[Python-Dev] Re: C new-style classes and GC

[Tim Peters]

[Guido]
> Yes, I think this is the right thing to do -- either only inherit
> tp_free when the GC bit of the base and derived class are the same,

Jim is keen to have gc'able classes defined in C get the right deallocation
function by magic.  In these cases, he leaves tp_free NULL, but indicates
gc-ability in tp_flags.  tp_base becomes "object" by magic then, and the GC
bits are not the same, and neither inheriting object.tp_free nor leaving
derived_class.tp_free NULL can work.  It seems like a reasonable thing to me
to want it to work, so on to the next:

> or -- in addition -- special case inheriting PyObject_Del and turn it
> into PyObject_GC_Del when the base class adds the GC bit.

That's what I had in mind, s/base/derived/, plus raising an exception if a
gc'able class explicitly sets tp_free to PyObject_Del (probably a
cut-'n-paste error when that happens, or that gc-ability was tacked on to a
previously untracked type).

If that's all OK, enjoy your vacation, and I'll take care of this (for 2.3
and 2.2.3).