There is a timing problem between the call of 
"call_trace(profile_func,...,'return',...)" and 
"reset_exc_info" in Pythons main interpreter loop.

The main loop first calls "call_trace" (at the end of
function execution). With the
standard "profile.Profile" profiler this leads to a pop
of the current frame from the profiler stack while
the current frame is still on the interpreter stack.
Then "reset_exc_info" is called. When this call releases 
an instance with a destructor ("__del__" method), the 
"call_trace(profile_func,...'call',...)" for the destructor 
observes the inconsistency between the profiler and the 
interpreter stack and raises a "Bad call" exception. This 
exception disables profiling effectively. However, the 
exception is later ignored (as we are in a destructor) and 
program execution continues. When the profiling is later 
finished, all time after the exception is accounted for the 
last function, that was on top of the profiler stack when 
profiling was disabled. This can be extremely confusing.

The attached script reproduces the problem. Run it 
through the Python interpreter. When you see an 
"Exception Bad call ... ignored", the interpreter has the 
described problem. We observed the problem in Python 
2.1.3
(on Linux, Solaris and Windows).

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The good news is that this has been fixed in Python 2.2.x
and beyond.

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Apparently, a colleague observed the bug also in Python 2.2.2.

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I've run your script on Py2.2.3 and 2.3b1+ and did not 
observe "Exception Bad cad ... ignored".

Marking this one as already fixed.

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I believe this bug has cropped up again.  On my Debian system:

glyph@kazekage:~% python -V ; python Downloads/prof2.py |
head -3
Python 2.3.3
Exception exceptions.AssertionError:
<exceptions.AssertionError instance at 0x403b270c> in <bound
method C.__del__ of <__main__.C instance at 0x403b26ec>> ignored
exceptions.ZeroDivisionError
         5 function calls in 0.000 CPU seconds

This is not the same error as before, but it is just as
clearly wrong.

This bug seems to have resurfaced in newer python versions.

I have tested the file attached in the original report (prof2.py) in python 2.6.6 and 2.7 (x86 versions) under Windows 7, and both give the same output:

c:\temp>c:\Python27\python.exe prof2.py
<type 'exceptions.ZeroDivisionError'>
Exception AssertionError: AssertionError('Bad call', ('prof2.py', 19, 'h'), <frame object at 0x023880E0>, <frame object at 0x00586E18>, <frame object at 0x02388518>, <frame object at 0x02388248>) in <
bound method C.__del__ of <__main__.C instance at 0x02342A80>> ignored
         5 function calls in 0.007 CPU seconds

   Ordered by: standard name

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
        1    0.000    0.000    0.007    0.007 <string>:1(<module>)
        1    0.001    0.001    0.001    0.001 prof2.py:11(g)
        1    0.006    0.006    0.007    0.007 prof2.py:19(h)
        1    0.000    0.000    0.000    0.000 prof2.py:7(f)
        1    0.000    0.000    0.007    0.007 profile:0(h())
        0    0.000             0.000          profile:0(profiler)