crash in Py_EnterRecursiveCall

[René J.V. Bertin]

Hello,

I have embedded Python into and extended it with functionality from a
graphical tool I use. One of the things it allows me to do is to
export Python objects to a simple scripting language ("ascanf"), and
call them as if they were native functions.

I have the following situation in which I get a systematic
segmentation violation in Py_EnterRecursiveCall(), in Python 2.3
(Apple's Mac OS X 10.4 system version), 2.4 2.5 and 2.6 (OS X) and on
Cygwin with 2.5 and 2.6

I enter an interactive Python 'console' from within my application,
either the one from the interact package, or the IPython shell. My
application has a callback defined for the readline routines that
calls the graphical event handler, allowing for instance
refresh/redraws to continue while working in the Python console. The
crash occurs when during such events handled through the readline
callback, I call an exported Python object. This does not appear to be
related to recursion per se, but rather to "calling a python
interpreter behind the back of the currently active
console/interpreter".

To be clearer, suppose I have some Python code

def Py_travDistCalc(a,b,c):
     ...
     return x

ascanf.ExportVariable("travDistCalc", Py_travDistCalc )

I can then issue a call
1) travDistCalc[a,b,c] from an ascanf script.
2) ascanf.Eval( 'travDistCalc[a,b,c]' ) from the Python console

Call 1) provokes a crash in Py_EnterRecursiveCall() when invoked
through the readline callback when the Python console is open, but
call 2) succeeds normally.

My workaround is to keep track of the readline callback recursion
level, and compare the current level with the level recorded when
entering a Python console before doing the PyObject_CallObject()
required in call 1) and 2) above.

I'm not sure if this is a bug in Python. It is the sort of crash
situation I'd try to avoid, though.