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<DIV><FONT face=Arial size=2>I would like to thank everyone for politely
ignoring this post and not stating the obvious...</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Dave Harris is clueless!</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I completely misapprended the problem. Instead of a
code problem, the abort occurs during maintenance of the garbage collection
chain. In particular, cm_dealloc() makes the call:</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2> _PyObject_GC_UNTRACK((PyObject
*)cm);</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>and the process collapses when the assignment to
the previous element link is attempted. The address of the previous element
appears to be 0xfffffffd (-3). Now I have to find out why.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I'll post again when I have an answer.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Thanks for your patience,</FONT></DIV>
<DIV><FONT face=Arial size=2>Dave Harris</FONT></DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=dpharris76@msn.com href="mailto:dpharris76@msn.com">David Harris</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=osuchw@ecn.ab.ca
href="mailto:osuchw@ecn.ab.ca">W.Osuch</A> ; <A title=zope3-dev@zope.org
href="mailto:zope3-dev@zope.org">zope3-dev@zope.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Friday, January 16, 2004 12:44
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [Zope3-dev]
Zope3+W2k+mingw=Python crash</DIV>
<DIV><BR></DIV>
<DIV><FONT face=Arial size=2>----- Original Message ----- </FONT></DIV>
<DIV>
<DIV><FONT face=Arial size=2>From: "W.Osuch" <</FONT><A
href="mailto:osuchw@ecn.ab.ca"><FONT face=Arial
size=2>osuchw@ecn.ab.ca</FONT></A><FONT face=Arial size=2>></FONT></DIV>
<DIV><FONT face=Arial size=2>To: <</FONT><A
href="mailto:zope3-dev@zope.org"><FONT face=Arial
size=2>zope3-dev@zope.org</FONT></A><FONT face=Arial size=2>></FONT></DIV>
<DIV><FONT face=Arial size=2>Sent: Wednesday, January 14, 2004 1:05
AM</FONT></DIV>
<DIV><FONT face=Arial size=2>Subject: [Zope3-dev] Zope3+W2k+mingw=Python
crash</FONT></DIV></DIV>
<DIV><FONT face=Arial><BR><FONT size=2></FONT></FONT></DIV>
<DIV><FONT face=Arial size=2>> Since there seems to be an increased
interest on the list in Zope3 on<BR>> Windows tests result I am<BR>>
posting an error that I have seen showing up for quite a
while.<BR></FONT></DIV>
<DIV><FONT face=Arial size=2>> test_descr_abuse
(zope.context.tests.test_wrapper.WrapperTestCase) ...<BR></FONT></DIV>
<DIV><FONT face=Arial size=2>I've analyzed this failure down into the C code
and understand why it fails. But it leaves three questions to be
answered...</FONT></DIV>
<DIV><FONT face=Arial size=2>1) Why is the failure only manifested on Windows
(XP in my case) and mingw32?</FONT></DIV>
<DIV><FONT face=Arial size=2>2) Is the unit test wrong (as I describe
below)?</FONT></DIV>
<DIV><FONT face=Arial size=2>3) Is the wrapper.c code incorrect?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>The abort does occur in the test_descr_abuse unit
test at the ContextMethod() call. The current code looks like
this:</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Courier size=2> def
test_descr_abuse(self):<BR> def
abuse():<BR>
def foo():
pass<BR>
ContextMethod(ContextMethod(foo)).__get__(1)<BR> self.assertRaises(TypeError,
abuse)<BR></FONT></DIV>
<DIV><FONT face=Courier size=2><FONT face=Arial>Breaking it down a bit
further, I found that it's the second ContextMethod() call which triggers the
failure.</FONT></FONT></DIV>
<DIV><FONT face=Courier size=2><FONT face=Arial></FONT> </DIV></FONT>
<DIV><FONT face=Courier size=2> def
test_descr_abuse(self):<BR> def
abuse():<BR>
def foo(): pass<BR>
adebug =
ContextMethod(foo)<BR>
bdebug =
ContextMethod(adebug)<BR>
bdebug.__get__(1)</FONT></DIV>
<DIV><FONT face=Courier
size=2> self.assertRaises(TypeError,
abuse)<BR><BR><FONT face=Arial>ContextMethod resides in wrapper.c. cm_init()
sets the stage for the failure which is subsequently realized in cm_dealloc().
