[Jython-bugs] [Bug #122819] Multi-level Java method overriding fails

[<no...@so...>]

Bug #122819, was updated on 2000-Nov-18 11:11
Here is a current snapshot of the bug.

Project: Jython
Category: Core
Status: Open
Resolution: None
Bug Group: None
Priority: 4
Submitted by: bckfnn
Assigned to : nobody
Summary: Multi-level Java method overriding fails

Details: Consider the following script --

==========
#!/usr/bin/env jpython

from java.util import Date

class SubDate(Date):
    def toString(self): return 'SubDate.toString() -> ' +
Date.toString(self)

class SubSubDate(SubDate):
    def toString(self): return 'SubSubDate.toString() -> ' +
SubDate.toString(self)

print Date().toString()
print SubDate().toString()
print SubSubDate().toString()
==========

The output is as follows --

==========
Fri Oct 22 12:53:58 CDT 1999
SubDate.toString() -> Fri Oct 22 12:53:58 CDT 1999
Traceback (innermost last):
  File "test.py", line 12, in ?
  File "test.py", line 8, in toString
  File "test.py", line 6, in toString
java.lang.StackOverflowError
        at org.python.core.PyClass.lookupGivingClass(PyClass.java:137)
        at
org.python.core.PyJavaClass.lookupGivingClass(PyJavaClass.java:673)
        at org.python.core.PyClass.lookup(PyClass.java:155)
        at
org.python.util.PythonInterpreter.execfile(PythonInterpreter.java:132)
        < ... >
        at org.python.proxies.SubDate$0.toString(Unknown Source)
        at org.python.proxies.SubSubDate$1.super__toString(Unknown
Source)
        at
org.python.core.PyReflectedFunction.__call__(PyReflectedFunction.java:156)
        < ... >
        at org.python.proxies.SubDate$0.toString(Unknown Source)
        at org.python.proxies.SubSubDate$1.super__toString(Unknown
Source)
        at
org.python.core.PyReflectedFunction.__call__(PyReflectedFunction.java:156)
        < ... > 
        at org.python.util.jpython.main(jpython.java:123)
==========

What seems to happen is that SubSubDate.toString() calls
SubDate.toString()
calls Date.toString() ... which then turns around and calls the
derived-most
implementation of toString() all over again, ie, the one at SubSubDate.
This
goes on and on until the above stack overflow occurs.

Note that with only one level of inheritance, ie, calling
SubDate.toString(),
it worked correctly with no problems.

I originally observed this problem with overriding
java.lang.Thread.interrupt(),
so the above simplified test case has been reproduced elsewhere.

I can reproduce this with Sun Solaris JDK versions 1.3, 1.2.2 and 1.1.8.


Follow-Ups:

Date: 2001-Feb-19 01:26
By: ianzsk

Comment:
Any python subclass that contains a java class as a parent 
will have a proxy created for it. Also, in the PyReflectionFunction
__call__
there is code to "translate" unbound methods to bound "super__" methods.
However the "self" argument passed to this method is null so that
the superclass (Here SubDate) again looks for a "super__" method ( viz:
super__super__toString()!) This of course fails and so the
call drops through.

I can't really make heads or tails of this code so I have no idea where the
"bug"
is (altough the search for "super__super__" is surely wrong).  I also think
the fact
that the SubSubDate class has a java proxyClass created for it (--because
SubDate 
has a proxyClass--- see PyClass.init()) somehow contributes to the
recursion.

-------------------------------------------------------

Date: 2000-Dec-16 12:52
By: pedronis

Comment:
Just checked that the nasty bug is still there.
It should be solved for sure, at least the 
stack overflow.
Not analyzed yet.
-------------------------------------------------------

For detailed info, follow this link:
http://sourceforge.net/bugs/?func=detailbug&bug_id=122819&group_id=12867