gh-132775: Add _PyCode_GetVarCounts()

[ericsnowcurrently]

This helper is useful in a variety of ways, including in demonstrating how the different counts relate to one another.

It will be used in a later change to help identify if a function is "stateless", meaning it doesn't have any free vars or globals.

Note that a majority of this change is tests.

• Issue: Improvements to test.support.interpreters.Interpreter #132775

[iritkatriel]

compiler warning here

[iritkatriel]

LGTM. But I'd run the refleaks buildbots before merging.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot s390x RHEL8 LTO + PGO 3.x (tier-3) has failed when building commit 94b4fcd.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/442/builds/9227) and take a look at the build logs.
4. Check if the failure is related to this commit (94b4fcd) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/442/builds/9227

Failed tests:

• test_code

Summary of the results of the build (if available):

==

Click to see traceback logs

remote: Enumerating objects: 27, done. remote: Counting objects: 3% (1/27) remote: Counting objects: 7% (2/27) remote: Counting objects: 11% (3/27) remote: Counting objects: 14% (4/27) remote: Counting objects: 18% (5/27) remote: Counting objects: 22% (6/27) remote: Counting objects: 25% (7/27) remote: Counting objects: 29% (8/27) remote: Counting objects: 33% (9/27) remote: Counting objects: 37% (10/27) remote: Counting objects: 40% (11/27) remote: Counting objects: 44% (12/27) remote: Counting objects: 48% (13/27) remote: Counting objects: 51% (14/27) remote: Counting objects: 55% (15/27) remote: Counting objects: 59% (16/27) remote: Counting objects: 62% (17/27) remote: Counting objects: 66% (18/27) remote: Counting objects: 70% (19/27) remote: Counting objects: 74% (20/27) remote: Counting objects: 77% (21/27) remote: Counting objects: 81% (22/27) remote: Counting objects: 85% (23/27) remote: Counting objects: 88% (24/27) remote: Counting objects: 92% (25/27) remote: Counting objects: 96% (26/27) remote: Counting objects: 100% (27/27) remote: Counting objects: 100% (27/27), done. remote: Compressing objects: 7% (1/13) remote: Compressing objects: 15% (2/13) remote: Compressing objects: 23% (3/13) remote: Compressing objects: 30% (4/13) remote: Compressing objects: 38% (5/13) remote: Compressing objects: 46% (6/13) remote: Compressing objects: 53% (7/13) remote: Compressing objects: 61% (8/13) remote: Compressing objects: 69% (9/13) remote: Compressing objects: 76% (10/13) remote: Compressing objects: 84% (11/13) remote: Compressing objects: 92% (12/13) remote: Compressing objects: 100% (13/13) remote: Compressing objects: 100% (13/13), done. remote: Total 14 (delta 13), reused 2 (delta 1), pack-reused 0 (from 0)  From https://github.com/python/cpython * branch main -> FETCH_HEAD Note: switching to '94b4fcd806e7b692955173d309ea3b70a193ad96'. You are in 'detached HEAD' state. You can look around, make experimental changes and commit them, and you can discard any commits you make in this state without impacting any branches by switching back to a branch. If you want to create a new branch to retain commits you create, you may do so (now or later) by using -c with the switch command. Example: git switch -c <new-branch-name> Or undo this operation with: git switch - Turn off this advice by setting config variable advice.detachedHead to false HEAD is now at 94b4fcd806e gh-132775: Add _PyCode_GetVarCounts() (gh-133128) Switched to and reset branch 'main' configure: WARNING: no system libmpdecimal found; falling back to bundled libmpdecimal (deprecated and scheduled for removal in Python 3.15)find: ‘build’: No such file or directoryfind: ‘build’: No such file or directoryfind: ‘build’: No such file or directoryfind: ‘build’: No such file or directorymake[2]: [Makefile:3339: clean-retain-profile] Error 1 (ignored)make: *** [Makefile:2453: buildbottest] Error 2

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot s390x RHEL8 LTO 3.x (tier-3) has failed when building commit 94b4fcd.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/567/builds/9141) and take a look at the build logs.
4. Check if the failure is related to this commit (94b4fcd) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/567/builds/9141

Failed tests:

• test_code

Summary of the results of the build (if available):

==

Click to see traceback logs

Note: switching to '94b4fcd806e7b692955173d309ea3b70a193ad96'. You are in 'detached HEAD' state. You can look around, make experimental changes and commit them, and you can discard any commits you make in this state without impacting any branches by switching back to a branch. If you want to create a new branch to retain commits you create, you may do so (now or later) by using -c with the switch command. Example: git switch -c <new-branch-name> Or undo this operation with: git switch - Turn off this advice by setting config variable advice.detachedHead to false HEAD is now at 94b4fcd806e gh-132775: Add _PyCode_GetVarCounts() (gh-133128) Switched to and reset branch 'main' configure: WARNING: no system libmpdecimal found; falling back to bundled libmpdecimal (deprecated and scheduled for removal in Python 3.15)make: *** [Makefile:2453: buildbottest] Error 2

[ericsnowcurrently]

FYI, I'm looking into the failures.