[boost] [Python] Improved exception handling for Python embedding

Subject: [boost] [Python] Improved exception handling for Python embedding
From: Michael Koenig (michael.koenig_at_[hidden])
Date: 2014-08-01 07:40:19

Hey guys!

Boost.Python throws boost::python::error_already_set exceptions whenever 
calls to embedding functions such as boost::python::import() or 
boost::python::exec() fail.

This exception is just an empty class. It does not provide any 
information on the error which occurred on the Python side. It is not 
even a standard exception in the C++ sense.

As a result, debugging problems with embedded Python code or even the 
Python environment (available packages etc.) with the current exception 
handling mechanism is difficult. So far, in our company we wrap most 
Boost.Python functions with custom exception handling code.

In our exception handling code, we basically work the CPython API to 
extract details of Python exceptions such as
* Exception types,
* Error messages, and
* Stack traces.

We want to put this part of our embedding library back into the 
Boost.Python project. At the EuroPython 2014 conference in Berlin, I had 
a few discussions with Reinhard Wobst, Austin Bingham, and others, and 
the current exception handling mechanism was perceived an impediment on 
the usability of Boost.Python.

I am most grateful for feedback of seasoned Boost contributors (and 
users) whether my proposal is of sufficient interest and how best to 
pursue it.

Cheers

Michael

-- 
Dr. Michael König
Software Engineer
Blue Yonder GmbH
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