[C++-sig] RAII for the GIL in Boost.Python?

[John Zwinck]

I posted this to the Boost list, where it was suggested this list as a 
next step.  If you saw it there, the rest of this message is the same.

There are many questions and example classes online for dealing with 
Python's Global Interpreter Lock (GIL) using RAII.  I think Boost.Python 
should provide this functionality, rather than having users who build 
hybrid C++/Python applications copy-pasting code from various places.  I 
was one of those users recently, and the code I developed to deal with 
it is now public:

https://github.com/jzwinck/pccl/blob/master/InterpreterLockGuard.hpp
https://github.com/jzwinck/pccl/blob/master/InterpreterLockGuard.cpp
https://github.com/jzwinck/pccl/blob/master/test/InterpreterLockGuard.test.cpp

Comments in the header explain how to use it in the context of 
Boost.Python, and contain a link to a wiki from which some of the code 
was originally copied.

Why add this to Boost?  It's clearly code that a bunch of people need, 
often people who are already using Boost.Python.  It has a permissive 
license, and I can re-license it if need be.  And it depends on Boost 
(mostly for thread-specific storage--I hope this dependency won't be 
seen as a liability here, though it could be removed if needed).

This particular implementation was used successfully in a few programs 
in a commercial setting on Fedora and RHEL systems.  It has some extra 
checks that we found helpful compared to some of the versions you'll 
find posted online.  The code also builds and passes its tests with GCC 
on Mac OS X.

I welcome any feedback regarding the suitability for inclusion in Boost 
of this particular code and/or the concepts it implements.

John Zwinck