[Python-bugs-list] [ python-Bugs-457360 ] Nested scopes crash when tracing (v2.1)

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Bugs item #457360, was opened at 2001-08-31 12:13
You can respond by visiting: 
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Category: Python Interpreter Core
Group: None
Status: Open
Resolution: None
>Priority: 5
Submitted By: Stephan R.A. Deibel (sdeibel)
Assigned to: Jeremy Hylton (jhylton)
Summary: Nested scopes crash when tracing (v2.1)

Initial Comment:
Python will crash on post-trace processing if
the tracer is installed during a class def nested
inside of a nest function def, under certain conditions
at least.

I tried to make a small test case but that didn't bring
out the bug.

As a result, this is best illustrated by installing
Zope 2.4.0 (I did this on Linux) and altering z2.py by
inserting the following near the top of the file:

def tracer(*args):
  print "trace"
  return tracer
import sys
sys.settrace(tracer)

Then run with the './start' command.  Python will 
segfault during the following around line 570
of z2.py:

exec "import "+MODULE in {}

The real problem is the LocalsToFast() call after
the tracer has been called while the interpreter is
doing the 'line' tracing for line 118 of
libs/python/RestrictedPython/Gaurds.py in Zope, where
"class Wrapper" is defined nested inside of a nested
function.

The innermost part of the C backtrace is:

#0  PyCell_Set (op=0x0, obj=0x8322e04) at
Objects/cellobject.c:32
(gdb) up
#1  0x808068a in dict_to_map (map=0x81d5cc4, nmap=1,
dict=0x81d269c, 
    values=0x8195db0, deref=1, clear=1) at
Objects/frameobject.c:287
(gdb) up
#2  0x8080903 in PyFrame_LocalsToFast (f=0x8195c68,
clear=1)
    at Objects/frameobject.c:371
(gdb) up
#3  0x80587e3 in call_trace (p_trace=0x8195c88,
p_newtrace=0x8195c88, 
    f=0x8195c68, msg=0x809c3a2 "line", arg=0x80b5c0c)
at Python/ceval.c:2595

I tested this under RedHat 6.1 with Python 2.1 (both
the copy that comes with Zope and one I built from
source with debug symbols).

For more info, contact via email: info at wingide.com.



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

>Comment By: Jeremy Hylton (jhylton)
Date: 2001-09-10 08:29

Message:
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user_id=31392

I made a half-hearted effort to reproduce.  I tried to just
import and execute the code in Guards with a trace function
installed.  I got that to work correctly with Python 2.1.1.

There was a nested scopes core dump that was fixed in 2.1.1.
 The bug that triggered it was reported by Evan and
triggered by RestrictedPython.  Can you try to reproduce
against 2.1.1?  I suspect that the fix in 2.1.1 fixes this, too.


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