Wrote down the invariants of some common objects whose structure is
exposed in header files. Fixed a few comments in these headers.
As we might have expected, writing down invariants systematically exposed a
(minor) bug. In this case, function objects have a writeable func_code
attribute, which could be set to code objects with the wrong number of
free variables. Calling the resulting function segfaulted the interpreter.
Added a corresponding test.
diff --git a/Include/intobject.h b/Include/intobject.h
index 61ef0f0..1bbd59c 100644
--- a/Include/intobject.h
+++ b/Include/intobject.h
@@ -11,7 +11,7 @@
None of the functions should be applied to nil objects.
The type PyIntObject is (unfortunately) exposed here so we can declare
-_Py_TrueStruct and _Py_ZeroStruct below; don't use this.
+_Py_TrueStruct and _Py_ZeroStruct in boolobject.h; don't use this.
*/
#ifndef Py_INTOBJECT_H