While working on a unit test for the issue #14432, I hit a bug. My C thread got the GIL with PyGILState_Ensure(), but it was strange because the main Python thread also had the GIL...

Then I saw that gil_created() returned false. The solution is to call PyEval_InitThreads() to create the GIL.

I was reading "Non-Python created threads" documentation, but this section doesn't mention PyEval_InitThreads().

I don't know if it's something new in Python 3.2 with the new GIL.