bpo-40170: Convert PyObject_IS_GC() macro to a function

[shihai1991]

https://bugs.python.org/issue40170

[pablogsal]

@shihai1991 Could you rebase the PR to pick the latest changes?

[shihai1991]

@shihai1991 Could you rebase the PR to pick the latest changes?

Got it, done ;)

[pablogsal]

Hummmm, I think we still need a macro version for internal use for performance reasons. @vstinner was that your original intent?

[bedevere-bot]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I have made the requested changes; please review again. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[vstinner]

Hummmm, I think we still need a macro version for internal use for performance reasons.

Right, please add a static inline function _PyObject_IS_GC() in pycore_object.h and modify gcmodule.c to use it (replace PyObject_IS_GC with _PyObject_IS_GC).

PyObject_IS_GC() function body should just call _PyObject_IS_GC().

[shihai1991]

I have made the requested changes; please review again

[bedevere-bot]

Thanks for making the requested changes!

@pablogsal: please review the changes made to this pull request.

[vstinner]

Suggested change

	if (PyType_IS_GC(Py_TYPE(obj))) {
	return (Py_TYPE(obj)->tp_is_gc == NULL || Py_TYPE(obj)->tp_is_gc(obj));
	}
	return 0;
	return (PyType_IS_GC(Py_TYPE(obj))
	&& (Py_TYPE(obj)->tp_is_gc == NULL
	|| Py_TYPE(obj)->tp_is_gc(obj)));

[shihai1991]

this code style looks more simple?

[vstinner]

Thanks @shihai1991!

[shihai1991]

Thanks @shihai1991!

Thanks, folks. I learned much in this PR(especially in docs(what is user really need).