And here's where the questionable things come in.</FONT></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Courier size=2>static int<BR>cm_init(PyObject *self, PyObject
*args, PyObject *kwds)<BR>{<BR> ContextMethod *cm =
(ContextMethod *)self;<BR> PyObject *callable;</FONT></DIV>
<DIV><FONT face=Courier></FONT> </DIV>
<DIV><FONT face=Courier size=2> if (!PyArg_UnpackTuple(args,
"ContextMethod", 1, 1,
&callable))<BR> return
-1;<BR> if (!PyCallable_Check(callable))
{<BR> PyErr_Format(PyExc_TypeError,
"'%s' object is not
callable",<BR>
callable->ob_type->tp_name);<BR>
return -1;<BR> }<BR>
Py_INCREF(callable);<BR> cm->cm_callable =
callable;<BR> return 0;<BR>}<BR></FONT></DIV>
<DIV><FONT face=Courier size=2><FONT face=Arial>The ContextMethod(adebug)
call results in PyCallable_Check() returning 0, which leads to PyErr_Format()
and a return value of -1. The initialization of the resulting ContextMethod
object (bdebug) is incomplete and cm_dealloc() aborts when trying to handle
the debris.</FONT></FONT></DIV>
<DIV><FONT face=Courier size=2><FONT face=Arial></FONT></FONT> </DIV>
<DIV><FONT face=Courier size=2><FONT face=Arial>Why does PyCallable_Check()
fail? Because the tp_call field is not set for ContextMethod object adebug. I
traced into PyCallable_Check() (which is in Python23's object.c file) and
found that the following line of code was exercised and returned
0.</FONT></FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Courier size=2> return
x->ob_type->tp_call != NULL;</FONT></DIV>
<DIV><FONT face=Courier size=2></FONT> </DIV>
<DIV><FONT face=Courier size=2><FONT face=Arial>So, back to the three
questions:</FONT></FONT></DIV>
<DIV><FONT face=Courier size=2><FONT face=Arial></FONT></FONT> </DIV>
<DIV><FONT face=Courier size=2><FONT face=Arial>1) I don't see anything
Windows-specific here. The empty tp_call field should be happening on all
systems. However, it could be that cm_dealloc() survives the encounter with
bdebug on *NIX systems, where Windows is less forgiving. Purely conjecture, I
don't know for sure.</FONT></FONT></DIV>
<DIV><FONT face=Courier size=2><FONT face=Arial></FONT></FONT> </DIV>
<DIV><FONT face=Courier size=2><FONT face=Arial>2 and 3) The abuse() method
does not (cannot??) check for a failure in ContextMethod(). I'm still new
enough to Python that I can't begin to suggest how the event should be
resolved. The real issue is how cm_dealloc() is invoked - does it happen when
cm_init() fails or when abuse() exits?</FONT></FONT></DIV>
<DIV><FONT face=Courier size=2><FONT face=Arial></FONT></FONT> </DIV>
<DIV><FONT face=Courier size=2><FONT face=Arial>The situation really boils
down to this: I can't tell if the empty tp_call field is intentional or not.
That ContextMethod is a method seems to imply that it is callable and tp_call
should be set. At the same time, the wrapper unit tests have been running fine
for somebody which implies that ContextMethod is operating within normal
parameters.</FONT></FONT></DIV>
<DIV><FONT face=Courier size=2><FONT face=Arial></FONT></FONT> </DIV>
<DIV><FONT face=Courier size=2><FONT face=Arial>I could really use some
insight at this point.</FONT></FONT></DIV>
<DIV><FONT face=Courier size=2><FONT face=Arial></FONT></FONT> </DIV>
<DIV><FONT face=Courier size=2><FONT face=Arial>Thanks,</FONT></FONT></DIV>
<DIV><FONT face=Courier size=2><FONT face=Arial>Dave
Harris</DIV></FONT></FONT>
<P>
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