Defer functions defined in nested classes in free-threaded builds

[mpage]

Feature or enhancement

Proposal:

We currently only defer functions that do not have the CO_NESTED flag set:

cpython/Objects/funcobject.c

Lines 213 to 218 in 26ff32b

	if ((code_obj->co_flags & CO_NESTED) == 0) {
	// Use deferred reference counting for top-level functions, but not
	// nested functions because they are more likely to capture variables,
	// which makes prompt deallocation more important.
	_PyObject_SetDeferredRefcount((PyObject *)op);
	}

This also excludes functions defined on nested classes. In the example below, the Foo.__init__ function will not use deferred reference counting because the __init__ method's code object has the CO_NESTED flag set.

def func():
    class Foo:
        def __init__(self):
            pass

We would like to relax the restriction on CO_NESTED to allow functions that are defined on nested classes to use deferred reference counting.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-127274: Defer nested methods #128012

[erlend-aasland]

I suspect this can be closed, @mpage.