To fix bpo-40170, I would like to modify Py_TRASHCAN_BEGIN() macro to use PyType_GetSlot() to get the deallocator function, rather than accessing directly the PyTypeObject.tp_dealloc member. The problem is that currently PyType_GetSlot() only works on heap allocated types.

Would it be possible to add support for statically allocated types to PyType_GetSlot()?

Py_TRASHCAN_BEGIN() is currently defined as:

#define Py_TRASHCAN_BEGIN(op, dealloc) \
    Py_TRASHCAN_BEGIN_CONDITION(op, \
        Py_TYPE(op)->tp_dealloc == (destructor)(dealloc))

Hi, victor. If you have much bpo need to manage, I could take a look in this week :)

historical discuss: bpo17162

I create a PR in: https://github.com/shihai1991/cpython/pull/13/commits.
Looks like It works.

If we extend PyType_GetSlot() to accept non-heaptype, we need find a way to judge the max slot of non-heaptype.

> historical discuss: bpo17162

bpo-17162 added PyType_GetSlot(), but static types were not discussed there.

> bpo-17162 added PyType_GetSlot(), but static types were not discussed there.
Thanks to correct my info. I paste this bpo just Larry have mentioned the static type in PyType_GetSlot() :)

> If we extend PyType_GetSlot() to accept non-heaptype, we need find a way to judge the max slot of non-heaptype.

Static types can have some sub-slots structs but not others. A "max slot" will not help for types that have tp_as_mapping but not tp_as_number, for example.
You'll probably need some table like typeslots.inc to record which sub-slots struct each slot belongs to.

> You'll probably need some table like typeslots.inc to record which sub-slots struct each slot belongs to.

Looks like it's a good way to solve this probleam, Let me try it ;)

New changeset a13b26cac1519dad7bbc8651de7b826df7389d75 by Hai Shi in branch 'master':
bpo-41073: PyType_GetSlot() can now accept static types. (GH-21931)
https://github.com/python/cpython/commit/a13b26cac1519dad7bbc8651de7b826df7389d75

> bpo-41073: PyType_GetSlot() can now accept static types. (GH-21931)

Nice! It will be simpler to use PyType_GetSlot() in an extension with the limited C API, without having to care if the type is a static type or a heap type.