bpo-37337: Add _PyObject_VectorcallMethod()

[jdemeyer]

https://bugs.python.org/issue37337

[jdemeyer]

CC @vstinner since this is increasing the size of the C API.

[vstinner]

This PR adds too many functions at once, it's hard to see how each function is used. Would it be possible to start by adding _PyObject_VectorcallMethod() and its _PyObject_VectorcallMethodId() variant.

Only once it's merged, propose a new PR to only add the private _PyObject_CallMethodNoArgs() and its _PyObject_CallMethodIdNoArgs() variant.

Adding a public PyObject_CallMethodNoArgs() should be the last PR. You should elaborate "efficiency" rationale: measure how many times it's called, the performance benefit (if any), effect on the stack usage, etc.

[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.

[jdemeyer]

Would it be possible to start by adding _PyObject_VectorcallMethod() and its _PyObject_VectorcallMethodId() variant.

Sure. It's just that sometimes you actually need to use the function in more places to see which effect it has. If I would have made a PR adding _PyObject_VectorcallMethodId but never using it, people might complain about adding a new function which isn't used anywhere.

But now that we see that these functions would certainly be used, we can indeed split this up.

I assume that by asking this, you agree to add the functions _PyObject_VectorcallMethod() and _PyObject_VectorcallMethodId().

[vstinner]

I suggest to only add _PyObject_VectorcallMethod() and its _PyObject_VectorcallMethodId() variant, but also use them. My mean: remove the 3 other functions.

[jdemeyer]

So what should I do with all the changes of the form

-    loop = _PyObject_CallMethodId(policy, &PyId_get_event_loop, NULL);
+    loop = _PyObject_CallMethodIdNoArgs(policy, &PyId_get_event_loop);

[jdemeyer]

I suggest to only add _PyObject_VectorcallMethod() and its _PyObject_VectorcallMethodId() variant, but also use them.

Done.

[jdemeyer]

You set this to awaiting merge, so you plan to merge it? Or are you waiting for more reviews?

[methane]

Bot changed the label, not l.
It looks good to me. But I'm waiting for other core-dev's review.

@vstinner Would you check this again?

[jdemeyer]

I have made the requested changes; please review again

[bedevere-bot]

Thanks for making the requested changes!

@vstinner, @methane: please review the changes made to this pull request.