Most mutable data is protected by a striped lock that is keyed on the
referenced object's address. The weakref's hash is protected using the
weakref's per-object lock.
Note that this only affects free-threaded builds. Apart from some minor
refactoring, the added code is all either gated by `ifdef`s or is a no-op
(e.g. `Py_BEGIN_CRITICAL_SECTION`).
Remove _PyWeakref_GetWeakrefCount() and _PyWeakref_ClearRef() from
the public C API: move them to the internal C API.
Refactor also _weakref_getweakrefs() code to make it more readable.
* Add _PyWeakref_IS_DEAD() internal function.
* Modify is_dead_weakref() of Modules/_weakref.c and
_pysqlite_drop_unused_cursor_references() to replace
PyWeakref_GET_OBJECT() with _PyWeakref_IS_DEAD().
* Replace "int i" with "Py_ssize_t i" to iterate on cursors
in _pysqlite_drop_unused_cursor_references().
mpage
Donghee Na
Victor Stinner