
class Object does return distinct integers for distinct  objects.
(This is typically implemented by converting the internal address of
the object into an integer, but this implementation technique is not
required by the JavaTM programming language.)


 --------- FILE: test099.py  --------- 

d = {}

for i in xrange(100000):
    s = "test" + `i`
    j = id(s)
    if d.has_key(j):
        print "Duplicate id %s<%d> & %s<%d>" % (s, j, d[j],
id(d[j]))
    d[j] = s

 --------- END  --------- 


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Comment By: gunter bach (gbgbgb50)
Date: 2006-11-24 16:29

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I do get many duplicates (137) when running test099.py!

I came across this bug, when I was trying to debug my own application
which yields very strange results when
deep-copying a dictionary many times...
Looks for me like this id()-bug is the reason.

I ran the test099.py on windows jdk1.6.0-beta and on two different
debian-boxes, both java version "1.5.0_03".
Ah, and I used the jython2.1-relase.

yours

Gunter



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Comment By: Samuele Pedroni (pedronis)
Date: 2006-09-18 19:58

Message:
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mark as fixed because it actually was

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Comment By: Samuele Pedroni (pedronis)
Date: 2006-09-07 11:12

Message:
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this was fixed by me using an object->id mapping quite some 
time ago. 

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Comment By: Charles Groves (cgroves)
Date: 2006-09-07 04:45

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Has anyone ever seen test099.py fail?  Since we haven't seen
an actual bug from this in 6 years, I'm going make this
pending won't fix.

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Comment By: Finn Bock (bckfnn)
Date: 2000-11-26 13:07

Message:
Tim Peters think this should be solved even if it mean that every object
should carry some id field around in PyObject. I think we can live with
this difference. Since I trust Tim more then I trust myself I keep the bug
open for now. See the python-dev archives for the discussion.

http://www.python.org/pipermail/python-dev/2000-June/thread.html#22346

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